SOVIET ATOMIC ENERGY VOL. 42, NO. 1
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Russian Original Vol. 42, No. 1, January, 1977
. , July, 1977,
ATOMHAFI 3HEP!'I1H
(ATOMNAYA ENERGIYA)
TRANSLATED FROM RUSSIAN
CONSULTANTS BUREAU, NEW YORK
SATEAZ 42(1) 1-90 (1977)
SOVIET
ATOMIC
ENERGY.
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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 Abstracts, Current Contents, and
Nuclear Science Abstracts.
Soviet Atomic Energy is a cover-to-cover translation of,Atomnaya
Energiya, a publication of the Academy of Sciences of theUSSR.
An agreement with the Copyright Agency of the USSR (VAAP)
makes available both advance copies of the Russian journal and
original glossy photographs and artwork. This serves to decrease
the necessary time lag between publication of the original and
publication of. the translation and helps to improve the quality
of the latter. The translation began with the first issue of the,
'Russian journal.
Editorial Board'of;Atomnaya Energiya:
Editor: 0. D. Kazachkovskii
Associate Editor: N. A. Vlasov
A. A. Bochvar V. V. Matveev
N. A. Dollezhal' M. G. Meshcheryakov.
V. S. Fursov , V. B. Shevchenko
I. N. Golovin V. I. Smirnov
V. F. Kalinin A. P., Zefirov
A, K. Krasin
ti
Copyright ? 1977 Plenum Publishing Corporation, 227 West 1 7th Street, New York,
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mechanical, photocopying, microfilming, recording or otherwise, without vyritten,
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Consultants Bureau journals appear about six months after the publication oi,the
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CONSULTANTS BUREAU, NEW YORK AND LONDON.
b
0
227 West 17th Street
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Published monthly. Second-class postage paid at Jamaica, New York 11431.
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SOVIET ATOMIC ENERGY
A translation of Atomnaya Energiya
July, 1977
Volume 42, Number 1
January, 1977
CONTENTS
Engl./Russ.
ARTIC LES
.i Reactivity Effects in a BN-350 Reactor - V. V. Orlov, M. F. TroyaTiov, V. I. Matveev
G. B. Pomerantsev, N. D. Tverdovskii, G. M. Pshakin, E. M. Khalov,
A. P. Ivanov, V. S. Shkol'nik, A. I. Voropaev, and A. V. Danilychev ...........
1
3
Model of Irradiation Creep of Ceramic Fuel Materials - V. B. Malygin,
Yu. K. Bibilashvili, I. S. Golovnin, and K. V. Naboichenko ....................
6
8
Temperature Dependence of Erosion of Alloys of Vanadium and Niobium during
Bombardment with Helium Ions - B. A. Kalin, N. M. Kirilin, A. A. Pisarev,
D. M. Skorov, V. G. Tel'kovskii, and G. N. Shishkin .........................
12
13
Investigation of Radiation Swelling in the Zirconium-Hydrogen System - P. G. Pinchuk,
V. N. Bykov, V. A. Karabash, Yu. V. Alekseev, and A. G. Vakhtin ............
15
16
Estimate of Perturbations in Solving Nonuniform Neutron Transport Problems
by the Monte Carlo Method - D. A. Usikov ..................................
18
19
Measurement of Average Energies of 233U, 235U, and 239Pu Fission Neutron Spectra by a
Relative Method - L. M. Andreichuk, B. G. Basova, V. A. Korostylev,
V. N. Nefedov, and D. K. Ryazanov ...................... ................
23
23
Spectrum of Low-Energy Neutrons from the Spontaneous Fission of252Cr
- P. P. D'yachenko, E. A. Seregina, L. S. Kutsaeva, V. M. Piksaikin,
N. N. Semenova, M. Z. Tarasco, and A. Laitai ..............................
26
25
Theory of Separation Cascades Consisting of Elements with Several Outlets
- B. Sh. Dzhandzhgava, V. A. Kaminskii, N. I. Laguntsov,
G. A. Sulaberidze, and V. A. Chuzhinov ......................................
30
29
RE VIEWS
Detection of Flaws in Metal of Atomic Power Plant Equipment during Operation
- B. R. Brodskii and E. F. Monina .........................................
35
34
DEPOSITED PAPERS
Optimization of the Cost of the Structural Design of the Radiation Shielding and the
Sanitary-Safety Zone of Charged-Particle Accelerators - Yu. A. Bolchek and
A. Ya. Yakovlev ...........................................................
42
41
Theory of Unsteady y Transport in the Small-Angle Scattering Approximation
- V. S. Galishev and G. Ya. Trukhanov ......................................
43
41
Intensity of y Radiation from an Activated Cylinder - G. S. Vozzhenikov and
A. L. Zagoryuev ...........................................................
44
42
Analysis of the Procedure for Measuring Fast Monoenergetic Neutron Fluxes with
Proton Recoil Proportional Counters - A. N. Davletshin and V. A. Tolstikov ....
44
43
LETTERS TO THE EDITOR
Application of Direct-Charge Detectors for Power Monitoring in Water-Cooled Water-
Moderated Power Reactors - L. I. Golubev, V. A. Zagadkin, M. G. Mitel'man,
A. B. Morev, N. D. Rozenblyum, and V. V. Fursov ...........................
46
44
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CONTENTS
Engl./Russ.
Heat Production and Fragment Capture Cross Section in Thermal Reactors
- P. E. Nemirovskii and V. A. Chepurnov ................................... 48 45
Effect of Approximating the Scattering Indicatrix and Representation of the Constants on
the Results of Calculating the Field Characteristics beyond an Iron Barrier
- G. Sh. Pekarskii, Yu. Ya. Katsman, and G. A. Kucher ...................... . 50 47
Flow rate Measurement by Means of Correlating the Random Signals of Thermocouples
in Circuits with a Natural Circulation of Coolant - V. M. Selivanov,
A. D. Martynov, Yu. A. Sergeev, V. S. Sever'yanov, A. P. Solopov,
V. I. Sharypin, D. Pallagi, S. Horanyi, T. Hargitai, and S. Ty6gyer ........... 53 49
Neutron Resonance Parameters of 245Cm for Neutron Energies in the 1-30-eV Range
- T. S. Belanova, Yu. S. Zamyatnin, A. G. Kolesov, V. M. Lebedev, and
V. A. Poruchikov ........................................... ............. 57 52
Effect of Pressure in Light Water and Benzene Vapors on the Total Interaction Cross
Section for Slow Neutrons - V. E. Zhitarev and S. B. Stepanov ................ 59 53
Certain Characteristics of a Personal Film Dosimeter with "K" Emulsion
- M. G. Gelev, M. M. Komochkov, I. T. Mishev, Yu. V. Mokrov, and
M. I. Salatskaya ............................................................ 61 55
Cross Sections for the Fission of 235U and 239Pu by 2-; 24-, 55-, and 144-keV Neutrons
- K. D. Zhuravlev, N. I. Kroshkin, and L. V. Karin .... .................. 62 56
Possibilities of Recording Thermal Neutrons with Cadmium Telluride Detectors
- A. G. Vradii, M. I. Krapivin, L. V. Maslova, O. A. Matveev,
A. Kh. Khusainov, and V. K. Shashurin .......... 64 58
Total Cross Section Measurement for the Reaction T(t,2n)4He - V. I. Serov,
S. N. Abramovich, and L. A. Morkin ....................................... 66 59
CHRONICLES OF THE COMECON
Journal of Cooperation ........................................................... 70 62
INFORMATION: SEMINARS, CONFERENCES, AND MEETINGS
i Soviet-French Seminar on Fast Reactors - P. L. Kirillov ......................... 73 64
/Soviet-American Symposium on Fusion-Fission Reactors - V. I. Pistunovich and
G. E. Shatalov ............................................................. 75 65
-Eighth International Conference on Nondestructive Testing - V. V. Gorskii .......... 76 66
Chemical Equipment at ACHEMA-76 Exhibition - S. M. Karpacheva ................. 78 68
Meeting of IAEA Experts on the Technology of Inertial Plasma Confinement Systems
V. M. Korzhavin and V. Yu. Galkin ......................................... 80 69
Third Session of Soviet-American Coordinating Commission on Thermonuclear Energy
- G. A. Eliseev ........................................................... 82 71
The International Conference Neutrino-76 V. D. Khovanskii ...................... 84 72
Second Seminar on Mossbauer Spectroscopy - V. A. Povitskii ...................... 86 74
BIBLIOGRAPHY
Problems of the Metrology of Ionizing Radiation - Reviewed by M. V. Kazarnowskii ... 88 75
E. G. Rakov, Yu. N. Tumanov, Yu. P. Butylkin, A. A. Tsvetkov, N. A. Beleshko,
and E. P. Poroikov. The Principal Properties of Inorganic Fluorides
- Reviewed by S. S. Rodin and Yu. V. Smirnov .............................. 89 76
The Russian press date (podpisano k pechati) of this issue was 12/24/1976.
Publication therefore did not occur prior to this date, but must be assumed
to have taken place reasonably soon thereafter.
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ARTICLES
REACTIVITY EFFECTS IN A BN-350 REACTOR
V.
V.
Orlov, M. F. Troyanov,
UDC 621.039:516.25:621.
V.
I.
Matveev, G. B. Pomerantsev,
039.516.2:621.039.519
N.
E.
V.
and
D.
M.
S.
A.
Tverdovskii, G. M. Pshakin,
Khalov, A. P. Ivanov,
Shkol'nik, A. I. Voropaev,
V. Danilychev
Temperature Effect of Reactivity
First measurements of the temperature effect of reactivity were carried out on a BN-350 reactor during
a zero load test from December 1972 to January 1973. These measurements were of a preliminary nature and
were carried out basically to estimate temperature corrections to the critical state of the reactor in experi-
ments.
The basic difficulty in measuring the isothermal temperature coefficient is connected with the determina-
tion of the reactor temperature and stabilizing it during the measurements. Temperature control in the BN-350
reactor was achieved by means of thermocouples set above the fuel elements (-80 cm above the upper bound-
ary of the active zone) and close to the output manifold.
The first measurements of the temperature coefficient showed a considerable scatter - (2-6)?10-5(Ok/k)
?C-I, which was caused by the small interval of temperature measurements (5-10?C), the inaccuracy of the
temperature measurements made with standard apparatus, as well as by the non-steady-state nature of the
temperature field in the reactor, as evidenced by the discrepancy of thermocouple readings at different mea-
suring points.
The most representative experiment during this run was one [1,2] in which the change in reactivity was
measured on heating the reactor from 152 to 242?C and subsequently cooling it to 222?C. The experiment was
carried out with continuous heating of the reactor at a rate of 3-5 deg C/h as a result of electrical heating of
the primary and secondary circuits switched on to full power. The pumps in the primary circuit operated at
250 rpm, and the reactor power was maintained at a level of ti 100 W.
Slow heating and constant flow rate ensured a sufficiently uniform temperature field throughout the re-
actor volume. Uniformity of heating was controlled from the thermocouple readings and the drift of the reac-
tivity meter [3]. Error in temperature measurements was reduced to ?0.2?C in the experiments.
Measurements of the temperature effect were repeated during the power trial. In these experiments the
reactor was heated and subsequently cooled in the range 209-289?C as a result of the energy released by the
operating pumps of the primary circuit and the power of the reactor itself, which was 3-5 MW. The temper-
ature was stabilized with the aid of steam generators. Coolant circulation was achieved by the operation of
four pumps working at their rated revolutions. Two loops each of the secondary and tertiary circuits were
also switched in. The temperature was measured by stages corresponding to the stages of pressure in the
steam generators. For reliable temperature stabilization the reactor was maintained at each stage for 3-7 h.
The criterion of stabilization was a discrepancy in the thermocouple readings within the limits -'1.5?C, and a
drift of the reactivity meter of less than 0.01 cent/h.
The experimental results are shown in Fig. 1. In processing results of the measurements the connection
between the reactivity and temperature was established from readings of the thermocouples situated above the
fuel elements. These were processed by the least-squares method on the assumption that the experimental
errors were independent.
Translated from Atomnaya Energiya, Vol.42, No.1, pp.3-8, January, 1977. Original article submitted
April 20, 1976.
This material is protected by copyright registered in the name 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 $7.50.
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500 550 600 T,? K 300 500 7000
Fig.1 Fig.2
Fig. 1. Variation of reactivity with isothermal heating of the reactor: ) calcula-
tions; 0 and +) first and second experiments, respectively.
Fig. 2. Doppler effect, from investigations on uranium and iron, as a function of the
temperature (calculations with perturbation theory): 1) whole reactor; 2,4) zones of
low and high enrichment; 3, 5) lateral and end-face shields; 6) iron in the whole reactor.
In determining the error of the isothermal temperature coefficient of reactivity the statistical error in
measurements of the temperature, reactivity, and their connection with each other was taken into account as
well as the systematic error associated with the fact that the regulating devices have an efficiency that is not
specified.
Processing of the experiments yielded the mean value of the isothermal temperature coefficient of reac-
tivity in the interval 180-280?C, which was equal to - (3.48 ?0.32)?10-5(Ok/k)?C-1.
Calculated results were obtained using the catalogs of constants BNAB-70 and ARAMAKO based only on
nuclear data, and the programs written in [1,2,4]. Calculations of the change in reactivity from the expansion
of the sodium on heating (sodium component of the temperature effect) were carried out with first-order per-
turbation theory in one-dimensional geometry [4]. Corrections were introduced into the calculated results for
changes in self-shielding factors of the medium cross sections, and changes in the reflecting properties of the
end-face shields. This last correction was found by calculating the change in the effective breeding coefficient
by a synthetic method in two-dimensional geometry (ARAMAKO-RADAR program) [2].
The reactivity effect with the change in geometric characteristics during heating of the reactor is nega-
tive because of the increased neutron loss. It was calculated from first-order perturbation theory using the
similarity method [5].
Radial expansion, determined by the expansion of the steel slab of the lower collector, leads to a change
in reactivity given by the relation PR = -0.457 (OR/R), where R and OR are the radius of the active zone and
its change, respectively.
The calculated value of the change in reactivity as a result of axial expansion depends on the model
adopted. For the initial stage of reactor operation under consideration, it was assumed that the fuel is not
attached to the shielding and can expand freely. In this case the axial expansion of the reactor is determined
by the increase in height of the fuel rod. The effects of expansion of the steel structures in the axial direction
and the displacement of the regulation devices relative to the active zone. on heating turned out to be small
compared with expansion of the fuel. The dependence of reactivity on axial expansion of the reactor is defined
by the relation PH = - 0.222 (OH/H), where H and OH are the height of the active zone and its variation, re-
spectively.
The Doppler effect on reactivity, caused by the temperature dependence of the resonance cross sections,
was calculated from perturbation theory. Application of perturbation theory for comparatively small changes
of fuel temperature allow us to take into account the change in self-shielding factors for resonance cross sec-
tions more accurately than the calculation of two reactor states with different temperatures, and is convenient
for analyzing components of the Doppler effect.
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Fig. 3. Change in reactivity for change in
power in the range 0-52% of the rated power:
?) measurements during a power test with
power being taken up by three loops; later
outputs on three (p O) and four (+?0) loops;
1) calculations for rated operation of the plant;
2) for operation with three loops.
It was shown in [2] that a more accurate determination of the neutron spectrum in the region below 10
keV is very important in calculating the Doppler effect. For this purpose the ARAMAKO-M-26 program was
used [4], in which the group neutron delay cross sections are determined after multigroup calculations of the
spectrum inside each group.
The contribution from the end-face shields was found from calculations of the change in Keff by a pro-
gram using a synthetic method in a two-dimensional model (ARAMAKO-RADAR program [2]).
The magnitude of the Doppler constant was calculated in the range 300-2100?K [T(ak/8T) = 0.007], as
well as the Doppler component of the temperature effect on heating of the fuel.
