SOVIET ATOMIC ENERGY - VOL. 35, NO. 4

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• Document Creation Date: December 27, 2016
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• Sequence Number: 4
• Publication Date: April 1, 1974
• Content Type: REPORT

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Russian Original Vol. 35, No. 4, October, 1973 \
April, 1974
SATEAZ 35(4) 883-976 (1973)
SOVIET
ATOMIC
ENERGY
ATOMHAH 3HEP1-14f1
(ATOMNAYA iNERGIYA)
TRANSLATED FROM RUSSIAN
CONSULTANTS BUREAU, NEW YORK
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4
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? SOVIET
ATOMIC
? ENERGY
Soviet Atomic Energy, is abstracted or in-
- dexed in Applied Mechanics Reviews, Chem-
ical Abstracts, Engineering Index, INSPEC?
Physics Abstracts and Electrical and Elec-
tronics Abstricts, Current, Contents, and
" Nuclear Science Abstracts.
?
Soviet Atomib Energy is a cover-to-cover translation of Atomnaya
Energiya, a publication of the Academy of Sciences of the USSR.
An arrangement with MezhdunarOdnaya Kniga, the Soviet book
export agency, makes available both advance copies of the Rus-
sian journal and original glossy photographs and artwork. This
serves' to decrease the necessary time laq between publication
of the original and publication of the translation and helps to im-
prove the quality of the latter. The translation began with the first
issue of the Russian journal. ;
Editorial Board of Atomnaya EnergiyEi:
Editor; M. D. Millionshchikov
Deputy Director
I. V. Kurchatov Institute of Atomic Energy
Academy of Sciences of the USSR
Moscow, USSR
Associate Editors: N. A. Kolokol'tsov
, N. A. Vlasov ?
A. A. Bochvar V. V. Matveev
, N. A. Dollezhar M.' G.' Meshcheryakbv
V. S. Fursov . P. N. Palei
I. N. Golovin V. B. Shevchenko'
V. F. Kalinin D. L. SimOnenko
A. K. Krasin V-. I. Smirnov
r
A. I. Leipunskii A.,P. Vin'ogradov
A. P. Zefirov
Copyright? 1974 Consultants Bureau, New York, a division of Plenum Publishing
Corporation, 227 West 17th Street, New York, N.Y. 10011. All rights reserved.
? No article contained herein may be reproduced for any purpose whatsoever
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?
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SOVIET ATOMIC ENERGY
A translation of Atomnaya Energiya
April, 1974
Volume 35, Number 4 October, 1973
OBITUARIES
CONTENTS
Engl./Russ.
Danila Lukich Simonenko
883
225
IN MEMORIAM
Aleksandr IPich Leipunskii ? A.P. Aleksandrov, I.K. Kikoin, Yu.B. Khariton,
V.V. Orlov, B.V. Gromov, O.D. Kazachkovskii, and V.I. Subbotin
884
226
ARTICLES
First Results of Working with Beams of Separated Particles in the Institute of
High-Energy Physics Accelerator ? F. Bernard, N.A. Galyaev, A. Grand,
V. E. Zelenin, V.I. Kotov, R. Lazerus, G. Lengeler, B. Marechal, J. Prela,
A.A. Prilepin, B.V. Prosin, and Yu.S. Khodyrev
886
227
Choice of a Cooling Moderator in Order to Increase the Intensity of the Beam of Cold
Neutrons from the Radial Channel of the IVV-2 Reactor ? B.N. Goshchitskii,
V.V. Gusev, L. V. Konstantinov, P.M. Korotovskikh, M.G. Mesropov,
S.K. Sidorov, A.G. Chudin, and V.G. Chudinov
890
231
Radiation-Induced Swelling of OKh18N9T Steel ? V.N. Bykov, A.G. Vakhtin,
V.D. Dmitriev, L.G. Kostromin, A.Ya. Ladygin, and V.I. Shcherbak
894
235
Radiolysis of Solutions of TBP in Contact with Nitric Acid. Formation of Radiolysis
Products of the Extraction Reagent ? E. V. Barelko and I.P. Solyanina
898
,-"239
Aging of Impregnated Carbons for Trapping Radioactive Iodine ? I.E. Nakhutin,
N.M. Smirnova, G.A. Loshakov, and V. N. Vezirov
903
245
Instrumental Neutron Activation Analysis of Rocks and Rock-Forming Minerals by
Using Ge(Li) Detectors and a Computer ? E.M. Lobanov, Yu. A. Levushkin,
and S.P. Vlasyuga
905
247
Plasma Losses in the Ring Gap of an Electromagnetic Trap ? Yu.I. Pankrat' ev,
N.A. Tulin, E.F. Ponomarenko, and V.A. Naboka
911
253
BOOK REVIEWS
V. I. Vladimirov. Practical Problems in the Operation of Nuclear Reactors
? Reviewed by M. A. Chepovskii
916
257
Yu. V. Gott and Yu. N. Yarlinskii. Interaction of Slow Particles with Matter and
Plasma Diagnostics ? Reviewed by Yu. V. Martenko
917
258
D. Bedenig. Gas-Cooled High-Temperature Reactors ? Reviewed by B. Yashma ?
?
917
258
ARTICLES
Electromagnetic Fields in a Plasma Heated near the Lower Hybrid Resonance
? Yu. V. Skosyrev, N. A. Krivov, and V. M. Glagolev
919
259
ABSTRACTS
Optimization of the Cyclicity of Operation of a Research Reactor ? K. A. Konoplev
and Yu.P. Semenov
923
263
Special Features of the Resonance Absorption of Neutrons for Intermediate Levels
? A.P. Platonov and A.A. Luk'yanov
924
264
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CONTENTS
(continued)
Engl./Russ.
Use of Superposition in Calculating the Temperature of a Reactor Core Cooled by a
Liquid Metal ? A.A. Sholokhov and V. E. Minashin
925
264
Buildup of Scattered Radiation behind a Shadow Shield ? V. L. Generozov,
V.A. Sakovich, and V.M. Sakharov
926
266
LETTERS TO THE EDITOR
Thermodynamic Properties and Mutual Diffusion in the System UC? ZrC
G.B. Fedorov, V.N. Gusev, V.N. Zagryazkin, and E.A. Smirnov
928
267
An Apparatus for Studying the Kinetics of the Liberation of Inert Gases from Materials
during Isothermal Annealing ? D.M. Skorov, A.I. Dashkovskii, A.G. Zaluzhnyi,
and O.M. Storozhuk
932
269
Effect of Electron-Beam Remelting on the High-Temperature Ductility of Steel
1Kh18N1OT Irradiated with an Integrated Flux of 2.7 .1021 neutrons/cm2
? A. N. Vorob'ev, V. N. Bykov, Yu. S. Belomyttsev, V. D. Dmitriev, and M. E. Smelova
934
271
Approximation for Time Relationships in Pulsed Gamma ? Gamma Logging
? I.G. Dyad'kin, B.N. KrasiPnikov, and V.N. Starikov
936
272
Gamma-Ray Attenuation in Applied Scintillation Spectrometry ? V.I. Polyakov
and Yu. V. Chechetkin
939
274
Natural Gamma-Ray Background Measured with Ge(Li) Detector ? L.M. Mosulishvill,
N. E. Kharabadze, and T.K. Tevzieva
941
275
Determination of a Hafnium Impurity in Zirconium and Its Alloys by a Neutron Activation
Method ? V.V. Ovechkin and V.S. Rudenko
943
277
Nonobservance of Spontaneous Fission in Kurchatovium at Berkeley ? V. B. Druin,
Yu. V. Lobanov, D.M. Nadcarni, Yu .P . Kharitonov, Yu.S. Korotkin,
S.P. Tret' yakova, and V.I. Krashonkin
946
279
COMECON NEWS
XXIV Session of PKIAE SEV ? V.A. Kiselev
949
281
Collaboration Daybook
951
281
INFORMATION
Soviet ? French Collarboation in the Field of Peaceful Uses of Atomic Energy
? B. I. Khripunov
952
283
Session of Soviet ? French Commission on Scientific Topics ? A. V. Zhakovskii
953
283
CONFERENCES
II All-Union Conference on Microdosimetry ? V.I. Ivanov
954
284
MIFI Science Conference ? V.V. Frolov and V.A. Grigor' ev
956
284
Symposium on Heavy-Current Field-Emission Plasma Electronics ? G.O. Meskhi
958
286
Yb Izotop Agency Conferences and Seminars
960
287
VII International Conference on Nondestructive Testing (Warsaw, June 1973)
?A. N. Maiorov
962
288
III International Symposium on Plasma Confinement in Toroidal Systems
? V.V. Alikaev, N. N. Brevnov, and V.S. Mukhovatov
964
289
National MHD Symposium in USA ? A.V. Nedospasov
968
292
SCIENTIFIC AND TECHNICAL LIALSONS
Visit of USSR GKAE Delegation to Switzerland to Learn about Plasma Physics Research
Program ? V.I. PistunOvich
970
292
EXHIBITIONS
Low-Temperature Plasma in the Service of the National Economy ? E.S. Trekhov
972
293
The Russian press date (podpisano k pechati) of this issue was 9/20/1973.
Publication therefore did not occur prior to this date, but must be assumed
to have taken place reasonably soon thereafter.
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OBITUARIES
DANILA LUKICH SIMONENKO
The editorial staff of the periodical Atomnaya Energiya expresses its profound grief on the occasion
of the untimely demise of Professor Dantla Lukich Simonenko, member of the editorial panel of the period-
[cal, head of the I.V. Kurchatov Institute of Atomic Energy sector, winner of the Lenin Prize, and Doctor
of Physical and Mathematical Sciences, on August 21, 1973 in the 63rd year of his life, and shares the deep
sorrow of that loss with the relatives and close acquaintances of the deceased.
Translated from Atomnaya Energ-iya, Vol. 35, No. 4, p. 225, October, 1973.
0 1974 Consultants Bureau, a division of Plenum Publishing Corporation, 227 West 17th Street, New York, N. Y. 10011.
No part of this publication may be reproduced, stored in a retrieval system, or transmitted, in any form or by any means,
electronic, mechanical, photocopying, microfilming, recording or otherwise, without written permission of the publisher. A
copy of this article is available from the publisher for $15.00.
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IN MEMORIAM
ALEKSANDR IL'ICH LEIPUNSKII
A.P. Aleksandrov, I.K. Kikoin,
Yu.B. Khariton, V.V. Orlov,
B. V. Gromov, 0.D. Kazachkovskii,
and V.I. Subbotin
The power startup of the BN-350 full-scale industrial fast reactor took place on July 16, 1973, in the
town df Shevchenko on the shores of the Caspian Sea.
The founder and scientific pacesetter of developmental work on fast breeder reactors in our country
was Academician Aleksandr Il'ich Leipunskii of the Academy of Sciences of the Ukrainian SSR, the anni-
versary of whose death is marked by August 14. Thanks to the work which he initiated in good time, our?
country has taken the leading position in the development of several of the principal aspects of fast power
reactors, and in building fast power reactors. Fast reactors are instrumental in the thorough solution of
? the problem of fuel reserves for the nuclear power industry, and are presently acknowledged the world
over as one of the principal areas of promise in the overall power picture.
A.I. Leipunskii was an outstanding Soviet physicist, one of the founders of Soviet nuclear physics and
nuclear power.
The scientific activities of A.I. Leipunskii began in 1926 at the Leningrad Physics and Engineering
Institute [LFTH with his research into elementary atomic processes. Among the most significant research
achievements of that period was the detection and study of energy transfer from excited atoms and mole-
cules to free electrons (impacts of the second kind). An extensive research program was devised for study-
ing molecular dissociation and recombination phenomena, and the formation of negative ions.
Translated from Atomnaya Energiya, Vol.35, No.4, p.226, October, 1973.
O 1974 Consultants Bureau, a division of Plenum Publishing Corporation, 227 West 17th Street, Nezu York, N. Y. 10011.
No part of this publication may be reproduced, stored in a retrieval system, or transmitted, in any form or by any means,
electronic, mechanical, photocopying, microfilming, recording or otherwise, without written permission of the publisher. A
copy of this article is available from the publisher for $15.00.
884
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Starting with 1930, the basic interests entertained by A.I. Leipunskii shifted to problems in the
physics of the nucleus. As one of the organizers of the Ukrainian Physics and Engineering Institute [UFTI],
A. I. Leipunskii developed an extensive research program at Khar'kov geared to investigations of nuclear
reactions, and one of its first projects dealt with neutron physics research. He studied processes involv-
ing interactions between thermal neutrons and matter, and photoneutron production and scattering pro-
cesses. Specifically, A.I. Leipunskii was the first to detect resonance effects in scattering of neutrons
on light nuclei. His neutrino detection experiment (1936) was one of A.I. Leipunskii's significant contri-
butions to nuclear physics.
A.I. Leipunskii devoted his last twenty-five years, with all his energies, to the development of Soviet
nuclear power. He was in fact the first in the world to point out how fast reactors can provide the most
effective solution-to the problem of reproduction of nuclear fuel. While arriving at this concept in the
1948-1949 period, A.I. Leipunskii headed up the work on fast-neutron breeder reactors in the country.
At the Power Physics Institute [FEI] in- Obninsk, A.I. Leipunskii devoted a broad program of re-
search on nuclear physics, reactor physics, heat transfer and technology of liquid-metal coolants. This
research, backed up by operating experience with the BR-2, BR-5, and BOR-60 fast reactors build under
his supervision, laid down solid scientific and technical foundations for future full-scale power generating
stations using fast reactors.
A.I. Leipunskii died only one year before the startup of the first full-scale nuclear power station
based on a BN-350 fast reactor, and built under his scientific supervision. An even more productive power
station using a BN-600 fast reactor is now under construction in the Urals, and large power generating
stations are being developed to bring fast reactors definitely into the nuclear power picture in the country.
In addition to his many-sided scientific research activities and activities in organizing scientific pro-
grams, A.I. Leipunskii has also devoted many of his efforts to the training and education of scientific
cadres. As one of the founders of MI FI [Moscow Engineering and Physical Institute], he continued in his capa-
city as head of a department of that institute up until his very last days. Many of his pupils developed into
major scientists at the head of leading scientific teams.
A.I. Lelpunskii's contribution to the cause of developing Soviet nuclear physics and the Soviet nuclear
power industry has received a high estimate from the Soviet government. He was awarded three Orders of
Lenin, the Order of the October Revolution, the Badge of Honor order, and various medals. For his work
on fast reactors, A.I. Leipunskii, together with some of his colleagues, was awarded the Lenin Prize. In
1963, A.I. Leipunskii was awarded the title of Hero of Socialist Labor.
As a scientists and as a person, Aleksandr ich Leipunskii won the most profound respect of all
those who worked with him, and of all those fortunate enough to know him. His bright memory will always
be cherished in our hearts.
885
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ARTICLES
FIRST RESULTS OF WORKING WITH BEAMS OF SEPARATED
PARTICLES IN THE'INSTITUTE OF HIGH-ENERGY
PHYSICS ACCELERATOR
F. Bernard,* N. A. Galyaev,
A. Grand,* V. E. Zelenin,
V.I. Kotov, R. Lazerus,*
G. Lengeler,* B. Marechal,*
J. Prela,* A. A. Prilepin,
B.V. Prosin, and Yu. S. Khodyrev
UDC 621.3.038.617:621.384.8
In accordance with the arrangements which have been made for cooperation between the Institute of
High-Energy Physics and CERN, a magnetooptical channel forming a beam of separated particles and a
high-frequency separator have been developed and constructed for the French liquid-hydrogen chamber
"Mirabelle." This channel provides the bubble chamber with kaons and antiprotons over range of momen-
tum 17-40 GeV/c, and pions with momenta up to 50 GeV/c. The high-frequency separator developed and
constructed in CERN over the period 1967-1971 was set up and tested in the Institute of High-Energy Phys-
ics in August 1971. Over the same period a magnetooptical channel was designed and set up in the Institute
of High-Energy Physics. Testing of the whole complex was completed in 1972, and the first photographs
in a beam of K- mesons were obtained in the Mirabelle chamber in May-June, 1972.
*CERN colleagues.
42, Q3 04
Cl
Cl
F2
/12 c34 Q5 P14 '8/1758
es tdo
QM Q12
Q13 Q14
46,67mrad
I\
441111IL .466\
JL
SF
Q15 516
513
BC
EC C5 017 QM' QM 520 C6 Cl 521 15 55 Q22 Q21 C8 Q24
r-
r"
i
L
475
0,50?
?,25 ?
-200 -100
y,mm
F ig. 1 Fig. 2
Fig. 1. Optical system of the channel and course of the rays in the horizontal (
and vertical ( ----) planes: T) outer target; C) collimators; Q) quadrupole lenses;
M) deflecting magnets; RF) deflectors of the separator; BS) absorber; BC) Mirabelle
bubble chamber.
100
200
Fig.2. Vertical profile of the beam in the Mirabelle bubble chamber: ) experi-
mental distribution of the particles; ----) calculated distribution.
Translated from Atomnaya Pnergiya, Vol.35, No.4, pp .227-230, October, 1973. Original article
submitted February 1, 1973.
? 1974 Consultants Bureau, a division of Plenum Publishing Corporation, 227 West 17th Street, New York, N. Y. 10011.
No part of this publication may be reproduced, stored in a retrieval system, or transmitted, in any form or by any means,
electronic, mechanical, photocopying, microfilming, recording or otherwise, without written permission of the publisher. A
copy of this article is available from the publisher for $15.00.
886
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88m
184,6 m
174m
130 m
126,3 m
I R
Fig.3. Block diagram of the separator: 1) phase bridge; 2) reference phase
shifter; 3) klystron power amplifier; 4) finishing phase shifter; 5) high-sta-
bility master generator.
The main design characteristics of the channel and the high-frequency separator were presented ear-
lier [1]. Figure 1 shows the final version of the optical system of the channel, which differs from that
given in [1] mainly in relation to the final section, the latter providing a repeated momentum analysis of the
particles and shaping the particle beam passing into the bubble chamber. The new version of the optical
system gives a uniform particle distribution in the working space of the bubble chamber (Fig. 2). The
main parameters of the optical system of the channel are as follows:
Dimensions of the copper target (horizontal
?vertical?length) 2 X 1.5 X 150 mm3
Angle of formation of the particles 00
Angles of capture of the particles into the
channel:
horizontal ?5 mrad
vertical ?3.8 mrad
Maximum solid angle of capture . . . . ..... 76 ?sr
Momentum resolution ?0.25%
Number of quadrupole lenses (length 2 m). 23
Number of rotating magnets (length 6 m) . 6
Number of collimators 8
Interdeflector distances:
Li2 88m
L23 164.6 m
L13 252.6 m
Total length of the channel 511.5 m
Hort- Verti-
Magnifications
zontal cal
First momentum collimator C4 ?1.68
Center of deflectors 2.31 5.69
Redetermination of target, collimators
C6, C7 ?3.06 9.83
Second momentum collimator C8 3.33
The high-frequency separator was constructed with due allowance for the conditions of optimum ac-
ceptance of the particle beam in the momentum range 30 GeV/c, with the maximum possible value of the
high-frequency deflecting field. A block diagram of the separator is shown in Fig. 3, and its main charac-
teristics are presented below:
887
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1,0
Fig. 4. Profile of the undeflected beam in
the absorber in the vertical plane (1), and
profiles of the deflected beam when work-
ing with one (2), and simultaneously with
vertical straight lines indicate the bound-
aries of the absorber.
two deflectors of the separator (3). The
-16 -12 - y, mm
Design frequency (at 25?C, in vacuum, and for Vph = c) 10 2855.167 MHz
Phase shift per cell 27r/3
Deflector aperture 2 a 45.0 mm
Effective deflector length 1 5.845 m
Total deflector length 6.025 m
Group velocity (normalized) 13g = Vg /C ?0.0248
Amplitude damping factor a 0.102 Np/m
Shunt impedance R 16.3 MS2/m
Quality factor Q 1180
Series impedance fz = [(R/Q) ? (27r/A) ? (1/0g)11/2 1.82 Vial/cm
Deflector constant k1=-VZ ?
a 8.03,/ko
Transverse momentum (for a power of P0 = 20 MW)
fPolci 35.9 MeV/c
The first setting of the operating conditions of the channel and high-frequency separator was carried
out for a particle beam with a momentum of 32.17 GeV/c. For this momentum the phase shift between the
pions and protons (antiprotons) on a base of 252.6 m is equal to 360?. It thus follows that by using the first
and third deflectors of the separator we may separate kaons from pions and protons (antiprotons). Accord-
ing to calculations, the kaon flux to the bubble chamber reaches a maximum for this value of the momen-
tum [1].
From the measured difference Ay between the phases corresponding to the deflections of the 7r me-
sons and protons we may accurately determine the momentum of the particles. For a momentum of p
= 32.17 GeV/c this difference is equal to zero (or 360') and the deviation Ap of the momentum from the spe-
cified value will be given by the expression
Ap Ay
p 4a ?
Thus the actual value of the momentum belonging to the separated particles may be determined to an ac-
curacy of better than_0.5%.
From the image of the particle beam in the absorber in the vertical plane (Fig.4) we may measure
the angle of deviation communicated to the particles in each deflector. This is approximately ?0.9 mrad
instead of the theoretically expected ?1.0 mrad. The difference is comparable with experimental error.
The purity of the separated beam of kaons was determined by means of Cerenkov and scintillation
counters placed in front of the bubble cha.mber (Fig. 5). The same figure presents the results of some
measurements; these show that the background of pions and protons (antiprotons) is no greater than 2%.
However, these measurements cannot provide an accurate estimate of the muon background, since the
spatial distribution of the muons is considerably greater than the particle beam itself.
888
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,v
1,0
48
46
0,4
0,2
5
I 42
0,4 46 p,atm
Fig. 5. Arrangement of Cerenkov counters, and threshold curves for
mesons with a momentum of 32.17 GeV/c. The horizontal axis
gives the CO2 (K-) and freon-12 (K+) pressure, the vertical axis gives
the ratio of the readings in the counters S1S2C2S3 to S1S2S3 set for co-
incidence. The continuous curves correspond to the set phase be-
tween the deflectors; the broken curves are obtained on changing this
phase by 27 () and 32? (L).
In order to carry out these measurements we used a special rapid-extraction operating mode [2, 3]:
instead of a single group of accelerated protons (with a duration of about 15 nsec), approximately 1-2% of
the protons which were left after the operation of the other experimental installations were extracted from
the accelerator at the end of the flat part of the magnetic field. The proton beam was thus conveyed to the
external target over a period of some 5 Asec. This enabled us to use standard electronics with coinci-
dences, and also Cerenkov counters.
The first exposure of the Mirabelle bubble chamber was carried out in a beam of K- mesons with a
momentum of 34 GeV/c. In this we used one extracted group of accelerated protons with an intensity of
some 3 .10" particles. We obtained about 20,000 photographs with anaverage number of K- mesons amount-
ing to 3-4 particles per frame. Preliminary analysis of the photographs gave the following composition of
the particle beam: K- 80%; 7r- 2%; II- (18-20)%. In order to reduce the muon background, shielding
was installed at several points along the channel, and especially in front of the bubble chamber. In the next
irradiation of the Mirabelle chamber in K? meson beams the composition of the beam was accordingly
much improved: K1 98%, traces of other particles 2%.
In conclusion, the authors wish to express their sincere thanks to the Directorates of the Institute of
High-Energy Physics and CERN for constant cooperation in the work, and to all colleagues who took part in
the present research at various stages of its execution.
LITERATURE CITED
1. N. A. Galyaev et al., Seventh International Conference on High-Energy Charged-Particle Accelera-
tions [in Russian], Vol.1, Izd. AN ArmSSR, Erevan (1970), p'.531.
2. B. Kuiper et al., ibid., p.549.
3. A. A. Aseev et al., Preprint of the Institute of High-Energy Physics 72-50 [in Russian], Serpukhov
(1972).
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CHOICE OF A COOLING MODERATOR IN ORDER TO
INCREASE THE INTENSITY OF THE BEAM OF
COLD NEUTRONS FROM THE RADIAL CHANNEL OF
THE IVV-2 REACTOR
B.N. Goshchitskii, V.V. Gusev,
L. V. Konstantinov, P.M. Korotovskikh,
M.G. Mesropov, S.K. Sidorov,
A. G. Chudin, and V. G. Chudinov
UDC 621.039.556
Cold neutrons (En:5- 0.005 eV) are widely used for studying the structure and dynamics of matter in
the condensed state. However, the number of cold neutrons in ordinary thermal-neutron beams extracted
from the channels of a nuclear reactor is very low, and this limits the potentialities of many physical ex-
periments. Special measures are therefore adopted in research reactors in order to increase the inten-
sity of cold-neutron beams, particularly by cooling the volume of the moderator lying close to the reactor
channel. As a result of the thermalization of the neutrons, the low-temperature moderator displaces the
mean neutron energy into the low-energy region. Devices of this kind have become known as cold-neutron
generators. In principle, this method greatly increases the cold-neutron intensity. If we assume that
there is a complete thermal equilibriumbetween the neutron spectrum and the cooled moderator and that no
absorption occurs, the transition from an equilibrium neutron distribution at T = 295?K to one at T = 78 and
20?K should increase the intensity of neutrons with an energy of 0.005 eV by 8 and 13 times, respectively
[1]. In practical cases this increase is less marked, falling by a factor of 2-4 for a moderator cooled with
liquid nitrogen, and by a factor of 5-8 for a moderator cooled with liquid hydrogen [1-7].