Data on the temperature dependence of the capture cross sections of iron, chromium, and nickel [6]
were used as a basis for determining the contribution from the Doppler effect to the change in reactivity for
these materials, which constituted - 8 ro of the total Doppler effect. The calculated dependence of the Doppler
effect on reactor temperature for uniform heating is given in Fig. 2.
Calculated data on the temperature coefficient of reactivity are given in Table 1 comparing it with the
measured quantity. It can be seen that the results are roughly 10% lower than the experimental data, and are
within the limits of the estimated error of measurement. The calculated quantity can be refined chiefly by
increasing the accuracy of the calculations of the Doppler effect and the sodium expansion effect. With regards
to the latter, the BFS [7] experiments definitely indicate that there is an excess in the calculations of the con-
tribution from the positive component in the overall change in reactivity as the density of sodium decreases.
As a result of this, the calculated temperature coefficient should turn out to be larger than that given in Table
1 after the constants are refined.
Power Reactivity Effect
For a constant boolant flow rate the power reactivity effect is determined by the same processes as the
temperature effect. The difference lies in the fact that, as a result of nonuniform heat liberation, a nonuni-
form temperature field arises in the fuel, in connection with which the relative contribution of the various
processes changes compared with the temperature effect. The Doppler component makes the basic contribu-
tion (up to ^-70%) to the effect. The contribution from the change in reactor volume is determined by the axial
expansion of the fuel (' 20%) and by the appreciably smaller radial expansion (-5%). The contribution from
the change in coolant density is also small (-5%).
The experiments for measuring the power effect were carried out with a more fully loaded active zone
as compared with the zero load trial stage. The loading was carried out according to the condition for the
reactor to operate at a power of - 50% of the rated power. The power effect measurements were performed
while the reactor was being run up to power. Results of the power effect measurements are given in Fig. 3
for various states of the active zone with regard to fuel consumption, and for different numbers of operating loops.
In processing the experimental data, the following facts were taken into account: since the sodium tem-
perature at the reactor input varied from one power level to another, that part of the reactivity effect due to
isothermal heating of the reactor was eliminated by reducing all the states to an input temperature of 220?C,
using the temperature coefficient of reactivity 3.5.10-5 (Ak/k)?C-1; the power effect was determined as the dif-
ference in reactivity states for different power levels, all other conditions being equal (input temperature, po-
sition of the control apparatus, and coolant flow rate). The power was determined from the thermal output of
the tertiary circuit.
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TABLE 1. Isothermal Temperature Coeffi-
cient of Reactivity and Its Components (aver-
age value in the range 180-280?C)
rated coolant
operation on
k
flow rate
three loops
oc-r
s0?, k
0-100 %1
0-:.0 0
u-:30 ' , I 0-50
Sodium expansion
-0,62
Sodium expansion
64
47
Radial expansion of zone
-0,83
Axial expansion of zone (calc.
Radial expansion
62
31
41
from fuel)
Axial expansion
228
114
76
126
ler effect: on fuel
Do
-1,39
Doppler effect
729
436
336
472
pp
on steel
-0,10
Total effect
1083
613
465
6813
coeff.
Total caic
-3,18
Power coeff. in given
.
Experimental value
-3,48+(),32
power range.
5
10
Lsk'k MW
While special measurements were being made of the power effect during a power test, a good deal of
attention was paid to stabilizing the reactor state for which the effect was being determined. Thus, the ex-
perimental results have only a small scatter. When using data obtained while running the reactor up to power
after shutdowns, the states were not stabilized carefully enough, and the experimental points have a greater
scatter (see Fig. 3). In the comparison of calculations and experiment, the theoretical model allowed for the
appropriate coolant flow rate and power level.
Corresponding to the power distribution of the active zone, the reactor was divided into zones where
the flow rate was throttled in such a way that the heating of coolant in each zone and the casing temperature
of the most heavily loaded fuel elements in them were roughly the same. On this basis, the sodium compo-
nent of the power effect is defined as follows:
n
P - 2 ( d p ) i ,t; _ 4 _ ) u.es. (fit` At u.est?)
Na dt Na 2 ' dt , pia
where n is the number of throttling zones, (8p/at)Na is the sodium component of the i-th zone in the isothermal
temperature coefficient of reactivity, (8p/8t)u.e.s? is the sodium component of the upper end-face shield in
the isothermal coefficient of reactivity, Oti and Ltu.e.i are the mean coolant heating in the i-th zone and the
upper end-face shield of this zone. This approach lets us allow accurately enough for the contribution to
the power effect from each zone of the reactor in accordance with the heating of its coolant content, including
the contribution from the end-face shields as well.
Radial expansion in the power effect is determined by heating of the walls of the fuel cassettes. Buckling
of individual cassettes as a result of nonuniform temperature over the cassette perimeter is quite negligible.
Two extreme cases were considered when analyzing the radial expansion of the reactor:
a. The cassettes are set in the reactor in such a way that the gaps between them are maintained, and
the cassette walls expand within the limits of the gaps. In this case the effect is minimal since the
change in radius of the active zone is determined only by the expansion of the cassettes at the edges.
b. The cassettes touch each other and the active zone expands like a single steel structure. As a re-
sult of this the zone assumes the shape of a truncated cone instead of a cylinder. In this case the effect
is a maximum.
Since the true position of the cassettes is undetermined, the mean position was used in the calculations.
It should be noted that the inaccuracy of the expansion model is unimportant for the total power effect in view
of the negligible contribution made by this component. The axial component of expansion is more important.
The indeterminacy of this component depends on the connection between the fuel and its jacket, and on the ac-
curacy with which the temperature field of the fuel, and the expansion of fuel and jacket have been calculated.
The calculated value of the axial component of the expansion effect was determined from the mean fuel temper-
ature over the whole active zone. Because of the small fuel consumption it was assumed that the fuel expands
independently of the jacket.
In addition to the error in determining the Doppler effect, calculations of the fuel temperature in the
reactor and making allowance for its nonuniformity play an important part in calculating the Doppler component
of the power effect.
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The total value of the Doppler component is
T
PD = J \ pD (T, r) dr dT,
V To
where p'D (T, r) is the Doppler coefficient of reactivity for a volume element dr at the fuel temperature,
pD is the total value of the Doppler component as the power is varied from zero to the rated power, V is the
volume of the reactor, and To and T are the fuel temperatures at zero power and at the rated power, respec-
tively.
The fuel temperature was calculated for fresh fuel from the power distribution for the initial loading
of the active zone. A component associated with the construction materials was taken into account in calculat-
ing the magnitude of the Doppler effect.
Calculated data for the power effect are given in Table 2 with a breakdown into individual components,
while Fig. 3 compares calculated and experimental results for the reactivity effect as a function of power. For
a power of - 50% the experimental value for the change in reactivity averaged over all the points is roughly
10% higher than the calculated value. At power levels of -30% the discrepancy is greater, but the scatter of
the points is also more important here.
In connection with the fact that the Doppler effect makes the main contribution to the change in reactivity
as the power varies, the cause of values of the calculated power effect-which are lower as compared with ex-
periment must be sought above all in the calculations of the fuel temperature and of the neutron spectrum in
the region below 10 keV.
Reactivity Effect Dependent on Fuel Depletion
Determining the reactivity effect connected with the change in isotope composition of the fuel on being
consumed and the efficiency coefficient is of considerable interest both directly as well as from the point of
view of its use together with other functionals in order to correct the constants.
Operation of the reactor at power for a fairly long time enabled us to obtain a first experimental esti-
mate of the effect of depletion on a basis of -36 effective days. The reactivity effect was defined by the dif-
ference in reactivity states of the reactor for various power outputs, but with other conditions the same (posi-
tion of the rods, power, input temperature of the coolant and its flow rate)..
The error in determining the depletion effect in this way is basically connected with the accuracy of
determining the operation integral for the reactor at power. The experimental value for the depletion effect
reduced to a single month of reactor operation at rated power (30 days at 1000 MW), came to -(0.46 ?0.06)%
Ok/k.
The fundamental difficulty in determining the depletion effect theoretically is connected with making
sufficiently correct allowance for the nonuniformity of depletion over the active zone and the accumulation of
plutonium in the shields. The calculated value of the depletion effect was found by perturbation theory from
the volume integral
Pdep- (r),.-1; (r) dr,
where n is the number of nuclides whose concentration changes during the process of operation, pi (r) is the
efficiency of a single nucleus of the i-th nuclide at the point r, DAi (r) is the change in concentration of the
i-th nuclide at the point r after 30 effective days.
The calculated value of the effect obtained in this way came to - 0.411% Ok/k (depletion of 235U and 238U,
-1.25 and 0.065% Ak/k; accumulation of 236U, fission fragments, and 239pu, - 0.046, - 0.149, and 0.972% Ok/k,
respectively).
Comparison of calculation and experiment shows that they agree well enough within the limits of experi-
mental error.
The experiments were the first check on values of the temperature and power reactivity effects and the
depletion effect for a fast power reactor. These results and their theoretical analysis enable us to estimate
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the reactivity balance in a BN-350 reactor, and to check and refine the methods of calculation. The models
and methods used for calculations in designing fast power reactors turned out to be effective and gave quite
satisfactory results.
Calculations of the temperature and power reactivity effects somewhat underestimate their values (by
15%). The largest error in the temperature effect comes from the Doppler and sodium components, and in
the power effect from the Doppler effect and the indeterminacy in temperature field calculations.
Calculations give a fairly good estimate of the depletion effect also, although in this case obvious care
has to be exercised in choosing the method of calculation. This fact is connected with the necessity of cor-
rectly allowing for nonuniformity of fuel depletion and the accumulation of plutonium.
Investigation of the reactivity effect for prolonged use of the reactor is of great practical and theoretical
interest. The effect of depletion and change in structure of the fuel pellets on the temperature and power
effects, the nonlinear nature of the power effect, and the influence of plutonium accumulation on the reactivity
effects in the reactor, all these are questions of reactor physics the study of which allows us to increase the
accuracy of physical calculations in designing fast power reactors.
1. V. V. Orlov, At. Energ. , 36, No. 2, 97 (1974).
2. V. V. Orlov et al. , in: Fast Reactor Power Stations, BNES, London (1974), p. 255.
3. B. G. Dubovskii et al., At. Energ. , 36, No. 2, 104 (1974).
4. I. P. Markelov et al. , Collected Proceedings on Programming and Methods of Physical Calculations of
Fast Reactors SEV [in Russian], NIIAR, Dimitrovgrad (1975), p.34.
5. V. V. Orlov et al. , Kernenergie, 12, No.4, 112 (1969).
6. H. Takano and V. Ishiguro, in: EACRP Working Group Meeting, "The keV capture of structural ma-
terials Ni, Fe, Cr," Karlsruhe (1973), KFK-2046, p.317.
7. V. V. Orlov et al., in: Proceedings of International Symposium on Physics of Fast Reactors, Vol.1,
Tokyo, 16-19 Oct. (1973), p.571..
V. B. Malygin, Yu. K. Bibilashvili, UDC 621.039.531
I. S. Golovnin, and K. V. Naboichenko
To construct economic fast-neutron reactors, it is necessary to develop fuel elements capable of with-
standing deep burnup without disintegrating. The efficiency of a fuel element is determined by the change in
its dimensions owing to core swelling. Therefore, the plasticity of the fuel during the interaction of the core
and the fuel-element container is the determining factor on which the reliability of the fuel element depends.
Much attention is devoted to the study of fuel creep under conditions as close as possible to the operating
conditions. Analytic models are being developed for irradiation creep to make it possible to justifiably extrap-
olate experimental data and to use generalized relations in programs for designing different fuel elements.
Many researchers link irradiation creep with the formation of point defects. For the low-temperature
range, Brucklacher and Dienst [1] propose a model based on the Nabarro mechanism [2]. Soloman [3] gives a
satisfactory explanation of the experimental data by means of a model taking account of the formation of dis-
location loops as a result of vacancy condensation. Another mechanism is based on the climb of dislocations
because of accelerated vacancy diffusion [4]. An attempt to create a unified model [5] led to a complex depen-
dence of irradiation creep on the stress and neutron flux.
Translated from Atomnaya Energiya, Vol.42, No.1, pp. 8-13, January, 1977. Original article sub-
mitted January 7, 1976.
This material is protected by copyright registered in the name 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 $7.50.
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12 16 20 24 28 t,10'0?C Z 3 4 5 6 7 T_',
3 103-i
Fig.1 Fig.2
Fig. 2. The dependence e = lo.l, ne>,tt on the temperature of the ambient material.
Some investigators explain radiation creep on the basis of the concept of thermal and displacement
spikes. Irradiation creep is tied in with the relaxation of elastic stresses in the zone of a thermal spike [4]
or with the annealing of the ceramic fuel within the volume of the thermal spike [6].
The present paper suggests a model describing the process of irradiation creep on the basis of mea-
sured nonstationary creep in out-pile tests.
Strain hardening, as is known, leads to a reduction in the creep rate under constant load up to the onset
of steady-state creep characterized by a constant strain rate. Since strain hardening is exhausted during an-
nealing of the material [7], and a renewed loading of such a sample leads to the reappearance of nonstationary
creep.
Let us assume that a thermal spike from the fission of heavy atoms, produced by an elevated temper-
ature in some portion of the sample, anneals this portion. As a result, the portion of the sample annealed by
the spike is strained in the nonstationary creep stage.
Let us consider a sample of unit volume. Suppose that a constant fission density is established in the
sample. The amount of material passing through the thermal spike state in the time to is equal to the volume
of the sample, i.e.,
to = I3!V,q), (1)
where V. is the volume of the spike; P is the coefficient of spike overlap and is equal to 1.6 according to [8];
(D is the flux density in divisions/cm 3?sec.
The time elapsed from the onset of the spike will be taken to be the spike age. Because the strain after
annealing corresponds to the range of steady-state creep, the volume of the sample containing spikes of various
ages are at different stages of the strain curve. Characteristic of ceramic fuel materials in the range of strains
a_ 4 kgf/mm2 is a linear dependence of the stationary creep rate on the stress [1, 3, 9,10]. If the creep in the
nonstationary and stationary regions is controlled by a single mechanism, the time dependence of the creep rate
at constant temperature can be written as
e (t) = _i (t) o. (2)
All cross sections of the sample have the same creep rate, i.e., the material within the volume of spikes
of various ages is strained at the same rate but has a differing creep resistance, determined by the spike age
and the time dependence of the nonstationary creep rate.
An elementary cross section Se of the sample containing spikes of age 0-to can be treated as a system of
n parallel rods of differing rigidity, due to differing creep resistance Ai =A(ti), where ti is the age of the i-th
spike at a given instant.
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1OB 10? 0
0
F 10.9? 10 5 ? ?
?
10_t
10-n _ 10-1 ,, _,. _v. 11a
Fig. 3 Fig. 4
Fig.3. Dependence of creep rate on 4)0: O ,A , ^,S) UO2 [1,4,3,12], respectively; C`) U02 + 15PuO2
[12]; ?, ?) U02 + 22PuO2 [9,12]; a,b) UN [1]; 4, = 3.5.1013; 2.5.1014 fissions/cm3?sec; A) UC [17].
Fig.4. Irradiation creep rate vs fission density. Calculation data: 1,2,3,4) U02 + Pu02; U02; L'C;
UN; experimental data: A,[]) U02 [1,31; 0,0) U02 + Pu02 [9,12]; I) UN [1]; ^ , A) UC [13,17].
eta=-lt6f i= i, 2 ... n;
=ep:l;. (3)
where ai is the stress in an individual rod and g (O is the resultant creep rate.
If the time dependence of the creep rate is known for a stress tt = F/So, an expression can be obtained
for the irradiation creep rate:
- I -I ) dr
Fp t to uFiri
where E(9 is the irradiation creep rate and 8(t) is the time dependence of the creep rate, determined outside
the pile radiation field.
It follows from Eq. (4) that the model under consideration enables the irradiation creep rate to be deter-
mined if the laws of nonstationary creep in the absence of radiation are known.
In designing fuel elements it is of interest to describe the processes that occur in the fuel during tran-
sient reactor operating conditions.
The instantaneous increase in the fission density from 0 toy results in the following relation for irradia-
tion creep:
to
FW(t) = t
dt to - t
i F (t) B (T)
where T is the time after the sample loading and t is the time after the increase in the fission density.
When the fission density diminishes instantaneously from 4 to 0,
r+tot`
ew(t)=
J :a
The proposed model permits the variation in the irradiation creep rate to be found for any law of time varia-
tion of the fission density.
The dependence of the strain creep on time is described well by a relation [15] in which
e(t)=eo_LTstltr{1+cim Est[1-exp(-rt)]1--es4, (7)
l ea
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Fig.5 Fig.6
Fig. 5. Irradiation creep rate vs fission density at a high temperature: ) calculated curve
for UO9; [10]; 0, C) [14].
Fig. 6. Irradiation creep rate vs temperature: ) calculation data; 1,3) UO2; 4' = 2.5.1014;
1.2.1013; 2) UO2 + PU021 4' = 1.2.103; 4) UN, 1- = 2.5.1014; experimental data: a,I, ?) UO2 [1,3,10];
1.) UO2 _ 15PuO9 [12]; ^, ?) UO2 + 22PuO2 [9,12]; b) UN [1].
where E0 is the instantaneous strain; Eini is the initial creep rate, Est is the steady creep rate, and r is a
coefficient characterizing the rate of exhaustion of the nonstationary creep.
Differentiating Eq. (7) with respect to time and inserting the result in Eq. (4), we obtain the dependence
of the irradiation creep rate on the fission density and the size of the thermal spike,
rKcst
rl-cxp 1 I rte) I (b-1) >
rb - V,, (1)
tine
li =
Est
Relation (8) implies that if 4, -- 0, then the irradiation creep rate approaches the steady laboratory rate,
and as c - 00 the irradiation creep rate tends to Eini = KEst.
At a relatively low temperature, if K >> 0 and rt > Vss>, then the
irradiation creep rate is a linear function of the fission density. Indeed, using relation (11) we obtain
e = 2aV s eff Leff - 2a0 cp
W
Figure 3 presents the dependence of e~p/a on the product for UO2, UO2 + PU021 UC, UN approximating
the data of [1,3,9,12,13,17]. All experimental results are reduced to a density equal to 96% of the theoretical
value. The experiments were carried out at a temperature of 100-850?C and a density of 7.1012-2.4. 1014
fissions/ cm3 ? sec. The results of these investigations in the coordinates adopted are approximated by a straight
line whose slope can be used to find the value of 2a/teff in Eq. (13), equal to 2.7a?. Using Fig.2 and Eq. (13),
we can calculate the irradiation creep rate for various fuel materials.
The value of a in Eq. (13) must be determined in order to calculate the effective volume of a thermal
spike. Typical values of a and v in Eq. (10) were found at 800?C and a strain of 3 kgf/mm2 for UO2 samples
with a grain size of 12-15 ?; obtained by cold pressing and subsequent sintering at 1920?K in an argon atmo-
sphere. Under these conditions a Le 10-5 and v = 10-2 sec-1. Substituting this value in Eq. (13), we can find
teff [14]. Then using Eq. [11], we find that Veff = 4.0.105 9 (T).
Thus, knowing the value of a, v, and Veff, we can write the equation for determining the irradiation
creep rate in the low-temperature range.
Figure 4 gives the irradiation creep rate as a function of the fission density, calculated by Eq. (9) with
the values found for Vs eff,'cx; and v. The calculated relation for UO2, UO2 + PU021 UC, and UN is in satis-
factory agreement with the experimental results of [1, 3, 9,12,13,17], reduced to 600?C .
To calculate the irradiation creep rate at temperatures in excess of 1000-1100?C under laboratory con-
ditions, it is necessary to determine the quantities in Eq. (7). In laboratory experiments with UO2 samples
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it was found that the results obtained at 1150-1300?C and g = 1-4 kgf/mm2 are described well by Eq. (7) pro-
vided that Eini/ESt = 5. The value of r depends on the temperature and stress; for a = 3 kgf/mm2, T = 1150-
1200?C, we find r = 1.2.10-5 sec-1. The ratio eini/Est practically does not change in the given temperature
interval. The experimental curves were processed on a computer by the least-squares technique. In Fig. 5
the calculated dependence of E,,)/Est on the fission density is given along with data of [10,14]. It is seen from
Fig. 5 that the experimental results are in good agreement with the calculated curve.
To calculate the temperature dependence of the irradiation creep rate it is more convenient to use Eq.
(14), consisting of thermal and athermal terms. In this case
? _ _) raKexpi-H/RT) + 2avoVseff4)
rh -Vseff I l-exp(-r'Vseff4)](R-1)
2Vs efO +V
where T is the absolute temperature, R is the gas constant, H is the activation energy, and A is a structure
factor in the study of creep without irradiation. The use of Eq. (14) is related to the fact that at a low temper-
ature it is easier experimentally to determine the parameters of Eq.,(10).
The effective spike volume in Eq. (14) is determined by the method presented above whereas the other
parameters are found from experiments on creep under laboratory conditions. At a high temperature the
second term in Eq. (14) is small and at low temperatures, the first term can be neglected. At a temperature
of 900-1000?C both terms of Eq. (14) must be taken into account.
Figure 6 presents the results of calculation of the irradiation creep rate by Eq. (14), which are in good
agreement with experiment.
The model presented here was employed to calculate the irradiation creep rate of columnar crystals
that are formed while the fuel elements are in use. The results of these calculations, with allowance for the
differences in thermal diffusivity of the UO2 polycrystal and single crystal [16], are given in Table 1.
The authors express their gratitude to Yu. N. Sokurskii for his assistance in preparing the paper and
for his useful comments in discussing the results.
1. D. Brucklacher and W. Dienst, J. Nucl. Mater., 42, 285 (1972).
2. F. Nabarro, in: Bristol Conference on Strength of Solids, The Physical Society, London (1948), p.75.
3. A. Soloman, J. Am. Ceram. Soc., 56, No.3, 170 (1973).
4. J. Brinkman and H. Wiedersich, American Society for Testing and Materials, Special Tech. Publ.,
N380, 3 (1965).
5. F. Nichols, J. Nucl. Mater., 30, 249 (1969).
6. E. P. Gilbert, Irradiation Creep of Reactor Materials. Reactor Technology [in Russian], No.3,
TsNllatominform, Moscow (1972).
7. R. W. Cahn (editor), Physical Metallurgy, Am. Elsevier (1971).
8. S. T. Konobeevskii, Effect of Radiation on Materials [in Russian], Atomizdat, Moscow (1967).
9. J. Perrin, J. Nucl. Mater., 42, 101 (1972).
10. J. Perrin, J. Nucl. Mater., 39, 175 (1971).
11. F. Garofallo, Laws of Creep and Long-Term Strength for Metals and Alloys [Russian translation],
bletallurgiya, Moscow (1968).
12. D. Brucklacher and W. Dients, in: Proceedings of the IAEA Symposium "Fuel and Fuel Elements for
Fast Reactors," July 2-6, Brussels (1973), Rep.No.31.
13. D. Glough, in: Proceedings of the IAEA Symposium "Fast Reactor Fuel and Fuel Elements, " Sept. 28-
30, Karlsruhe (1970), Rep. No.6.
14. Yu. V. Miloserdin et al., At. Energ., 35, No. 6, 371 (1973).
15. Jo Li, Acta Metallurgica, 11, 1269 (1963).
16. J. Daniel, in: Proceedings of the Conference "Thermal Conductivity of UO21 " HW-69945, Sept. (1962).
17. D. Glough, J. Nucl. Mater., 56, No.3, 279 (1975).
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TEMPERATURE DEPENDENCE OF EROSION OF ALLOYS
OF VANADIUM AND NIOBIUM DURING BOMBARDMENT
WITH HELIUM IONS
B.
A.
Kalin, N. M. Kirilin,
A.
A.
Pisarev, D. M. Skorov,
V.
G.
Tel'.kovskii, and G. N. Shishkin
One of the principal processes leading to breakdown of the primary wall of thermonuclear installations
is swelling of the material surface (blistering) owing to uniting of the gas cavities formed directly beneath the
surface during ionic bombardment [1]. After thermonuclear installations have been in use for 20 years the
coefficient of erosion induced by blistering should not exceed 10-2 atom?ion-1 when the ion flux at the wall is
3.1019 ion- m-2?see-1 [2]. It is therefore necessary to select materials stable under bombardment by light ions.
At present vanadium and molybdenum alloys [1] and stainless steel are promising materials for the
primary wall, but insufficient work has been done on the behavior of these alloys under bombardment by helium
ions and isotopes of hydrogen [3,4].
Our aim is to investigate the temperature dependence of the erosion coefficient of vanadium obtained by
electron-beam melting, alloy V + 2.5% Zr + C, and niobium alloys Nb + 4.21; Mo + 0.841( Zr, and Nb + 1.1 ,c Zr +
C as a result of swelling during bombardment with 20-keV helium ions at 300-1400?K and doses in the range
(1-50)-1021 ion ? m2.
Experimental Procedure. The specimens for bombardment were obtained by electrolytic polishing of
rolled foil 1.10-4 m thick. The compositions of the test materials are listed in Table 1. Bombardment with
helium ions was performed in a double-focusing mass monochromator under the conditions described in [3].
The character of the surface breakdown after bombardment was investigated in a UEMV-100K electron micro-
scope using single-stage carbon replicas. The erosion coefficient was determined from electron micrographs
by measuring the geometric size of the broken blisters and calculating the number of atoms in the split-off
domes, i.e.,
ti'
where N is the number of detached atoms of the alloy, NA is the Avogadro number, p is the alloy density, V
is the volume of the split-off domes, and A is the mean atomic mass of the alloy.
The overall error in the determination of the erosion coefficient was less than 50%.
TABLE 1. Composition of Materials Investigated
Zr -1 Mo
Si i 1
V
99,90
U,li(
V--2,5% Zr4-C
2,50
97,07
(1,411
11.12
Nb 4,2% Mo-!-0,8 ?o Zr
94,73
0,7(i
0. Ill
0,03
((.02
(1,112
0,005
Nh-;-1,1% Zr-'-C
98,80
1,1u
0.0(1
(1,12
0,01
0,011
Translated from Atomnaya Energiya, Vol.42, No.1, pp. 13-15, January, 1977. Original article sub-
mitted March 29, 1976.
This material is protected by copyright registered in the name 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 $7.50.
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b
Fig.1 Fig.2
Fig.1. Swelling of alloy Nb + 1.1 Zr + C (a) and vanadium (b), bombarded with doses of helium
ions 7.8. 1021 and 1. 1022 ion ? m-2 at 800?K.
Fig.2. Erosion of vanadium subjected to a radiation dose of 3.0.1022 ion?m-2 at 800?K.
Results and Discussion. An investigation of the character of breakdown of the specimens revealed that
surface erosion depends on the radiation dose. When subjected to a radiation dose of up to 6.1021 ion? m-2, all
the alloys exhibit dome-like swelling of the surface without disintegration of the domes. As the radiation dose
is increased to 1.1022 ion- M-2 the blister density increases and we observe partial breakoff of the domes (Fig.
la). When the dose is 1.10V2 ion?m-2 or more, second-generation blisters appear (Fig.2) and we observe dis-
integration and detachment of the domes, but the erosion coefficients of the materials scarcely increase, and
coincide (within the measurement error) for different radiation doses.
The variation of erosion of the materials with the radiation temperature was revealed for all the alloys
investigated (Fig. 3); it will be seen that the curves have maxima, the maximal erosion coefficients of vana-
dium and niobium alloys being observed at 800 and 1000?K, respectively.
We found that 1000 and 1300?K are the temperatures for vanadium and niobium, respectively, above
which the surface of the materials does not undergo breakdown by swelling (Fig.4). However, below this tem-
perature (right down to room temperature) the material surface is intensely damaged; the coefficient of ero-
sion due to blistering is several orders of magnitude higher than in the case of physical pulverization, data
for which are given in [1].
The dependence of the erosion coefficient for vanadium alloys can be explained on the basis of experi-
ments on evolution of helium from vanadium [5], and from the temperature dependence of the strength charac-
teristics of vanadium alloys. In fact, as the radiation temperature is raised (other conditions being equal) the
strength of the alloys decreases and the gas pressure in the blisters increases, promoting disintegration of the
surface layer and erosion of the materials.
With a further increase in temperature (above 800?K) we observe stimulated helium diffusion by various
vacancy mechanisms together with heightened probability of emergence of helium on the material surface, and
also its diffusion to the grain boundaries and to dispersion particles of the second phase. The proportion of gas
involved in bulge formation therefore decreases as the temperature is raised.
The temperature dependence of the erosion coefficient for niobium alloys can be explained in the same
way. Two factors should be noted: firstly, diffusion processes (other conditions being equal) in these alloys
13
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Fig. 4
Fig. 3. Erosion coefficients of niobium and vanadium alloys vs radiation temperature (the num-
bers near the curves are the alloy Nos. in Table 1).
Fig.4. Surface of alloy Nb + 4.2% Mo + 0.8% Zr subjected to a dose of helium ions 1.6. 1022 ion-
m-2 at 1230?K.
take place at a higher temperature than in vanadium alloys [6]; secondly, a marked change in the strength
properties of niobium alloys is observed at a higher temperature. Owing to these processes, the erosion
maximum of niobium alloys is apparently shifted toward higher temperatures (1000?K).
Thus, alloys of vanadium and niobium, alloyed with zirconium and carbon, exhibit high resistance to
blister formation at 900-1100 and 1200-1400?K, respectively. In this range the alloys have a minimum SZ,
where S is the erosion coefficient and Z is the atomic number of the element. The alloys can therefore mini-
mize energy losses by the plasma, which are proportional to the square of the atomic number of the impurity
present in it [7].
CONCLUSIONS
It has been established that maximal erosion of vanadium and its alloys is observed at 700-900?K, the
corresponding range for niobium alloys being 900-1100?K. The maximal value of the erosion coefficients of
alloys for vanadium and alloys V + 25% Zr + C, Nb + 4.2% Mo + Zr, and Nb + 1.1% Zr + C is 1.5 ?0.7, 0.6
0.3, 0.4 ?0.2, and 0.15 ?0.07, respectively.
LITERATURE CITED
1. G. Kulcinski and G. Emmert, J. Nucl. Mater. , 53, No.1, 31 (1974).
2. N. Lacgreid and S. Dahlger, J. Appl. Phys. , 44, No. 3, 2093 (1973).
3. B. A. Kanin et al. , At. Energ., 39, No. 2, 126 (1975).
4. B. Kahn, Proceedings of the Twelfth International Conference on Phenomena in Ionized Gases, Pt. 1,
North-Holland, Am. Elsevier (1975), p.241.
5. W. Bauer and G. Thomas, J. Nucl. Mater., 53, No.1, 127 (1974).
6. A. A. Pisarev and V. G. Tel'kovskii, At. Energ., 38, No. 3, 152 (1975).
7. D. Meade, Nucl. Fusion, 14, No.2, 289 (1974).
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P.
G.
Pinchuk, V. N. Bykov,
V.
A.
Karabash, Yu. V. Alekseev,
and
A.
G. Vakhtin
In order to study the effect of gaseous elements and structural nonuniformities on the vacancy swelling
of injection phases, the varying properties and structure of the 6 and E phases of zirconium hybrides were
investigated after irradiation in the VVRTs and BR-5 reactors at temperatures of 50 and 460-560?C with a
fluence of up to 8.1021 neutrons/cm2. The hydrostatic density d, microhardness Hp, electrical resistance p,
crystal lattice periods a and c, phase composition, microstructure (with an increase of 102-105) and the hydro-
gen content (by the vacuum extraction method) were determined before and after irradiation. The results of
the measurements of the properties are shown in Table 1 and also in Figs.1 and 2.