Although the use of moderators cooled with liquid hydrogen or deuterium provides far greater cold-
neutron intensities, it is in a number of cases preferable (particularly for neutrons with an energy of the
order of 0.005 eV) to use cold-neutron generators cooled with liquid nitrogen, bearing in mind their rela-
tive operation safety and simplicity of construction. The greatest increase in the intensity of the cold neu-
trons may be obtained for such wealdy-absorbing moderators as graphite, beryllium, and compounds of
these [6]. However, owing to the small scattering cross section, the dimensions of the moderators are in
this case very considerable, and this leads to an increase in the radiative energy evolution, a greater con-
sumption of the coolant, and so on. On the whole it is therefore better to use hydrogen-containing moder-
ators, which are much less bulky and yield a fairly substantial increase in the cold-neutron intensity.
The efficiency of cold-neutron generators is largely determined by the material, the size, and the
shape of the moderator, and also by the position of the latter relative to the active zone of the reactor, the
type of reactor employed, and so forth. It is clearly this aspect which explains the contradictions in pub-
lished experimental and computed data as to the choice of the best moderator dimensions (from 10 to 100
mm [1, 3-5]). Hence in developing a cold-neutron generator for a specific reactor it is essential to deter-
mine its optimum physical characteristics experimentally. In the present investigation we make a detailed
si.dy of the manner in which the cold-neutron yield varies with the material, temperature, and dimensions
of the moderator for the liquid nitrogen-cooled cold-neutron generator of the water-cooled, water-moder- ?
ated IVV-2 pool-type reactor.
EXPERIMENTAL METHOD
All the measurements were carried out in the physical-simulation test-bed of the IVV-2 reactor, in
which the conditions-governing the formation of the real neutron spectrum at the proposed site of the
Translated from Atomnaya Energiya, Vol.35, No.4, pp.231-234, October, 1973. Original article
submitted December 6, 1972.
0 1974 Consultants Bureau, a division of Plenum Publishing Corporation, 227 West 17th Street, New York, N. Y. 10011.
No part of this publication may be reproduced, stored in a retrieval system, or transmitted, in any form or by any means,
.electronic, mechanical, photocopying, microfilming, recording or otherwise, without written permission of the publisher. A
copy of this article is available from the publisher for $15.00.
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1 2
,/ / / I
3 4 5 6 7 8
10
ii
12 13
14
Fig. 1. Arrangement of the experimental apparatus: I) test-bed providing physi-
cal simulation of the reactor; II) cold-neutron generator; III) collimator; 1, 11)
polyethylene; 2) "active zone"; 3, 10) graphite; 4) lead; 5) beryllium (graphite);
6) liquid nitrogen; 7) moderator; 8) beryllium screen; 9) vacuum thermal-insu-
lation gap; 12) beryllium filter; 13) detector; 14) cadmium sheath.
cold-neutron generator in the reactor were closely reproduced. Figure 1 gives a general idea of the cold-
neutron generator test-bed. The immediate surroundings of the cold-neutron generator, the reflector, and
the graphite thermal column were reproduced on a full-scale basis. As first units of the thermal column,
graphite 150 mm thick was employed instead of beryllium. In order to simulate the water surroundings,
the thermal column and the reflector cassettes were provided with polyethylene blocks at least 100 mm
thick. The generation of fast neutrons in the fissile material and the leakage of neutrons from the active
zone were simulated by using a Po?Be source with a strength of 5 .107 neutrons/sec placed in a solution of
boric acid. The age of the neutrons T and the square of the diffusion length L2 in the solution were then
close to the corresponding values in the reactor. The source was automatically held at various points of
the "active zone" for a time corresponding to the calculated values of the neutron fluxes at these points in
the actual reactor. The IVV-2 reactor test-bed with an analogous simulation of the active zone was used
earlier in choosing the characteristics of the diffuser used for extracting the neutron beam from the tan-
gential reactor channel [8]. The results obtained with the test-bed practically coincided with those mea-
sured in the actual reactor, thus justifying the use of the physical-simulation test-bed in the present in-
vestigation as well.
In order to cool the neutron moderators to liquid-nitrogen temperature we used a full-scale model of
the cold-neutron generator with a material and construction corresponding to those of the cold-neutron gen-
erator in the reactor itself. The model consisted of two-hermetically-sealed aluminum tanks placed one
inside the other, with a gap of about 8 mm, the pressure in these being maintained equal to 10-3-10-4 mm
Hg, so as to ensure vacuum thermal insulation of the inner sectionalized tank. The first section was filled
with liquid nitrogen in order to cool the moderator from the end surface; the remaining sections were filled
with the liquid moderator, its thickness being determined by the number of sections so filled. The level of
liquid nitrogen in the cold-neutron generator was monitored with level gages. The temperature of the mod-
erator was measured at several points over the volume, using precalibrated copper? constantan thermo-
couples. The neutrons coming from the cold-neutron generator were recorded with a group of three He3
counters of the SNM-16 type set in a protective collimator unit, the axis of which coincided with the axis
of the physical-simulation test-bed channel (Fig. 1). The collimation was chosen so that the detector
should "see" only the working surface of the cold-neutron generator. For separating the proportion of cold
neutrons (En s 0.005 eV), a polycrystalline beryllium filter 167 mm long was placed in front of the detec-
tor in the collimator channel carrying the total flow of thermal neutrons (the extraction cross section of
this filter was 104 times greater for thermal than for cold neutrons). The total error in measuring the
neutron yield was determined by the statistical error and by the instability of operation of the time sensor;
it amounted to ?3% for a measuring time of approximately 1 h. The temperature of the moderator was
kept constant to ?1?C during the measurements.
Results of the Measurements and Discussion
Depending on the material, thickness, and temperature of the moderator and the other experimental
conditions, the yield of cold neutrons was characterized by a quantity g equal to the ratio of the flux of cold
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10 20 JO 40 50 t,rnm
a
1 1
10 20 JO 40 50 t mm
? b
Fig.2. Dependence of the cold-neutron yield on the thickness of the moderator t at T
= 300 (a) and 78?K (b). Without the beryllium screen: A) C2H5OH; 11) C3H60; 0) H20.
With an uncooled (T = 300?K) beryllium screen: A) C2H5OH; 0) H20. With a cooled (T
= 78?K) beryllium screen: A) C2H5OH.
TABLE 1. Maximum Values of g and Opti-
mum Thickness of the Moderators topt at
T = 78?K
Material of moderator
toPt, mm
Yield of cold neu-
trons g
effector
4 mm
eryllium
reflector
80 mm
graphite
Water (H20)
Ethyl alcoho1(021-160H)
Methyl alcohol(CH3OH)
Acetone(C3H60)
Hexane (C6H14)
Heptane (C71116)
Octane ( C8H/8)
40
30
30
30 -
30
30
3,2
4,1
4,9
3,2
4,0
4,1
4,0
4,1
4,1
neutrons from the channel containing the cold-neutron gen-
erator to the flux of cold neutrons from the empty channel.
As moderating materials we studied the following substances,
which had a fairly high density relative to hydrogen: water,
ethyl alcohol, methyl alcohol, acetone, hexane, heptane,
and octane.
On placing the cold-neutron generator in the channel
without cooling the moderator, the yield of cold neutrons
remained almost constant with increasing thickness of the
moderator for all the materials studied (Fig.2a); this evi-
dently indicates that there is only a slight perturbation of the
field of thermal neutrons in the reflector and thermal col-
umn close to the cold-neutron generator. On cooling the
moderator the yield of cold neutrons first increases with
moderator, thickness; it reaches, a maximum for a certain
specific thickness and then falls. Figure 2b shows the de-
pendence of the cold-neutron yield- on the thickness of the moderator at 78?K (reflector 64 mm of beryllium)
Table 1 gives analogous relationships for the other materials studied.
The dependence of the cold-neutron yield on the temperature of the moderator is illustrated in Fig.3.
The measurements were made at the optimum thickness of the moderators (30 mm), corresponding to the
maximum value of g at T = 78?K. We also studied the effect of the additional beryllium screen on the flux
of cold neutrons. We assumed that the presence of such a screen would lead to a certain rise in the ther-
mal-neutron flux in the moderator and hence to an increase in the cold-neutron yield. Figure 2 shows the
measured values of g for the cases inwhich a "thermal" (T = 300?K) or "cold" (T = 78?K) beryllium screen 50 mm
thick lay immediately behind the moderator (Fig. 1). We see from the curves that the beryllium screen
leads to a rise of approximately 10% in g for the same temperature of the screen and the moderator. The
fall in g which occurs on placing a "thermal" screen behind the cooled moderator (T = 78?K) is evidently
associated with the rethermalization of the neutrons in the "thermal" beryllium and the great scattering
cross section for cold neutrons at T = 300?K.
In order to examine the possibility of placing the cold-neutron generator directly in the reflector of
the reactor, 1,Ne measured the yield of cold neutrons obtained when the cold-neutron generator was placed
tightly against the model of the active zone (without any reflector). In this case the intensity of the cold
neutrons increased by approximately 25%. However, with this arrangement a thin film of water would be
able to form between the outer surface of the cold-neutron generator and the' end of the experimental chan-
nel in the reactor tank. In special measurements with the physical model, this layer was simulated by
placing thin polyethylene plates after the cold-neutron generator along the neutron beam. The water-con-
taining interlayers shaprly reduced the cold-neutron yield. Thus for a 2 mm thickness of the polyethylene
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?
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150 200 250 300 1?K
Fig.3. Dependence of the cold-neutron
yield on the moderator temperature T:
A) C2H5OH; 0) C3H60; ?) C61114.
plate the cold-neutron flux fell by more than a factor of
two.
We see from the figures and Table 1 that the alcohols and
saturated hydrocarbons cooled to the boiling point of liquid ni-
trogen provide approximately a fourfold, and water a three-
fold, increases in the cold-neutron flux. This increase occurs
for a certain optimum thickness of the moderator, determined
by the competition taking place between the thermilization and
absorption of the neutrons in the moderator. For practical
purposes it is thus better to use saturated hydrocarbons or
mixtures of these, since their molecular compositions contain
no oxygen, an element which may form highly-active com-
pounds on irradiation. However, additional investigations into
the radiation resistance of saturated hydrocarbons under re-
actor working conditions are required before making a final
choice of material for the moderator.
In order to secure the maximum increase in cold-neu-
tron flux it is essential to maintain the moderator tempera-
ture as close as possible (within some 3-50) to the boiling point of liquid nitrogen, since in this region the
temperature dependence of g(T) is very strong, as may readily be seen from Fig. 3 (a rise of 1? reduces
the flux by about 1.2%). Under practical reactor conditions it is extremely important to reduce the tem-
perature gradients in the moderator arising as a result of the fairly substantial radiative heat evolution.*
The cooling of the moderator from the end surface facing the active zone provided for in the cold-neutron
generator greatly increased the heat-release surface and reduced the temperature gradients. For the
same purpose, additional aluminum fins occupying some 20% of the volume were introduced into the ma-
terial of the moderator. Special measurements showed that a layer of liquid nitrogen in the path of the
thermal-neutron beam and the additional aluminum fins in the volume of the moderator had hardly any ef-
fect on the cold-neutron yield for the optimum moderator thickness (30-40 mm). The installation of an additional
beryllium screen cooled to T = 78?K should in principle increase the cold-neutron yield from the generator by
some 10%. However, the use of such a screen in the actual reactor is clearly undesirable, since there
would be a considerable increase in the consumption of liquid nitrogen for cooling the beryllium. The plac-
ing of the cold-neutron generator tightly against the active zone is also quite clearly undesirable in view of
the much greater radiative heat evolution and the possible formation of water interlayers in the path of the
cold-neutron beam, reducing the intensity of the latter.
In conclusion, the authors wish to thank Academician N.A. Dollezhal' for. constant interest in the
work and help in the investigations.
LITERATURE CITED
1.
F. Webb, in: Optimization of Neutron Beams [Russian translation], Atomizdat, Moscow (1965), p.79.
2.
H. Rauch and H. Schmidt, Atomkernenergie, 10, No. 7/8, 243 (1965).
3.
P. Persson, J. Nucl. Energy, 21, No.9, 701 (1967).
4.
W. Van Dingenen, Nucl. Instrum. and Methods, 16, No.1, 116 (1962).
5.
E. Tunkelo and A. Palmgren, Nucl. Instrum. and Methods, 46, No.2,
266
(1967).
6.
P. Ageron et al., Cryogenics, 9, No.1, 42 (1969).
7.
C. Chen and R . Struss, Cryogenics, 9, No.2, 131 (1969).
8.
B. N. Goshitskii et al., At. Energ. , 25, No. 1, 21 (1968).
9.
V.P. Gerasimenko et al., At. Energ., 31, No.1, 7 (1971).
*Preliminary measurements in the IVV-2 reactor [9] showed that the radiative heat evolution in the cold-
neutron generator, on placing this behind one row of beryllium cassettes and a lead screen 20 mm thick,
was approximately 0.5 W/cm3.
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RADIATION-INDUCED SWELLING OF OKh18N9T STEEL
V.N. Bykov, A.G. Vakhtin,
V. D. Dmitriev, L. G. Kostromin,
A.Ya. Ladyg.in, and V.I. Shcherbak
UDC 621.039.531:669.012.8
There have recently been a large number of papers devoted to the radiation-induced porosity of aus-
tenitic steels after irradiation in fast reactors and the ion beams of accelerators [1, 2]. The swelling of
stainless steels of the 304 and 316 types has been studied the most fully. Information relating to the swell-
ing of OKh18N9T steel is limited to data which have been obtained for particular temperatures and inte-
grated doses [3]. In this paper we shall set out the results of an electron-microscope examination of ra-
diation-induced porosity in OKh18N9T steel.
MATERIALS AND METHOD
The samples for electron-microscope examination were discs 3.5 mm in diameter and 0.4 mm thick
cut from different fuel-element cans made of OKh18N9T steel and irradiated with integrated fluxes of up to
4.4 -1022 neutrons/cm2 in the temperature range 430-590?C. The method of thinning the samples in a
stream of electrolyte (60% H3PO4+ 40% H2SO4) was described in [4].
Fig. 1. Dependence of the change in the
microstructure of OKh18N9T steel ir-
radiated with an integrated flux of 2.5
? 1022 neutrons/cm2 on the irradiation
temperature, ?C (magnified 75,000
times): a) 430; b) 510; c) 570.
Translated from Atomnaya Energiya, Vol.35, No.4, pp.235-237, October, 1973. Original article
submitted January 8, 1973.
01974 Consultants Bureau, a division of Plenum Publishing Corporation, 227 West 17th Street, New York, N. Y. 10011.
No part of this publication may be reproduced, stored in a retrieval system, or transmitted, in any form or by any means,
electronic, mechanical, photocopying, microfilming, recording or otherwise, without written permission of the publisher. A
copy of this article is available from the publisher for $15.00.
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cPt.1022, neutrons/cm2
Fig. 2
2 3 4
Ci9t x1022, neutrons/cm'
Fig. 3
Fig. 2. Dependence of the swelling of steel on the integrated flux at 4600 (A),
(s), and 530?C (0).
Fig. 3. Dependence of the mean diameter and concentration of the cavities in OKh-
18N9T steel on the integrated flux at 460? (0) and 530?C (0).
510?
The results were analyzed directly from the negatives using an instrumental microscope. The error
in measuring the diameters of the cavities was 20 A The concentration of the cavities in the sample was deter-
mined by measuring not less than 600 cavities, the sample thickness being taken as 1500 A. The total er-
ror in determining the swelling of the material was 50%; however, the spread in the values relative to the
arithmetic mean was no greater than 20% for several measurements of the same sample.
Study of the Swelling of OKh18N9T Steel
As a result of the electron-microscope examination of the samples we found that the cavities were
uniformly distributed over the main body of the grain, their concentrations and dimensions varying with the
conditions of irradiation. Close to the grain boundaries there was a zone 1000 A wide free from cavities
and dislocation loops. The microstructure of some of the samples studied is shown in Fig. la, b, c.
Of the large number of experimental results here obtained we only used those required to plot the
functional dependence of the swelling of OKh18N9T steel on the integrated dose and the temperature (Figs.
2-5). In the analysis we had to allow for the fact that the irradiation temperature only was known to an ac-
curacy of ?30?C, and this clearly produced a spread in the experimental results for samples obtained from
different fuel-element sheaths and cans. The spread may also be partly due' to possible variations in the
structure of the original material.
Some Laws Governing the Development of R ad la t o n- Induc e d
Porosity in OKhl8N9T Steel
Dependence of the Swelling on the Integrated Dose. It is generally considered that the increase in the
volume of material as a result of the formation of radiation-induced porosity AV/V is a function of the in-
tegrated flux 'in and not of the rate of creating point defects [1]. This relationship, which has been estab-
lished by a number of authors, is described by a power function ANT/V CD (43t)11; in the majority of cases n
= 1.6-1.8 [l]. The dependence of ,AV/V on cl3t for OKh18N9T steel (Fig.2) also bears a power character with
an index of n = 1.7, in agreement with the data relating to steels of the 304 and 316 types.
The total degree of swelling is of course determined by the concentration of the cavities Pv and the
cavity size d. Figure 3 shows the dependence of pv and d on cl.t for OKh18N9T' steel at 460 and 530?C. With
increasing integrated flux there is a rise in the cavity concentration to 1015 cm-3. This relationship may be
closely approximated by a function pvc (44)2/3.
With increasing integrated dose the average diameter of the cavities 71- rises to 700 k. The relation-
ship in question may be approximately described by the function d ((kt)1/3. It should be noted that the
rise in Pv and?d with increasing (1.t is in qualitative agreement with theoretical considerations relating to
the swelling of materials [5].
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cl,21
600
400
7.00
400 450 500 tirr, ?C
Fig. 5
Fig. 4. Dependence of the swelling bf OKh18N9T steel irradiated with
integrated fluxes of 3 ? 1022 neutrons/cm2 on the irradiation tempera-
ture.
Fig. 5. Dependence of the mean diameter (*) and concentration (0) of
the cavities in 0Kh18N9T steel irradiated with an integrated flux of
3 -1022 neutrons/cm2 on the irradiation temperature.
Temperature Dependence of the Swelling. The temperature dependence of AV/V for 0Kh18N9T steel
subject to an integrated radiation dose of 3 .1022 neutrons/cm2 is shown in Fig. 4. With rising temperature
(over the comparatively narrow temperature range of 430-550?C for the integrated fluxes studied) the swell-
ing of the steel increases rapidly, reaching 3% at 510?C, after which it falls sharply. Figure 5 shows the
way in which the ,concentration and mean diameter of the cavities vary with irradiation temperature for the
same integrated doses. On increasing the temperature the size of the cavities increases almost linearly.
It is well known that the size of the cavities is determined by the equilibrium concentration of vacancies
formed as a result of the irradiation, NV, and the self-diffusion coefficient Dv. According to [5], this re-
lationship takes the form d cp (NvDv)1/2. With rising irradiation temperature and self-diffusion coeffi-
cient, the value of d m.ay also increase, although the saturation of the matrix with point defects will di-
minish. The experimental data also indicate that the thermal dissociation of the cavities in the range of
temperatures studied will certainly play a less important part. Harkness and Che-Yu Li [5] associate the
temperature dependence of the cavity density with the rate of nucleation, which is proportional to the prod-
uct of the difference in the diffusion fluxes of the point defects times the surface area of a critical nucleus,
and to the concentration of these nuclei.
The supersaturation of the matrix with point defects diminishes with rising temperature. Hence on
exceeding a certain temperature the rate of nucleation should fall, and this will lead to a reduction in cavity
concentration.
It thus follows from the data presented that, on raising the irradiation temperature above 510?C, the
decisive part in the swelling of OKh18N9T steel is Played, not by the size of the cavities, but by their con-
centration. This result indicated that, although there may be a rise in the cavity-annealing rate with in-
creasing temperature, yet nevertheless the mechanism associated with the fall in the rate of formation of
critical nuclei would appear to be the more important. This is also indicated by the fact that the annealing
of cavities in neutron-irradiated OKh18N9T steel only starts from temperatures above 800-900?C [3]. At
the same time, no cavities are detected at temperatures of over 550?C in the irradiated steel. This dif-
ference can hardly be explained simply by virtue of the mechanism associated with the thermal dissociation
of the cavities.
LITERATURE CIT ED
1. Proc. of Brit. Nucl. Energy Soc., European Conference on Voids Formed by Irradiation of Reactor
Materials, Reading (1971).
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2. Proc. of IAEA Symp. on Radiation Damage in Reactor Materials IAEA, Vienna, Vol. II (1969).
3. V.N. Bykov et al., At. Energ., 34, No.4, 247 (1973).
4. G. Thomas, Electron Microscopy of Metals [Russian translation], IL (1963), p.200.
5. S. Harkness et al., Nucl. Appl. and Technol., 7, 24 (1970).
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RADIOLYSIS OF SOLUTIONS OF.TBP IN CONTACT. WITH
NITRIC ACID
FORMATION OF RADIOLYSIS PRODUCTS OF THE EXTRACTION REAGENT
E.V. Barelko and I. P. Solyanina UDC 541.15
One of the basic factors influencing the properties of an extraction system containing tributyl phos-
phate (TBP) as the extraction reagent, widely used in the technology of processing of nuclear fuel, is the
radiation chemical decomposition of TBP with the formation of alkylphosphoric acid [1-3].
The radiolysis of individual TBP and its solutions in hydrocarbons of various compositions has been
investigated in a number of studies [4-11]. It is known that an increase in the concentration of dibutyl phos-
phate (DBP) in the organic solution leads to a sharp increase in the distribution coefficient (Kd) of zirconi-
um [12], when the latter is present in trace amounts. Analogous results were obtained in [10, 11] in an in-
vestigation of the radiolysis of solutions of TBP, where it was shown that the changes in Kd of zirconium
depend on the nature of the diluent and are rather well correlated with the concentration of the DBP formed.
Data on the radiolysis of TBP in contact with a solution of nitric acid containing zirconium and uranium ni-
trates were cited in [13].
Both in our studies and in other published studies, until recently the deterioration of the extraction
characteristics was explained by the appearance of DBP. And yet it is clear that at sufficiently large doses
of radiation, monobutyl phosphate (MBP) and phosphoric acid should also be accumulated in the system.
As was shown in [4, 8], in the radiolysis of individual TBP in the absence of an aqueous phase, the
concentration of MBP is only 5-10% of the concentration of DBP. In the presence of an aqueous phase, in
accord with the distribution coefficient [14], MBP should be accumulated primarily in it, and if we take into
consideration the low radiation yield of MBP as well, it might seem that its influence on the extraction of
zirconium should be minor. Nonetheless, there were indications of the participation of this compound in
the process of extraction at relatively high concentrations of zirconium in solution [3].
In this work we discussed the formation of the basic radiolysis products of the extraction reagent
? DBP, MBP, and H3PO4, "polymer" ? and their influence on the extraction of zirconium when its concen-
tration in solution is high.
The radiation source was 60Co with an activity of the preparation equal to 200,000 gram radium equiv-
alents. The dose was 20 Whiter, interval up to 0-100 W ? h/liter. The doses were calculated according to
the energy absorbed by the entire system. Irradiation was conducted in glass ampoules equipped with a
mixer, supply lines for the passage of gas and collection of samples.
The ratio of the volumes of the organic and aqueous phases in the irradiated system was equal to 1: 1.
Composition of the phases: organic ? 25% TBP + synthine; aqueous ? 3 M HNO3, 3 M HNO3 + 2 .10-2 Zr02
? (NO3)2.
The experiments were conducted while bubbling oxygen through the solution under conditions of its
equilibrium with air and a temperature of 18-20?C and in the presence of a "deficiency" of it, when oxygen
was not bubbled through, but there was an atmosphere of air above the solution. It was shown that in this
case, in the geometry of our experiments at doses L?5 W ?h/liter, the system was identical with deaerated
systems with respect to the yield of the radiolysis products of TBP.
Translated from Atomnaya t nergiya, Vol.35, No.4, pp.239-243, October, 1973. Original article ?
submitted February 8, 1973.
0 1974 Consultants Bureau, a division of Plenum Publishing Corporation, 227 West 17th Street, New York, N. Y. 10011.
No part of this publication may be reproduced, stored in a retrieval system, or transmitted, in any form or by any means,
electronic, mechanical, photocopying, microfilming, recording or otherwise, without written permission of the publisher. A
copy of this article is available from the publisher for $15.00.
898
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d- ox/O-Inif
1, 0
20 40
Dose, W. h/liter
Fig. 1
60
6
? 3
? 2
20 40 50
Dose, W?h/liter
Fig. 2
80
100
Fig. 1. Dependence of the distribution coefficient of zirconium on the dose of irradia-
tion. Irradiation in contact with a solution of 3M HNO3 + 2 .10-2 M Zr02 (NO3)3: 1 (x)
in an atmosphere of 02; 2 (A) in the presence of an 02 deficiency in the system. Irra-
diation in contact with 3 M HNO3 not containing Zr salt; 3 (0) in an atmosphere of 02;
4(S) in the presence of an 02 deficiency in the system.
Fig.2. Dependence of the DBP and polymer concentration on the dose of irradiation,
Irradiation in contact with 3 M HNO3: 1(0), 4 (x) DEP in the organic phase; 2 (o), 5
(A) DBP in the aqueous phase; 3 (A), 6 (D) polymer [1-3) atmosphere solution of 02;
4-6) deficiency of 02 in the system]. Irradiation in contact with a solution of 3 M HNO3
+ 2 .10-2 M ZrO2(NO3)2; 7 (4) DBP in the organic phase in an atmosphere of 02; 8 (ii)
DBP in the organic phase under conditions of 02 deficiency in the system.
TBP was freed of traces of acid esters by shaking with a 5% solution of potash, then redistilled at a
pressure of 1 mm Hg and a temperature of 125?C. Purified oleum and synthine redistilled under vacuum
were used as diluents.