E Phase. The hydrogen-content, type of crystal lattice (face-centered tetragonal), and also the "parquet"
substructure (dislocation voids consisting of t-vvzns [1]) of E ZrH1, 9 were unchanged as a result of irradiation.
At an irradiation temperature of 50?C, there were no vacancy pores, but at an irradiation temperature
of 500-560?C up to 3.1016 pores are found per 1 cm3, with a diameter of up to 50 A, whose total volume is equal
to 0.2%, of the volume of the sample, i. e. , less by a factor of 11 than the macroswelling. It is not possible to
explain the main part of the swelling by the accumulation of injected zirconium atoms, as there is no significant
increase of the volume of an elementary cell, and also by the accumulation of hydrogen atoms displaced from
the normal tetrahedral positions to octahedral positions, as the octahedrons are larger than the tetrahedrons.
Consequently, the swelling can be explained almost entirely by the buildup of zirconium vacancies and their
fine complexes, which are not revealed by means of the electron microscope (-'10 A). The absence of a signi-
ficant increase of volume of an elementary cell does not agree with the concepts of [2], assuming that the cause
of swelling of the E phase of zirconium hydride can be only an increase of the volume of an elementary cell.
The irradiation temperature of 50 and 470?C amounts to ^-0.15 and 0.35Tm?K, respectively, if it is assumed
that in this case the melting point of the metal (Tm) and of its hydride are close to one another, as in the
uranium-hydrogen system [3].
In the hydride ZrH1 9 when Tirr "," 0.15 Tm it follows from estimates by the curve of increase of density
in the divacancy (III) and vacancy (IV) stages of annealing (Fig. 2), that ^ 0.5 at. % of the zirconium vacancies
has remained while the concentration of vacancies in metals, e.g. , in molybdenum, found by extrapolation of
the data of [4], should be less by a factor of - 10. Obviously, recombinations of the zirconium vacancies and
injections in E zirconium hydride prevent the numerous twin-boundaries forming its."parquet" substructure,
and separated from one another in all by 500-1200 A, as the electron microscope has shown. In metals, these
boundaries are significantly less; it is well known, however, that they either contribute to an increase of the
local concentration and dispersivity of the dislocation sinks of injections, or themselves serve as such sinks
[5].
Prevention of recombinations of point defects of the metal sublattice in the hydride, obviously, is pos-
sible, and also their amalgamation with defects of the hydrogen sublattice. The presence of the latter is con-
firmed by the fact that the change of the periods a and c of the lattice of the hydrides ZrH1778-ZrHi.90 as a
result of irradiation by a fluence of 1.8.1021-8.0.1021 neutrons /cm2 corresponds to the release from hydrogen
atoms of 4-7% of the tetrahedral positions during dehydrogenation, and a change of the periods a and c as a
result of annealing the irradiated sample up to a temperature of 550?C corresponds to population of the tetra-
hedral positions during hydrogenation (see Figs. 1 and 2). In the case of the unchanged hydrogen content, this is
Translated from Atomnaya Energiya, Vol.42, No.1, pp.16-19, January, 1977. Original article sub-
mitted April 23, 1976.
This material is protected by copyright registered in the name 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 $7.50.
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41 42 43
q~40
1,5 1,6 1,7 1,8 1,9 Cx Tan:. Tm
Fig.1 Fig.2
Fig. 1. Crystal lattice periods of the original and irradiated zirconium hydrides. Be-
fore irradiation: 1) [11]; 2) [12]; 3) present paper, after irradiation at 50?C, with a
fluence of 1021 neutrons/cm2; A) 1.8; V) 3.2; () 8; x) 1.8 and annealing up to 550?C; C )
experimental points before irradiation.
Fig.2. Stages of recovery of properties of the hydride ZrHl.9, irradiated at 50?C with
a fluence of 1.8.1021 neutrons /cm2 and with isochronal annealing for an exposure of 1 h.
The melting temperature of the hydrides is assumed to be equal to the melting point of
zirconium. The annealing stages and their temperature ranges are denoted according
to the data of [13] for the face-centered metals: C!) Ad; ?) Op; A) &2; A) Ac.
obviously explained by the buildup during irradiation and recombination during annealing, of approximately
the same quantity of hydrogen vacancies and displaced atoms, which allows their number to be estimated.
In addition, the increase of electrical resistance in the e region, initiated by irradiation at 50?C, in-
creases rapidly with increase of the hydrogen content, which also affects the presence of radiation defects
of the hydrogen sublattice. It is obvious that the considerable decrease of changes of the lattice periods and
of the electrical resistance observed with increase of the irradiation temperature, and also the very consid-
erable advance of the return of these characteristics by comparison with the return of the density in stage V
(see Fig. 2), are associated with the annealing of these defects. The latter would be difficult to explain only
the segregation of the zirconium vacancies, if we take into account the large degree of dispersion of the de-
fects at an irradiation temperature of 500-560?C and the dependence [6] of the vacancy contribution to the
.electrical resistance on the size of the pile-up formed.
?
When Tirr 0.35Tm, a pile-up of vacancies in the pores with a size, as a rule, of not less than 200 A,
is characteristic for metals. The thermal stability of the fine (^-10 A) defects of the vacancy type of the zir-
conium sublattice of the hydride, causing large swelling with a small total pore volume, is possibly due to the
capture of hydrogen atoms by these defects.
Its condition in the voids with a radius of r ^- 5 A is not known; it is easy to show, however, that the
mechanism of stabilization does not lead to a counter effect of the hydrogen pressure in a pore p with a surface
tension y, as occurs, e.g. , in the case of gas swelling, for which the condition of equilibrium in the cavity is
the equation p = 2y/r. Actually, at a temperature above 400?C, when the hydrogen. in the hydride ZrHl.9 is
quite. soluble and mobile, the pressure cannot be higher than the thermal equilibrium value, and during irradia-
tion of. the hydride of this composition [7], it is many times less. than 2y/r when r = 5-50 A and y = 0.06 eV-A-2,
-found by the formula
y = U/4nr2[81,
where Uv = 1.75 eV [9].
fZr
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TABLE 2. Change of OX Properties of Zir-
conium Hydrides as a Result of Irradiation*
TABLE 1. Properties of Zirconium Hy-
drides before irradiation
t l.0
1.88
G 1,511
Mean square
error, ?io
Confidence inter-
val for 90'io
probability
Den-
sity,
g cm3
5,610
5.6 16
5.641
ocE
EaS
s~
145
265
U
Fluence,
1021 neu-
trons%cm2
c
0
CH
Ad
4p
Aa
AC
AH?
.v
0
I
1,9
50
1.8
0,1
-f,3
?111
-0,49
?0,99
?50
1,88
470?30
6,2
2,0
-2,4
=12
-0,04
?0,07
?72
1,91
500- 560
6,7
2,2
-2,2
1,56
50
8,0
0,5
-1,2
?41
0'
?34
1.56
470?30
4,3
1,4
-1,6
-
-
-
,n,X = (X irr-Xorig)' 100:'Xorig%, where X is the prop-
erty.
t E ? 1; 0.8 MeV when tirr=50; > 400?C, respectively.
The energy stimulus of the vacancy segregation, their emergence at the surface or recombinations with
injections, is the reduction of the surface energy and therefore the stability of the vacancies and of their fine
complexes will be the greater, the less is the coefficient of the surface tension. It is probable that the cap-
ture of hydrogen by zirconium vacancies and their fine pile-up strongly reduces the surface tension by com-
parison with the calculated value.
6 Phase. It can be seen from Table 1 that the 6 phase swells only a little more weakly than the E phase.
The microhardness increment also is small, while its fcc lattice remained unchanged. The interpretation of
the results is the same as for the e phase. In [2], the dimensions of samples of 6 phase irradiated at a tem-
perature of 550-570?C with a fluence of 1.3.1021 neutrons/cm2 (E >_ 1 MeV) were unchanged. However, the
samples were obtained by the hydrogenation of zirconium, but in our case they were obtained by dehydrogena-
tion of the e hydride ZrH1.9. Although in both cases there was no appearance in the 6 phase of any substruc-
ture, an analysis of the facts cited shows that the system of preferential sinks of zirconium injections, orig-
inating during the conversion of 6 to s, disappears without trace during the reverse conversion, but continues
to serve as sinks for the injected atoms. The density of samples of yttrium hydride YH1.9, which do not have
a substructure and were irradiated in the BR-5 reactor with a fluence of 6.2.1021 neutrons/cm2 at a temperature
of 460?C (0.4Tm), remained unchanged with an accuracy of 0.2%. Obviously, during swelling of the hydrides of
the transition metals, the role of hydrogen with increase of temperature is less significant than the role of the
structural characteristics. This allows us to suggest that in other alloys with a substructure similar to the
substructure of the e hydride of zirconium, the rate of recombination of vacancies and injections will be consid-
erably less than in normal metals. To these alloys are related, e.g. , the face-centered tetragonal phases of
the systems. indium-thallium, chromium-manganese, etc. formed as a result of transitions of the second
species [10].
The radiation swelling of the hydrides ZrHI778-ZrH199o at a temperature of 50?C is due to the accumula-
tion of zirconium vacancies and their fine pile-ups. At 430-560?C, swelling is determined by the accumulation
of fine (=10A) vacancy complexes. In this case, micropores are also formed, with a diameter of 50 A, but
their total volume does'not exceed one-tenth of the macroswelling.
The considerable buildup of vacancies in the hydrides studied is related with the substructure of the E
hydride, formed by dislocation voids and the boundaries of twins, which promote an increase of concentration
and dispersivity of the injection sinks or themselves serve as these sinks. In samples of the 6 hydride ob-
tained by dehydrogenation of the e phase, the numerous dislocations remaining in the 6 hydride after decay of
the e-phase substructure obviously fulfill this function. The weak tendency of the zirconium vacancies in the
hydride to amalgamation in the pores during increased irradiation temperature (by comparison with the behav-
ior of vacancies in metals) is explained by the reduction of their surface energy as a result of interaction
with hydrogen atoms.
The displacement of hydrogen atoms from the tetrahedral positions during irradiation and their return
during annealing changes the periods of the crystal lattice of F zirconium hydride in the same way as the change
of hydrogen content, which enables the number of defects of the hydrogen sublattice to be estimated.
Electri- I Lattice
cal resis-
tance, period, A
?f2 ? cm I a I
35.6
4U.0
r4,0
4,975
4,969
4,780
4,454
4.455
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The authors thank V. I. Shcherbaka and S. I. Porollo for assistance in the electron-microscope inves-
tigations, and also Yu. V. Konobeeva for discussions and valuable comments.
1. R. Chang, J. Nucl. Mater. , 2, No.4, 355 (1960).
2. P. Paetz and K. Lucke, J. Nucl. Mater., 43, No.1, 13 (1972).
3. J. Lakner, Nucl. Sci. Abstrs., 17, No.4, 579 (1962).
4. J. Brimhall, E. Simonen, and H. Kissinger, J. Nucl. Mater. , 48, No. 3, 339 (1973).
5. D. Norris, Radiat. Effects, 15, Nos.1-2, 1 (1972).
6. A. C. Damask and G. J. Dienes, Point Defects in Metals, Gordon (1964).
7. V. S. Karasev, V. G. Kovyrshin, and V. X. Yakovlev, At. Energ., 37, No.1, 65 (1974).
8. M. W. Thompson, Defects and Radiation Damage in Metals, Cambridge Univ. Press (1969).
9., Ya. A. Kraftmakher, in: Papers on Solid State Physics [in Russian], No.1, Nauka, Novosibirsk (1967).
10. L. Keys and J. Motteff, J. Nucl. Mater. , 34, No. 3, 260 (1970).
11. P. Paetz and K. Lucke, Z. Metallkunde,. 62, No. 9, 657 (1971).
12. R. Beck, Trans. ASME, 55, No.2, 542 (1962).
13. A. C. Damask and G. J. Dienes, Point Defects in Metals, Gordon (1964).
ESTIMATE OF PERTURBATIONS IN SOLVING NONUNIFORM
NEUTRON TRANSPORT PROBLEMS BY THE MONTE CARLO
METHOD
As computers develop there is a steadily increasing interest in using the Monte Carlo method to model
radiative transport processes. The present paper gives computational formulas for an important class of
reactor physics problems, the calculation of nonlocal perturbations of linear functionals. We consider a
group representation of the dependence of neutron cross sections on energy. We describe the case of finite
perturbations resulting from a limiting transition when the perturbation parameter tends to zero, and we ob-
tain formulas for the derivatives of linear functionals (the sensitivity coefficients). The dispersion of the
computational scheme is studied in an example of a homogeneous one-velocity medium.
The paper presents typical accuracies in calculating the Doppler coefficients of reactivity and density
reactivity effects by the Monte Carlo method in reactors and cores of various types.
Method of Correlated Trajectories. We assume that all the medium cross sections are functions of a
certain parameter a. With a = 0 we obtain a medium in which the particle motion is random. The "effective
weight" of a particle belonging to a medium with a x 0 but following a trajectory drawn by lot in a medium
with a = 0, we shall designate W. By Xn we denote the set of particle phase coordinates (r, E, S2) at the n-th
collision. The energy E and the flight angle S2 are taken at the moment of collision. The effective particle
weight Wn at the n-th collision is determined as follows:
,t- r
S (X0, a) 2, (Xi, a) m?, (Ei, 4i - Ei+l. Sii+f, ri, a) E (Xn; a)
11%n = S (X0, 0) exp (-JT1) Zs (Xi, 0) ws (Ei, 4i - Ei+i, 2i+i, ri, 0) e\p (- ~T?) E (X n, i=1
0 li
i.e., from the definition II fr = 1. In Eq. (1) S(X?'a) is the source ratio; A (r, 0)) dl is
i-i S(Xo,(i) ri t
the perturbation of optical depth between the points of collisions i- 1 and i; E (X,a) is the total cross section
Translated from Atomnaya Energiya, Vol.42, No.1, pp.19-22, January, 1977. Original article sub-
mitted January 13, 1976.
This material is protected by copyright registered in the name 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 $7.50.
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for the medium [if elastic scattering of the particle is chosen isotropically in the laboratory coordinate sys-
tem, and the transport cross section is taken as E(X,a)1; Es (X,a) is the scattering cross section*.; and ws
(E1, f - Ei+1, i2 +1, r,-a) is the angular energy index corresponding to the type of scattering. The values
of Is and ws in the numerator and denominator of. Eq. (1) are chosen for the specific scattering process oc-
curring in the medium, where the random process holds (a medium with a = 0). The ratio Es (a) rvs (a) must
Es (0) ws (0)
be finite (a medium with a = 0 must not be "narrower" than a medium with a # 0) in a multitude of possible
values of the particle phase coordinates X [1].
We now turn to a detailed determination of the ratio it _ I-(') ws (a in a group model for the dependence
cs(0)U's(0)
of cross section on energy [2 ]: u = (a)` ~' , if the neutron remains in the same group r, where Es (a) r--r
is the reaction cross section for "remains in the same group"; u? = 3(e (1) , if the neutron transfers to the
next group r + 1, where EE(e)(a) is the cross section for transition to the next group.
There is a continuous degradation of neutron energy: 1. The reactions are selected from the macro-
scopic medium constants. If the neutron transfers to the next energy group after being scattered, then
{, __ 1(a) (`) where . is the average loss of lethargy; and Es (a) is the elastic scattering cross section. If
10 1) the neutron remains in the same group, then iv = `(a)(," '(a)( where Au is the group lethargy interval.
2. We determine the nuclide i in which the scattering occurs. iv and Esi(a) is the scatter-
ing cross section for the i-th nuclide.
For inelastic scattering and the n-2n reaction iv and Ein n-2n) is the cross section for
an inelastic transition (or the n-2n reaction) from group i to group j.