The content of DBP, MBP, and H3PO4* was determined with the aid of the method described in [8],
using colorimetric determination of the "blue" complex of phosphates with ammonium molybdate [15]. The
"polymer" was determined by the method of distilling off the irradiated organic solvent [4]. A solution of
zirconium with a concentration of 2 ? 10-2 M was prepared from "Zr nitrate, labeled with 96Zr [16].
Figure 1 presents the change in the distribution coefficient of zirconium as a function of the dose in
the case of radiolysis in an atmosphere of 02 and under conditions of a deficiency of it in the irradiated sys-
tem (curves 1, 2). In these experiments the formation of suspensions in the aqueous phase was detected.
In Fig.1 the doses at which the appearance of a precipitate was observed are marked by arrows. In the
case of radiolysis in an atmosphere of oxygen, the precipitate appeared at doses of 15-20 W ? hinter, while
in the case of an oxygen deficiency it appeared at doses of 25-30 W ? h/liter. With increasing dose, the
volume of the precipitate forming increased, and the zirconium content in it increased (at a dose of 50-60
W ? h/liter it was 15-20% of the total zirconium content). When uranium was introduced into the aqueous
phase with a concentration of 200 g/liter (with respect to the metal), in the case of irradiation of the solu-
tion in the dose range 15-170 W ?h/liter, no formation of suspensions was observed.
Since the radiolysis products of synthine had no appreciable influence on Kd of zirconium and the state
of the phases in the case of radiolysis at the stage of extraction [17], the observed changes can be attributed
to the action of the radiolysis products of TBP. This is evidenced by experiments conducted so that there
was less MBP in the organic phase. In the case of contact of a nonirradiated nitric acid solution of a
*Only the joint determination of MBP and H3PO4 is possible according to this method.
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noolm
2,4
8
7
20 40 60 80 100 0 20 40 60 80 100
Dose, W?hiliter Dose, W?h/liter
Fig.3
Fig. 4
Fig.3. Dependence of the concentration of MBP and H3PO4 on the dose of irra-
diation. Atmosphere of 02: 1(I) aqueous phase; 2 (X) organic phase. Deficiency
of 02 in the system: 3(A) aqueous phase; 4(0) organic phase.
Fig. 4. Dependence of the ratio GDBp/GmBp on the dose in radiolysis of an at-
mosphere of 02.
zirconium salt with an organic phase, preliminarily irradiated with 3 M HNO3, into which the racliolytically
formed MBP was transferred, higher values of Kd of zirconium are achieved (see Fig. 1, curves 3 and 4),
while appreciable appearance of a precipitate is recorded at doses of 50-60 W ? h/liter. These experiments
showed that the formation of MBP substantially influences the extraction of zirconium.
We studied the formation of DBP, MBP + H3PO4, and the "polymer" as a function of the dose. The
dependence of the concentration in the indicated products on the dose, obtained under conditions of oxygen
deficiency in the system and in the case of its passage through the solution, is presented in Figs.2 and 3.
The distribution coefficients of the DBP and MBP formed during radiolysis, calculated from these data,
are close in order of magnitude to the results obtained in model experiments in the absence of radiation
[14].
In the case of radiolysis under conditions of oxygen deficiency, the yield of DBP is 0.4-0.5 molecules
/100 eV. In an atmosphere of oxygen, the initial yield of DBP reaches 1.2 molecules/100 eV and as the
dose is increased, it drops to 0.9 molecule/100 eV.
The rate of formation of MBP in the presence of 02 is also higher, and when the dose increases, in
contrast to DBP, it does not drop, but increases. Figure 4 shows the change in the ratio of the yields of
DBP to MBP as a function of the dose in the case of irradiation in an atmosphere of oxygen. Up to a dose
of 10-15 W ?h/liter, the ratio GDBp/GmBp = 7-8; when the dose is further increased, it drops, and at
doses of the order of 100 W ? h/liter reaches 2-2.5.
To evaluate the yield and the origin of the "polymer," we studied its nature and chemical composi-
tion.
The elementary composition of the polymer corresponds to the atomic ratio P: C: 0: H = 1:13.4: 4.4
: 29, which is close to the ratio of the elements in TBP itself and confirms the hypothesis of a phosphate
composition of the polymer [4, 6]; however, this contradicts the hypothesis of [7, 18] of its hydrocarbon
structure. The presence of a P ? C ? 0 group in the polymer was also indicated by the absorption band at
1025 cm-1 that we detected in its IR spectrum [19]. In a calculation of the corresponding yield of the de-
composition of TBP, due to the channel of "polymer" formation, we believe, assuming its molecular weight
equal to 840 [4], that three molecules of TBP correspond to the formation of one molecule of the polymer.
In Fig.2 (curves 3 and 6) the concentration of the polymer was calculated on the basis of the molecular
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TABLE 1. Composition of Precipitate
Dose,
W?hiliter
Concentration 40-3, M
Zr, precipi-
tated
DBP
organic phase
irradiation irradiation
without Zr with Zr
aqueous
phase
precipitated
MBP(pre -
cipitated
ratio Zr:
DBP: MBP in
precipitate
18,6
37,4
46,0
1,6
3,1
4
8
14
17,8
5,9
9,2
11,8
0,4
1
1,7
3,8
5,0
1,2
3,0
4,0
1 : 1,1 : 0,8
1 : 1,2 : 1
1 : 1,25 : 1
weight indicated above. In contact with the aqueous phase, in the presence of an 02 deficiency, the value
Of G of the "polymer" calculated according to the number of molecules of TBP consumed, is equal to 0.5-
0.6 molecule/100 eV; in the presence of 02 this value is 1.5-2 times lower. These results agree with the
data for the same systems irradiated in the absence of the aqueous phase.
New experimental results, which require explanation, are the acceleration of the formation of MBP
with increasing dose in the presence of an aqueous phase. It was established that this acceleration is cor-
related with the drop in the yield of DBP. Within the limits of the experimental error it can be considered,
for example, that when the yield of DBP decreases (in experiments in the presence of 02) from 1.2 to 0.9
molecule/100 eV, the yield of MBP increases from 0.14 to 0.45 molecule/100 eV and, consequently, an ac-
celeration of MBP formation occurs on account of the decomposition of DBP.
In principle the presence of an aqueousphase can have an influence on the radiolysis of the system:
either as a result of the elimination of MBP from the organic phase or on account of the extraction of DBP
into the aqueous phase, where its molecules are subject to the influence of active intermediate radiolysis
products of water. The first factor cannot be significant, although the aqueous phase actually effectively
extracts MBP, since not a slowdown of MBP formation, but an acceleration of the decomposition of DBP is
observed. The second of the indicated factors is more applicable. Actually, since it is difficult to assume
that DBP was decomposed in the organic phase in the presence of an approximately 100-fold excess of TBP
on account of the accepting of active particles in an indirect influence,* the role of the aqueous phase in this
process may be decisive (all the more in that in the absence of an aqueous phase, no increase in the yield
of MBP was noted).
Actually, although at equilibrium only ?1/20 of the amount of DBP should be observed in the aqueous
phase, nonetheless, at doses when the decrease in the yield of DBP becomes appreciable, its absolute con-
centration in the aqueous phase reaches -40-3 M (see Fig.2, curves 2 and 5), while under conditions when
the concentration of other acceptors is appreciably lower, DBP may decompose on account of the indirect
action of active radiolysis products of water.
Evidently we should consider the oxidative component, which agrees with the conclusions of [20],
since the reductive component should be effectively accepted by HNO3, present in solution in excess. It can
be expected that when the doses are further increased, and, correspondingly, with increasing concentra-
tion of DBP in the aqueous phase, the yield of MBP will increase even more. Thus, an explanation for the
influence of oxygen, especially sharply manifested in two-phase systems, should evidently be sought in
analogies with other processes in which an increase in the content of molecular oxygen promotes processes
that proceed through accepting of the reductive component of radiolysis of water [21].
At the first of the experimental results discussed above, we indicated the formation of a precipitate in
systems containing sufficiently high concentrations of zirconium, and the role of monobutyl phosphate in
this process. It is known that in the absence of neutral phosphates, dialkylphosphoric acids form a precip-
itate with concentrated solutions of zirconium [21, 221. However, it was found that in model mixtures con-
taining TBP, in the absence of MBP no precipitate is formed.
We also determined the interval of MBP (H3PO4) concentrations within which zirconium in a concen-
tration of 10-2 M begins to precipitate on model mixtures. It is shown in the form of a band in Fig.3, which
presents the kinetic curves of the formation of MBP (H3PO4) during radiolysis. The point of intersection of
the curves with this band corresponds to the value of the dose at which the precipitate should be formed.
These results are in good agreement with the data of visual observations.
*According to the data of [4], the value of G of DBP from TBP is approximately only 1.5 times lower in
comparison with G of MBP from DBP.
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? Since, however, it was also discovered that when a system is irradiated in the presence of zirconi-
um there is less DBP in the organic phase (see Fig. 2, curves 7 and 8) then it follows from the data on ra-
diolysis in the absence of zirconium (see Fig. 2, curves 1 and 4), in a consideration of the composition of
the precipitate, we also considered DBP.
These results are confirmed by the decrease in the distribution coefficient of DBP in model experi-
ments conducted with mixtures of DBP and MBP in the organic phase in contact with a nitric acid solution
of zirconium. On the basis of the results obtained, we suggested that the DBP removed from the organic
phase, as well as all of the MBP formed during radiolysis, are components of the precipitate.
Table 1 presents data according to which we calculated the molar ratios of the components contained
in the precipitate. Analogous ratios of the components were obtained at the same concentrations of DBP,
MBP, and zirconium in a model experiment.
LITERATURE CITED
1. J. Goode, Nucleonics, 15, No.2, 68 (1957).
2. A. Bathelier, Bull. Docum. et Inform. Sci. and Technol., 127, 35 (1968).
3: G. Lefort and P. Miguel, ibid., p.43.
4. L. Wagner et al., Indstr. and Engng. Chem., 51, 45 (1959).
5. L. Burger and E. MacClanachan, Indstr. and Engng. Chem., 50, 159 (1958).
6. J. Burr, Radiation Res., 8, 214 (1958).
7. V.P. Shvedov and S. N. Roiyanov, Zh. Fiz. Khim., 35, 561 (1961).
8. R. Wilkinson and T. Williams, J. Amer. Chem. SoC., 4, 4098 (1961).
9. J. Canva and M. Page, Radiochim. Acta, 4, 88 (1965).
10. E. V. Barelko, I.P. Solyanina, and Z.N. fsvetkova, At. Energ., 21, 281 (1966).
11. E. V. Barelko, I.P. 8olyanina, and Z.N. Tsvetkova, Khim. Vys. Energ., 4, 229 (1970).
12. V.B. Shevchenko and V.S. Smelov, in: Extraction [in Russian], Vol.2, Goatomizdat, Moscow (1962):
p.257.
13. A. Huggard and B. Warner, Nucl. Sci. and Engng., 17, 638 (1963).
14. A.P. Hozhevi I.V. Poddubskaya, and A.M. Rozen, Sm. [12], 71.
15. A.S. Solovkin, P.G. Krutikov, and A.N. Panteleeva, Zh. Neorg. Khim., 24, 3376.
16. R.I.Shamaev, Radiokhimiya, 10, 479 (1968).
17. I.P. Solyanina and E. V. Barelko, At. Energ., 32, 395 (1972).
18. A. A. Vashman, Radiokhimiya, 12, No.1, 12 (1970).
19. L. Bellamy, Infrared Spectra of Complex Molecules Russian translation], IL, Moscow (1963).
20. C. Sonntag et al., Z. Naturforsch, 276, 471 (1972).
21. I. V. Vereshchinskii and A.K. Pikaev, Introduction to Radiation Chemistry [in Russian], Izd-vo AN
SSSR., Moscow (1963).
22. V.V. Fomin and S.A. Potapova, Zh. Neorg. Khim., 12, 530 (1967).
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Declassified and Approved For Release 2013/01/22 : CIA-RDP10-02196R000400020004-5
AGING OF IMPREGNATED CARBONS FOR TRAPPING
RADIOACTIVE IODINE
I.E. Nakhutin, N.M. Smirnova, UDC 628.543
G.A. Loshakov, and V.N. Vezirov
Impregnated carbons are fairly widely used to remove radioactive iodine and its compounds from
gases, both in continuous extraction apparatus and in devices for operation in an emergency. However,
little work has been done on the so-called aging of impregnated carbons (in this article, we shall under-
stand this term to mean a loss of efficiency with respect to methyl iodide). One difficulty of this type of
research is the long time required for aging experiments.
In this article we give some results obtained in an investigation of aging of impregnated carbons in a
current of ordinary atmospheric air. We used carbons impregnated with PbI2, Cul, and AgI [1], since no
information was available on the aging of these compounds.
EXPERIMENTAL METHOD
We investigated three columns, each of which contained one of the above impregnated carbons. The
columns were connected in parallel, and equal linear gas flow rates were maintained in all three. They
were divided into 1 cm sections. Transfer of dust between sections was prevented by aerosol filters. The
activity of 131.1 in each section was measured by means of a scintillation-type T-ray counter with a colli-
mator
Dust-free atmospheric air was passed through the column for a long time (with interruptions at night);
the absorptive capacity of the column was then measured section by section. For this purpose, every 48 h,
radioactive methyl iodide was briefly passed through the column in a mixture with air, and the activity of
each section was then measured. To accelerate aging, the experiment was performed at high gas flow
rates (up to 120 cm/sec). It was assumed that aging does not depend on time as such or on the quantity of
air passing through the carbon. As we shall show, this assumption is adequately justified.
After the first measurement we continued to pass air, and made the last measurement when the 1311
accumulated in the columns had practically completely decayed.
RESULTS AND DISCUSSION
Instead of the usual monotonically falling curve, the distribution of gamma activity along all three
columns shows a curve with a clearly-marked maximum. This means that the earlier sections have re-
duced absorptive capacity. As the amount of air passed increases, the maxima on the curves shift further
from the initial sections of the columns towards the outlets.
Figure 1 plots the absorptive capacity of the first section of the PbI2 column vs the amount of air
which has been passed. After passage of 8 ? 105 liters/cm2 of air, the absorptive capacity of the first sec-
tion was reduced by 60%. In the second section, the reduction in similar conditions was 46%, and in the
third section, 26%. This phenomenon cannot be attributed to erosion by the gas current, because we should
then expect to find uniform changes along the whole column. It is natural to suppose that the air contains
some sort of impurities which are absorbed in the column and which reduce the absorptive capacity of the
carbon for methyl iodide. These impurities move along the column in the form of a chromatographic front.
Translated from Atomnaya inergiya, Vol.35, No.4, pp.245-246, October, 1973. Original article
submitted November 9, 1972.
0 1974 Consultants Bureau, a division of Plenum Publishing Corporation, 227 West 17th Street, New York, N. Y. 10011.
No part of this publication may be reproduced, stored in a retrieval system, or transmitted, in any form or by any mean's,
electronic, mechanical, photocopying, microfilming, recording or otherwise, without written permission of the publisher. A
copy of this article is available from the publisher for $15.00.'
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Declassified and Approved For Release 2013/01/22 : CIA-RDP10-02196R000400020004-5
3,0
2,5
2,0
P.00
Fig. 1. Absorptive capacity A
of first section of column con-
taining PbI2 vs quantity of air
passed, P.
The very slow movement of the distribution curve maximum along the column (only 6-7 cm in the
course of the entire experiment) shows that the impurity is present in the air in very small amounts.
On the basis of the above data, the observed effect of change in the absorptive capacity can be quite
confidently attributed to poisoning of the impregnated carbons.
Similar results on poisoning of impregnated carbons were obtained by Acklej and Adams [2]. How-
ever, they used carbons with different impregnating agents, and therefore only a qualitative comparison
can be made with our results. They also observed a change in the purification efficiency; the change was
greater in the first layer of impregnated carbon than in the second. These observations are also consistent
with the hypothesis that harmful microimpurities are absorbed from the air.
Substances which might cause this effect include oxides of nitrogen which are always present in air
in small amounts. It is known that they react with iodides of metals forming nitroso compounds. For ex-
ample, complete neutralization of the lead iodide in one section of the column requires about 5 mg of ni-
trogen peroxide, which agrees with the quantity of nitrogen peroxide in the air passed through the column,
i.e., 2.5 .10-5%. This figure is of the same order of magnitude as the nitrogen oxides contained in atmos-
pheric air (1.5-2.9) ? 10-5% [3].
Account must also be taken of the influence of SO2 and SO3 which are always present in the air, es-
pecially in large towns. These substances can also poison impregnated carbons by reacting with iodides.
Regardless of the cause of the aging, these values can give some idea of the service lives of impreg-
nated carbons in a current of atmospheric air.
The amounts of oxides of nitrogen and other microimpurities in gaseous discharges from nuclear pow-
er stations may differ markedly from the amounts in atmospheric air. In particular there may be radiation
synthesis of oxides of nitrogen in the air. This process is the subject of additional investigation. However,
even from the data at present available, we can conclude that the service life of impregnated carbons is
shorter than that of nonimpregnated carbons, which are also used to remove iodine.
Impregnated carbons are sensitive to microimpurities and other chemically-active substances in the
gas phase, and therefore their service lives in different purification apparatus may be very varied.
Thus we can draw the following conclusions. The absorptive capacities of carbons impregnated with
PbI2, CuI, and AgI towards methyl iodide decrease after prolonged passage of a current of atmospheric air
through a layer of the carbon. This is due to microimpurities contained in atmospheric air which act on
the impregnants: this is confirmed by the nature of the variation of absorptive capacity.
LITERATURE CIT ED
1. I.E. Nakhutin et al., Fourth Geneva Conference (1971), report 49/P/703 (USSR).
2. R. Acklej and R. Adams, Tenth AEC Air Cleaning Conference, New York (1968).
3. A. Altschuller, Anal. Chem 41, No.5 (1969).
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Declassified and Approved For Release 2013/01/22 : CIA-RDP10-02196R000400020004-5
INSTRUMENTAL NEUTRON ACTIVATION ANALYSIS OF
ROCKS AND ROCK-FORMING MINERALS BY USING'
Ge(Li) DETECTORS AND A COMPUTER
E.M. Lobanov, Yu.A. 'Levushkin, UDC 543.53:539.107.5
and S.P. Vlasyuga
The practical and theoretical necessity of more complete knowledge of the chemical elements in na-
tural formations and the widespread introduction of mathematical statistics methods and the interpretation
of the results of geochemical research [1, 2] require increasing the sensitivity, and accuracy of analytic
procedures [3]. In this respect the most reliable and promising is neutron activation analysis [4]. The si-
multaneous determination of several elements in a single specimen and the elimination of contamination of
the samples in the instrumental version of neutron activation analysis permit the preservation of the sim-
ilarity of the natural ratios of chemical elements in the objects being studied [5].
The use of Ge(Li) detectors, which have a resolving power an order of magnitude larger than that of
sodium iodide scintillization crystals, in an instrumental version of neutron activation analysis of geolog-
ical objects offers the best solution of the problem of the simultaneous determination of a large group of
chemical elements contained in the specimen without destroying it. Gordon et al. [6] determined the ele-
mental composition of the US geological standards by an instrumental method of neutron activation anal-
ysis using Ge(Li) detectors.
We present the results of our practical procedure of instrumental neutron activation analysis for the
simultaneous determination of several chemical elements in rocks and basic rock-forming minerals.
Gross samples of rocks (granitoids) and basic rock-forming minerals (plagioclase, potassium feld-
spars, biotites, muscovites, and quartzes) extracted from them were selected for analysis. Five-hundred
mg test specimens, crushed to pass through a 200 mesh screen, were packed in aluminum foil with stand-
ards and monitors and irradiated in a reactor by a flux of 1.8 ? 1013 neutrons/cm2 sec for 10 h.
The 'y-spectra of the irradiated specimens, kept for 8-30 days, were measured on a 'Y-spectrometer
consisting of a coaxial Ge(Li) detector, a high-performance stabilization circuit, and an Ai-4096 pulse-
height analyzer. The detectors had volumes of 8.5, 10.5, 25.5, and 50.5 cm3, and their resolutions at the
Cs137photopeak (Ey = 661.65 keV) were 0.59, 0.74, 0.95, and 1.48%, respectively.
Figure 1 shows a typical Y-spectrum of plagioclase measured on the spectrometer with a Ge(Li) de-
tector. The large volume and the complexity of the information contained in the spectral measurements
require a new methodical approach to the processing of spectrometric data [7-17]. It is practically im-
possible to extract all the information from the spectra without using a computer.
We present below a brief description of a program for the computer processing of 'Y-spectra mea-
sured with Ge(Li) detectors in an instrumental neutron activation analysis of geological samples.
The spectra were analyzed in four stages: 1) preparation of the initial data for the calculation; 2)
search in the 7-spectrum of regions containing single photopeaks or groups of closely spaced peaks; 3)
tabulation of the photopeaks found in the spectrum and the calculation of their energies and intensities; 4)
identification of the isotopes in the spectrum and the calculation of the amounts of the chemical elements
in the spectrum.
Translated from Atomnaya -Energiya, Vol.35, No.4, pp.247-252, October, 1973. Original article
submitted November 23, 1972.
0 1974 Consultants Bureau, a division of Plenum Publishing Corporation, 227 West 17th Street, New York, N. Y. 10011.
No part of this publication may be reproduced, stored in a retrieval system, or transmitted, in any form or by any means,
electronic, mechanical, photocopying, microfilming, recording or otherwise, without T.Oritten permission of the publisher. A
copy of this article is available from the publisher for $15,00.
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10
,.,:-.,. z....
-,......
- v .,.1- '"i "2
+ + + .
0.? *
\ P2
I
Ne'f'
N
8 foi,,* A
0
10
1085,8 -,1089,7 Eu 152
/0? I I I 1 I I I I
200 400 . 600 800 1000 1200 1400 1600 1800
1800 2000 2200 2400 2600 2800 5000 3200 3400
Channel number
Fig. 1. Typical Y-spectrum of plagioclase measured on a spectrometer with a 10.5
cm3 semiconductor Ge (Li) detector.
The catalog of standard data includes: Erkz, the energies of photopeaks in the spectra of the standard
isotopes (k = 1-32 is the index of the isotope: / = 1-15 is the index of the photopeak of the given isotope);
Ski, the intensities of the photopeaks in the spectra of the standard isotopes; ASrki, the errors in the val-
ues of the intensities of the photopeaks; Tik, the shielding factors of the elements in the specimen during ir-
radiation; mk, the masses of the standards; 1.1/2, the half-lives of the standard isotopes; ATlicp, the errors
in the values of the half-lives; Ims , the intensity of the photopeak of the monitoring isotope irradiated with
the standards.
The constants used in the analysis of the 'y-spectrum of a specimen are: 4 the values of the ener-
gies of the reference photopeaks in the spectrum of a specimen for calculating the coefficients of internal
energy calibration of the spectrum = 1-16); xt, the approximate values of the centers of the reference
photopeaks in the spectrum of the specimen; 6,x, the limiting deviations from the approximate values of the
centers of the reference photopeaks for identification of internal references of the energy calibration of the
spectrum; a and /3, coefficients for scaling the Y-spectrum of the specimen to take account of the dead time
of the spectrometer; (p, a coefficient for scaling the intensities of the photopeaks to take account of the geo-
metry of the measurement; Kw, coefficients for calculating the smoothed out spectrum of the specimen (co
= 0-4); Fco, coefficients for calculating the spectrum of first derivatives (co =(0-3); Po and vi, coefficients
describing the dependence of the resolution of the detector on the T-energy.
Control numbers which are fed into one computer with the 'Y-spectrum of the specimen are Te001, the
"cooling" time of the specimen; Tmeas, the time the Y-spectrum was measured; mo, the mass of the speci-
men, Zi, the photopeak of the monitoring isotope irradiated with the specimen (j = 1-32 is the channel num-
ber), h, the geometry factor of the measurement.
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Block diagram of the program:
Input of catalog of standards, spectrum, and con-
trol numbers
Scaling of standards to take account of decay of
isotopes, geometry of spectral measurement, and
monitoring
Correction of spectrum for dead time of spector-
meter
Smoothing of spectrum
Calculation of the spectrum of first derivatives
Determination of boundaries of spectral regions
containing photopeaks
Internal energy calibration of spectrum
Determination of parameters of photopeaks of a
given spectral region by an iteration method
Calculation of energies and intensities of peaks
and their errors
Identification of catalog isotope in spectrum
Calculation of amount of element in specimen
and its error
Calculation of "residual intensities" of peaks in
spectrum corresponding to given isotope
Printout of results of processing spectrum
The catalog of standard data and constants, the initial 7-spectrum of the specimen yEn (i = 1-3200 is
the channel number in the spectrum), and the control numbers are fed into the computer with punchcards
or magnetic tape. The standard data are modified to correspond to the irradiation and cooling of the spe-
cimen and the measurement of its 7-spectrum. The processed 7-spectrum is smoothed by the method of
least squares using nine adjacent channels with a second degree parabola approximation [18, 19]: ?
44
Y;:n= Kcor { 7, (Y ?
(0=0 (0=0 ?
The results of the smoothing are usecito calculate the spectrum of first derivatives:
(1)
= Fo F. (y?_`1_,,?Yln_ .)? (2)
Preliminary values of the centers My of the photopeaks in the spectrum and their boundaries ny are
determined by the changes in sign of the first derivative [11, 18, 20]:
? {my, if 6i> 0, Sii1O.
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The values found foi? the centers of the peaks are used in the identification of the reference photopeaks for
internal energy calibration of the spectrum. A search is carried out among the values of the my given in
the catalog of constants of reference photopeaks with centers in channels xt corresponding to energies E.),
The values of my satisfying the condition
(4)
and the corresponding values of the energies of the reference photopeaks Ey are used to determine the co-
efficients a, b, c, d, and f in the calibration relation
E, ax4 bx3 cx2 +dx . (5)
The pseudopeaks not statistically represented in the spectrum are eliminated by using the inequality
(m)?Y (nv) < 8 Yy (nV), (6)
where y(my) is the value of the spectrum at the center of the photopeak; y(ny) is the value of the spectrum
at the left boundary point of the peak. The value of the coefficient e is determined by the value of the con-
fidence interval. The values of the centers of closely spaced peaks in the spectrum are combined into
groups. Twice the width of the peaks at half-height is taken as a criterion of closeness of neighboring
peaks with centers in channels my and mr+i. This is a function of the Y-energy:
ar,?mv+i< 2o- (Ev). (7)
The boundaries of a spectral region containing several photopeaks are determined by the boundary channels
of the outside peaks.
The expression [9]
yi= Ai + B R? exp {-4 In 2 (i?x?)2 ai,2}
, p=i
(8)
is a mathematical model of a spectral region with photopeaks. The initial values of the parameters A and
B are calculated as coefficients of the straight line passing through the boundary points of the region. To
determine the initial values of the centers xp of the photopeaks the values of the energies Eyid from the
catalog of standard data are converted to the values of the channels of the spectrum by Eq. (5), after which
a search is carried out among the values thus obtained which fall in the given spectral region. The initial
value of the width of the photopeak at half-height Crp is determined by using the given dependence of this
quantity on the y-energy:
p=vo+viEv(x?).
The initial value of the height of the photopeak Rp is calculated by the formula
R ? = y (x?)? (Ax, B). (10)
A value of the height Rp which does not satisfy the condition
R, > e B,
is eliminated from the parameters of the spectrum along with the corresponding values of xp and ap.
The parameters of the photopeaks xp, Rp, and up are refined by the method of nonlinear least squares
[9]. The result is achieved in a prescribed number of iterations. After each iteration the refined param-
eters are analyzed and the incorrect values are eliminated from the calculation. The refined values of the
parameters of a photopeak are used to calculate its energy by Eq.(5) and its intensity by
S, = R exp { ? 4 In 2 (i? x)2
(9)
The error in the values of the intensity is given by
i OS, ) '
AS, ? {1 ( ?.?. ? vare)i + I 1 ( ) (
j=1J=i1,?..1,
. . .71 .
where coi =R, co2 =X, and co3 = a.
908
as;
awk
covar (cop).k)}
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TABLE 1. Sensitivity (in wt. %) of the Simultaneous Determination of the Chemical Ele-
ments in Various Geological Objects by Instrumental Neutron Activation Analysis Using
Semiconductor Ge(Li) Detectors and a Computer
?.
o
w
.
2
"s1 el.
2
Granitoids
Plagioclase
Potassium
feldspars
Biotites
Quartzes
Muscovites
A B
A B
A B
A
B
A
B
A
B
Ilt,111111,1111t11111111
0 0 0 0 0 0 0 0 0 0 0 0 0 0 o
eq - to-fl COtO too
7"777-:'77"7"7777-'
Sc
46Se
6,3.10-6
1,2.10-6
5,4.10-7
1,0.10-7
6,0.10-7
1,1.10-7
1,1.10-5
4,1.10-7
7,8.10-8
2,1.10-5
3.9.10-6
Cr
5ICr
3,4.10-4
9,4.10-5
1,6.10-4
4,4.10-5
2,7.10-4
7,3.10-5
2,0.10-3
1,3.10-4
3,6.10-5
5,4.10-3
1,5.10-5
Fe
50Fe
2,4.10-4
4,2.10-5
1,1.10-2
2,0.10-3
9,3.10-4
1,7.10-4
2,0.10-1
9,3.10-3
1,7.10-3
2,7.10-1
5,1.10-2
Co
6000
2,1.10-5
3,4.10-6
7,4.10-6
1,2.10-6
7,6.10-6
1,3-10-6
1,5.10-4
6,1.10-6
1,0.10-6
2,0.10-4
3,2.10-5
Zn
652n
7,3.10-4
1,3.10-4
2,3.10-4
4,1.10-5
2,2.10-4
4,0.10-5
1,8.10-3
1,6.10-4
2,9.10-5
6,2.10-3
1,1.10-4
Rb
86Rb
0,5-10-4
1,2.10-4
3,2.10-4
5,7.10-6
1,9.10-4
3,4.10-5
4,2.10-3
2,3.10-4
4,2.10-5
5,1.10-3
9,2.10-4
Sr
85Sr
1,6.10-3
1,6.10-3
3,9.10-3
8,9.10-4
4,9.10-3
1,1.10-3
6,7.10-3
1,2.10-2
2,8.10-3
3,4.10-2
7.8.10-3
Zr
65Nb
7,6.10-3
1,5.10-3
9,2.10-3
1,8.10-3
7,9.10-3
1,6.10-3
1,9.10-2
6,2.10-3
1,2.10-3
8,2.10-2
1.7.10-2
Sb
124Sb
2,0.10-5
3,1.10-6
3,8.10-6
5,8.10-7
5,4.10-6
8,2.10-7
6,1.10-5
4,1.10-6
6,2.10-7
1,2.10-4
1,8.10-6
Cs
34Cs
2,9.10-5
5,6.10-6
9,1.10-6
1,7.10-6
1,8.10-5
3,4.10-6
1,5.10-4
5,3.10-6
1,0.10-6
3,4.10-4
6,5.10-5
Ba
1328a
5,2.10-3
1,2.10-3
2,9.10-3
6,6.10-4
2,5.10-3
5,8.10-4
4,4.10-2
2,8.10-3
6,5.10-4
6,7.10-2
1,5.10-2
La
i3OLa
1,5.10-3
2,3.10-4
1,8.10-3
2,8.10-4
1,8.10-4
2,9.10-5
3,0.10-3
9,3.10-2
1,4.10-9
'2,7.10-3
4,3.10-4
Ce
i4lCe
1,2.10-4
4,5.10-5
1,0.10-5
3,6.10-6
1,2.10-4
4,2.10-5
2,4.10-4
6,0.10-5
2,2.10-5
2,3.10-3
8,3.10-4
Nd
147Nd
3,7.10-3
8,4.10-4
1,9.10-3
4,2.10-4
7,0.10-4
1,6.10-4
1,8.10-3
8,9.10-4
2,0.10-4
3,6.10-5
8,2.10-4
Sm
153,Sm
2,2.10-4
8,3-10-s
4,7-10-5
1,8.10-5
0,1 ? 10-6
2,4.10-6
5,0.10-5
5,7.10-4
2,2.10-4
1,2.10-4
4,4.10-5
Eu
I52Eu
7,4-10-5
1,5.10-5
3,5.10-5
7,0.10-6
4,4.10-5
8,8.10-6
1,7.10-4
1,3.10-5
2,7.10-6
2,7.10-4
5,4.10-5
2d
15309
7,8.10-6
1,0.10-6
1,5.10-5
6,2.10-6
1,8.10-6
7,4.10-7
1,6.10-5
5,1.10-7
2,1.10-7
2,3.10-5
9,3.10-6
rb
160Th
1,5.10-4
2,9.10-5
6,2.10-5
1,2.10-5
3,8.10-5
7,2.10-6
4,2.10-4
2,6.10-5
4,9.10-6
7,3.10-4
1,4.10-4
Tm
170Tm
A1.10-6
8,3.10-7
1,5.10-6
6,1.10-7
1,7.10-7
6,9.10-8
2,6.10-6
4,7.10-8
1,9.10-8
2,1.10-5
8,6.10-6
Yb
168Yb
1,5.10-5
5,2.10-6
6,9.10-6
2,3.10-6
6,6.10-6
2,2.10-6
1,0.10-4
4,2.10-6
1,4.10-6
1,5.10-4
5,2.10-5
Lu
177Lu
8,7.10-6
2,8.10-6
4,0.10-6
1,3.10-6
3,9.10-6
1,3.10-6
3,6.10-5
5,4.10-6
1,8.10-6
3,6.10-5
1.2.10-6
110
181110
2,1.10-5
5,1.10-6
7,8.10-6
1,9.10-6
1,2.10-5
2,8.10-6
1,4.10-4
4,6.10-6
1,1.10-6
1,0.10-4
2,5.10-5
To
I82Ta
1,2.10-5
2,2.10-6
5,1.10-6
9,4.10-7
2,0.10-6
3,7.10-6
9,9.10-5
2,6.10-6
4,7.10-7
9,8.10-5
1,8./0-5
Th
252Pa
2,7.10-5
7,4.10-6
1,1.10-5
3,1.10-6
1,4.10-5
3,9.10-6
1,1.10-4
8,9.10-6
2,4.10-6
3,0.10-4
8,2.10-5
Note: Confidence coefficient 9870 time of measurement of gamma spectra one hour; volume of detectors:
A = 10.5 cm3; B = 50.5 cm3.
The isotopes in the spectrum of a specimen are identified in the following way. From the set of cal-
culated values of Ey there is determined the energy of the photopeak with the highest intensity which agrees
within half the resolution of the detector at that energy with one value of Eyki from the catalog of standard
data. The amount of the corresponding element in the specimen is calculated by the formula
?,h
MI, svi,' mo ? 100%,
The error in the value of the amount of the element is given by [21]
AM?(AS
_ svkimo 5,77 AS,
81 ?ki) ?100% (15)
.
(14)
The sensitivity of the determination of a chemical element in the specimen is found from the expression
Mikinn= 8 1/14 mh ? 100%,
14.. /no
(16)
where Ry is the height of the corresponding photopeak, and Rip is the "pedestal" of the photopeak at its cen-
ter.
The values of the energies gyj (j /) of the photopeaks of a given isotope in the catalog of standard
data are compared with the energies Ey) found in the spectrum of the photopeaks, and, if the values
of El; and Eyi agree within the limits of half the resolution of the detector the "residual intensity" of the
photopeak with energy E4,j, is calculated
(17)
If the residual intensity of the photopeak is less than the error in the initial intensity the photopeak is
not considered further. The next isotope is identified by using the rest of the set of energies and intensi-
ties of the photopeaks in the spectrum and the catalog of standard data with the exception of the values of
the energies and intensities of the photopeaks of the identified isotope.
The processing of a 3200 channel Y-spectrum of a specimen and the quantitative determination of the
amounts of 15-30 chemical elements require from five to ten minutes on an M-220 computer, depending on
the complexity of the spectrum being analyzed. After the computer has processed a spectrum it prints out
the symbols of the identified isotopes, the energies of the photopeaks by means of which these isotopes were
identified, the amounts of the corresponding elements in the specimen and their errors, the sensitivity of
the determination of the elements, and the residual spectrum of energies and intensities of the unidenti-
fied photopeaks in the spectrum of the specimen.
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Table 1 lists the experimentally determined sensitivies for the simultaneous determination of 24
chemical elements in various geological objects. It is clear from the table that the minimum determinable
concentrations of elements in most cases are an order of magnitude smaller than those which can reliably
be determined by Klarkov [22].
The accuracy of determining the amounts of chemical elements in samples is 8-12% for Sc, Cr, Fe,
Co, Zn, Rb, Sr, Cs, Ba, Ce, ?Eu, Yb, Lu, Hf, Ta, and Th, and 12-18% for Sb, La, Nd, Sm, Gd, Tm, Zr,
and Tb.
The amounts of elements found by the method described above are in good agreement with those de-
termined by chemical and quantitative spectral analysis, within the limits of their sensitivities and accu-
racies.
LITERATURE CIT ED
1. B. I. Bolov, in: Mathematical Methods of Geochemical Research [in Russian], Nauka, Moscow (1966),
pp.99-105.
2. L. N. Ovchinnikov and N. F. Chelitsev, Geokhimiya, 11, 1328-1335 (1967).
3. M. V. Limonova and I.N. Nyuberg, Geologiya i Geofizika, 11 (1970).
4. I.P. Alimarin and Yu. V. Yakovlev, in: Nuclear Physics Methods of Analysis of Matter [in Russian],
Atomizdat, Moscow (1971), pp.5-14.
5. D. M. Shou, Geochemistry of Trace Elements in Crystalline Rocks [in Russian], Nedra, Leningrad
(1969), pp. 44-45.
6. G. Gordon, Geochim. et Cosmochim. Acta, 32, 369 (1968).,
7. V. Gadzhokov, Preprint OIYaI, P10-5035, Dubna (1970).
8. R. ArPt et al., Preprint OIYaI, P6-6227, Dubna (1972).
9. R. Helmer and R . Heath, Nucl. Instrum. and Methods, 57, 46 (1967).
10. M. Mariscotti, Nucl. Instrum. and Methods, 50, 309 (1967).
11. V. Barness, IEEE Trans. Nucl. Set., 15, 437 (1968).
12. J. Routti and S. Prussin, Nucl. Instrum. and Methods, 72, 125 (1969).
13. J. Phillipot, IEEE Trans. Nucl. Sci., 17, 446 (1970).
14. A. Connely and W. Black, Nucl. Instrum. and Methods, 82, 141 (1970).
15. J. Slavic and S. Bingulac, Nucl. Instrum. and Methods, 84, 261 (1970).
16. G. Borchardt et al., J. Radioanal. Chem., 6, 241 (1970).
17. F. Adams and R . Dams, J. Raclioanal. Chen., 7, 329 (1971).
18. A. Savitzky and M. Golay, Anal. Chem., 36, 107 (1964).
19. H. Yule, Nucl. Instrum. and Methods, 54,61 (1967).
20. H. Yule, Anal. Chem., 38, 103 (1966).-
21. G. V. Sukhov and V.I. Firsov, in: Nuclear Physics Methods of Analysis of Matter [in Russian], Atom-
izdat, Moscow (1971), pp.52-60.
22. S.P. Salov' ev, Chemism of Magnetic Rocks and Some Problem of Petrochemistry [in Russian],
Nauka,, Leningrad (1970), pp.32-33.
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PLASMA LOSSES IN THE RING GAP OF AN
ELECTROMAGNETIC TRAP
Yu. I. Pankrat'ev, N.A. Tulin, UDC 533.9
E. F. Ponomarenko, and V.A. Naboka
In electromagnetic traps [1, 2] it is necessary to make the magnetic gaps narrow in order to in-
crease the confined plasma density. Narrow gap's are needed to minimize the space-charge potential of
the electrons oscillating through the gaps. Theoretical analyses [2] show that the thickness of the electron
layer in the ring gap must be on the order of a millimeter for confinement of a thermonuclear plasma.
However, the theory of electron beams in crossed electric and magnetic fields predicts instability of thin
layers [3].
For electromagnetic plasma confinement the ion lifetime is determined by the duration of the nega-
tive potential well inside the trap, that is, by the electron lifetime. The additional plasma losses caused
by instability of the electron layer in the magnetic gap prevent increasing the plasma density in the trap by
simply narrowing the gaps without taking precautions to suppress the instability. The results of an experi-
mental study of the diocotron instability in the ring gap were presented in [4]. The present work is a con-
tinuation of this research.
Plasma was produced in an electromagnetic trap (Fig. 1) by ionization of neutral gas by an electron
beam with 100 mA at up to 3 keV and confined by a cusped magnetic field produced by coils 1 and 2. The
width of the ring gap and the diameter of the axial openings were 1 cm. The ions inside the trap were also
confined by the negative potential well of the space charge of the electrons injected from the gun 5. The
losses of electrons leaving the trap along the magnetic field lines were suppressed by the retarding elec-
tric fields of the electrodes 7, 8, which were maintained at negative potentials exceeding the energy of the
injected electrons. The ring electrode 7 was cut into eight sections. The particle current from each sec-
tor, produced by loss of plasma from the trap, was recorded on a separate channel of an oscillograph.
Plasma loss across the magnetic field was measured by means of swall collectors 3 located on each side
of the ring gap. The plasma density inside the trap was measured by a microwave interferometer 4. With
Fig.1
Fig.'. Diagram of electromagnetic trap.
Fig.2. Plasma decay in the trap. (H = 3000 Oe, ne = 109 cm-3,
and 1-123 = 33.5 iisec.)
10 20 30 40 ty P sec
Fig. 2
T1 = 4.6 Asec
P
Translated from Atomnaya Liergiya, Vol.35, No.4, pp.253-257, October, 1973. Original article
submitted May 30, 1972. Revision submitted February 6, 1973.
? 1974 Consultants Bureau, a division of Plenum Publishing Corporation, 227 West 17th Street, New York, N. Y. 10011.
No part of this publication may be reproduced, stored in a retrieval system, or transmitted, in any form or by any means,
electronic, mechanical, photocopying, microfilming, 'recording or otherwise, without written permission of the publisher. ii
copy of this article is available from the publisher for $15.00.
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e.1
0,3wII
sec
5011sec
Fig. 3
0
8 1 2 3 4 5 6 7
Sector number
Fig. 4
Fig.3. Oscillograms of plasma losses from the trap. (H = 3000 Oe, p
= 10-5 torr). I) electron current across the magnetic field in the gap;
II-IV) ion current into the ring gap at three sectors of the retarding
electrode; V) injection current; VI, VII) electron current across and
through the ring gap with no applied voltage on the ring electrode.
Fig. 4. Distribution of ion losses around the ring gap. ():( ) p = 5 ? 10-6
torr; A) p = 4 10-5 torr; 0) p = 10-4 torr.
an 8 mm interferometer the electron gun was pulsed by the modulator 6. (Other regimes of operation of
electromagnetic traps are described in [1, 4, 5].)
Plasma was produced in the trap by ionization of neutral gas by an injected electron beam. The plas-
ma density grew only during the initial stages of injection. Plasma accumulation ceased when a density
around 108-109 cm-3 was reached. Since the plasma density is determined by the balance of two processes
(the plasma formation rate and loss rate), an attempt was made to raise the plasma density by increasing
the ionization rate. However, neither an increase of neutral gas pressure nor an increase of injected elec-
tron beam current lead to an increase of plasma density inside the trap.
The decay of plasma density after the end of injection is shown in Fig. 2. Immediately after the ces-
sation of injection the decay time is Tpl r""-1 4-5 ?sec. Then, with a lower plasma density in the trap, the de-
cay rate decreases. The slower decay time To2 30-100 ?sec and is inversely proportional to neutral gas
density. Since T1 determines the decay at higher densities, more attention was paid to studying how this
decay time varied with the conditions of plasma accumulation in the trap.
The variation of the experimental ion lifetime T1 with neutral gas density no was found to fit the em-
pirical relation [1]
itrz 1/To -1.3?10-7no.
The presence of the 1/T0 term indicates that in addition to losses caused by collisional processes
with neutral gas, other loss processes are active. The magnitude of lhodependsonconditions in the trap;
magnetic field strength, injected electron current, position of the electron layer in the ring gap, and the
plasma density. Measurements with the collectors on the chamber walls indicated that anomalous losses
were maximum in the ring gap, and that these losses are caused by plasma instability.
The development of the instability is shown in Fig.3. The amount of ion current is different to dif-
ferent sectors. The azimuthal variation of ion loss rates is shown in Fig.4. The curves were taken at
different pressures. At low pressures (p'",1 5.10-6 torr) the inhomogeneity of the current is still weak.
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a
magnetic field
u4405
2
electron drift
chamberlwall, velocities
e.V./
/
0 42 0,4- 46 0,8
Fig. 5
t,o ka
Aton
Fig. 6
Fig. 5. Unperturbed situation of the electron cloud in the ring gap (a)
and the dispersion relation for the diocotron oscillations (b). Numbers
on the curves indicate the ratio b/a. Dashed curves) Im(w/cos).
Fig.6. Variation of instability growth rate with residual gas pressure.
With an increase in pressure the flow loses its azimuthal symmetry, and when p = 10" torr the losses
occur mainly at an azimuthal angle -90-1200. Measurements of electron losses across the gap indicated
that their distribution is similar to the ion loss distribution.
The azimuthal inequality of plasma losses was also observed for plasma confinement in the usual
magnetic trap regime. Oscillograms VI and VII (Fig.3) show the variation of electron current across and
through the ring gap when the potential of the electrode ring was zero. At low injection currents (2-5 mA)
and low pressures the current of electrons leaving the trap along the magnetic field was independent of
azimuthal angle. With an increase of either injection current or gas pressure the azimuthal symmetry was
lost at some time T after the beginning of injection. Oscillograms VI and VII (Fig. 3) show a decrease of
electron current along the magnetic field and an increase of losses across the field. With a transition to
the regime of electromagnetic plasma confinement, that is, with a gradual increase in negative voltage on
the ring electrode, the electron losses along the magnetic field finally were suppressed. However, a si-
multaneous increase of electron losses across the field in the gap prevented increasing the plasma density
in the trap.
These, data provide basis for supposing that the initially thin layer of electrons in the ring gap buckles
or becomes thicker during the development of the instability to the point where the electrons touch the walls
of the gap.
It should be noted that the azimuthal distribution of plasma losses did not vary with the interchange of
the direction of the magnetic field and the rotation of the electron beam around its own axis. If a negative
potential two or three times the energy of the injected electrons was applied to the collectors on the wall of
the ring gap where the losses were a maximum, then the angular loss distribution was shifted by about 1800
.
DISCUSSION OF RESULTS
Increasing the plasma density in the trap by increasing the ionization rate was prevented by the onset
of an instability in the ring gap. An expanded view of the ring gap is shown in Fig. 5, with notation defined.
The electron layer undergoes a drift along the X axis in the electric field E of the space charge layer and
perpendicular magnetic field H (out of the paper). The drift speed increases towards the outer boundary of
the electron layer. The "slipping" of the flow, defined by the quantity
cos- I rot v I ?d cE 47-tcne
* H H
(1)
causes the onset of diocotron oscillations [3,4], running in opposite directions along the two boundaries of
the flow. The distance of the conducting walls from the flow boundary can exert a significant influence on
the development of the oscillations. The dispersion equation from [6]
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( = {ka ?[(ch 2kb ? ch 2ka)/2 sh 2kb]}2?{[sh2 k (b ? a)]/ sh 2kb}2, (2)
is shown in Fig. 5. It is evident that the conducting walls can provide a stabilizing effect when they are
close to the boundary of the flow. Large values of the electron layer's half-thickness a should cause in-
stabilities at wavelengths 10a in the region between the electron beam and the wall.
Because of the finite dimensions of the ring gap the wave vector k can only take on discrete values.
Thus, ka = ma/R, where m = 1, 2, 3, ... is the mode number of the oscillations; R is the radius of the ring
gap; and a is the half-thickness of the electron layer. The size of a depends on the conditions of the elec-
trom beam injection: on the electron beam radius and on the magnetic flux at the electron gun cathode. In
the present experiments 2a 0.4 cm, 2b = 1 cm, and R = 10 cm, so b/a >2. In the instability region
waves with m from 1 to 30 grow, and the maximum growth increment is for m 15. The experimental data
give information only on the nonlinear stages of the instability. As can be seen in Fig. 4, only one or two
periods are located within the circumference of the ring gap, so m = 1 or 2. This does not contradict the
results of [6], where it was shown that an initial kink perturbation leads to the formation of a vortex with
m = 1. Evidently, modes with finer scale (higher mode numbers) fall into the region with ka > 0.6 after
the onset of the instability.
The growth rate of the diocotron instability is
IrmoI I 4stcne
4
H
(3) sica ?
4 ?
This growth rate is a function of time in an electromagnetic trap, because the electron density in the gap
varies during accumulation of plasma in the trap. Therefore only a qualitative comparison of theory and
experiment is possible. With a small or zero retarding potential on the ring electrode, the rate of plas-
ma accumulation in the trap is significantly less (by a factor of 1000) than during electromagnetic confine-
ment [1, 7]. The time T, during which the electron current onto the ring electrode is azimuthally sym-
metric, is inversely proportional to residual gas pressure, as shown in Fig. 6. Thus, the growth rate of
the instability is proportional to the electron density
n'eno=74?6?109/n. (4)
The quantity pT, determined from the slope of the straight line of Fig. 6, is equal to 2 ? 10-9 torr sec.
From this it follows that at the moment of the onset of the instability the density of secondary electrons
ne" (produced by ionization) exceeds the density of the primary (beam) electrons nte by approximately an
order of magnitude.
The time required for development of the instability increases linearly with magnetic field H at
small field strengths (H < 1500-2000 Oe), in accordance with theory, but then T saturates.
In the regime of electromagnetic confinement the instability occurred with greater speed, since the
retarding electric field eliminates losses along the field lines not only of the primary beam electrons but
also of the secondary electrons.
Thus, the accumulation of cold electrons formed by ionization of neutral gas in the magnetic gaps
causes the long-wavelength diocotron instability to develop. The onset of the instability ends the accumu-
lation of plasma in the trap, since the rate of plasma generation is balanced by the rate of plasma loss in
the ring gap. The particle lifetime defined by the initial decay of plasma density after the termination of
injection is approximately 1/Y = (I/Imco) H/0.9 nm, calculated from Eq. (3). For example, for the con-
ditions indicated in Fig.2, 1/1/ 3.3 ?sec, and Ti ^-1 4.5 ?sec. This indicates that the particle lifetime in
the trap is mainly determined by the loss rate of electrons across the magnetic field of the gap in the azi-
muthal electric field of the developing instability:
dtle
? nen? < > tOcE,
dt VH
(5)
where V is the volume of the plasma in the trap; S is the effective loss area; Ec, is the average magnitude
of the electric field of the instability. An estimation of Eco from Eq.(5) gives a value of about 10 V/cm.