If there is an energy degradation on a continuous scale in the scheme of random motion, then u = c H(a)
=sH (0)
for hydrogen scattering (with cross section E5H) . In the group approach w is determined in the same way as
for inelastic transitions, as a ratio of the corresponding matrix elements [3]. However, in this case, since
the matrix elements are notperturbed, w = ?sH )
0
For fission events iv = v(a)_t(a)Z (EO, a) where X (E,a) is the spectrum of ejected particles.
v(U)E*(0)Z. (En, 0)
The perturbation of the linear flux functional
JI= J [Ei,(a) D(a)-Ep(0)ID(0)1 dx,
obtained by evaluating the collisions, can be calculated from the. formula [1]
1 H i' r E,, (An, a) EP (An, 0)
AI= H L' l it", (X,,, a) E (Y,,, 0)
i-1 n=1
where Ep is a certain weight function, e.g., vE j, if the multiplication coefficient is determined [3]; li is the
number of collisions in the i-th history; 'I is the flux; and H is the number of histories considered.
The evaluation of Eq. (2) is unbiased, since the minuend and the subtrahend are not biased [4].
Evaluation of Derivatives of the Linear Functionals. We can obtain a formula for the derivatives ? I?=o
directly, by going to the limit lim in Eq. (2) [5,6]. The analog of the effective weight W is the "differen-
tial weight" D, obtained by differentiating Eq. (1) with respect to a:
r
S' (101 s 7.5 MeV. This effect can easily be accounted for,
for example, by the worsening of the time resolution of the apparatus. In the present case this is improbable
since the spectra of the various nuclides were measured alternately, and in addition a control measurement of
252C f/233U performed with better time resolution showed the same trend.
According to estimates in [4] the effect of time resolution (At = 4 nsec) on average values can be ne-
glected. The values of AT were calculated on the basis of the error of the standard and the statistical error
AK without taking account of SK. The average energies of the spectra can be found from the relation f = 3T/2.
In the 0.6-8-MeV energy range the values of E found for 233U, 235U, and 239Pu were, respectively, 1.996 ?0.040,
1.926 ?0.030, and 2.050 ?0.040 MeV.
Our data are in good agreement with the results of [5] (1.950 ?0.030 and 2.055 ?0.030 MeV for 235U and
239pu) which were obtained by the time-of-flight method, and with the data of [6] (1.950 ?0.030 and 2.070 ?0.030
MeV for 235U and 239Pu) determined by a single-crystal stilbene spectrometer. The value of the average ener-
gy E = 1.982 ?0.006 MeV of the slow neutron induced 233U fission neutron spectrum found in [7] by the time-of-
flight method relative to the spectrum of 235U neutrons with E = 1.935 MeV was confirmed also.
1. A. Koster, in: Proceedings of the IAEA Symposium on Prompt Fission Neutron Spectra, Vienna, Aug.
25-27 (1971), p.19.
2. A. Smith, Nucl. Sci. and Eng. , 44, No. 3, 439 (1971).
3. L. Green, J. Mitchell, and N. Steen, Nucl. Sci. and Eng., 50, No. 3, 257 (1973).
4. N. V. Kornilov, Preprint FEI-276, Obninsk (1971).
5. D. Abramson et al., in: Proceedings of the Conference on Neutron Physics [in Russian], Pt. 3, ONTI
FEI (1974), p.46.
6. Z. Aleksandrova et al. , At. Energ. , 38, No. 2, 108 (1975).
7. L. Green, J. Mitchell, and N. Steen, Nucl. Sci. and Eng., 52, No. 3, 406 (1973).
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SPECTRUM OF LOW-ENERGY NEUTRONS FROM
THE SPONTANEOUS FISSION OF 112C f
P.
P.
D'yachenko, E. A. Seregina,
UDC 539.173.84
L.
N.
and
S.
N.
A.
Kutsaeva, V. M. Piksaikin,
Semenova, M. Z. Tarasco,
Laitai*
A detailed study of the spectrum of prompt neutrons from the spontaneous fission of 252Cf is of consider-
able interest both for nuclear physics and for a number of practical problems related to the use of californium
as a standard neutron source. In spite of the large number of published papers the accuracy of the existing
data is still inadequate for most of these problems. The region of low neutron energies has been least studied.
According to the data of [1-4] an excessive number of neutrons is found in the 0 < En < 1-MeV range as com-
pared with the number predicted by extrapolating the data from higher energies using the exp(-E/T) law.
The nature of this excess is still not clear. All the measurements reported in [1-4] were made by the time-
of-flight method. Thus there is a possibility that the observed effect is a consequence of systematic errors in
this method related, for example, to inaccurate knowledge of the detector efficiency e(En) or, as noted in [5],
to an inaccurate account of the background of scattered neutrons. In view of this it is expedient to perform the
corresponding measurements with a 6Li spectrometer using semiconductor counters. Although the 6Li spectrom-
eter has an energy resolution which is inferior to that of the time-of-flight method, it has a number of im-
portant advantages. Neutrons can be recorded in an appreciably larger solid angle (close to 27r) and this sub-
stantially decreases the uncertainty of the data on the background of scattered neutrons. By using a thin layer
of 6LiF the efficiency of the spectrometer can be taken as the cross section of the 6Li(n,a)3T reaction without
correcting for self-shielding and multiple scattering of neutrons as is necessary for scintillation detectors.
In addition, the semiconductor detectors used in the 6Li spectrometer are insensitive toy rays.
Figure 1 shows a schematic diagram of the experiment. The products of the 6Li(n, a) 3T reaction were
recorded by two silicon surface-barrier detectors 1 cm in diameter and 0.1 mm thick. The 6Li target was a
layer of 6LiF 25 ig/cm2 in thickness and 1 cm in diameter on an aluminum oxide backing 30 ?g/cm2 thick. The
background from reactions occurring in the detector material and backing was measured by a special arrange-
ment in which the target with the lithium layer could be replaced by a pure aluminum oxide backing. It was
carefully constructed to ensure identical conditions in measuring background and effect, and to minimize the
amount of scattering material. The backings with and without lithium were fastened to a rectangular frame of
thin brass which under the action of its own weight could be shifted in a thin-walled cassette located halfway
between the detectors which were 1.2 mm apart. The target was changed by rotating the vacuum chamber 180?
around the longitudinal axis. The chamber was made of Duralumin with walls 0.5 mm thick. A sample of iron
^-2.5 mm in diameter saturated with californium salts and enclosed in a stainless steel container with walls
0.3 mm thick served as a neutron source emitting 3.5.107 neutrons/sec. The container was fastened to the
outer base of the chamber in such a way that the center of the source was on its axis. The distance between
the source and target was 6 mm. After matching the amplification factors the pulses from the detectors were
combined, amplified, and fed to the analyzer. The coincidence circuit operated through the analyzer to select
counts of the 6Li(n,a)3T reaction products from both detectors. The channel in which the combined pulses
(amplifier and analyzer) were recorded was covered by automatic digital stabilization. The background and
effect were measured alternately in 20-min cycles. Once per day the amplification in the channels of each de-
tector was monitored and if necessary corrected by using a precision pulse generator. In addition, for energy
calibration and to determine the resolution function a measurement was performed once per day for an hour
* Central Institute of Physics Research, Budapest.
Translated from Atomnaya Energiya, Vol.42, No.1, pp.25-29, January, 1977. Original article sub-
mitted February 24, 1976.
This material is protected by copyright registered in the name 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 $7.50.
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6 7
recision
pulse
generator
Amplifier
1'
mplifier
2
Amplifier
2'
Coinci-
dence
circuit
Fig.1. Block diagram of experiment: 1) frame; 2) cassette; 3) 252Cf source; 4) 6LiF
target; 5) semiconductor detectors; 6) vacuum chamber; 7) backing of pure aluminum
oxide.
with thermal neutrons obtained by slowing down the fast neutrons in a 12-cm-thick polyethylene block. The
experiment took 3.5 months.
The results of the measurements are shown in Fig. 2. There is good agreement between data correspond-
ing to the measurement of background and effect plus background in the region below the thermal peak. This
shows that the procedure for measuring the background is correct. The width of the thermal neutron peak at
half maximum is 200 keV. This energy resolution is accounted for by the considerable spread in the energy
lost by the reaction products in the dead layer (layer of 6LiF, backing, and the entrance windows of the detec-
tors), since the detectors were placed at a minimum distance from one another to minimize corrections due
to the dependence of the angular distribution of the 6Li(n,a)3T reaction products on En. It is obvious that in
measurements with fast neutrons the resolution function obtained with thermal neutrons will be broadened by
the superposition of effect and background pulses. Additional measurements performed with the precision
pulse generator and a 233U a particle source gave corresponding results and showed that the broadening func-
tion is Gaussian in form with a dispersion a2 = 140 ?30 channel2. Therefore, the real resolution function was
assumed to be the thermal neutron peak Ni', , broadened according to the law
i-k= \
Rk_ N; (1/o)e p[(i-k)2/2a2],
i=k-.1
where c2 = 140 channel2, and i and k are analyzer channel numbers. The results of calculating the background
from data corresponding to the measurement of effect plus background are shown in Fig. 3. The distribution
obtained is the spectrum of neutrons from the spontaneous fission of 252Cf, where N(E) is measured with the
resolution function Rk which can be written in the form
Ni = C 2 a' I e (Ei-k) N (Ej-k) Rk,
where C is a constant, a is a quantity characterizing the dependence of the energy lost by the reaction products
in penetrating the dead layer on neutron energy, and A is the domain of definition of the resolution function.
The data were processed on the assumption that the neutron spectrum is described by a Maxwellian dis-
tribution, and consisted in using Eq. (2) to find the parameter T by the method of least squares. Data estimated
from the 6Li (n, a)3T cross section [6] and corrected for the dependence of the angular distribution of reaction
products on En reported in [7] were used to determine the efficiency e(E). Figure 4 shows the dependence of
the correction 6 and the 6Li(n, a)3T cross section a on neutron energy. The energy of neutrons corresponding
to the i-th analyzer channel was calculated from the expression
Ri=ai - Ri, (3)
where a is the value of the analyzer channel determined from the positions of the a particle, triton, and ther-
mal neutron peaks, taking account of losses, and is equal to 0.0191 MeV/channel; (3i is the difference of the
average energy losses of reaction products in penetrating the dead layer in measurements with thermal neutrons
and neutrons of energy Ei. The function /3 (En) is shown in Fig.4. It was determined, as was 6 (En), by using
data from [7] on the angular distributions of products of the 6Li(n,a)3T reaction.
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0 1 2 En Me V
z Z?10-
01 i 1 r
200 250 300 350 400
Channel number
Fig.2 Fig.3
200 300 400
Channel number
Fig. 2. Results of measurements. Upper: ?) effect plus background; X) background.
thermal neutron peak; ) actual resolution function.
Fig. 3. Results of data processing. ?) Measured neutron spectrum; , --------) results of
parametrization of 170 and 115 points of the spectrum.
The results of the parametrization of 170 points of the experimental spectrum (0 < En < 2MeV) using
Eq. (2) under the assumption that
N(E)=VEexp(-E;T), (4)
are shown by the solid curve of Fig. 3. The parameter T = 1.18 ?0.05, and x2 = 2.32. The error in T was de-
termined from the spread of the results of processing ten sets of measurements, and included the error in the
determination of the dispersion of the resolution function. The open curve shows the results of processing 115
experimental points (0 < En < 1 MeV). In this case T = 1.09 ?0.05 MeV and X2 = 3.06.
It should be noted that the corrections 6 and R used in the calculations are small, and their inclusion
does not change the results significantly. This is shown by the data of the monitoring calculations in which
F_ (En) was taken equal to a(n,a) and Eq. (3) was replaced by the expression Ei = ai, and without taking account
of losses a was found equal to 0.0175. In this case T = 1.13 ?0.05 MeV and X2 = 2.51.
In [8-11], devoted to the study of spectra and angular distributions of prompt fission neutrons in the
energy range En >, 1 MeV, the question of the presence of a neutroncomponent with an isotropic angular dis-
tribution in the laboratory coordinate system was discussed. It was shown in [11] that the spectrum of the iso-
tropic neutron component of the spontaneous fission of 252Cf has the form of a Maxwellian distribution with T =
1.01 MeV, and these neutrons comprise about 20% of the total number of neutrons per fission. This effect
must lead to a softening of the integral neutron spectrum, and may be the cause of the observed decrease in
the parameter T with decreasing En. To test this hypothesis we performed a parametrization of the mea-
sured data using Eq. (2) under the assumption that
N(E)=C,1/Eexp(-E/T!) +C2l/Ee p(-E/T2).
In accord with [11] we took C1 = C2 = 0.5, and for T2 we used the value T = 1.43 MeV determined in the En ;:1-
MeV energy range. For X2 = 2.28, T = 0.98 ?0.05 MeV, which within the limits of error agrees with the value
of this parameter for the isotropic component given in [11]. The corresponding curve of Fig. 3 coincides with
the solid line.
To compare the data obtained with the results of the time-of-flight measurements it is of interest to
process the ?latter in a similar way. To do this the numerical data from [3] for the 0 < En < 1-MeV range
were transformed to an- equivalent form and parameterized by -using Eqs. (4) and (5).. For X2 = 0.56 and 0.54,
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d'b0 5
411,
300 350 400 450
Fig. 4. Dependence of a-, 6, and 0 on
neutron energy and analyzer channel
number.
T = 1.15 =0.03 and T1 = 0.96 ?0.03, respectively. It is clear that these data are in satisfactory agreement
with the corresponding quantities we obtained with a 6Li spectrometer.
Thus, the measurements of the 252Cf spontaneous fission neutron spectrum by a 6Li spectrometer with
semiconductor counters confirm the time-of-flight measurements showing an excess number of low-energy
neutrons as compared with the estimate obtained by extrapolating data from higher energies by using the
exp(-E/T) law. One possible cause of the observed phenomenon may be the presence of an isotropic neutron
component in the laboratory coordinate system.
The authors thank B. D. Kuz'minov and V. S. Stavinskii for a discussion of the results, A. I. Gonchar
for help in setting up the experiment, and A. V. Lukashkin, I. A. Gorokhov, and L. V. Egorova for their part
in the work.
1. J. Meadows, Phys. Rev., 157, 1076 (1967).
2. Yu. S. Zamyatnin et al. , in: Proceedings of the IAEA Symposium Nuclear Data for Reactors, Helsinki,
June 15-19 (1970), p.183.
3. L. Eeld et al., in: Proceedings of the IAEA Symposium Prompt Fission Neutron Spectra, Vienna, Aug.
25-27 (1971), p.81.
4. M. V. Blinov et al., in: Proceedings of the Conference Neutron Physics [in Russian], Pt.4, Obninsk
ONTI FEI (1974), p.138.
5. O. I. Ivanov and V. A. Safonov, At. Energ. , 36, No. 5, 397 (1974).
6. E. A. Seregina and P. P. D'yachenko, in: Problems of Atomic Science and Technology, Ser. Nucl.
Constants [in Russian], No.19, Atomizdat, Moscow (1975), p.10.
7. J. Overley, R. Sealock, and D. Ehlers, Nucl. Phy.s. , A221, 573 (1974).
8. S. Kapoor, R. Ramanna, and P. Ramo Rao, Phys. Rev., 131, 283 (1963).
9. K. Skarsvag and K. Bergheim, Nucl. Phys. , 45, 72 (1963).
10. H. Bovman et al. , Phys. Rev. , 126, 2120 (1962).
11. V. M. Piksaikin, P. P. D'yachenko, and L. S. Kutsaeva.,.Program III All-Union Conference on Neutron
Physics [in Russian], Kiev, June 9-13 (1975), p.35.