The diocotron instability is caused by the growth of waves on the surfaces of the electron layer in the
magnetic gaps of the trap. In [3] it is shown that for small ka, that is, for large wavelengths, the layer
must be stable if a2 > r/ (where r and 1 are the distances from the edge of the electron layer to a conduct-
ing surface). In other words, for stability it is sufficient to have not two, but just one conducting surface,
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in order to "short circuit" the electric field of one of the surface waves. By varying the magnetic fields
in the two halves of the trap, the electron layer may be moved across the ring gap. The instability was
suppressed when the electron layer grew near to either side wall of the gap. The suppression of the in---
stability was accompanied by an increase of plasma density in the trap from 108 up to 2-5 .1011 cm-3.
The second method for accumulating plasma in an electromagnetic trap ? the gradual buildup of
plasma at low neutral gas pressures (p = 10-7 torr) ? was described in [4, 5].
In conclusion the authors express deep gratitude to K.N. Stepanov, O.A. Lavrent'ev; and A.A.
Kalmykov for valuable advice and discussion of the results.
1.
2.
LITERATURE CITED
O.A. Lavrent' ev, in: Magnetic Traps [in Russian], Vol.3, Naukova Dumka, Kiev (1968), p.77.
A. Ware and J. Faulkner, Nucl. Fusion, 9, 953 (1969).
3.
O. Buneman et al., J. Appl. Phys., 37, 5309 (1966).
4.
Yu.I. Pankrat'ev et al., At. Energ., 31, No.3,
274
(1971).
5.
Yu.I. Pankrat' ev et al., At. Energ., 32, No.2,
131
(1972).
6.
R. Levy and R. Hockey, Phys. Fluids, 11, 766
(1968).
7.
W. Strijland, Physica, 47, 617 (1970).
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BOOK REVIEWS
V. I. Vladimirov
PRACTICAL PROBLEMS IN THE OPERATION OF
NUCLEAR REACTORS*
Reviewedby M. A. Chepovskii
Despite the extensive materials available in the literature on nuclear reactors at the present time,
one lack clearly felt in the literature is on engineering aspects of heat transfer and heat physics.
This three-chapter text, covering and surveying the basic problems encountered in work with nuclear
reactors in a consistent manner, discusses the physical processes occurring in a reactor with power on
and in a shutdown reactor, bringing a power reactor up,to criticality, reactor performance at the rated
power output level, reactor cooldown, and also various problems pertaining to reactor safety and radia-
tion safety. Special attention is reserved for how to calculate reactor startup characteristics (critical
position of absorber rods) in a variety of situations.
The first chapter deals with procedures for estimating exposure doses, dose rates, and residence
times for different sets of conditions affecting the radiation situation, and offers a presentation of the
physical meaning of breeding factor and reactivity.
The second chapter is devoted to the physical processes accompanying reactor operation (release of
energy in the core, reactor power output, burnup, poisoning, reactor poisoning by fission products), and
the temperature effect of reactivity. A procedure for calculating samarium poisoning and xenon poisoning
of a reactor is described in detail. The effect of the temperature coefficient of reactivity on stable reactor
performance and on reactor on-power lifetime is also treated.
The third chapter takes up reactor control from startup and until cooldown. Procedures for calcu-
lating the critical (starting) position of reactor control rods and compensation rods are presented. Prob-
lems concerning the choice of a feasible reactor startup program and schedule are covered along with
problems dealing with changes in power level up to the point of shutdown and cooldown of the reactor. The
chapter ends with a very important section reflecting various aspects of reactor safety under normal op-
erating conditions, and when malfunctions arise in reactivity control and compensation equipment. Close
attention is given to variable reactor operating conditions.
The book encompasses virtually the entire range of questions that can arise in the operation of a nu-
clear reactor. Nevertheless, we feel it advisable to make some further demands on the author:
1. Fuel breeding is almost totally left out of account in the discussion of burnup calculations. While
that is allowable when dealing with reactors burning highly enriched fuel, it cannot be left out of
a treatment of reactors burning weakly enriched uranium.
2. The reader's attention should have been directed to such a phenomenon as a possible reactor re-
activity increase that might occur after the reactor has been shut down, on account of a buildup of
plutonium from decaying neptunium. This is typical of reactors burning natural fuel or weakly
enriched fuel.
3. Problems involving calculations of the remaining on-power lifetime in the case of reactors with
burnable poisons are not discussed in the text.
4. It would have been helpful in a text of this kind to include some problems left to the reader to
solve in each section.
*Atomizdat, Moscow (1972
Translated from Atomnava tnergiva, Vol.35, No.4, pp.257-258, October, 1973.
1974 Consultants Bureau, a division of Plenum Publishing Corporation, 227 West 17th Street, New York, N. Y. 10011.
No part of this publication may be reproduced, stored in a retrieval system, or transmitted, in any form or by any means,
electronic, mechanical, photocopying, microfilming, recording or otherwise, without written permission of the publisher. A
copy of this article is available from the publisher for $15.00.
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In conclusion, we may point out that this book will be of interest and value to those directly involves3
in the operation of nuclear reactors, and also to students majoring in related areas.
Yu. V. Gott and Yu. N. Yarlinskii
INTERACTION OF SLOW PARTICLES WITH MATTER
AND PLASMA DIAGNOSTICS*
Reviewedby Yu. V. Martenko
This book deals with interactions of slow particles (energy range extending from hundreds of elec-
tron-volts to tens of kiloelectron-volts) with solids. While this is a somewhat narrow topic, it is of the
utmost timeliness.
The first two chapters offer a survey of theoretical and experimental research on stopping of parti-
cles in matter, the charge state of the particles interacting with solids, and scattering of particles by a
solid target. The third chapter describes experimental techniques for measuring energy losses in thin
films.
The fourth chapter handles applications of phenomena observed as particles traverse thin films.
This chapter is based primarily on research findings arrived at by the book's authors. These topics are
of great interest, particularly in that they are not reflected in any of the monographs that have appeared
to date on this topic.
The book assembles a wealth of material. The authors strove not only to provide a detailed presen-
tation of theoretical and experimental techniques, but also to facilitate ready use of those techniques and
of the results obtained with them. The formulas are presented in the most convenient way, their range of
error and validity are clearly delineated, and hence the text can be useful as a reference work. Different
ways of investigating the iteraction of slow particles and matter are treated in detailed fashion and are
evaluated critically.
The book will be of value both to experimental physicists working on plasma diagnostics, ionic al-
loying of semiconductors, the structure of solids, field emission electrons, and to specialists in other
fields of science and industry.
D. Bedenig
GAS-COOLED HIGH-TEMPERATURE REACTORSf
Reviewed by B. Y a sh m a
This book is the 44th volume in a series of pocket editions published by the West German firm.
The book is in nine chapters, with appendices and a subject index. Each chapter ends with a list of
reference literature that may be of interest to a reader wishing to acquaint himself with some particular
aspect of the topic.
*Atomizdat, Moscow (1973).
tVerlag K. Thiemig, Munich (1972).
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The introduction lists the basic features of the design and technology of high-temperature reactors
(HTR) as compared to reactors of other types,. and goes into detail on the development of 11T11 in other.
countries.
The second chapter is devoted to the reactor primary loop. The choice of helium as coolant is val-
idated, the design of prestressed reinforced concrete pressure vessels is discussed. A description is
given of the gas cleanup system, steam generators, and gas blowers. The design of HTR is elucidated by
examples such as the Fort St. Vrene and THTR reactors.
The third chapter renders'a very concise account of the ancillary systems, and discusses specifi-
cally the possible formation of tritium in the secondary loop.
The fourth chapter, which goes into adequate detail on the subject of nuclear fuel and breeding ma-
terials for HTR, and their physical and radiation properties, as well as coated fuel particles, the design
of fuel elements for the AVR, THTR, Peach Bottom, Dragon, and Fort St. Vrene reactors, as well as
the results of in-pile and out-of-pile fuel testing, is of great interest. There is also a discussion of re-
processing and reuse of irradiated fuel (with particular emphasis on recycling of thorium-containing fuel).
Fuel reloading (to which the fifth chapter is devoted) centers mainly around the example of the West
German AVR reactor, and the THTR reactor now being built.
Breeding of secondary nuclear fuel, various fuel cycles, nuclear physics characteristics and heat
transfer characteristics of 11TH are discussed in the next chapter, which also touches on the dynamics of
that type of reactor.
The seventh chapter deals with the safety of HTR reactors in any accident situation (up to and in-
cluding rupture of the concrete pressure vessel), and formulates requirements and specifications for the
11TH control system and its instrumentation.
The next two chapters deal with the current state of 11TH development'. These chapters describe de-
signs and present results of operating experience with reactors already in operation or now being built.
The highly intriguing developmental outlook for high-temperature reactors, and their prospective use in
combination with gas turbines, are discussed, as well as applications of high-temperature reactors in the
chemical process industry and in the metallurgical industry, and in MHD generators. Summarized infor-
mation is given on fast gas-cooled reactors, and thd place open for HTR in the nuclear power development
picture extrapolated to the year 2020 is analyzed.
An appendix presents the basic characteristics of all gas-cooled high-temperature reactors now in
operation or now under construction.
This book is a unique publication on 11TH. The text reviews and analyzes a host of data taken from
different journals and the periodical literature. It is written in straightforward laconic language, and pre-
sents a fairly complete characterization of all aspects of HTR. The text is fully deserving of translation
into Russian.
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ARTICLES
ELECTROMAGNETIC FIELDS IN A PLASMA HEATED
NEAR THE LOWER HYBRID RESONANCE
Yu.V. Skosyrev, N.A. Krivov, UDC 621.039.643:533.951
and V. M. Glagolev
Theory shows that the ions of a plasma can be heated when electromagnetic waves retarded along the
magnetic field are excited in the plasma. Conditions were found in [1] under which an electromagnetic
wave propagating across the magnetic field in a plasma with an increasing density is reflected at a certain
point in the form of a plasma wave. A detailed review of the transformation of electromagnetic waves into
plasma waves is given in [2].
The strong absorption of a plasma wave due to Cerenkov interaction with the plasma must result in
the heating of the ions. Experimental studies of the hybrid resonance are reported in [3, 4].
Paper [5] reports the heating of a plasma initially produced by means of a microwave injector [6].
In these experiments the plasma propagates along the lines of force of the magnetic field and enters a high-
frequency resonator resonating at a frequency c0/27r = 140 Mc/sec. This frequency is close to the frequen-
cy of the lower hybrid resonance, which corresponds to the condition1 of a
= wile wHi (1 +
plasma with a density "1012 cm-3 situated in a magnetic field ?3 k0e. Here wHe, will are the electron and
ion cyclotron frequencies and coo is the plasma frequency. The resonator was located in the magnetic field
of an adiabatic trap with a mirror ratio 1.4. The resonator was formed by a two-conductor line coupled to
a "100 kW high-frequency generator. At the end of the line a turn of diameter 150 mm and width 200 mm
encompassed the plasma column of diameter 60 mm. The plasma was heated in this manner to nT = 2 ? 10"
eV ? cm-3. The transverse energy of the plasma was measured in terms of its diamagnetism. Probe mea-
surements established that the ion temperature was in excess of 150 eV. The plasma density increased
during heating. The initial plasma density produced by the microwave injector was ?7 ? 1011 cm-3. In pro-
portion to the heating the signal from the sensor measuring the plasma diamagnetism increased enormously
more rapidly than the density. However, when the density increased to ? 1012 cm-3 the diamagnetism
signal decreased, despite continued operation of the high-frequency generator. The cessation of heating
was explained by the displacement, with increasing density, of the region where electromagnetic waves are
transformed into plasma waves along the radius to the periphery of the plasma column, and on the other
hand by a diminution in the energy input per particle. A reduction in the absorption of high-frequency pow-
er as the singular point shifts towards the plasma boundary, when the wavelength is comparable to the di-
mensions of the systems, was noted in [7]. The singular point corresponded to equality of the radial com-
ponent of the dielectric tensor to zero. If the theoretical ideas on the nature of the heating are correct,
one would expect the wavelength in the radial direction to decrease in proportion to the density increase.
Further, electromagnetic fields must have been able to exist in the plasma during the time the density was
varying over a definite range (from the density at which wave propagation is first possible to the density
at which absorption occurs). Since the conditions of the experiment are consistent with the possibility of
magnetoacoustic resonance, the heating of the plasma may perhaps be explained by an increase in the fields
as a result of geometric magnetoacoustic resonance [4, 8]. In this connection it would be interesting to
establish how electromagnetic waves behave in a plasma whose density is increasing as a result of heating.
Description of the Experiment
The fields were measured using electric and magnetic probes introduced into the plasma column in
glass tubes. The probes were used to measure the spatial distribution of the field and for phase
Translated from Atomnaya Energiya, Vol.35, No. 4, pp. 259-262, October, 1973. Original article
submitted January 15, 1973.
C 1974 Consultants Bureau, a division of Plenum Publishing Corporation, 227 West 17th Street, New York, N. Y. 10011.
No part of this publication may be reproduced, stored in a retrieval system, or transmitted, in any form or by any means,
electronic, mechanical, photocopying, microfilming, recording or otherwise, without written permission of the publisher. A
copy of this article is available from the publisher for $15.00.
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measurements. In the phase measurements use was made of a standing-wave line supplied, through de-
coupling attenuators, with a signal from the measuring probe and with a reference signal from a loop lo-
cated in the jacket of the heating resonator. The attenuation of the reference and measured signals in-
troduced by these attenuators was -10 dB. The signal from a probe moving in the slot of the standing-wave
line is fed through a detector to an oscilloscope. This signal was photographed simultaneously with the di-
amagnetism signal and the density. The oscillograms were used to determine the position of the standing-
wave minimum in the line at different moments of heating. The phase variation of the signal was calculated
from the ratio of the displacement of the minimum in the field distribution along the line, Al, to the free-
space wavelength A: A(p = 2R-(2A/A). The sign of the phase change was found from the direction in which
the minimum shifts when the probe is moved along the radius.
Figure 1 shows the measured amplitude distribution of the fields along an axis coincident with the
chamber axis and the axial magnetic field. The half-width of the Hz distribution equals / (200 mm), which
corresponds to the width of the turn. This sort of distribution guaranteed the necessary retardation of the
wave, since the main harmonic in the Fourier expansion of the magnetic field structure has a wavelength
= 2/. The outermost peaks in the Er and Ez distributions are probably connected with field distortions
near the ends of the metal jacket. Theory indicates that the best conditions for wave transformation oc-
cur when E waves (the boundary wave) having a component Ez are excited on the plasma surface, since E
waves have a greater refractive index than H waves. Excitation of H-mode fields is preferable, however,
since a field Hz which increases away from the center of the plasma column can exert a stabilizing influ-
ence on the plasma [6]. With our method of energy insertion an H wave was excited in the plasma. How-
ever, E waves could thereby be excited in the plasma by virtue of the coupling between E and H waves im-
plicit in the equations for wave propagation in a gyrotropic unbounded medium.
The plasma formed by the microwave injector decayed with a time constant of a few hundred micro-
seconds. By varying the delay of the high-frequency pulse relative to the end of the injection pulse it is
possible to find out how the plasma density no at the moment the high-frequency generator is switched on
affects the magnitude of the electromagnetic field in the plasma. If no < 1.2 .1012 cm-3 heating (recorded in
terms of the diamagnetism signal) was not observed. If the high-frequency generator was switched on at
-
a moment of time when no > 1010 cm3, the electric field of the wave Ez at the center increased by a factor
of 4 and the magnetic field Hz by a factor of -1.5 in comparison with the field values in the absence of
plasma. If no > 1.2 .1012 cm-3 the electromagnetic fields are a few times smaller than the vacuum values.
Finally, when no > 5 .1012 cm-3, Ez was reduced by an order of magnitude and Hz disappeared completely.
The "skinning" of the fields occurs because with increasing density the transformation point shifts outwards
from the center of the plasma column. The diamagnetism signal stops increasing after the density in-
creased to 5 ? 1012 cm-3. There are probably two reasons for this: reduction in introduced energy per par-
ticle, and reduction in heating efficiency as the transformation point approaches the wall. The radial dis-
tributions of the fields Er and Hz measured by displacing the probes are shown in Fig. 2.
At moment of time ti (Figs.2 and 3) the field Er at the center is greater than at the periphery, while
at t2 it falls somewhat towards the center. The magnetic field is diminishing by the skin effect at this mo-
ment and at the periphery does not exceed the vacuum value. The heating of the plasma thus cannot be ex-
plained by geometric magnetoacoustic resonance of the plasma column. The radial field distributions
shown in Fig.2 demonstrate that there is no large-amplitude reflected wave. In this case the phase of the
electromagnetic fields in the plasma must vary smoothly along the radius.
The phase measurements were performed as described above. The results (Fig. 4) show that at mo-
ment ti the phase variation corresponded to an increase of phase velocity of the wave in the radial direc-
tion. At this time the radial electric field of the wave, Er, exceeded the field value in the absence of plas-
ma (see Fig.3a).
The increase in the phase velocity and amplitude of the electromagnetic wave can be explained by the
reduction to zero of the radial component of the wave vector kr of the extraordinary (H) wave at some val-
ue of the plasma density. The theory of wave propagation in an unbounded plasma can be used to estimate
the plasma density corresponding to this condition. The estimates give coo2e He Under the conditions
of the experiment this corresponds to n 1010 cm-3. It can be seen from Fig. 3 that the plasma density at
moment ti is appreciably less than 1012 cm-3. It follows from Maxwell's equations that, for a given Hz and
(Eco/Hz) (ko/kr), i.e., kr -'' 0, the azimuthal electric field Eco increases in an unbounded manner. Here
ko = co/c. The increase of Eco is accompanied by an increase in the radial drift of the electrons, and the
radial polarization electric fields accordingly also increase. This can explain the experimentally observed
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/Turn Jacket
lasma
Hz, teL units
-ZOO -100
Errel. units
too zoo Z,in-rm
-200 -100 0 100 200 Z,rnm
E7,irel. units
-200 -100 0 100 .200 Z,Mm
Fig.1
10 20 30 R,mm
t,
10 20 30 Rmm
Fig.2
40140 60 t, Msec
T It.rt
Ca)
0120140 60 80 t, ?sec
-If A T t
ltz
C
4
0 20 40 60 80 100 t
20 40 60 80 100 t
Fig.3
Fig.l. Distribution of electromagnetic fields along axis of device.
Fig.2. Radiation distributions of: a) electric; b) magnetic field of wave. The time val-
ues ti and t3 are specified in Fig.3.
Fig. 3. Time variation during high-frequency pulse of: a) radial electric field Er on
discharge axis (E0 is field in absence of plasma); b) diamagnetism signal; c) plasma
density; d) magnetic field; Hz) of wave in plasma.
rise of Er at moment ti. The radial phase variations of the fields at moments t2 and t3 corresponded to a
slowing down of the wave along the radius. At these moments a rise was observed in the amplitude of the
radial field and the diamagnetism signal increased. These facts demonstrate that the heating is connected
with the appearance of a retarded wave. Such a wave probably occurred through the transformation of the
electromagnetic wave into a plasma wave. The maximum radial variation of phase was observed at mo-
ment 4, i.e., when the diamagnetism signal (plasma heating) is increasing most rapidly, at a radius 5-10
mm. At moment t3 maximum phase variation was observed at a larger radius. This sort of behavior of the
maximum phase variation can be explained by the displacement of the transformation point towards the
outer region of the plasma column as the plasma density increases. This accords with the "skinning" of
the electric fields at moment t3 (see Fig.2).
Regimes in which a hotter plasma was obtained corresponded to larger variations of phase. The
local refractive index can be calculated from Nr(r) = (c/c0)(d(P/dr) [5], where co is the wave frequency, c
is the velocity of light, and r is the radius of the plasma column. Maximum Nr = 100 and corresponded
to a: radius r = 7-10 mm. For a Cerenkov mechanism of energy accumulation the ion velocity must not
exceed the velocity of the retarded wave. The wave velocity corresponding to the maximum measured
refractive index and equal to 3 ? 108 cm/sec is comparable with the maximum ion velocity observed exper-
imentally (ion energy ?2 keV). The accuracy of the Nr determinations was limited by the dimensions of
the probe, since the efficiency of recording waves of wavelength smaller than the dimenions of the probe
is 18w. Similar measurements were carried out with a magnetic probe in the plasma. The magnitude of
the Hz phase variation was 3-5 times smaller than for the electric field (see Fig.4b). This confirms that
E waves have a larger refractive index than H waves. With increasing axial magnetic field the phase Va-
riation of the electromagnetic wave after traversal through the plasma increased almost in proportion to
the magnetic field.
The measurements reported above lead to the following conclusions:
1. The method of energy insertion used in our experiments assured the excitation and penetration
into the plasma of H and E.
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13(p?
0
a -4
-8
Fig.4. Radial phase variation of wave in
plasma. The wave is slowed down for a
positive phase and speeded up for a nega-
tive phase. a) Radial phase variation of
Er at moment ti; b) radial phase variation
of Er at moments t2 and t3 (curves 1) and
of Hz (curve 2).
2. As the ion component of the plasma heated up (to ^'100 eV) there was an accompanying increase in
the amplitude of the electric fields in the plasma and decrease in the phase velocity of the elec-
tromagnetic wave.
3. During heating the substantial increase in the magnetic field of the wave characteristic of magneto-
acoustic resonance was not observed.
4. Volume resonances of the plasma column were not observed. The heating of the ion component of
the plasma must accordingly be ascribed to the collisionless Cerenkov mechanism of absorption
of slow plasma waves.
LITERATURE CITED
1. V.M. Glagolev, "Propagation and absorption of ion hybrid waves in a weakly inhomogeneous plas-
ma layer" [in Russian], Preprint Institut Atomnoi Energii (1970). See also: V.M. Glagolev, Plas-
ma Physics, 14, 301-314 (1972).
2. V. E. Golant and A.D. Piliya, Usp. Fiz. Nauk, 104, No.3 (1971).
3. V. F. Tarasenko et al., Zh. Tekh. Fiz., 42, No.9, 1996 (1972).
4. I. A. Kovan et al., At. Energ., 25, 503 (1968).
5. V.M. Glagolev, N.A. Krivov, and Yu. V. Skozyrev, Proc. Fourth International Conference on Plas-
ma Physics and Controlled Thermonuclear Fusion Magate [in Russian], Report CN-28/L-6. (1971).
6. V.M. Glagolev, I. N. Khromkov, and N.S. Cheverev, At. Energ., 20, 401 (1966).
7. Yu. N. Dnestrovskii, D.N. Kostomarov, and G. V. Pereverzev, International Conf. on Phenomena
in Ionized Gases, Oxford (1971), p.343.
8. N.V. Ivanov, I. A. Kovan, and E. V. Los', At. Energ., 32, 389 (1972).
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ABSTRACTS
OPTIMIZATION OF THE CYCLICITY OF OPERATION
OF A RESEARCH REACTOR
K. A. Konoplev and Yu.P. Semenov UDC 621.039
Nuclear reactors as tools for physical investigations are very common devices, their power and cost
of operation have been increasing; therefore, the question of the most economical operation of the reactors
acquires very significant importance [1, 2].
In the present paper we attempt to optimize the cyclicity of reactor operation (without solving the
questions of the refinement of the physical parameters and reprocessing of fuel) and we determine the -
parameters of the cycle for which the cost per unit thermal energy developed is a minimum. We consider
cores that permit cassette reloading to be made.
By the cycle of operation of a reactor we shall mean the time interval from a start-up to the following
start-up, i.e., the sum of the times of operation of the reactor (a days) and its station (3 days).
The cost of 1 MW ?day of thermal energy developed by a reactor is
A?V (a 4-P)-1-13q ag Q
+ ? , (1)
Wct y ' W
where 'Y is the cost of maintaining a reactor neglecting the cost of the fuel, electrical energy, and materi-
als consumed during the operation, rubles/day; g is the cost of fuel in the fuel assembly, rubles/g; W is
the plower of the reactor, MW; y is the mean depletion of the fuel assemblies unloaded from the reactor at
the elnd of each operating cycle; Q is the consumption of electrical energy and materials when the reactor
is plioducing power, rubles/day; q is the consumption of electrical energy and materials when the reactor
is shut down, rubles/day; a is the amount of fissionable material needed to develop 1 MW ?day, which
weakly depends on the type of fuel and the neutron spectrum, taken equal to 1.3 g U235/(MW ?day).
To analyze the cost A as a function of a-we must give the dependence of the mean depletion of the un-
loaded fuel y on the mean depletion of the fuel in the zone We assume that
2k
x,
k+n
where k is the number of fuel assemblies that form the core; n is the number of fuel assemblies reloaded
at the end of the cycle, where
aWa
n=by ?
10. 20 30 40 50.
? cc, days
Fig. 1. The function A = f (a ) (a iopt
= 27 days; azopt = 12.3 days): 1) 1.t
= 0.27; k = 78; 2) 14. = 0.14; k = 62.
Translated from Atomnaya fnergiya, Vol.35, No.4, pp.263-266, October, 1973. Original article
submitted July 21, 1972.
1974 Consultants Bureau, a division of Plenum Publishing Corporation, 227 West 17th Street, New York, N. Y. 0011.
Vo part of this publication may be reproduced, stored in a retrieval system, or transmitted, in any form or by any means,
electronic, mechanical, photocopying, microfilming, recording or otherwise, without written permission of the publisher. A
copy of this article is available from the publisher for $15,00.
923
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We can show that there exists an optimal value aopt, for whieh the cost for the operation of the re-
actor is a minimum, and that
2bkx13
2bk43 2
a t?
op
aw gbk \ [ aw gbk
k y?q k TH-9 vi \?q
azw2zirkg2bx:p_ p )
(2)
where b is the number of grams of U235 in one fuel assembly.
The dependence of A on a for le = 3 for the VVR-M reactor of the Leningrad Nuclear-Physics Insti-
tute is presented in Fig.l. Similar dependencies are shown for a number of values of the parameters ap-
pearing in Eq. (2).
For reactors of type VVR-M the quantity A varies most significantly for increase in cycle length in
the limits up to two weeks. If we extend the operating period from fOur to eleven days under specified con-
ditions the cost of the thermal energy can be decreased by 20%.
LITERATURE CITED
1.
A.S. Kochenov, At. Energ.,
21, No.2,
97
(1966).
2.
V.A. Tsykanov, At. Energ.,
31, No.1,
15
(1971).
SPECIAL FEATURES ON THE RESONANCE ABSORPTION
OF NEUTRONS FOR INTERMEDIATE LEVELS
A. P. Platonov and A. A. Luk'yanov UDC 539.125.5.173.162.3:539.125.5.162.3
The value of the effective resonance integral is a quantitative characteristic of the resonance escape
probability. In determining this quantity various approximations are commonly made for the energy de-
pendence of the neutron spectrum in the resonance region. The straightforwardway of estimating the ac-
curacy of the approximate calculations is to compare themwith accurate results. We use a numerical pro-
cedure for solving the equation for the slowing down of neutrons in an infinite homogeneous medium devel-
oped in [1] to determine the spectrum of the neutron flux in the neighborhood of two intermediate U238 res-
onances at 189.6 and 208.6 eV for the systems U? H, U? 0, U? Fe, and U? Pb (Fig.1). The spectra ob-
tained were used to calculate the effective U238 resonance integrals for various values of the scattering
cross section of a nonresonance moderator gm and varlous temperatures of the medium.
180 190 200 210 8.7 eV
Fig.l. Neutron collision density 0(E)
in homogeneous mixtures of U238 with
H, 0, Fe, and Pb (curves 1-4, res-
pectively) for am = 10b and the me-
dium at 300?K.
Original article submitted November 9, 1972; abstract submitted May 21, 1973.
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The values of the resonance integrals for the U238 levels mentioned above calculated by using the lam-
liar approximations differ from the results of numerical calculations for concentrated media by up to 25-
30%. The effective resonance integrals for the moderators studied vary with the concentration and tem-
perature of the medium, taking account of the fine structure of the collision density spectrum in the same
way as in the NR-approximation, taking account of the interference of resonance and potential scattering
[2]. For media with the same concentrations and temperatures the resonance integral is found to depend
strongly on the atomic weight of the nonresonance moderator. The "intermediacy" of selected U238 levels
was investigated for parameters of the IR-approximation scheme [3]. The significant differences in the
values of these parameters determined from the numerical calculation and by the analytic method for con-
centrated media are due to a detailed accounting of the energy dependence of the cross sections and the col-
lision density spectrum in the neighborhoods of the resonances.
LITERATURE CITED
1. A.P. Platonov, Zh. Vychisl. Matem. i Matem. Fiz., 12, 1325 (1972).
2. L.P. Abagyan et al., Byull. Inform. Tsentra Yadernykh Dannykh. Prilozhenie, Atomizdat, Moscow
(1968).
3. R. Goldstein and E. Cohen, Nucl. Sci. and Engng., 13, 132 (1962).
USE OF SUPERPOSITION IN CALCULATING THE TEMPERATURE
OF A REACTOR CORE COOLED BY A LIQUID METAL
A. A. Sholokhov and V. E. Minashin UDC 621.039.5:536.24
The steady-state temperature distribution in a reactor core is adequately described by the linear
equation [1]
at (x. y, z)
w (x, c 11) y) az V?, (x, y)Vt (x, y, z) z--q?(x, y, z).
The temperature which results from many sources is equal to the sum of the temperatures due to the in-
dividual sources, and therefore the temperature at an arbitrary point in the core can be calculated by the
forml
t (x, y, z)=Ck nh, jAh. () t (x, y, z
h=1
where tk, i is a particular solution for the release of heat in the k-th fuel element of the i-th group; ii(z) is
the distribution along the fuel element. For liquid metals molecular heat conduction makes a large contri-
bution to heat transfer, and the coefficients in the equation vary slowly with velocity. Under these condi-
tions temperature for a varying velocity w can be calculated in terms of the Green's functions tk*, found
for a previous velocity wo:
t (x, y, z) ECkE nh, oh, 11 () i, 1 (z?)]
where (3 =wo/w.
The nonstationary temperature distribution in the core is described by the equation
Ot Ot
we?-??c' y, z, -c).
C/Z
Original article submitted November 15, 1972; abstract submitted June 11, 1973.
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4440
8 104,,
f
a
rd
5
4
2
Fig. 1. Experimental and simulated reactor cells: a) a fuel rod as-
sembly; b) tubes containing electric heaters to mock up fuel ele-
ments; c) solid rod mock-ups; 1) shell; 2) coolant; 3) fuel elements;
4) tubular heater; 5) helix; 6) fuel elements or mock-ups of them.
Let qv = qv, of(x, y)77 (z) (1 + 9(T)). Then the time-dependent temperature distribution is given by
N h
/ (X, y, Z, = c1 nk, Oh, 11 (D (z? r= O] ? (V) ek, [13 (z?),T'1} dT',
where tk * . is an elementary Green's function given by
, t
ala ala
um)) ?07 cy--Fr-
Here 77*(z) and 9*(1) are unit functions.
The Green's functions are found experimentally by a substitution method [2]. For example, in order
to investigate a subassembly of the core (Fig. la) a model must be constructed with electric heaters as
shown in Fig. lb. It is sufficient to perform a series of experiments with one heater (Fig. lc), putting it in
place of a mock-up or a fuel element whose Green's function is to be determined. In this way the accuracy
of the simulation is increased.
LITERATURE CITED
1. V. E. Minashin, A.A. Sholokhov, and Yu.I. Gribanov, Thermophysics of Liquid Metal Cooled Reac-
tors and Methods of Electric Simulation [in Russian], Atornizclat, Moscow (1971).
2. V.E. Levchenko, V.E. Minashin, and A.A. Sholokhov, Byull. Izobret., 35, 67 (1968).
BUILDUP OF SCATTERED RADIATION BEHIND A
SHADOW,SHIELD
Generozov, V.A. Sakovich, UDC 621.939.78:539.12.172
and V. M. Sakharov
The Monte Carlo method has been used to calculate doses of scattered radiation at various distances
from the surface of a shield of finite transverse dimensions for monodirectional and cosine disk sources of
neutrons and Y-rays.
The same programs were used in the calculations as in [1-3]. The source and the adjoining cylin-
drical shield had diameters d = 50 cm. The biological dose produced by neutrons with a reactor spectrum
was calculated at points behind slab shields of polyethylene (p = 0.92 g/cm3) 10, 20, 30, and 40 cm thick.
The energy flux of y radiation was calculated at points behind tungsten slab shields of thicknesses 2, 4, 6,
and 8 mean free paths at the source energy Eo for E0 equal to 0.5, 1.25, and 5 MeV.
Original article submitted November 23, 1972; revision submitted May 4, 1973; abstract submitted
May 21, 1973.
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The calculations were performed for a detector placed on the axis of symmetry on the surface of the
shield and at distances of 0.2, 0.5, 2.0, and 5.0 m from it. The statistical error was estimated by the
method of successive distributions; in simulating 6000 histories it was 2-10%.
From the results obtained we can recommend the following formulas for the dose behind a finite shield
in terms of data for an infinite shield:
Ds (t) for Red;
D (t, R)-=s (t) ?{ (t En)
D?for R d,
Rz
where t is the shield thickness, R is the distance from the shield in meters, Ds is the radiation dose at the
surface behind an infinite slab shield and E0) is a scale factor depending on the angular distribution of
the source, the kind of radiation, and the shield thickness.
For the neutron dose behind a polyethylene shield for a cosine source with a reactor spectrum the
value of E0) for t = 20-40 cm is 0.093-0.1. For Y rays with energies E0 equal to 0.5, 1.25, and 5 MeV
from a cosine source the values of behind a tungsten shield are the following: for a thickness of one mean
free path = 0.13-0.15; for 6 mfp = 0.17-0.26, and for 8 mfp = 0.2-0.4.
We have not calculated for a large number of materials or for other angular distributions of the
source, but the results obtained show clearly that the range of values is rather narrow.
LITERATURE CITED
1. V. L. Generozov and V.A. Sakovich, At. Energ., 28, 175 (1970).
2. V. L. Generozov and V.A. Sakovich, At. Energ., 30, 536 (1971).
3. Yu.A. Vakarin et al., in: Dosimetry and Radiation Shielding Problems [in Russian], L.R.Kimel'
(editor), Atomizdat, Moscow, No.12, p.117.
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LETTERS TO THE EDITOR
THERMODYNAMIC PROPERTIES AND MUTUAL DIFFUSION
IN,THE SYSTEM UC ? ZrC
G.B. Fedorov, V.N. Gusev, UDC 539.219.3:669.822
V.N. Zagryazkin, and E.A. Smirnov
This article continues our work on the diffusion properties of the system UC ? ZrC [1]. To calculate
the coefficients of mutual diffusion we used the results of an analysis of diffusion in three-component sys-
tems with one interstitial element [2]. With certain approximations, the relation between the coefficients
of mutual diffusion and the coefficients of diffusion of radioactive atoms of the components of the system
and the thermodynamic properties is as follows:
where
flit ==D22= N2Dtg11+NiDtg22;
1313= ?D23 = 1VN1
N2
(Drg13? Dtg23);
b33=Dtg33? (N1Drg13+ N2Dtg23);
233i =N3-- /31g3i ?N3 (Drgi1?Dtg22),
Ni
a In yi
a in N '
(1)
(2)
is the delta function, NE? is the ratio of the number of atoms of species i in a local volume to the number
of lattice yi is the coefficient of thermodynamic activity of the i-th component, and Dt is the coefficient of
diffusion of radioactive atoms of the i-th component. Here and below, Ni and N2 refer to the elements of
substitution (uranium and zirconium, respectively), and 1\13 to the interstitial element; Ni + N2 = 1.
In Eqs. (1), as Di we used the previously-measured diffusion coefficients of the components of the
system UC? ZrC [1]. The values of the thermodynamic factors gii were determined by means of models
of the thermodynamics of the system [3].
The monocarbides Ui_xCx and Zri_xCx form a solid solution in accordance with the reaction
(1? z) ui_,cx+ zzri_xc. u(i-z)0.-.)zrz(l-.)cs, (3)
where x is the atomic fraction of carbon, x 0
(2)
The parameters a, b, and to may depend on the probe length L and, to a lesser extent, on the recorded en-
ergy. We let t ? to = ti. Then timax, the time of arrival of the radiation maximum (dJ(ti)/dti = 0), and the
moments
S tJ (tt)dtt
m? 0
00
t
5 J (tt)dtt
0
; k=1, 2
are connected with a and b by the relations
ab (a+p1) b ; (a+ 2) (a +1) b2
timax ;
t1
P2
Hence the constants a and b can be defined as:
a= 10. 1;
!DTI
a+1
(3)
Figure 1 shows a comparison of curves calculated by the Monte Carlo method with those obtained from Eq.
(2) for a probe length L = 25 cm. The correct nature of the displacement of the maximum of the distribu-
tion with increasing p and the excellent agreement of the curves is clear.
In making comparison with experimental data, one should take into account the fact that Eq. (2) has
the form of a differential distribution with respect to ti and in real apparatus the measurements are carried
out for a time not less than the resolving time; this can be taken into account approximately by changing
the value of the time dispersion in the constant a by the quantity A which is proportional to the square of
the experimentally determined resolving time:
a=
-2 1 ?
I? +A?t1
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LITERATURE CITED
1. E.M. Kadisov et al., "Pulsed gamma?gamma logging," in: Pulsed Neutron Logging [in Russian];
Izd. VNIIYaG (1968), pp.184-189.
2. I. G.Dyadfkin, "Theory of borehole logging," Izv. AN SSSR, Ser. Geofiz., No.4 (1965).
3. G.M. Voskoboinikov, "The question of accuracy and limitations of applicability of the diffusion ap-
proximation in the solution of problems of 7-ray propagation," Zh. Tekh. Fiz., 30, No.1, 90-95
(1960).
4. R . Marshak, "On the theory of the slowing down of neutrons," Rev. Mod. Phys., 19, 185 (1947).
5. I.G. DyadTkin and E.P. Batalina, "Time variation of the spatial and energy distiibution of neutrons
from a pulsed source," At. Energ., 10, No.1, 5-12 (1961).
6. V. F. Zakharchenko, "Applicability of approximate schemes for neutron transport in a homogeneous
moderator," Ural. Fil., AN SSSR, Tr. In-ta Geofiziki, No.2, pp. 17-45 (1962).
938
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GAMMA-RAY ATTENUATION IN APPLIED
SCINTILLATION SPECTROMETRY
V.I. Polyakov and Yu. V. Chechetkin UDC 539.122.164
Scintillation y spectrometry is widely used in the determination of the activity of isotopes with rela-
tively simple Y spectra and in control devices in technical processes using radioisotopic methods for mea-
suring the absorptive properties of materials.
In determining the activity of point sources in containers, the specific radioactivity of isotopes in
pipes and tanks, and in the solution of a number of other problems, it is necessary to realize that 'Y photons
scattered in shielding or material at small angles may be recorded in the photopeak corresponding to the
initial energy because of the finite energy resolution of spectrometers [1, 2]. The amount of scattered ra-
diation which is recorded in the photopeak depends on the shield (medium) material and thickness, on the
energy resolution of the spectrometer, and on the method of determining the area of the photopeak.
Measurements with shielded cylindrical sources and collimated scintillation spectrometers showed
that for shielding thicknesses up to 3-5 mean free paths, the 'V-ray attenuation law is described by an ex-
ponential with an attenuation coefficient [Leff which is less than the theoretical narrow-beam atterivation co-
efficient ?0. It was experimentally found that ?eft. = 0.52 0.02 cm-1 (?0 = 0.57 cm-1) for cylindrical
sources with a 'V-ray energy E0 = 0.662 MeV and iron shielding. In first approximation, the effective "Y-
ray attenuation coefficient is independent of source and collimator dimensions. Similar experiments with
cylindrical and point sources of 141Ce and "Co behind shields of water, aluminum, iron, and lead showed
that the differences between kteff and 1.10 increase at low energies and for light absorbers.
For the theoretical calculation of Aeff, we considered a parallel beam of rays having a flux density
430 sec-1 .cm-2 incident on a slab of thickness t.
Depending on the spectrometer resolution ri = AE1/2/E0 and the method used for determining the area
under the photopeak, pulses will be counted for y rays scattered into an energy range from E0 to Ei = E0
a7iE0 where a S 1. -
The effective 7-ray attenuation coefficient is defined by
(Doe-t--P(D1-=-(D0e-efft,
where 4,i is the flux density of singly-scattered"), rays outside the shield.
Using the Klein?Nishina?Tamm formula, one can determine the angular distribution of singly scat-
tered 'Y rays outside a shield. Integrating the resultant expression over shield thickness, including the at-
tenuation of scattered 'V rays, and over energy between the limits of the photopeak area assumed in the cal-
culation, we obtain
(1)
Reif= - ln {1+ 0.15dz meocz
A E(i
742712 1 11
X [1+ (I ?ai)2 2rnec2cn Eo c +c4 Es a
(i _aro tto (1 e0-111)t( )1
where d is density, g/Cm3; z and A are respectively the atomic number and atomic weight of the shielding
material; mec2 is the rest energy of the electron, MeV; E0 is the energy of the incident 'V-ray beam, MeV;
Pi is the attenuation coefficient for scattered y rays of energy El.
According to the calculations, Aeff is independent of shield thickness with an error less than 3% for
shield thicknesses up to five mean free paths; consequently, one can set t = 1 cm in Eq. (2).
(2)
Translated from Atomnaya Energiya, Vol.35, No.4, pp.274-275, October, 1973. Original article
submitted January 15, 1973.
0,1974 Consultants Bureau, a division of Plenum Publishing Corporation, 227 West 17th Street, New York, N. Y. 10011.
No part of this publication may, be reproduced, stored in a retrieval system, or transmitted, in any form or by any means,
electronic,' mechanical, photocopying,' micro filming, recording or otherwise, without written permission of the publisher. A
copy of this article is available from the publisher for $15.00.
939
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10-2
IIli' I_ 1 I
f,D E,mev
Fig.'. Energy dependence of T-
ray attenuation coefficient (17
= 10% for E0 = 0.662 MeV):
calculated with Eq. (2); ---)
calculated without consideration
of scattered radiation [5]; 0,40)
experimental points for cylin-
drical and point sources respec-
tively.
Only single scattering is taken into account in Eq. (2). Using the results of [3], one can show the
contribution from double scattering is less than 8% of that from single scattering even in an infinite water
medium for 1-MeV 'Y rays and a spectrometer resolution of 10%; consequently, it need not be considered.
Figure 1 shows that calculation of the effective 1i-ray attenuation coefficient by means of Eq. (2) yields
results that are in good agreement with experimental values obtained from measurements of the activity
of cylindrical and point sources (in the calculation, it was assumed I] ? 1//E0).
The possibility of using Eq. (2), which was obtained for a plane source, in the calculation of self-
absorption and absorption in shielding for radiation from other types of sources (point and volume) can be
explained by the small differences between the scattered 'Y-ray spectra [4].
Thus in measurements with NaI(T1) crystals, Y-ray attenuation can be taken into account by means
of an exponential law; the effective attenuation coefficient depends little on measurement geometry and is
well described by Eq. (2).
LITERATURE CITED
1. V. M. Kodyukov et al., in: Radiation Technology [in Russian], No.1, Atomizdat, Moscow (1967),
p.215.
2. V.I. Polyakov and Yu. V. Chechetkin, At. Energ., 31, No.2, 139 (1971).
3. V.V. Pavlov, in: Problems in Dosimetry and Radiation Shielding [in Russian], V.I. Ivanov (editor),
No.2, Atomizdat, Moscow (1963), p.66.
4. E. L. Stolyarova, in: Problems in Dosimetry and Radiation Shielding [in Russian], L.R. Kimel' (edi-
tor), No.7, Atomizdat, Moscow (1967), p.54.
5. L.R.Kimel' and V.P. Mashkovich, Handbook for Shielding against Ionizing Radiation [in Russian],
Atomizdat, Moscow (1966).
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NATURAL 7-RAY BACKGROUND MEASURED WITH
Ge(Li) DETECTOR
L.M. Mosulishvili,-N. E. Kharabadze, UDC 543.54
and T.K. Tevzieva
In activation analysis, semiconductor Ge(Li) detectors are often used which have high resolution for
the detection of 7 rays with energies ranging from several keV to 4-5 MeV [1-3]. An exact determination
of the energy and intensity of each line is necessary in studies of 7-ray spectra from multicomponent me-
dia and particularly in the identification of various radioisotopes. As is well known, this procedure is
most difficult and very important in the activation analysis of complex multicomponent objects. In addi-
tion, an exact determination of the photopeaks belonging to the natural background is necessary in the iden-
tification of radioisotopes producing radiation of low intensity. The natural background results from many
factors of which one should mention radiation from natural radioactive isotopes in the Earth's crust and in
structural materials of laboratory buildings, cosmic rays, and radiation from the radioactive isotopes in
nuclear reactors if measurements are made in the neighborhood of one.
The background radiatiOn'is of low intensity; however, the counting time is long, as a rule, when
Ge(LI) detectors are used and many resolved lines appear in the spectrum when counting times are long.
This paper is devoted to a detailed study of the spectral composition of the natural background at the
nuclear reactor of the Institute of Physics, Academy of Sciences, Georgian SSR during 1971-1972.
20
18
?
y_
N ?cc
68 ?
,
il
0
N
F4
N
a
c,
,
,..,
2300
cc
2400
cc
cc
?2507
cc
cc
1600
?
1700
cc I-..
1800
cc
1900
2000
2100
cc
i
"
2200
cc
400
SOO
600
700
800
900
1000
1100
1200
1300
1400
Channel number
Fig.l. 7-Ray spectrum of natural background measured with a Ge(Li) Semiconductor
spectrometer.
Translated from Atomnaya ?Pnergiya, Vol.35, No.4, pi:1.275-276, October, 1973. Original article
submitted February 7, 1973.
0 1974 Consultants Bureau, a division of Plenum Publishing Corporation, 227 West 17th Street, New York, N. Y. 10011.
No part of this publication may be reproduced, stored in a retrieval system, or transmitted, in any form or by any means,
electronic, mechanical, photocopying, rnicrofilmibg, recording or otherwise, without written permission of the publisher. A
copy of this article is available from the publisher for $15.00.
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TABLE 1. Set of Radioisotopes Identified in 7-Ray Background by Means of a Ge(Li) De-
tector
Y-ray ener-
gy, keV"'
Line intensity
(total counts
.,
per 150 min)
Identified
radioisotope "
Y-ray ener-
gy [4]
Y-ray ener-
gY, keV s
Line intensity .
(total counts
per 150 min)
-Identified
radioisotope "
)'-ray en-
ergy [4]
185
690
226Ra
186,2
909
330
228Ae
911
207
290
228AC
209
962
50
214Pb
965
237
860
212Pb
238,6
968
110
228AC
968,8
250
260
230Th
250
1064
45
106Ru
1061
293
430
214Pb
295,4
1117
110
214Bi
1120
338
700
228Ac
338
1235
80
21613i
1238
351
780
214Pb
352
1458
1740
esoK
1460,7
509
360
lo6Ru-
511,9
1591
80
228AC
1588,3
581
310
2001'1
583,1
1726
30
211Bi
1731
608
640
214Bi
609,3
1761
80
21.4Bi
1765
660
60
l37cs
661,6
2201
35
23.4gi
2204
664
50
214Ri
665
2332
25
214Bi
2340
805
50
214Bi
806
2612
200
226Th
2614
This work,
The natural background was measured over a period of 2.5 h with a DGL-4E Ge(Li) detector made by
the French company SAIP connected to a 11Tridak-S" 4096-channel analyzer. The detector resolution is
2.5 keV for 1332 keV 7 rays. There are numerous photopeaks in the spectrum (Fig. 1) including some very
weak ones. Photopeak energies were determined by means of careful calibration with various isotopes
having y rays of known energies.
Knowing the energy of each line with a given accuracy and establishing that the intensity of the radia-
tion remained constant in time, a set of radioisotopes which produced one or more lines in the background
spectrum was determined. The experimentally deterined T-ray energies at 185, 250, 293, 351, 608, 664,
805, 962, 1117, 1235, 1726, 1761, 2201, and 2332 keV are in good agreement with the values given [4] for
the most intense lines from the radioactive isotopes 226Ra, 214ph, 230Th, 214Ri, which, in turn, are decay
products of 238U (Table 1). The lines with energies of 207, 237, 338, 581, 909, 968, and 1591 keV are
produced by the most intense 'Y rays from the isotopes 228AC, 212pb, 208T1, and 228Ra, which are in the 232Th
family.
In addition, lines from the isotopes 137Cs and 106Ru, which are fission products, are clearly observed
in the spectrum as well as the line at 1458 keV from 40K.
Background radiation was measured in the radiochemistry building near the nuclear reactor. Al-
though lines produced by artificial radioactive isotopes can be observed in the spectrum, the main contri-
bution to tile background spectrum is made by radiation from natural radioactive isotopes in the Earth's
crust, in structural materials, and in the atmosphere. This conclusion should be considered perfectly
natural if one considers that the average concentration of 2381J and 232Th in the crust is .--10-47o.
Background radiation should be taken into account particularly carefully in those cases where work
is carried on close to the limit of sensitivity of the equipment during activation determination of an ele-
ment.
1.
LITERATURE CITED
E. Steinnes et al:, J. Radioanal. Chem., 9, 267 (1971).
2.
Z. Randa et al., J. Radioanal. Chem., 117 305
(1972).
3.
K. Pillay and C. Thomas, J. Radioanal. Chem., 7, 107 (1971).
4.
R. Dams and F. Adams, J. Radioanal. Chem., 7,-127 (1971).
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DETERMINATION OF A HAFNIUM IMPURITY IN
ZIRCONIUM AND ITS ALLOYS BY A NEUTRON
ACTIVATION METHOD
V.V. Ovechkin and V.S. Rudenko UDC 543.54
Two variations of a method based on irradiation of samples with thermal reactor neutrons and mea-
surement of the 'Y radiation of the active products were proposed in [1] for the determination of low con-
centrations of hafnium in zirconium and alloys based on it. In one case the 'Y radiation of the short-lived
isotoPe 179mEf (T1/2 = 19 sec, Ey = 0.217 MeV) was used, while in the other the activities of the long-lived
isotopes 179H1 (Ti/2 --- 70 days) and 18111f (T1/2 = 46 days) were used. In a comparison of these variations of
analysis as applied to zirconium concentrates, it was found that the first ensures higher sensitivity, rapid-
ity, and better reliability of the results [2]. However, in both cases a reactor is required, which to some
degree hinders the possibility of practical application of such analysis.
A measurement of the hafnium content in the presence of zirconium according to the induced activity
of 179MHf can also be performed by irradiation of the samples with a neutron flux with an energy of 14 MeV
from a low voltage generator [3].
In the interaction of neutrons with an energy of 14 MeV with the nuclei of stable isotopes of hafnium,
the 19-second isomer 179mHf is formed in the following nuclear reactions: 1891if (n, 2n) and 179Hf (n, n').
However, the irradiation of zirconium with 14 MeV neutrons creates a strong interfering background
in the 'region of measurement of the 'Y spectrum of 179H1, due to the harder 1/ radiation of the isotopes 89mZr
(T1/2 L 4.2 min, ET = 0.59 and 1.51 MeV) and 89mY (T1/2 = 16 sec, ET = 0.91 MeV), which are formed in the
er of counts on the channel 1O
0,590
0,217'
0,910
50 100
Channel number
Fig.1
50
Channel number
Fig. 2
100
Fig. 1. Apparatus 'Y spectra of a sample of zirconium containing ?-0.3% by weight hafnium,
obtained on a neutron generator.