1,0 1,5 20 2.5 3,0 E,,,MeV
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THEORY OF SEPARATION CASCADES CONSISTING OF
ELEMENTS WITH SEVERAL OUTLETS
B. Sh. Dzhandzhgava, V. A. Kaminskii,
N. I. Laguntsov, G. A. Sulaberidze,
and V. A. Chuzhinov
In this paper, a further development of the theory of separation cascades is undertaken consisting of
'elements with many outlets [1]; in particular, the separative power of elements with three outlets is investi-
gated and a general procedure is proposed for calculating the optimum schemes of combination of similar
elements.
The scheme of an element is shown in Fig.l. The enrichment process is described by the relations:
$'=e0c(1-c) -1JB In ~. B ,
1(B 1, l3 _ E -4- B 1,
6?=eOC(1-c) In 1, In E+B /
( '
6-=e0c(1-c)ln T3
(1)
(2)
(3)
where E? is the equilibrium coefficient of enrichment, which defines the effect and is dependent on the operat-
ing cycle of the element and the specific method of separation.
We will assume that the specific worth of a mixture with concentration c is determined by a certain func-
tion (b(c). Then, the separative power is found from the relation
6U=x8L(h(c,-61)+(1-x)6L(h(c+6?) (1 -0)L(U(c-6-)-L(D(c).
With regard to the separation of isotopes, the quantities 6+, 6?, and S' are small, the functions 4) (c + 6+)
4)(c + 6), and 'b(c-6-) can be expanded in series in the vicinity of c. Retaining second-order terms, we re-
write Eq. (4) in the form
6U= z [x6L6+2+(1-x)0L602+(1-6) L6-~) a .
Substituting formulas (1)-(3) in expression (5) and isolating terms that are independent of concentration, the
separative power for the two boundary cases - equipment with a constant input flow L and equipment with a
constant flow of the light fraction L' = E + D - is represented, respectively, as
6U = Lo. XL; L = const,
1
-2(1-6)1n 1-,x
In 11 0 + (1-8) In2
- 1-0
6U= L0? XL'; L' = 9L= const,
xl =exL,
Translated from Atomnaya Energiya, Vol.42, No.1, pp. 29-33, January, 1977. Original article sub-
mitted February 3, 1976.
This material is protected by copyright registered in the name 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 $7.50.
I -x8 1-x8 1n2 1
xL = (1-x)0 L x 1-x
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xi;NZM~
-----1 B=(1-8)L,
Fig.1
Fig. 1. Separative element with three outlets.
I
Fig. 2
Fig. 2. Dependence of Xt and ?2/v on the flow separation factor of the light fraction it
[scheme (1, -1.4)].
and the numerical suffix with X indicates the number of barriers for dividing the flow of the light fraction.
It should be noted that when x -- 0 and x - 1, i.e., when the element with three outlets degenerates to
a normal element, the expressions for X convert to the well-known relations for elements with two outlets [2,
3].
We will consider an arbitrary scheme for combining the elements in cascade when the enriched flow Ds
from the s element arrives at the inlet of the subsequent element s + k and the depleted flow Bs reaches the
inlet of the subsequent s - (p -1) element, where k and (p -1) are whole numbers greater than zero. The
flow Es is fed to the inlet of the k + m element, where m is any whole number.
It is obvious that k, with respect to absolute value, should be less than m and (p -1). If the flow Es is
fed forward and in this case m = k, the element degenerates to a normal element. When I m I > k, into the sec-
tion of the cascade with a large concentration of the important component is fed a flow with a lower content,
which is disadvantageous. A similar pattern is observed when ImI (p-1).
It can be assumed in isotopic approximation that the difference in concentrations between neighboring
elements is a quantity that is small and equal to dc/ds [1]. Moreover, as the parameters of asymmetry are
not very large numbers (k > 1,
W (E) dE l1E-1 (EO=E)2 dE for E0-1 1 MeV,
application of the transport approximation for the indicatrix of elastic scattering by iron introduces an error
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I 103
60
010-' 2 4 10? 2 4 10? 2 4 100 2 4 10 '
E, Me v , Me v
Fig.3 Fig.4
Fig. 3. Effect of representation of the constants on the differential
characteristics of the field in the R approximation `I'res(AEi)/(1)subgr
(AEi) for R = 100 cm (the numbers of the curves give the barrier thick-
ness in cm).
Fig.4. Effect of approximating the scattering indicatrix on the differen-
tial field characteristics -tr(AEi)/4p7(AEi) for R = 100 cm (numbers of
the curves give the barrier thickness in cm).
such that for barriers of thickness 60 cm the overestimate in the high-energy component of the transmitted
radiation is observed to be of the order of ten or a hundred, although the integral overestimate of the flux com-
pared with the P7 approximation is less than 1.7 (see Fig. 2).
LITERATURE CITED
1. L. P. Abagyan et al. , Group Constants for Nuclear Reactor Calculations [in Russian], Atomizdat, Mos-
cow (1964).
2. V. F. Khokhlov et al. , in: Nuclear Constants [in Russian], Central Scientific-Research Institute for Atom-
ic Data (TsNllatominform), No. 8, Sec.3, Moscow (1972), p.3.
3. N. 0. Bazazyants et al. , in: Nuclear Constants [in Russian], Central Scientific-Research Institute for
Atomic Data (TsNlIatominform), No.8, Sec.1, Moscow (1972), p.61.
4. V. F. Khokhlov et al. , in: Nuclear Constants [in Russian], Central Scientific-Research Institute for Atom-
ic Data (TsNllatominform), No. 8, Sec. 4, Moscow (1972), p.154. .
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FLOW RATE MEASUREMENT BY MEANS OF CORRELATING
THE RANDOM SIGNALS OF THERMOCOUPLES IN CIRCUITS
WITH A NATURAL CIRCULATION OF COOLANT
V.
M.
Selivanov, A. D. Martynov,
Yu.
A.
Sergeev, V. S. Sever'yanov,
A.
P.
Solopov, V. I. Sharypin,*
D.
Pallagi, S. Horanyi,
T.
Hargitai, and S. TyBgyert
Control of coolant flow rate is a complex problem if the natural circulation of a single-phase liquid is
used to remove heat from the active zone [1], since in this casethe available useful pressure head is measured
in tens of millimeters of water.
With regard to natural circulation, it is worth considering those methods that use flowmeters in which
there is no restriction of the flow (tachometric and correlation methods). Practical experience with turbine-
type flowmeters shows that they are not reliable enough, and do not have a long enough life. Correlation
methods for measuring the flow rate apparently hold more promise [2-5]. Particularly attractive is a method
for detecting temperature fluctuations of the coolant using ordinary thermocouples as detectors. An indispu-
table advantage of correlation flowmeters is their reliability (as a result of the absence of moving parts), a
minimum of pressure loss, and the possibility of obtaining information from the noise of the technological pro-
cess itself.
The present paper considers questions connected with practical processing in the method of correlating
random thermocouple signals for measuring the flow rate of water in circuits with natural circulation (reac-
tors, test stands). The effect of the following factors on the results of correlation measurements were studied
experimentally, the time lag of the thermocouples (with insulation of the hot junction and without insulation),
the base distance between thermocouples (in the range of velocity variation from 0.1 to 1.3 m/sec), and the
positioning of the hot thermocouple junctions in the coolant flow. The investigations were carried out by Soviet
(FEI) and Hungarian (TsIFI) specialists. A dynamic model UKM test stand [6], a loop channel [7] of the First
Atomic Electric Station with fuel-element assembly from an ABV-1.5 reactor, and special measuring appara-
tus (TsIFI) were used for the experiments.
Experimental Apparatus. The UKM test stand (Fig. 1) is a model of a two-circuit nuclear steam-gener-
ating device with natural circulation of single-phase and two-phase coolants in the primary and secondary cir-
cuits, respectively. The active region of the test stand is simulated by four electrically heated units. The in-
puts to these units are made in the form of branch pipes inside of which are set turbine flow-rate sensors with
shaped electrodes. The steam-generator is incorporated into the body of the primary circuit and is collected
from Field tubes. The flow rate of water in the second circuit is controlled by Venturi tubes mounted in the
fall pipes.
The experimental measuring sections of the secondary circuit were situated in front of the inputs to the
cassette units, and consisted of sections of pipes inside of which were set thermocouples. Cable thermo-
couples were used with an external sheath diameter of 0.5 and 1.0 mm. The part of the thermocouples with
an external diameter 0.5 mm had an insulated hot junction. The thermocouples were set at a distance of 2.5-
5.0 tube diameters from the entrance to the tube section. The relative distance of the thermocouple junctions
from the walls y/R was- 0.35, 0.5, and 1.0. Different combinations of thermocouples enabled us to investigate
* USSR.
t Hungarian People's Republic.
Translated from Atomnaya Energiya, Vol.42, No.1, pp.49-52, January, 1977. Original article sub-
mitted February 3, 1976.
This material is protected by copyright registered in the name 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 $7.50.
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Fig.1 Fig.2
Fig. 1. Schematic diagram of the steam generator part of the UKM test stand: 1) active zone; 2)
experimental measuring sections of the first circuit; 3) rise column; 4) steam generator; 5) Ven-
turi tubes; 6) fall pipes; 7) experimental measuring section of the second circuit; 8) rise pipes;
9) separator drum; 10) turbine flowmeters.
Fig. 2. Block diagram of the measuring apparatus: 1) correlation sensor; 2) preamplifier (TsIFI);
3) amplifier (TsIFI); 4) correlator (Hewlett Packard); 5) two-channel recorder (Hewlett Packard);
6) MAS-54 tape recorder; 7) two-beam oscillograph C1-18 (FEI); T, and T2 are thermocouples.
base separations of 10, 20, 30, 80, and 100 mm. The measuring section of the secondary circuitwas equipped
with three sets of moveable thermocouples, and was fitted in one of the fall pipes. The distances between
thermocouples in this section were 10, 20, 30, and 40 mm, which defined nine variants of base separation from
10 to 100 mm. Each set was made up of five identical thermocouples with a hot junction not insulated from the
housing. The diameters on the thermocouple sheaths in the sets were 0.5, 1.0, and 1.5 mm.
The loop channel [71 was set in a regular cell of the active zone of a First Atomic Electric Power Station
Reactor (First AES reactor) and was intended for testing fuel elements of an ABV-1.5 reactor. Two Chromel-
Alumel thermocouples with sheath diameter 0.5 mm and base separation of 20 mm were used for correlation
measurements of the flow rate of natural circulation in the channel. The hot thermocouple junctions were not
insulated from the housing and were set at a distance of 2 mm from the inner wall of an annular channel of
cross-sectional width 8 mm, distant 200 mm from the outlet from the assembly.
Method of Measurement. The essence of statistical methods for measuring velocities consists in the fact
that any random or periodic signals propagating in a moving medium can, theoretically, be analyzed in order
to determine the time characteristics of the flow. In our case these signals were the temperature fluctuations
of the coolant.
The measuring apparatus consisted (Fig. 2) of a preamplifier, a basic amplifier with a filter, a universal
correlator, a two-channel automatic recorder, and a tape recorder for recording the thermocouple signals.
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tire,.
m /sect
1,4 F-
0
0 000 0000
U ?j
of o~ ? - 0 ? I
0,8
06
0,05 c,1 42 0,3 0,5 0,7 1,0 2,0
/(z= is S 0 01 0,2 w, m/sec
Fig.3 Fig.4
Fig. 3. Results of the measurements as a generalized function of the dimensionless quantity KT =Ta(W/S):
?) measurements in the primary and secondary circuits of the UKM test stand, respectively; A) mea-
surements at the output of the loop channel assembly. .
Fig.4. Results of velocity measurements on the flow axis in the first circuit of the UKM test stand: a , ? ,
A) TsIFI section; O,C,O) FEI section; , ) theoretical value of the velocity with y/R = 1.0 for stabi-
lized flow. Base separations S, mm: ^ and ^) 10; ? and 0) 20; land A) 30.
Over a specified time interval in the steady-state regime, the signals from two thermocouples separated by a
distance S in the flow were fed, after amplification and filtering, to the universal correlator, which reproduced
the autocorrelation function (ACF)
~T
C,_. (T) = liln 1 Ul (t) U2 (t=T) dt.
2T
T
The "flight" time T0(c) (time for the random signals to traverse the distance S between the thermocouples) and
coolant velocity Wk(m/sec) were determined from the position of the ACF maximum, Eq. (1). The results of
these measurements were compared with the theoretical value of the velocity over a section of stabilized flow,
and also compared with the mean flow velocity obtained in the primary circuit of the UKM test stand from tur-
bine flowmeters, in the secondary circuit from Venturi tube data, and in the loop channel of the First AES
reactor from heat balance data. The turbine flowmeters and Venturi tube were calibrated in the flow test
stand. The error in the calibration data was less than ?3%.
Discussion of Results. It is well known [3-5] that the form and amplitude of the ACF maximum, which
reflect the nature of the correlations between the sensor signals, depend on the placing of these sensors,
their base separation, their time lag, and the level of electromagnetic noise.
To allow for the complex interrelations between correlation stability of the thermocouple signals and
these factors the following dimensionless quantity was adopted in order to generalize the experimental data
which is the ratio of the thermocouple time constant Ta to the flight time To corresponding to the mean veloc-
ity of the flow. Thanks to this quantity it was possible to represent all the results obtained in the range of
parameters (meanvelocity 0.1 W 1.35 m/sec, base separation 0.1 S < 0.1 m, sheath diameters of ther-
mocouple cables 0.5!5 d0 < 1.5 mm) in the form of a single generalized function
wciW, = / IT. (W/S)], (3)
where Wc/Wst is the ratio of the velocity measured by the correlation method to the theoretical velocity of
stabilized flow in the place of measurement, T. is the time lag of the thermocouples (without and with insula-
tion of the hot junction from the housing) calculated according to the recommendations of [8].
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Results of the measurements are given in Fig. 3 in the form of the function Eq. (3). It was established
that a stable correlation exists between the thermocouple signals in the range of variation of the dimension-
less quantity 0.1 _ 140 keV the experimental
results are in good agreement. The smooth curve shows the computed variation of the cross section with
parameters S(0) and dS/dE.
Also given there are the experimental data on the differential transverse cross section at an angle of 0?
for this reaction obtained by us and in [2,4]. In this case as well the data of all the reports are in satisfactory
mutual agreement for Et >_ 140 keV. The observed deviations in the experimental data of [2, 3] at low triton
energies are explained by the inaccurate determination of the energy of the interacting tritons.
The basic inaccuracy in the measurements was presumed to be in the determination of the energy of
the tritons at the entrance to the gaseous target. The statistical measurement errors and the errors in deter-
mining the gas pressure and the tritium concentration were 1-5; ?3; ?5is, respectively.
Let us compare the cross sections for the mirror reactions T (t, 2n)9He and 3He(3He, 2p)4He at small
energies. A similar energy dependence
s (u~
is recommended in [10] for the total cross section of the second reaction (neglecting the second term of the
expansion in the zeroth approximation) with an astrophysical factor equal to S(0) = (50 ?5)10-22 cm?keV. From
this it follows that the ratio of the astrophysical factors for these reactions will be S(0) TT/S(0)tt = 24 ? 2.6. If
we include the pre-exponential coefficient in the expression for the Coulomb barrier permeability, proportion-
al to z2/zz = 4, then the ratio of these factors will be S' (0)TT/S' (0)tt = 6.00 ?0.65.
This difference in the cross sections is due to the nuclear interaction and seems somewhat surprising.
However, it can be qualitatively understood that these reactions involve three particles and that the interac-
tion of the particles in the final state must be taken into account.
In the reaction 3He(3He, 2p)4He it is possible to form a quasistationary state of the 5Li nucleus and a
virtual state of two protons. In the T (t, 2n)4He reaction a quasistationary state of the 5He nucleus and a virtual
dineutron, 2n, are formed in the final state. When a quasistationary state is formed the reaction cross section
must be proportional to the integral [11]
Eo+r r2i'4 "1 1/2 A
~g-E0)2 T`, 4
Eo--r
where E is the relative energy of the interacting particles; Q is the reaction energy; Eo is the energy of the
quasistationary state (E0 = 0.96; 1.96 MeV for 5He and 5Li); I'/2 is the width of the quasistationary state (r/2 =
0.58; 1.5 MeV for 5He and 5Li).