Fig.2. Apparatus 'Y spectrum of a sample of zirconium containing ^'0.3% by weight hafni-
um, irradiated with the neutrons of an isotope source.
Translated from Atomnaya Energiya, Vol.35, No.4, pp.277-278, October, 1973. Original article
submitted March 7, 1973.
1974 Consultants Bureau, a division of Plenum Publishing Corporation, 227 West 17th Street, New York, N. Y. 10011.
No part of this publication may be reproduced, stored in a retrieval system, or transmitted, in any form or by any means,
electronic, mechanical, photocopying, microfilming, recording or otherwise, without written permission of the publisher. A
copy 6/this article is available from t'he publisher for $15.00.
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TABLE 1. Hafnium Content in Zirconium
Samples, % by Weight
Material
Activation
method
Spectral
method
Zirconium
6,7.10-2
6,3.10-2
5,0.10-2
4,8.10-2
Zirconium alloy
4,6.10-2
4,4.10-2
The same
3,7.10-2
3,7.10-2
ff
5,3.10-2
5.6.10-2
ff
2,9.10-2
2,7.10-2
reactions 88Zr (n, 2n) and 88Zr (n, n'p), respectively, which
have high energy thresholds (12.53 and 8.79 MeV, respec-
tively). Consequently, if 14 MeV neutrons are moderated
to an energy below the threshold of these reactions, it
might be expected that the interfering influence of zirconi-
um would be somewhat reduced. In the published studies,
these peculiarities of the activation analysis of zirconium
for the hafnium content have not been discussed.
In this work we discuss the possibilities of quantita-
tive determination of hafnium in zirconium and its alloys,
based on the use of a low-voltage generator of 14, MeV neutrons, which are additionally moderated in a
paraffin block, as the source of activation. In addition, we studied the possibilities associated with the
use of neutrons for the irradiation of an isotopic 238PU?Be source.
A pulsed generator of 14 MeV neutrons of the NGI-5 type with a yield of (--.3 .108 neutrons/sec and an
isotopic 238PU ? Be source of neutrons with a yield of 108 neutrons/sec were used for the activation of the
samples.
A paraffin block with dimensions 300 X 160 mm with several vertical channels, in which samples
were placed for irradiation at different distances from the source, was used to moderate the fast neutrons.
The induced activity was measured on a scintillation 7 spectrometer was a NaI(T1) crystal with dimensions
40 X 50 mm with a well.
Figure 1 presents the apparatus 7 spectra of a sample of zirconium containing 0.3% by weight haf-
nium; the sample was irradiated with neutrons from a NGI-5 generator for 1 min with various geometries. The
spectrum 1 corresponds to an arrangement of the sample directly at the target of the generator without the
use of a moderator, while spectrum 2 corresponds to an arrangement of the sample in a paraffin block at
a distance of ?40 mm from the target. In the apparatus spectra, in addition to a photopeak with energy
0.217 MeV from 178mlif, photopeaks with energies 0.59 and 0.91 MeV from the isotope 88mZr and 88111Y
were observed. The results of the measurements showed that when the irradiated sample is removed
from the target of the generator and a paraffin shield is used, the interfering background of the zirconium
matrix in the region of 0.2 MeV of the apparatus spectrum is reduced by approximately 7-fold. In addi-
tion, intensity of the photopeak 0.217 MeV from 178mHf is increased, which is evidently explained by an
increase in the fraction of slow neutrons, which induce the reaction 178Hf(n, 'y) 179mHf with alarge cross ,
section of activation (75 barns). The area of this photopeak proves to be a maximumwhen the sample is placed
in a paraffin block at a distance of 40 mm from the target of the generators; moreover, it is five times
as great as the intensity of the peak of the same sample placed at the target of the generator during irra-
diation.
Thus, the use of a paraffin block as a moderator in work on a generator of 14 MeV neutrons lowers
the limit of measurement of hafnium in zirconium by more than 10-fold. The value of the lower limit of
measurement of hafnium calculated according to the 2(7 criterion (where a is the standard deviation of the
background in the region of 0.2 MeV), is 2 .10-2% by weight for a sample of zirconium weighing 10 g with
a neutron yield of the generator ^. 3 ? 108 neutrons/sec. It should be noted that this value is only approxi-
mately three times poorer than the value obtained in [3] with a substantially larger yield of 14 MeV neu-
trons (1018 neutrons/sec).
The use of an isotopic a-Be source of neutrons even more effectively reduces the interfering in-
fluence of the zirconium matrix, since the bulk of these neutrons have an energy below the thresholds of
the reactions on zirconium. The presence of slow neutrons in the energy spectrum of such a source in-
creases the value of the useful reaction 178Hf (n, 7) with the formation of the isotope 178mHf, according to
which hafnium is determined. These data are confirmed by the nature of the apparatus 7 spectrum of the
zirconium sample with a hafnium content ?0.3% by weight (Fig.2), irradiated with the neutrons of a 238PU
? Be source. Only one photopeak is observed in the spectrum, with energy 0.217 MeV, from the isomer
179mHf.
The photopeaks with energies 0.59 and 0.91 MeV, which always appear when zirconium is irradiated
on a generator of 14 MeV neutrons, are entirely absent in this case. The intensity of the photopeak 0.217
MeV is increased by 80%, if a 20 millimeter paraffin shield is placed between the isotope source and the
sample during irradiation. The rate of count in the region of the 7 peak 0.2 MeV in this case is 1.2 .105
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counts/min per gram of hafnium with a background of 100 counts/min from the zirconium sample weighing
10 g, which corresponds to a value of the lower limit of measurement of hafnium equal to 1.5 .10-3% by
weight, with a yield of the isotope source 108 neutrons/sec.
Table 1 presents the results of an activation determination of hafnium in zirconium and alloys based
on it, obtained by irradiation with an isotope source. The material to be analyzed was placed in a poly-
ethylene ampoule, irradiated for 1 min, and 5 sec after the end of irradiation, the induced activity of178mHf
was measured for 40 sec according to the photopeak 0.217 MeV.
The hafnium content in the samples was determined by comparison with control samples, prepared
on the basis of zirconium dioxide with the addition of hafnium dioxide.
From Table 1 it is evident that the results of activation determination of hafnium are in good agree-
ment with the results of the spectral method. The coefficient of variation of the activation method for haf-
nium concentrations ?5 .10-2% by weight in samples weighing g is ?8% rel. The time of one analysis is
4-5 min. The method described, using an isotopic 238PU - Be source of neutrons with a yield of 108 neu-
trons/sec, can be used successfully for the highly sensitive and rapid analysis of zirconium land its alloys
for hafnium content.
LITERATURE CITED
1. W. Macintosh and R . Jervis, Analyt. Chem., 30, No.7, 1180 (1958).
2. G. V. Leushkina et al., in: Neutron Activation Analysis [in Russian], Fan, Tashkent (1971), pp.33-
36.
3. V.T. Tustanovskii and U. Orifkhodzhaev, Zavod. Lab., 36, No.12, 1482 (1970).
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NONOBSERVANCE OF SPONTANEOUS FISSION IN
KURCHATOVIUM AT BERKELEY
V.B. Druin, Lobanov,
D.M. Nadcarni,* Yu.P. Kharitonov,
Yu.S. Korotkin, S.P. Tret'yakova,
and V.I. Krashonkin
UDC 546.799
Element 104, kurchatovium, was first observed experimentally in 1964 through the spontaneous fis-
sion of its isotopes [1]. Among the products of 242Pu irradiation by 22Ne ions in the internal beam of the
310-centimeter cyclotron there was observed three spontaneously fissioning activities with half-lives of
14 msec, -0.3 sec, and several seconds. The first turned out to be the fissioning isomer 242fAm. Of the
others, the most thoroughly studied behavior was the activity with T1/2 0.3 sec which was identified as
269Ku through measurement of the excitation function and cross irradiations.
In 1969-1970, the experimental studies of kurchatovium continued in the external beam of the accel-
erator. The half-life of 269KU was determined more precisely (T1/2 ">-" 0.1 sec) [2] and a second isotope,
259Ku (T112 4 sec), was also identified [3]. The identification of these isotopes was based on excitation
functions and integral angular distributions of the recoil atoms.
Realizing the importance of chemical identification of the atomic number of the new element, I. Zva-
ra et al. [4] developed a rapid method for chemical analysis of nuclear products. The first experiments
on the identification of element 104 were carried out in 1966 in the internal beam of the cyclotron using
frontal chromatography [5]. The experiments showed that the spontaneously fissioning activity produced
in the irradiation of 242Pu by 22Ne ions passed rapidly through a four-meter column and an aerosol filter
under conditions favoring the passage of hafnium tetrachloride molecules (typical representative of group
IV elements) separated from actinide elements, i.e., it was an ekahafnium.
In 1970-1971, new chemical experiments were set up in which the kurchatovium was separated in the
form of the chloride by gas-adsorption thermochromatography [6]. Irradiation conditions and the chroma-
tographic procedures were chosen to be optimal for 259Ku (To 4 sec). In particular, the time of gas
travel from the target to the portion of the column where group IV elements were deposited was 0.8 sec so
that the 269Ku (T1/2 0.1 sec) decayed in the beginning of the column and did not distort the shape of the
chromatogram. The behavior of "mSc and 179,171Hf was investigated in the experiments at the same time.
It was shown that the distribution of fission-fragment tracks from spontaneous fission of 259Ku along the
column -,:eproduced the distribution of hafnium accurately. This demonstrated that the four-second spon-
taneously fissioning isotope belonged to group IV of the periodic table, i.e., it was element 104, and it was
concluded that this element had also been detected in the chemical experiments of 1966.
Ghiorso and his associates [7] expressed doubts about the Dubna results for 269Ku and 259Ku. As an
argument, they first presented different estimates of the lifetimes of these isotopes with respect to spon-
taneous fission mainly based on extrapolations of certain empirical relations. They attempted to observe
spontaneous fission in a number of experiments but the technique they used was not sufficiently sensitive
[8]. However, the apparatus and experimental results were not published in detail [8, 9].
A later report from Berkeley [10] asserted that spontaneous fission is not observed and should not be
observed for 259Ku produced in the interaction of 245Cm with 160 ions; on the basis of their experimental
*Bhaba Atomic Research Center, Bombay, India.
Translated from Atomnaya Energiya, Vol.35, No.4, pp.279-280, October, 1973. Original article
submitted April 11, 1973.
C 1974 Consultants Bureau, a division of Plenum Publishing Corporation, 227 West 17th Street, New York, N. Y. 10011.
No part of this publication may be reproduced, stored in a retrieval system, or transmitted, in any form or by any means,
electronic, mechanical, photocopying, microfilming, recording or otherwise, without written permission of the publisher. A
copy of this article is available from the publisher for $15.00.
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JO
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results, the spontaneous fission branching ratio did not exceed 20%, but
it should not be more than 0.1% from their extrapolated estimates.
Because of this, the present work involving irradiation of 248Cm
by 180 ions was undertaken in order to show that spontaneous fission of
259Ku can be observed, and its branching ratio determined, for this tar-
get?particle combination with a technique of sufficiently high sensitivity.
4
0 2 45 8 10 sec
Fig. 1. Decay curve for 259Ku.
The solid line corresponds
to T112 = 3.2 ? 0.8 sec.
EXPERIMENTAL METHOD
A 246cm (>99%) target with an admixture of 242Cm (0.5%) was pre-
pared by electrolytic deposition on a thin titanium backing (5 ?m). The
short-lived 242Cm was introduced as a tracer which enables one to de-,
tect through its a activity slight contamination by target material of the
most important parts of the experimental equipment (recoil-atom col-
lector, detectors). Monitoring for a activity of curium showed that the
possible background from spontaneous fission of 246Cm was negligibly
small
The apparatus used in the experiments, having a tape recoil-atom collector transporter and phos-
phate glass fission-fragment detectors, was described previously in detail [2]. Additional shielding was
provided for the fission-fragment detectors in order to prevent possible penetrationby curium atoms ejected
from the target because of elastic scattering of 180 ions.
Irradiation of 246CM was accomplished in an external beam of 180 ions accelerated in the 310 cm cy-
clotron at JINR. The energy of the accelerated ions at the target was 100 MeV, which corresponds to the
maximum cross section for a reaction involving evaporation of five neutrons [9].
The average ion flux through a 1-cm2 target was 2 .1012 particles/sec. The total ion flux was measured with
a scanning device located between the beam collimator and target and calibrated with a Faraday cup.
For a fixed velocity of the collector tape (28 cm/sec), 31 tracks of fragments from spontaneous fis-
sion of product-nuclei in the reaction were observed in the detectors. The lifetime of the isotope was es-
timated from the distribution of tracks along the length of the detectors. Figure 1 shows the decay curve
for the isotope produced in these experiments. It is clear that the half-life is 3.2 ? 0.8 sec on the basis of
the measurements, which agrees rather well with the data for 259Ku obtained from spontaneous fission [3]
and a decay [11].
The partial cross section for 259Ku production as measured from spontaneous fission and for an 180
ion energy of 100 MeV, is 4 ? 10-34 cm2. An estimate of possible background from the decay of 252102 (SF
30%); which may be produced in the reaction 242Cm (180, a4n)252102, leads to a value of no more than 5-
10% based on data for the cross sections of the nuclear reactions
(22Ne, a4n) [12] and (160, a4n) [9].
RESULTS AND DISCUSSION
Calculations made by Sikkeland of the cross sections for the nuclear reactions 248CM (180, 4-5n)259, 260icu
and 248Cm(160, 4-5n)259, 260Ku have been reported [9]. The calculated values of the cross sections for the
reactions with evaporation of five neutrons turned out to be 1.5-2 times less than the cross section for the
(16,180, 4n) reaction. It was pointed out, however, that in experiments on the synthesis of 259Ku in the nu-
clear reaction 248Cm(160, 5n)2531cu, the measured cross section was approximately four times higher than
the calculated value. This is in agreement with experimental results from studies of similar nuclear re-
actions such as (180, 4-5) in 238u [13] and 242Pu [14]. It was established that in the transition to heavier tar-
gets, the values of the corresponding cross sections are reduced by a factor of 10 and the cross section for
the (180, 5n) reaction is 3-5 times greater than the cross section for the (180, 4n) reaction in both cases
[13, 14]. It is possible that the ratio of the cross sections for reactions involving the evaporation of five
and four neutrons observed with uranium and plutonium also holds for curium. One can then suppose that
the maximum cross section for the nuclear reaction 246Cm(180, 5n)256Ku is .10-33 cm2 for an 180 energy
around 100 MeV.
From the ratio between the measured cross section for 259Ku production derived from spontaneous
fission and the estimated total cross section, a spontaneous fission fraction SF/a ?c--- 7% is obtained. This
value is in agreement with the limit SF/a Is 20% given in [10]. It should be noted that the critical remark
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[10] with regard to the chemical separation of kurchatovium [6] were based only on an indirect analysis of
the quantity SF/a for 259Ku which led to the conclusion that this ratio should be less than 0.1%. The Ber-
keley authors then concluded that the cross section for the nuclear reaction 242pu(22Ne-,
5n) as measured
by the spontaneous fission of 259KU should not exceed 5.10'36 cm2 and therefore kurchatovium must not have
been observed in the chemical experiments [6].
The experimental data points up the unsoundness of such criticism. The yield of 259KU in the nuclear
reaction 242pu(22Ne, 5-n)25-.mq-u in the chemical experiments [6] is in good agreement with our data if it is as-
242pu(22Ne, 5n)259
Ku that the total cross section for the reaction ) Ku is 2 .10-33 cm2, as also follows
from the Sikkeland calculations [9]. The unwarranted faith of the authors of [10] in their semi-empirical
extrapolations and their repeatedly expressed scepticism [9, 15] about the possibility of discovering the new
element from spontaneous fission of its isotopes are cause for surprise.
Thus physical experiments on the spontaneous fission of kurchatovium isotopes supplemented by
chemical methods for the identification of transactinide elements yield an unambiguous result relative to
the synthesis of a new element.
In conclusion, the authors thank Academician G.N. Flerov for continuing interest in the work and for
enthusiastic support; they also thank V.A. Davidenko and V.N. Polynov, whose valuable help determined
the possibility of carrying out this work to a considerable extent. The authors are grateful to Yu. V. Polu-
boyarinov for help with the experiments and to the U-300 cyclotron group for providing efficient operation
of the accelerator.
LITERATURE CITED
1. G. N. Flerov et al., At. Energ., 17, No.4, 310 (1964).
2. Yu.Ts. Oganesyan et al., At. Energ., 29, No.4, 243 (1970).
3. G. N. Flerov et al., Proceedings of International Conference on Heavy-Ion Physics, Dubna (1971),
p 125.
4. I. Zvara et al., JINR Preprint D6-3281, Dubna (1967).
5. I. Zvara et al., At. Energ., 21, No.2, 83 (1966).
6. I. Zvara et al., Inorg. Nucl. Chem. Letters, 7, 1109 (1971).
7. A. Ghiorso and T. Sikkeland, Phys. Today, 26, 25 (1967).
8. A. Ghiorso et al., Report UCRL-18667, Berkeley (1968).
9. A. Ghiorso, Proc. 13 Conf. on Chemical Res., Houston (1969), p.107.
10. A. Ghiorso et al., Inorg. Nucl. Chem. Letters, 7, 1117 (1971).
11. A. Ghiorso et al., Phys. Rev. Letters, 22, 1317-(1969).
12. E.D. Donets, V.A. Shchegolev, and V.A-.-Ermakov, At. Energ., 16, No.3, 195 (1964).
13. E.D. Donets, V.A. Shchegolev, and V.A. Ermakov, Yad. Fiz., 271015 (1965).
14. V.L. Mikheev, Yad. Fiz., 5, 1186 (1967).
15. M. Nurmia, Report LBL-66-6, Berkelye (1971), p.42.
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COMECON NEWS
XXIV SESSION OF PKIAE SEV
V.A. Kiselev
In line with the work plan drawn up by the COMECON Permanent Commission on the peaceful uses of
atomic energy, the 24th session of the Commission was held on June 19-23, 1973, in Brno (Czechoslova-
kia).
Delegations from Bulgaria, Hungary, the German Democratic Republic, the Republic of Cuba, Po-
land, Rumania, the USSR, and Czechoslovakia took part in the work of the Commission. It was the first
time that a delegation from Cuba had taken part in the Commission's deliberations.
Upon invitation by the Commission, a representative of the international nuclear instrumentation
economic association known as Interatominiztrument also took part.
The session took up problems facing the Commission in the light of the resolutions adopted at the
XXIV session of COMECON, sessions of the Executive Committee of the Council, and the Comprehensive
Program of further deepening and improvements in collaboration and in the development of socialist econ-
omic integration of COMECON member-nations.
The Commission discussed measures and proposals on collaboration between COMECON member-na-
tions involving development of a reactor facility (water-cooled and water-moderated reactor) of 1000 MW
electric power output, procedures for safe disposal of radioactive wastes by burial, materials on shipping
spent nuclear fuel, topics concerning radiation technology and equipment, nucleonic instrumentation, and
other pertinent topics in nuclear science and engineering.
The Commission also discussed development of a draft program of scientific and technical collabora-
tion between COMECON member-nations with a long-term perspective, on radiation safety in connection
with the expanded use of atomic energy for peaceful purposes.
Appropriate recommendations and solutions are adopted on all of the topics discussed by the Com-
mission.
Translated from Atomnaya Energiya, Vol.35, No.4, p.281, October, 1973.
C 1974 Consultants Bureau, a division of Plenum Publishing Corporation, 227 West 17th Street, New York, N. Y. 10011.
No part of this publication may be reproduced, stored in a retrieval system, or transmitted, in any form or by any means,
electronic, mechanical, photocopying, microfilming, recording or otherwise, without written permission of the publisher. zi
copy of this article is available from the publisher for $15.00.
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COLLABORATION DAYBOOK
A conference on isotope production was held in Prague, April 9-13, 1973. Participating were auth-
orized representatives of Bulgaria, Hungary, the German Democratic Republic, Poland, Rumania, the
USSR. and Czechoslovakia.
The conference discussed a draft of an Agreement on multilateral international specialization and co-
operation in the production of isotope wares, and agreed on a list of such products (numbering 500-odd
items) to be a subject of specialized production in the period up to 1975. The list drawn up includes inor-
ganic compounds, over a hundred tritium-labeled organic compounds, and about 300 14C-tagged compounds;
also over 30 sets of medical isotope equipment and 20 types of sealed radiation sources, and so forth.
The conference judged it feasible to work out proposals aiming at further specialization in the prod-
uction of isotope wares for the 1976-1980 period. In line with this assessment, member-nations of COME-
CON are scheduling engineering cost studies for the 1973-1974 period in this area. The conference dis-
cussed the progress of work on problems taken up under the PKIAE SEV work plan for 1973.
Appropriate decisions were arrived at on all of the topics under discussion.
* * *
The fifth session of the coordination scientific-technical council of COMECON member-nations on
radiation equipment and technology (KNTS-RT) was held April 24-27, 1973, in Warnemunde (East Germany).
Members of the council and experts from Bulgaria, Hungary, the GDR, Poland, Rumania, the USSR, and
Czechoslovakia took part in the deliberations, as well as a COMECON Secretariat staffmember. Nine top-
ics were placed on the agenda.
The council heard a report from the GDR delegation entitled "On industrial realization of radiation
sterilization processes for medical wares," and pointed out that radiation sterilization is at present one of
the most highly developed processes in this area, and that it has been engineered into a full-scale tech-
nological process in a number of capitalist countries. Radiation sterilization processes are in the pilot
stage in the COMECON nations, and will be scaled up to industrial production conditions in the coming
three to five years.
The council discussed measures for industrial utilization of radiation sterilization processes in in-
terested COMECON member-nations. The burden of the measures discussed centered around working out
engineering cost validations of radiation sterilization processes: comparisons of the radiation method of
sterilization and other familiar technological approaches to the problem, selection of the optimum variant
of a full-scale sterilization facility, and ascertaining volumes of production and demand.
The council approved a draft paper entitled "Procedures for determining cost aspects of radiation
practice"; an agenda for a symposium on radiation processing of foodstuffs and agricultural products, to be
held in Sofiya October 15-17, 1973; basic trends and structure of scientific forecasting of the development
of radiation equipment and technology.
The council expressed its agreement with proposals on the structure and nature of the contents of
Unified public health regulations pertaining to the design and operation of radiation facilities; heard infor-
mation on the compilation of preparatory materials for the Unified dosimetric radiation technological pro-
cess monitoring procedures; heard a report delivered by the KNTS-RT chairman on the balance of work
done over the course of 2.5 years, and on ways of bringing measures worked out and approved by KNTS-RT
Translated from Atomnaya Energiya, Vol. 35, No. 4, pp. 281-282, October, 1973.
o 1974 Consultants Bureau, a division of Plenum Publishing Corporation, 227 ,West 17th Street, New York, N. Y. 10011.
No part of this publication may be reproduced, stored in a retrieval system, or transmitted, in any form or by any means,
electronic, mechanical, photocopying, microfilming, recording or otherwise, without written permission of the publisher. /1
copy of this artiele is available from the publisher for $15.00.
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to fruition; confirmed a tentative agenda for the forthcoming sixth session.
* * *
A conference of specialists on radiation processing of foodstuffs and agricultural products was held
in Moscow May 15-18, 1973. The conference was attended by food experts, public health personnel mi-
crobilogists, radiation experts, and other specialists from Bulgaria, Hungary, the GDR, Poland, Ru-
mania, the USSR, and Czechoslovakia, who had been participating in the deliberations of the COMECON
Permanent Commissions on the food industry and on the peaceful uses of atomic energy.
The delegates in attendance at the conference were brought up to date on work in progress in several
countries on the development of technology for applications of radiation processing of foodstuffs with the
object of lengthening storage time, cutting down losses, and intensifying technological processes. The
greatest amount of interest was shown in research findings on combined methods of processing as the most
promising approach on the horizon, as well as in biological and medical publich health oriented research
on deactivation and decontamination of irradiated products.
The conference took note of the need:
? for performing and coordinatingresearchwork of a biological nature to be carried out by specialists
in the food industry, and medical publich health research covering a broad range of topics connected
with studies of deactivation and the nutritional value of irradiated foodstuffs;
? working out quality criteria for irradiated products;
? working out unified approaches in procedures and techniques to be employed in medical and public
health assessments of irradiated foodstuffs, and drafts of unified legislative proposals on realization
of such techniques and procedures in COMECON member-nations.
The conference also discussed proposals for a draft plan of joint research in the field of public health
assessments of irradiated products, and some topics associated with various aspects of acceptance of the
methods, and put finishing touches on the research program for the year 1973.
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INFORMATION
SOVIET ? FRENCH COLLABORATION IN THE FIELD
OF PEACEFUL USES OF ATOMIC ENERGY
B.I. Khripunov
It is now more than a decade that France has occupied one of the leading places in international col-
laboration with the USSR State Committee on the peaceful uses of atomic energy. This collaboration has
been taking place primarily on the basis of two agreements drawn up between the USSR GKAE [USSR State
Committee on the Peaceful U ses of Atomic Energy] and the French Commissariat de P Energie Atomique:
one of these agreements covers joint research in high-energy physics using the 70 GeV accelerator (at
Serpukhov) and the French Mirabel liquid-hydrogen bubble chamber, while the other, a general agreement
dated May 20, 1967, covers a broad range of topics associated with the peaceful uses of atomic energy.
In the current year, the USSR GKAE and the French CEA envisage signing, within the framework of
the above general agreement, a new statement on collaboration which covers a schedule of measures to be
taken in the years 1973-1975. This statement will call for exchanges on fast reactors, plasma physics,
and controlled thermonuclear fusion, desalination of sea water, and other topics.
In May and June of this year, the Soviet Union was visited by a delegation of leading activists of the
French CEA headed by the body's general administrator Andre Giraud. The delegation was staffed by the
head of the CEA's board of international liaisons M. Goldschmidt. The status of Franco-Soviet colla-
boration and the outlook for the development of further such collaboration in the coming years were the
principal topics discussed during the visit.
The delegation visited the Institute of High Energy Physics at Serpukhov; where a large team of
French specialists is currently engaged in research, and also visited scientific research institutes in
Georgia and Armenia, as well as holding talks at the USSR GKAE center.
The two sides offered a high estimate of the results achieved through this visit. In a letter addressed
to the USSR GKAE at the termination of the visit, M. Giraud expressed a "firm conviction that the develop-
ment of collaboration between the USSR GKAE and the French CEA is necessary in an of itself, and also
from the vantage point of improving mutual understanding between our two peoples." '
Translated from Atomnaya nergiya, Vol.35, No.4, p.283, October, 1973.
0 1974 Consultants Bureau, -a division of Plenum Publishing Corporation, 227 West 17th Street, New York, N. Y. 10011.
No part of this publication may be reproduced, stored in a retrieval system, or transmitted, in any form or by any means,
electronic, mechanical, photocopying, microfilming, recording or otherwise, without written permission of the publisher. /I
copy of this article is available from the publisher for $15.00.
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SESSION OF SOVIET ? FRENCH COMMISSION ON
SCIENTIFIC TOPICS
A.V. Zhakovskii
At a regularly scheduled session held May 22-24, 1973 at the IFVE center (High-Energy Physics
Institute, Serpukhov), the Franco-Soviet commission discussed the progress of work with the Mirabel bub-
ble chamber, and the status of joint experimental research on beams of separated particles using that
chamber.
A report delivered by P. Preugny (Saclay) listed various problems that have come up in the opera-
tion and use of the Mirabel bubble chamber, and where notable success has been achievethin working to-
ward solutions. These problems include: reliability of the expansion system, adjustment of thermodyna-
mical parameters, minimization of dust on the walls of the chamber. Nonetheless, in order to achieve a
quality of plates that would render automatic processing of bubble-chamber plates possible, work has to be
continued on improving the performance of some of the systems of the chamber (the illumination system,
the data box, and so on).
Reports on the performance of the separated particles channel in this chamber were made by V.I.
,Kotov. Four work sessions have been completed since adjustment of the optics of the No.7 channel and of
the high-frequency separator was carried out. The separator was in operation a total of 1900 h (including
adjustment time) during that period, and the chamber downtime due to malfunctions of the separator was
kept to about 2%. It was also shown that it is in principle possible to obtain separated beams of K--mesons,
antiprotons, and deuterons with energies to 40 GeV.
E. Pauly (Saclay) and P. F. Ermolov provided the commission with information of the status of cham-
ber experiments and on progress in processing data secured with the use of the chamber (studies of p ? p
interactions and a review verification experiment). On the basis of material obtained after a portion of the
plates had been processed, it was proposed to present appropriate reports to the international conference
on the physics of elementary particles scheduled for September 1973 at Aix-en-Provence (France).
The commission discussed a proposed experiment to be carried out on a beam of 32 GeV antiprotons,
and recommended a further study of this proposal, while at the same time continuing a review verification
experiment with antiprotons.
Reports by B. Delaire (Saclay) and V.I. Moskalev to the commission noted the work load that can be
handled in processing in laboratories participating in the Mirabel bubble chamber program is estimated in
the neighborhood of 500 to 600 thousand viewings of photographs a year as of 1975, and about 500,000 mea-
surements.
The session of work with beams of K+- and K--mesons, with statistics of 30,000 photographs in either
case, is now scheduled to follow next.
In conclusion, the commission took up several topics of an organizational nature.
Translated from Atomnaya Energiya, Vol.35, No.4, p.283, October, 1973.
O 1974 Consultants Bureau, a division of Plenum Publishing Corporation, 227 West 17th Street, New York, N: Y. 10011.
No part of this publication may be reproduced, stored in a retrieval system, or transmitted, in any form or by any means,
electronic, mechanical, photocopying, microfilming, recording or otherwise, without written permission of the publisher. A.
copy of this article is available from the publisher for $15.00.
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CONFERENCES
II ALL-UNION CONFERENCE ON MICR ODOSIMETR Y
V.I. Ivanov
The second All-Union conference on microdosimetry was held June 12-15, 1973 at the Moscow Order
of the Labor Red Banner Engineering and Physics Institute [MIFI].
Microdosimetry is a comparatively young developing branch of applied nuclear physics. Microdosi-
metry is being enlisted in efforts to investigate processes involving transfer and distribution of absorbed
energies within the confines of radiosensitive microstructures upon irradiation of living and nonliving ob-
jects by ionizing radiations. The term "sensitive microstructures" applies here to those formations in
which observable radiation effects are brought about as a result of irradiation (e.g., the living cell or such
subcellular structures as chromosomes).
In view of the tiny dimensions of sensitive microstructures, fluctuations in transferred energy are
? substantial. Methods and ways and means of simulating the energy transfer process accompanying inter-
actions between ionizing radiations and sensitive microstructures are now being worked out, and the rela-
tionship between the microdosimetric variables to be measured and the radiation effects to be observed is
being established.
The second All-Union conference on microdosimetry was staged in line with recommendations adopted
at the first All-Union conference (also held at MIFI, February 5-6, 1970), which took note of the basic sci-
entific trends extent in the field, and then laid the basis for coordinated research inthis area. Balance
sheets on the development of microdosimetric research over the ensuing three-year period were drawn
up at the second All-Union conference on the topic, and a total of 32 scientific papers on the basic trends
were heard and discussed; topics covered included: theoretical aspects of microdosimetry (including the
structure of tracks), experimental equipment in microdosimetry, and interpretation of dose ? effect curves
on the basis of microdosimetric concepts. By the present time, a considerable amount of experimental and
theoretical data has been accumulated on the distribution functions of the principal microdosimetric vari-
ables: the dimension of events and the specific energy, for equivalent tissue volumes with linear dimen-
sions in the range from 0.1 to 10 kt. But these data have yet to be systematized, and even so do not encom-
pass many conditions of irradiation which are of practical importance.
The most common method for measuring microdosimetric variables remains the ionization-pulse
method based on the use of low-pressure proportional counters; wall-less counters have become increasingly
popular in more recent years.
One of the main problems is how to determine the range of applicability of microdosimetry, and also
how to establish the relationship between microdosimetric variables and radiation effects on the basis of
analysis of the experimental data. The special features of the microscopic distribution of absorbed energy
culminate in values of macroscopic dosimetric variables to be determined by the methods of conventional
dosimetry not being in a one-to-one relationship with radiation effects, if the latter are due to damage done
to the sensitive microstructures. The magnitude of the observable radiation effects should be correlated
with microdosimetric variables and with the parameters of the distributions of those variables; the pos-
sibility of establishing some one-to-one relationship between them is what determines the applied value of
microdosimetry.
Much space was given in the reports (and even more so in the discussions) to the practical signifi-
cance of microdosimetry for radiobiology. Most of the reporters concluded that microdosimetry should
be regarded as a tool which will enable radiobiologists to extract additional raw information on the absorbed
Translated from Atomnaya Energiya, Vol.35, No.4, p.284, October, 1973.
o 1974 Consultants Burau, a division of Plenum Publishing Corporation, 227 West 17th Street, New York, N. Y. 10011.
No part of this publication may be reproduced, stored in a retrieval,system, or transmitted, in any form or by any means,
electronic, mechanical, photocopying, microfilming, recording or otherwise, without written permission of the publisher. A
copy of this article is available from the publisher for $15.00.
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energy of radiation, which will expand opportunities for predicting the magnitude of radiation effects on
the basis of physical measurements. It has been pointed out that the possibilities inherent in microdosi-
metry should not be exaggerated insofar as the discovery of the mechanism underlying radiation damage
is concerned. Only in those cases where the model reflecting the mode of damage is known will a juxta-
position of the magnitude of the radiation effect to the microdosimetric variables and to the parameters
of the distributions of microdosimetric variables make it possible to find values of the constants used in the
theory (e.g., the dimensions and number of targets).
The need for microdosimetric backup of radiobilogical experiments relying on equipment simulating
radiosensitive microstructures of a concrete object to be irradiated immediately in the process of bom-
bardment of that object by radiation was underlined at the conference, and the feasibility of extending mi-
crodosimetry techniques to the study of biological effects brought about by radiations emitted by radionu-
clides incorporated into the living organism; background concentrations are included here.
The conference constituted a demonstration of the rising level of research work on microdosimetry.
Conferences of this type are contributing to the task of coordinating scientific research efforts. The third
All-Union conference on microdosimetry is scheduled for two to three years hence.
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MIFI SCIENCE CONFERENCE
V.V. Frolov and V.A. Grigor'ev
The regularly scheduled science conference of instructors, students, and colleagues of the Moscow
Order of the Labor Red Banner Engineering and Physics Institute [MIFI] was held in January 1973. A total
of 367 reports was heard at the sessions of the 24 panels.
The experimental nuclear physics panel heard an interesting report on research on cosmic Y photons,
delivered by B.I. Luchkov et al. Work done by a team of MIFI colleagues conducting research with the ar-
tificial Earth satellite Kosmos-251 revealed a discrete source of high-energy 'Y photons located in the con-
stellation Taurus, and tentatively identified with the peculiar galaxy SC 120. Four more sources of cosmic
1/ emission were detected, with the aid of a Y-ray telescope operating on board the Kosmos-264 satellite, in
the neighborhood of the north pole of the local galaxy, but these also appear to be extragalactic. The re-
port discussed some further pathways of development open to Y-ray astronomy.
A lively discussion was provoked by a report submitted by G. B. Bondarenko et al., on the first ex-
periments designed in a search for the W-boson. The results obtained to date are indicative of the exis-
tence of new and unusual mechanisms at work in generating high-energy muons in nucleon-nucleon colli-
sions.
A report on new nucleus-like systems presented by I.S. Shapiro was the most interesting one pre-
sented at the theoretical nuclear physics panel. The report went into bound states and resonant states of
nucleons and antinucleons with lifetimes corresponding to level widths on the order of 10 to 100 MeV (quasi-
nuclear mesons of mass R-'2 to 3 GeV). Theoretical investigation has demonstrated that there must exist
an integral spectrum of quasinuclear mesons counting over ten levels. Experimental data appearing in the
recent literature offers support to predictions based on theory.
The most interesting reports presented to the plasma physics panel dealt with building thermonu-
clear reactors. For example, a paper by O.A. Vinogradova et al., proposed a new design of electrostatic
recuperator in the form of a system of beveled diaphragms with a linear potential distribution; this system
is capable of producing a recuperation factor of the required value under conditions close to those found in
thermonuclear reactions. Reports by, A.A. Pisarev et al., discusse6 evolution of gas in response to par-
ticles becoming embedded in the vacuum containment shell of a thermonuclear reactor as the reactor in-
teracts with plasma present. As a result of those experiments and computer calculations, the diffusion
paramete-fs and parameters of gas evolution were obtained under conditions of ion bombardment. It was
shown, specifically, that virtually all of the hydrogen present is given off from metals forming the walls
of a thermonuclear reactor at the reactor operating temperature.
The physics of separatory processes panel heard a report by N.A. Kolokol'tsov which outlined a
theory of cascades with heavy enrichment at each stage, and provided formulas useful in calculating sym-
metrical and asymmetrical cascades.
The concluding plenary session of the conference heard an address by MIFI professor Academician
M.D. Millionshchikov. The report offered an analysis of the role played by fundamental scientific research
and by applied scientific research in the development of Soviet society, and in the construction of the ma-
terial-technical base of communism, and also formulated problems facing science colleagues on the facul-
ties of college-level institutions, both from the standpoint of their direct participation in scientific and
technical progress, and in efforts to train cadres and skilled personnel to serve and manage the national
economy of the country.
Translated from Atomnaya Energiya, Vol. 35, No.4, pp.284-286, October, 1973.
C 1974 Consultants Bureau, ,a division of Plenum Publishing Corporation, 227 West 17th Street, New York, N. Y. 10011.
No part of this publication may be reproduced, ;Stored in a retrieval syStem, or transmitted, in any form or by any means,
electronic, mechanical, photocopying, microfilming, recording or otherwise, without written permission of the publisher. /1
copy of this article is available from the publisher for $15.00.
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In addition, the plenary session also heard reports on some of the most interesting scientific ad-
vances achieved by MIFI colleagues. A report by V.G. Varlamov, Yu.P. Dobretsov, B.A. Dolgoshein,
and V.G. Kirillov-Ugryumov cited experimental findings on the interaction between muons and atoms of
the noble gases. It was shown that the reason for the absence of precession of the muon spin in inert gases
immersed in a transverse magnetic field at the muon frequency, as detected in earlier work by those
authors above, is the spin? orbital interaction between the muon and the electron shell of the muonic atom.
When a muon is stopped in neon, a "mesonucleus" or "mesonuclide" (11-2?Nei0)+9 is formed, and that is
equivalent to the nuclide 20F9 with the spin and magnetic moment of a negative muon. In collisions ex-
perienced with target atoms, the neon mesonucleus picks up the electron shell of the fluorine atom. The
presence of the magnetic moment at the electron shell of the fluorine atom is responsible for the paramag-
netic properties of the muonic atom manifested on the mesonucleus (11-20Ne10). Measurements were con-
ducted with the gas target filled with a mixture of gases Ne (p = 42 atm) + Xe (p = 1 atm). It was shown
that the experimental distribution of decay electrons produced as the total moment of the mesoneon atom
precesses in weak magnetic fields (1.1 Oe and 2.1 0e) contains precession frequencies corresponding to
the expected theoretical values, which are approximately 100 times in excess of the precession frequency
of a free muon.,
The study of mesoneon type muonic atoms is opening up fundamentally new opportunities for research
in muon physics and in applications of muon physics.
A paper by S.A. Gonchukov, M.A. Gubin, and E.D. Protsenko, which was awarded the Lenin Kom-
somol [Communist Youth League] prize, presented results of investigations into the properties of multi-
moded gas lasers It was specifically disclosed in the course of these investigations that a gas laser is
capable of operating, under certain conditions, on two closely adjacent axial modes of oscillations. In
that case the interaction or coupling between modes is so strong that otherwise insignificant losses or
amplification of one of the interacting modes will bring about a drastic redistribution of the intensities of
the modes. Utilization of this effect to advantage in lasers with a nonlinear absorbing cell has made it
possible to enhance contrast in resonances by almost two orders of magnitude in power output, and to nar-
row the width of the resonances appreciably. That has resulted in frequency stability R110-14 with an av-
eraging time of 100 sec (for a laser one meter in length).
A report submitted by M.A. Kuzimin and V.V. Khromov dealt with the development and practical
acceptance in theoretical investigations of a set of ROKBAR programs designed to facilitate the search for
the,optimum variant of a fast reactor with due account taken on interactions between the thermal, neutron-
physics, strength, and cost characteristics of such a reactor. The optimality criteria invoked in this ap-
proach are: specific computed losses in generating 1 kWh electric power, the doubling time of the system
of breeder reactors, the specific fuel loading in the cycle, and so forth. The solution of the optimization
problem is arrived at through an iterative procedure on the basis of the generalized theory of small per-.
turbations and the method of linear programming.
Operating experience with this set of programs has shown that the ROKBAR program can be used to
find ways of improving the engineering cost features of a nuclear power station based around fast reactors,
with a substantial reduction in computer time.
A report by I. S. Shedrin dealth with the nation's first functioning U-30 electron accelerator, which
operates in the three-centimeter wavelength range. Conversion to that range now expands possibilities
for building miniature sources of radiation useful bringing about radiation effects in a variety of instru-
ments and materials, for devising simulations of sources of 13-radiation with flux density greater than 1010
cm-2 ? sec-1, for simulation of certain other problems and verification of concepts related to design pro-
jects, and for designing large accelerator complexes, etc.
The U-30 accelerator is itself a variant of a stationary laboratory facility and is designed to raise
the ,energies of the accelerated electrons to 2 MeV, with a mean current of 10 AA. The machine can be
operated in conjunction with various focusing systems. The control and supply systems are transistorized,
so that size is greatly reduced, while reliability is improved, and it is now possible to employ an auto-
matic system for bringing the accelerator to operating conditions. The system is broken up in design
terms into functional modules, is compact, transportable, and reliable in service. The external format
of the accelerator conforms to current esthetic requirements. The U-30 model is the base model for a
series of accelerators to be designed for the three-centimeter wavelength range. A possible new genera-
tion of 4.6 MeV and 8 MeV accelerators designed by size and concomitant increments in both the accel-
erator and the control system is in the wings.
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SYMPOSIUM ON HEAVY-CURRENT FIELD-EMISSION
PLASMA ELECTRONICS
G.O. Meskhi
For over thirty years, research on electric insulation provided by vacuum gaps, and on phenomena
associated with breakdown in vacuum, has been carried on at many laboratories throughout the world.The
nature of the insulating properties of vacuum and of discharges struck in vacuum is associated with a vari-
ety of phenomena occurring both on the surfaces of electrodes and in the vacuum gap per se. Extensive
research on those phenomena over the course of recent decades has been rendered possible by the avail-
ability of equipment for shaping high-voltage pulses with widths of several nanoseconds, and by the develop-
ment of methods for recording rapid processes. This research has culminated in the design of powerful
sources of electrons and x-rays for this work.
We should take note of the two most salient trends in this area: 1) designing powerful CW and pulsed
sources of electrons utilizing an arc discharge struck in a vacuum. The advances attained in this trend are
characterized by the electron guns employed in various technological processes (such as welding, cutting
metals in vacuum, etc.); 2) electron sources based on field emission and meeting the needs of the elec-
tronics industry, and specifically those widely utilized in electron microscopes, to which we can added
powerful sources of electrons and x-rays that have been devised in recent years and which make use of the
initial stage of vacuum breakdown (processes developing within the first 100 to 200 nsec after voltage is
applied). Facilities useful in producing electron beams with currents as high as several megaamperes and
energies to 15 MeV, with pulse widths to 100 nsec, are now available as an outcome of this work.
Symposia held once every two years in the USA since 1964 on coordination of research in the field of
electrical insulation and discharges in vacuum were broadened to an international status starting with 1968.
A symposium on field-emission plasma heavy-current electronics organized by the Siberian Division
of the USSR Academy of Sciences and the Ministry of Higher and Middle Special Education of the RSFSR
(MV i SSORSFSR) on the initiative of the Atmospheric Optics Institute of the Siberian Division of the USSR
Academy of Sciences [IAO SO AN SSS11] and the Tomsk Institute of Automated Control Systems and Radio
Electronics of the MV is SSORSFSR, was held in Tomsk May 15-17, 1973. This symposium attracted over
130 scientists from various cities throughout the country. Fifty-odd original papers and tutorial review
papers were presented. The work of the symposium took place in two panels: the first discussed electron
emissior properties of a stationary plasma and gas-discharge sources of electrons; the other discussed
electron emission properties of nonstationary plasma and generation of powerful electron beams. The
huge volume of information presented at this symposium rules out any but a brief coverage in this short
article. We therefore restrict the discussion here to the basic problems under discussion at that gather-
ing.
?
1. Elucidation of the mechanism of "explosive emission" and conditions governing the transition from
field emission to "explosive emission." These topics were discussed in contributions by G. N. Fursei,
G.A. Mesyats, S.P. Bugaev, and others.
The electric field responsible for emission of electrons from a metal is determined by the surface
microgeometry, and can be increased by a factor of ten to a hundred, on microscopic corona points, over
the field governed by the macrogeometry of the electrodes. The gain of such a field on microscopic corona
points is a function of the ratio hir, where h is the height and r the filleting radius of microasperities.
Translated from Atomnaya Energiya, Vol.35, No.4, pp.286-287, October, 1973.
? 1974 Consultants Bureau, a division of Plenum Publishing Corporation, 227 West 17th Street, New York, N. Y. 10011.
No part of this publication may be reproduced, stored in a retrieval system, or transmitted, in any form or by any means,
electronic, mechanical, photocopying, microfilming, recording or otherwise, without written permission of the publisher. A
copy of this article is available from the publisher for $15.00.
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When large currents are taken off an emitter in response to a strong electric field, and also as a re-
sult of Joule heating and the Nottingham effect, the corona micropoint explodes within a certain time, to
form a cathode-sheath flare. From that instant on, the plasma of the cathode-sheath flare becomes the
emitting zone. The rate of expansion of the plasma so formed is more or less the same 2 .106 to 3 ? 106
cm/sec, for several materials investigated (copper, tungsten, aluminum). A low rate of expansion of the
flare has been detected in the case of lead 106 cm/sec). The time of onset of the "explosive emission"
process, reckoned from the instant the voltage pulse is applied (time delay td), fluctuates over a wide range
(approximately from 10 nsec to 10 ?sec) and is associated with the density of the current being drawn off.
The relationship j2td P-Iconst is now established. This dependence has been confirmed in some theoretical
and experimental research efforts. In this formula, the constant is dictated by the properties of the cath-.
ode material, and is 4.5 '109 in the case of tungsten.
2. The development of cathodes in which the plasma prepared beforehand serves, as the emitting zone.
D.I. Proskurovskii, G.P. Bazhenov, and colleagues have demonstrated through direct measurements
that the plasma of the cathode-sheath flare stimulates effective emission of electrons from portions of the
cathode enveloped by plasma. New cathodes based on emission of electrons from preorganized plasma
were reported on at the symposium. The plasma can form in this case as a result of surface breakdown
on A cathode, either in response to a preliminary pulse, or by preliminary filling of the anode ? cathode
gap.
3; The utilization of polymeric films in diagnostics of heavy-current relativistic beams of electrons.
Contributions by V. B. Sannikov discussion work using viniproz and astrolon type polymeric films
sandwiched with thin conducting interlayers in order to eliminate space charge determine the geometric
I
dimensions of the beams and the energy spectrum (according to the degree of fogging of the films when
traversed by the electron beam). The film fogging mechanism remains obscure to date. The maximum
allowable current density up to which the film remains intact is 5 kA/cm2. The energy resolution in this
method is several kiloelectron-volts at 100 keV electron energy.
4. Development of heavy-current electron accelerators through reliance on inducative shaping corn-
ponents.
Designs of electron accelerators using an inductance as the shaping component were discussed at
the symposium, and well as experimental research findings obtained with such accelerators. Current
switching on a diode is achieved by means of a circuit breaker which utilizes the explosion of thin wires and
a high-pressure spark discharge switch. Pulses of electron current to 8 kA were produced with energies
to 1 MeV, and pulse width .> TE, i.e., the anomalous electron-
ic thermal conductivity predominating. It was affirmed in contributions by American physicists working
with the ST machine and reporting out their results at the Madison 1971 conference and Grenoble 1972 con-
ference, that TE Tp, and that there was no need to suggest the existence of anomalous electronic thermal
conductivity as a relevant factor.
It is noteworthy that this view is shared by the physicists working on the Ormak machine. At the
same time, results of the latest ST experiments, reported out at this symposium, show TE Tp/5.
Matters are somewhat different with the thermal conductivity of plasma ions. All of the available
experimental data on ion temperatures are in close agreement with the familiar L.A. Artsimovich formula
derived under the assumption that the sole mechanism of energy loss by ions is neoclassical thermal con-
duction, while the collision frequencies correspond to the plateau on the frequency dependence of the ther-
mal diffusivity. On that basis, Soviet physicists several years ago inferred the classical nature of the
behavior of ions in the Tokamak. That inference has not been at variance with results reported later by
American investigators. While paying close attention to more recent indications that the ion temperatures
continue to conform to the plateau formula, we see that the plasma parameters are indicated by estimates
to correspond to the region of infrequent collisions. The same effect was encountered with the Ormak
machine, where the shift observed was even further onto the region of infrequent collisions. The observed
discrepancies between experimental data and neoclassical theory according to the Ormak findings can be
eliminated by taking into consideration the fact that energy losses by ions occur through charge transfer.
Consequently, the ionic thermal conductivity in the region of infrequent collisions apparently conforms to
the neoclassical law. But that conclusion is based on the assumption that a coulomb mechanism of en-
ergy exchange between ions and electrons is operative. If the flow of energy from electrons to ions ex-
ceeds the coulomb variant, then the ionic thermal conductivity must be anomalous. A serious argument in
support of the neoclassical ionic thermal conductivity, which is not associated with the above assumption,
can be found in the experimental results on adiabatic compression of plasma on the ATC machine that were
reported at the symposium.
One major problem is that of investigating whether a stable plasma can be obtained at low values of
the stability ratio 44. It is known that when q declines to three-quarters, there is a runaway instability in
the plasma. A report devoted to research on the Ormak machine pointed out that a decline in q in the
range q(a) < 5 (where a is the radius of the diaphragm) brings about a shorter plasma confinement time
even in the absence of such a runaway instability. A report dealing with experiments on the T-6 machine
(USSR) showed that discharges such that q(a) "-=, 1.2, retaining their stability for 1-2 msec, can be success-
fully obtained in cases where the surface of the plasma pinch is situated fairly close to the surface of the
conducting liner, i.e., a/b >0.8 (where b is the radius of the transverse section through the conducting
liner). On the basis of these data, as well as experiments conducted on the Alcator machine (USA), in
which a relatively stable plasma was generated at q 1.7, we can infer that the range of values 1 < q(a)