Similar expressions may be written for other cases of virtual state formation.
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In such a case the ratio of the factors for the cross sections for reactions involving the formation of
5He and 5Li may be equal to S'(O)TT/S'(O)tt 3.5; while for formation of the 5He* and 5Li* systems, S'(0)TT/
S'(O)tt 1-1.5. From similar estimates for the cases of 2n and 2p systems being formed in the final state
we find that the ratio of the factors will be
S'(O)TT/S'(O)tt 10.
From this it follows that the contribution of the channels involving formation of 5He* and 5Li* must be small
(6 < 0.4) while the contribution of the channels with formation of 5He and 5Li may be 6 0.6. These estimates
do not contradict the form of the proton and neutron spectra from these reactions [9,10].
LITERATURE CITED
1. V. Crocer, S. Blow, and C. Watson, in: Proceedings IA.EA Symposium on Nuclear Data for Reactors -
1970, Helsinki (15-19 June, 1970), Vol. I, p. 67
2. H. Agnew et al., Phys. Rev., 84, 862 (1951).
3. A. M. Govorov et al. , OIYal Preprint, R-764, Dubna (1976).
4. Yu. V. Strel'nikovet al., Izv. AN SSSR, 'Fizika, 35, 165 (1971).
5. R. Wolke et al. , Phys. Rev. , 129, 2591 (1963).
6. J. Phillips, Phys. Rev. , 90, 532 (1953).
7. S. Warschaw, Phys. Rev., 76, 1759 (1949); D. Kahn, Phys. Rev., 90, 503 (1953).
8. H. Reynolds et al., Phys. Rev., 92, 742 (1953).
9. C. Wong et al. , Nucl. Phys. , 71, 106 (1965).
10. Al. Dwarakanath, Phys. Rev. , 4, 1532 (1971).
11. A. I. Baz', Ya. B. Zel'dovich, and A. Al. Perelomov, Scattering, Reactions, and Decay in Nonrelativ-
istic Quantum Mechanics [in Russian], Nauka, Moscow (1966), p. 328.
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CHRONICLES OF THE COMECON
Meeting of Executive Delegates of COMECON Countries
on Isotope Production (SOP-76)
The meeting took place September 6-9, 1976, in Predal (Rumania). The delegates agreed upon proposals
concerning further specialization in the manufacture of 50 isotopic preparates. The meeting also discussed
the development and organization of production in the COMECON countries of new products that are now being
imported.
In agreement with the operational schedule of the Planning Committee on the Uses of Atomic Energy
of the COMECON, model monographs have been prepared on several radioactive pharmaceutical preparates.
A list of general methods to be developed on the topic "Radioactivity," their executors, and time schedules
have been ratified for 1977-1978.
The meeting discussed proposals on the subject "Unification of Regulations. on the Preparation of Materi-
als for Licensing the Use of Sealed Radiation Sources." The desirability of unified certificates on sealed
sources has been stressed. The delegates approved the results and recommendations of the sleeting of Spe-
cialists conducted during SOP-76 on the cooperation of COMECON countries in the development of composi-
tions for radioimmunoanalysis.
A preliminary agreement has been reached on the discussion of the following standards on "Radioactive
Preparates" at the next meeting of the Commission in 1978-1980: 1) marking and certification; 2) gaseous krip-
ton-85; 3) gaseous tritium; 4) tritiated water. At the same time, the meeting considered the desirability of and
methods for the development of new regulations for marking labeled organic compounds to conform to inter-
national practice, and agreed upon a working schedule on this subject for 1977-1978.
The Session of the Committee of the Council of Science
and Technology - Radiation Engineering
The session took place September 7-10, 1976 in Debrecen (Hungary).
The council coordinated plans for the predicted developments in the basic fields of radiation engineer-
ing and technology to 1990, and submitted it for consideration before the next session of the council; approved
the Soviet delegation's proposals for methodical recommendations in the field of dosimetry of radiation-engi-
neering facilities using electron accelerators and in the unification of sanitary standards on their locations and
operation. The council also approved the structure and unified technical specifications for radiation-engineer-
ing facilities: the technical parameters of the radiation process, the basic technical characteristics of the
facility, the specifications of radiation sources, the requirements of radiation protection, automation systems,
and transportation, and monitoring and measuring instrumentation and automatic devices; general specifications
on construction, and on monitoring and measuring equipment. The council discussed the program of compre-
hensive research in standardization in radiation engineering. It coordinated the reports to be presented at the
coming Symposium on Radiochemical Modification of Polymers (Poland, September 1977), put forward a work-
ing schedule of the council for 1977-1978, and worked out a preliminary agenda for the next session of the council.
Conference of COMECON Specialists on the Development
of Compositions for Radioimmunoanalysis
The conference took place September 8-9, 1976 in Predal (Rumania). The conference noted that consid-
erable work is in progress on the development and manufacture of compositions intended, first of all, for the
Translated from Atomnaya Energiya, Vol.42, No.1, pp.62-63, January, 1977.
This material is protected by copyright registered in the name 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 $7.50.
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examination of donors in view of widespread cases of hepatitis, of compositions of triiodinethyronin, carcino-
embryonic antigen, phytoprotein, and others which can be used in prophylactic examinations of the population.
Conference of the Parties to the Agreement on Multilateral
Specialization and Cooperation in the Manufacture of
Isotopic Products
The conference took place September 10-11, 1976 in Predal (Rumania). The conference heard reports
on the execution of primary and secondary orders, on product quality, re-export, etc. The parties coordi-
nated proposals for expanding the list of specialized products, and refined and supplemented the technical
specifications and parameters of some of these products.
Participants of the conference expressed satisfaction with the way the agreement is executed and stressed
that the work of all negotiating parties on its realization brought appreciable results.
The Tenth Session of the Committee of the Council of Science
and Technology on Processing Irradiated Fuel of Atomic
Power Plants
The session and a meeting of specialists in the technology and construction of plants for regeneration of
fuel elements of water-cooled water-moderated power reactors took place September 14-17, 1976 in Budapest
(Hungary). The session heard reports of specialists from Hungary, GDR, Poland, Rumania, the USSR, and
Czechoslovakia on the work done in the various countries in 1971-1975. In Hungary, anorganic sorbents have
been investigated for the extraction of radioactive elements. The importance of further progress of studies
in the GDR on the kinetics of extraction of uranium, plutonium, neptunium, zirconium, niobium, ruthenium,
cesium, and iodine, and of expanding the studies to conditions with stronger phase mixing has been noted.
Polish scientists successfully worked on new methods of extractant regeneration free from the formation of
salt wastes. The possibility of using local petroleum fractions as tributylphosphate diluents in extraction
technology is studied in Rumania. The Soviet delegation reported on advances in extraction processing of
spent fuel elements of water-cooled water-moderated power reactors with short cooling times and on the de-
vising of various extraction equipment (mixer-settlers, pulsating columns, centrifugal extractors). Czecho-
slovak workers proved the possibility of selective extraction of cesium and strontium, and of trivalent actinide
elements with the aid of a cation exchange extractant of a new kind.
The council and conference approved the trend to specialization in the discussed works and stressed the
desirability of further concentration of efforts of specialists of the various countries on problems which are
expected to yield original results.
Technical tasks in the working schedule for 1976-1980 in the discussed field have been approved.
The preparation of an experiment on comparing the results of determination of elements in solutions
of the spent fuel elements of atomic power plants has been discussed. The plan of the experiment prepared
by GDR, Soviet, and Czechoslovak specialists and the schedule of the first stage of the experiment have been
agreed upon.
The committee reviewed and coordinated the operating schedule of the Planning Committee on the use
of Atomic Energy in the COMECON countries on the processing of irradiated atomic fuel for 1977-1978, and
redefined the schedules for certain subjects for 1976-1980.
The Seventh Session of the Committee of the Council of Science
and Technology on Nuclear Research Reactors
The session took place in Piestiany (Czechoslovakia) September 27-October 1, 1976. Participants of
the session discussed and approved a proposed report on the work of the council and on the results of investi-
gations in the subject "Design and Improvement of Nuclear Research Reactors and Their Use in Reactor
Physics and Engineering Research. " The session heard a report of Hungarian specialists on the results of a
conference of COMECON countries on training personnel for atomic engineering, and agreed upon a plan of
cooperation on the topic "Use of Low-Power Research Reactors, and Critical and Subcritical Assemblies for
Training Personnel for Reactor and Nuclear Power Engineering. " Various fields of cooperation between the
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COMECON countries and the IAEA were planned for 1976-1980. A project of a schedule of the council on
nuclear research reactors has been approved.
The Tenth Session of the Committee of the Council of
Science and Technology on Fast Reactors
The session took place October 4-8,1976 in Kiev (USSR). The session discussed the execution of the plan
on the topics "Investigation of Fast-Neutron Reactors" scheduled for September 1975 to August 1976.
Participants of the session approved the proposals of Soviet specialists on the creation of a common
experimental base for the design of equipment and instrumentation of fast sodium-cooled reactors.
The specialists discussed and approved the proposals of the Soviet delegation on the cooperation in 1976-
1980 in the introduction of high-power, sodium-cooled fast reactors after 1980.
The schedule of the work of the council in 1977-1978 has been discussed and coordinated. The session
discussed the preparation of a conference of COMECON specialists on the subject "Problems of Technology
and Corrosion in Sodium Coolant and Protective Gas" which is planned to take place in Dresden (GDR). A
supplementary plan has been agreed upon on nuclear data studies which are carried out for the council. A plan
for further studies in the development of methods and programs for physical calculations in fast reactors has
been discussed and coordinated with the participation of scientists of various countries.
The Twenty-Third Meeting of the Working Group on Reactor
Science and Engineering and on Atomic Power of the Planning
Committee on the Uses of Atomic Energy of the COMECON
The meeting took place October 5-8, 1976 in Ostrava (Czechoslovakia). Its participants heard a report
of the Secretariat on the resolutions of the 14th Session of the COMECON Committee on.Scientific and Techni-
cal Cooperation associated with the preparation of proposals of long-term programs for cooperation in the pro-
vision of economically justified needs of COMECON member countries with the principal kinds of energy, fuel,
and raw materials. The Working Group recognized the need of beginning the preparation of technical and eco-
nomical grounds for the problem.
A list of subjects the work on which is to be carried out separately by agreement between the various
countries has been discussed and coordinated.
Reports of Polish and Czechoslovak specialists have been heard and discussed on cooperation in the use
of VVER-440 water-cooled water-moderated power reactors in nuclear thermal power plants. The possibility
of cooperation of COMECON member. countries in the development of a reactor plant for an atomic boiler has
been discussed. The Working Group plans a seminar devoted to this topic to be conducted in 1977. Proposals
on the cooperation in predicting.the development of nuclear energy in the COMECON countries have been con-
sidered and the principal directions of work on this subject have been determined.
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INFORMATION: SEMINARS, CONFERENCES, AND MEETINGS
A Soviet-French seminar on "The conception of errors in fast-reactor layouts, and the construction
of the basic equipment and auxilliary systems" was held in France in June; 1976. Each side presented 10
papers and reports. The papers presented by the French specialists were concerned with the equipment of
the Super Phoenix reactor now under construction (fuel recharging system, control and safety rods, heat exchang-
ers, pumps, and sodium purification systems). They considered methods of strength calculations for reac-
tor assemblies as well as welding of tubes with tube plates for heat exchangers and steam generators. Ob-
servations were made about the construction of a fast reactor following Super Phoenix.
The papers delivered by the Soviet specialists were devoted in the main to the equipment of the BN-600
reactor and analysis of the layouts of the BN-350 and BN-600 and a future fast reactor,
The French program provides for the early development of a breeder reactor that would be economically
competitive with thermal reactors and organically fueled power stations.
The successful start-up of Phoenix, with a power of 250 AIW(E), was a stimulus for the construction of
the larger Super Phoenix reactor with a power of 1200 BIW(E); the designing has now been completed and a
decision has been made to go ahead with its construction. However, the ultimate economic indices (according
to the results of the construction, design, and research work) of an atomic power plant with such a reactor,
as noted by the designers, are still somewhat inferior to those of atomic power plants with water-moderated
water-cooled reactors. The latter circumstance has served as a stimulus for improving the characteristics
of Super Phoenix in order that it may be the basis for developing a much more powerful reactor, Super Phoenix
2 (1800-1900 MW), which will not be economically inferior to other electricity-generating facilities. Plans
call for the construction of Super Phoenix 2 on the Saone River (5-6 units) without the participation of foreign
capital but with the involvement of companies from the German Federal Republic (GFR) and Italy.
A characteristic of the general concept of creating commercial fast reactors is that of using an integra-
ted layout. The French specialists do not deny that neither of the two layouts (integrated, loop) considered
at the present time have any significant advantages. The decisive factor in the choice is the experience gained
in the design, start-up, charging, and operation of demonstration reactors. Such experience has been accumu-
lated in France as a result of the successful operation of Phoenix with integrated layout. However, even within
the framework of such a design there is a large number of alternative solutions. The following were adopted
as the most important for Super Phoenix (see Fig. 1).
The reactor tank is suspended by the top from a strong bearing plate, and the heat-exchanger installation
is mounted on the sliding support of the pumps on the bearing plate. No in-pile storage is provided for spent
fuel assemblies (FA). Consideration was given to unloading spent FA with an after heat of 20 kW from the
active zone into an external storage (drum) in a sodium-filled cylindrical case. These are also transported in
sodium-filled containers (the heat release of each FA is up to 10 kW).
Graphite is completely excluded from the neutron shielding and is replaced by steel. This is explained
by: firstly, the considerable swelling irradiated graphite experiences when it comes in contact with sodium
(if the can is unsealed, when the graphite rod is disturbed), which leads to rupture of the can; and, secondly,
the increase in the spacing between the active zone and the heat exchangers, as a result of which a sodium
layer ,in combination with steel constitutes effective shielding.
The reactor has no high-speed automatic mechanisms which act on the flow rate. The response time of
the slide valves cutting off the flow through pump (check valves were rejected) and heat exchanger is 30-40 sec;
the latter are operated by a remote-control manual actuator only if the reactor has been shut down.
Translated from Atomnaya Energiya, Vol.42, No.1, pp.64-65, January, 1977.
This material is protected by copyright registered in. the name 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 $7.50.
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Fig.1. Diagram of layout of assemblies
in the Super Phoenix reactor; 1) active
zone; 2) neutron shielding; 3) intermedi-
ate; 4) central column; 5) recharging
mechanism; 6) primary-circuit pump; 7)
reactor vessel; 8) safety housing.
There was a discussion of the various kinds of units and interlocks effecting the automatic transition of
the reactor from one set of operating conditions to another. If any pump in the primary or secondary circuit
is damaged, the reactor is shut down, the pertinent pump or heat exchanger is cut off, and the reactor is then
put at the appropriate power level. It is felt that false responses due to the large number of interlocks are
safter than shutdowns as a result of the failure of the basic equipment.
The neutron shielding in the upper part of the fuel assembly is acknowledged to be rational from the
point of view of reducing the shielding outside the side shield. However, French specialists are working to
produce a packet with dismountable upper shielding suitable for repeated use.
The hydraulic system used has a general collector at the heat-exchanger outlet and the inlet of the pumps.
In this system the heat exchangers and pumps function independently; the shutdown of one primary-circuit pump
does not entail the shutting down of the corresponding intermediate heat exchangers, secondary-circuit pump,
and steam generator (as is the case in the BN-600).
Because of the choice of a rational system for cooling the reactor tank and guided convection in the hot
and cold zones of the tank, a comparatively small heat transfer is -ensured in the shell separating the cold and
hot zones; as a result, more acceptable operating conditions are created for it. Radioactive systems outside
the reactor are practically completely eliminated by the placement of all units of the primary circuit, and even
the cold traps, inside the reactor tank. Inside the tank is heat insulation consisting of a large number of lay-
ers of steel mesh, arranged on the upper bearing plate and the walls of the vessel in an inert-gas medium.
The argon pressure in the gas cavity of the reactor is very low, 0.05 kgf/cm2 (0.5 kgf/cm2 in the BN-600).
With allowance for the swelling of the structural materials, the gap between the packets has been in-
creased to 7 mm (the "wrench" size of the hexahedron is180 mm). During recharging the upper part of a bent
packet may deviate from the vertical by 61 mm. The sodium temperature at its outlet is monitored by thermo-
couples (three thermocouples above each packet). The thermocouples can be replaced during the operation of
the reactor.
Further reduction of the costs of an atomic power plant is connected with a reduction in the metal inten-
sity of the assemblies. This is explained to some extent by the transition to the frame construction of the
steam generator. As-for the reactor, attempts are being made- to reduce the size of the vessel (or to signifi-
cantly increase the power in that vessel) through the rational layout of elements inside the tank, reduction of
their number (consolidation), combination of a number of elements (combined pump-heat exchanger unit),
changes in the characteristics determining the dimensions (rpm's of pumps, and intermediate heat exchangers),
74
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The Soviet delegation visited the Rhapsodic and Phoenix reactors. A maximum burn-up of 18% was
attained with mixed oxide fuel in six fuel elements of Rhapsodie (maximum can temperature 700?C, thermal
load 430 W/cm). A small rotating sample will be reconstructed and a new thermometric grid will be estab-
lished, two thermocouples being installed for each FA to monitor the sodium temperature at the outlet of
each fuel assembly. As of June 18, 1976, the power plant with the Phoenix reactor had produced 3.2 billion
kW- h of electricity at a cost of 3.5 centimes/kW-h. During the visit to the reactor fuel recharging was under
way and the throttle assembly on one of the steam generators was being inspected.
The delegation was also shown two groups of experimental stands in Cadarache and in Grand Quevy
(near Rouen).
The seminar enabled specialists to exchange scientific and technical information, and to compare engi-
neering solutions adopted in our country and in France in the. development of fast reactors. The consensus
was that this had been an extremely useful exchange.
A symposium on fusion-fission systems was held at the Lawrence Livermore Laboratory (California)
July 13-16, 1976. Twenty-three papers devoted to the physics, technology, and economics of hybrid fusion
(or thermonuclear) reactors were presented. Separate discussions were held on the economics of hybrid
systems, on the structural designs of various types of reactors, the design of the reactor blanket, safety
of reactor operation, and protection of the environment. The American party presented plans for financing
the development of projects of hybrid reactors in the USA by both federal organizations (ERDA) and individual
firms.
The hybrid fusion reactor is a system in which 14-MeV neutrons produced during the fusion of deuterium
and tritium nuclei are used for fission of nuclear raw materials and for producing fissionable isotopes. The
vacuum chamber of the fusion reactor is enveloped by a blanket, containing 238U or 232Th, where the bulk of the
heat is generated and nuclear fuel is produced. The symposium heard about projects for hybrid reactors based
on various fusion devices: open traps, tokamaks, and systems with laser ignition, 0-pinch, and solenoids. All
the papers noted that their advantage lies in the possibility of producing a large quantity of fissionable isotopes
239Pu and 233U) for subsequent burning in thermal reactors. A hybrid reactor can yield 700-1000 kg plutonium
a year per 1000 MW(T), which is, e.g. , 10 times as much as produced by a present-day breeder reactor of
the same power, and 3-4 times the possible yield, in principle, of fast breeder reactors. Most projects use
natural or depleted uranium in the blanket.
A reactor project based on an open trap was presented by the Lawrence Livermore Laboratory. It con-
sidered a modification of spherical blankets for the production of plutonium and 233U. The blanket was designed
in spherical form so as to ensure uniform irradiation of the nuclear fuel and to make for easy dismantling.
The combination of a hybrid reactor with a water-moderated water-cooled reactor produces electric energy at
acost of about 2.5 cents per kW-h, which is comparable with the cost in the nuclear power industry in the im-
mediate future. The basic design of this reactor is being developed by General Atomic.
The Princeton Plasma Physics Laboratory presented a group of papers on a hybrid reactor based on the
tokamak. The plasma parameters are similar to those of the TFTR which is to be built in 1980. The neutron
radiated power from the plasma, 0.75 MW/m2, is sustained by the injection of 180-keV deuterons. The papers
paid much attention to the construction of a divertor for removing contaminants from the plasma.
A paper on the development of a reactor to burn actinides was presented by Westinghouse. The idea of
burning radioactive waste and at the same time generating power is an interesting one, but efficient burning
requires a high density (up to 10 MW/m2) of the neutron radiation from the plasma. Papers from this area of
research are to be presented.
Translated from Atomnaya Energiya, Vol.42, No. 1, pp.65-66, January, 1977.
This material is protected by copyright registered in the name 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 $ 7.50.
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The Los Alamos and Livermore laboratories presented projects for hybrid fusion reactors based on
laser ignition of the target as well as papers on the parameters of such reactors based on 0-pinch and a
solenoid with plasma heating by a relativistic electron beam or a laser. The proposed variants provide an
opportunity to consider a reactor of convenient geometric form and not very high power level. Thus, a
pulsed reactor developed by the Livermore Laboratory has an output electrical power of 400 MW at a total
thermal power of 1400 MW and can produce 1.3 tons of plutonium a year. The drawback of most pulsed sys-
tems is that a large electrical power circulates in the internal circuit.
Papers presented by the I. V. Kurchatov Institute of Atomic Energy considered problems of the choice
of optimal plasma and neutron-physical parameters of hybrid reactors and studies on the possible use of
modules in the projected DTRT (T-20) unit.
A lively discussion took place during the symposium on the economic indices of hybrid reactors and the
choice of the fuel cycle. Regardless of the fact that the cost of an electric power plant with a hybrid fusion
reactor is 1.5-2 times that of an atomic power plant with a breeder reactor, the combined power generation
by hybrid fusion and thermal reactors is just as economical (according to price of power plant) as power ge-
neration by fast and thermal reactors. Appreciable advantages of the hybrid reactor are the possibility of
burning a significant quantity of 238U without recharging fuel, operation with natural or depleted uranium, and
the absence of limitations on fuel doubling.
The final outcome of the symposium is a conclusion about the promise held out by the use of hybrid re-
actors as producers of fuel for thermal reactors while at the same time generating electricity. The reduced
requirements with respect to plasma characteristics make it possible to count on the construction of the first
commercial hybrid reactors by the end of the century. The type of fusion unit and the range of the optimal
parameters of such a reactor will have to be chosen in the near future. It is proposed to discuss these topics
at the next symposium.
The eighth international meeting was held in Cannes (France) September 6-10, 1976, with 1245 specialists
from 35 countries attending. The plenary and section meetings heard more than 260 papers on practically all
methods of nondestructive testing of structural materials, finished products, and equipment in service. How-
ever, the majority of the papers were devoted to the theory and practice of methods based on the application of
ultrasound, acoustic emission, penetrating emissions, and electromagnetic fields. The subject matter of the
papers reflected the main directions in the development of nondestructive testing techniques; increased reli-
ability and accuracy of the techniques; use of computers for gathering, processing, and storing results; mecha-
nization and automation of testing processes; etc. A comparatively large number of papers considered the
techniques and-technical means of nondestructive testing for the needs of atomic engineering.
Active Zone of Nuclear Reactor. The accelerated development of the nuclear power industry is linked
with a significant increase in the production of extremely thin-walled tubes for fuel-element cans. An ultra-
sonic unit developed in France makes it possible to carry out the flaw detection and check the geometric di-
mensions of such tubes at one pass. A distinctive feature of this apparatus is that the tube moves progressi-
vely whereas the ultrasonic sensors remain immobile. The capacity of the unit is 8-15 times that of units
used for the purpose at present. Interesting data were given about the application of computers in the ultra-
sonic testing of extremely thin-walled tubes when, in addition to their own functions, the computers also per-
form the functions of the operator (Denmark).
Translated from Atomnaya Energiya, Vol.42, No.1, pp.66-68, January, 1977.
This material is protected by copyright registered in the name 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 $7.50.
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The stability of fuel elements depends to a significant degree on the quality of the light welded joints.
From this point of view an apparatus of practical interest is a 10-MHz one for testing the welded joints of
fuel elements in zirconium-alloy cans. With this apparatus it is possible to detect pores of more than 0.2
mm in diameter and zones of poor fusion measuring more than 0.06-0.08 mm in a seam root (France).
A detailed paper was delivered on the technique of inspecting defects, the content and distribution of
235U, thermal conductivity, and distribution of mass along the length of a hexadedral fuel element ("wrench"
size 12.7 mm, diameter of axial aperture 2.5 mm, length 1.22 mm) based on graphite with fissionable ma-
terial in the form of a solid solution of uranium carbides with zirconium, designed for operation at 2750?K
and a specific power of 4500-5000 MW/m3 (USA).
Neutron radiography has come into increasing use in recent years for studying the condition of irradia-
ted fuel elements. Therefore, particular interest was aroused by a paper containing comparative data about
the accuracy with which the diameters of the pellets and radial gaps in fuel elements are measured by radio-
graphic and neutron-diffraction methods, conducted on unirradiated simulators of fuel elements in zirconium
cans. Detection of damaged fuel elements in a packet (without dismantling it) was the subject of two papers
by American specialists. They reported on the results of research on the detection of fuel elements with
defects on simulators of fuel-element assemblies of FFTF and EBR-II fast reactors by neutron-diffraction
methods. In assemblies containing ^-100 fuel elements it will be evidently possible to detect fuel-element
damage. Neutron radiography is also employed in France to inspect working gaps in thermoelectric elements
and to determine the hydrogen content in zirconium getter pellets.
Channel-type reactors require apparatus for periodically monitoring the state of the channel tubes. In
Canada, longitudinal defects in zirconium-alloy channel tubes in CANDU reactors are detected by an apparatus
which has an ultrasonic head with four scanners to move axially, testing a channel tube over its entire peri-
meter and length (6.5 m) at the rate of 6 m/min during reactor shutdown. Defects of a depth of more than 0.12
mm are detected.
Heat Exchangers. The eddy-current method has found most extensive application in monitoring the
state of tubes in heat exchangers in use. Inspection at two or three frequencies makes it possible to enhance
the sensitivity to defects in tubes against the background of interference (GFR). Preliminary investigations
have been carried out in the USA on ultrasonic testing (from inside tubes) for defects in two-layered tubes,
with an inside diameter of 27.6 mm and a wall thickness of 4.6 mm, used in building steam generators for the
EBR-II fast reactor. Butt welds in heat exchangers are successfully inspected by the radioisotopic method.
A portion of 170Tu measuring 0.5 x 0.5 mm (half-life 128 days) is inserted into the tube, which has an inside
diameter of 14 mm. Panoramic radiography of the welded joint is carried out in six minutes. Pores of diam-
eter greater than 0.18 mm are detected in this way (Great Britain). For these purposes the Baltieu Co.
(Belgium) has developed the Nuclex apparatus with panoramic x-ray tube with an external movable anode of
outside diameter 12 mm (operating voltage 70-90 kV, focal-spot diameter 0.1 mm).
Reactor Vessel and Structural Elements. As is well known, great difficulties are encountered in the
ultrasonic testing of welded joints in components made of austenitic stainless steel. To detect hot cracks in
the process of multipass welding of thick-walled tubes during fabrication of atomic power plant equipment,
the Guard Co. (USA) irradiates the cracks with acoustic emission. In the Federal German Republic, equip-
ment has been constructed for ultrasonic fault detection of welded seams in the primary circuit of the SNR300
fast reactor; this circuit is made of the austenitic steel Kh6CrNi1811. The inspection is carried out with
several inclined scanners operating at 1-2 MHz. Some papers noted the advantages to be gained by employing
inclined separate and combined scanners for these purposes (Austria, GFR), and in a number of cases com-
bined or even focused scanners (France, Japan).
Papers presented at the conference also considered the pros and cons of systems developed for testing
reactor vessels from the outside (USA, Sweden) and from the inside (GFR, France, Japan, Great Britain,
USA). Quite a large amount of experimental material has been accumulated on the acoustic-emission testing
of structural elements of the reactors of atomic power plants at Calvert Cliffs (USA), Fessenheim (France),
and a boiling reactor in Sweden. The capabilities of the methods for periodic inspection of the primary con-
tour have been well verified and it is now being put into practice. In coming years operating reactors will be
equipped with systems for acousto-emission inspection of medium complexity and those to be constructed, with
more complex systems. A characteristic feature of the conference was the quite large number of papers on
the acousto-emission method of monitoring diverse phenomena which occur during testing of materials (phase
transformations, mechanical and thermal effects, corrosion, etc.).
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Of great interest to specialists were the papers on the determination of the origin and geometric dimen-
sions of defects detected by various methods (USSR, France, GFR, USA, Czechoslovakia, Polish People's
Republic, Bulgarian People's Republic, etc.), the electromagnetic stimulation of ultrasonic vibrations in test-
ing rods (Great Britain), on the determination of grain size by ultrasonic techniques (GFR), on the monitoring
of the ferrite content in austenitic steels (Bulgarian P. R.), on an ultrasonic method of monitoring the degree
of cold strain, depth of the hardened layer, and surface roughness (France), and many other applications.
As before, radiation methods occupy the leading position among nondestructive testing methods. Almost
one-fifth of the papers at the conference were devoted to questions of the theory and practice of the method.
In recent years, much attention has been paid to the automation of the testing processes. An example
of the comprehensive solution of the problem is the ultrasonic apparatus constructed by the Krautcramer com-
pany (GFR) for quality inspection of thick plates. The apparatus incorporates all the latest achievements: self-
adjustment of the testing zone, automatic control of the sensitivity with the depth of the defect, use of a com-
puter, etc. An original automatic unit for ultrasonic detection of flaws in welded seams in flat structures with
digital printout of the results of the testing has been developed in Japan. Many papers gave the technical spe-
cifications of automated equipment for testing rolled metal (USSR, USA, Japan, GFR, France, Great Britain,
etc.).
A large exhibition of nondestructive testing equipment was organized for the conference delegates. Sixty
of the leading companies of Western Europe, the USA, and Japan displayed all sorts of functioning equipment
(built mainly as modules), apparatuses and auxiliary equipment for nondestructive testing. Digital readout
of the quantity tested and graphical display of the results of the inspection are employed in the apparatus. High
quality of manufacture and an eye-pleasing external appearance are features of the apparatus.
On the whole, the conference proceeded in an organized and businesslike manner. Note should be taken
of the great attention which the French members of the organizing committee paid to the Soviet delegation.
Meeting during the conference, the International Committee on Nondestructive Testing decided to hold
the next conferences in Australia in 1979 and in the USSR in 1982.
CHEMICAL EQUIPMENT AT `ACHEMA-76 EXHIBITION
The purpose of the international exhibition which was held June 21-26, 1976 in Frankfurt-am-Main (GFR),
was to demonstrate the newest chemical equipment apparatus in order to complete commercial transactions.
All the major manufacturers of such equipment participated.
The latest equipment presented at the exhibition contained a wide assortment of nonmetallic materials
such as ordinary and metal-reinforced plastic, fiber plastic, and glass. The Quickfit company (GFR), e.g. ,
showed 5-m3 glass reactors and columns of 1-m diameter. Also shown were compensators made of metal-
reinforced rubber and gates closing the flow passage by squeezing a segment of tube of the same material.
As the exhibition showed, particular attention is being paid to the development of installations and appa-
ratus for environmental protection and for building closed technological systems. The Krauss-Maffei company
has analyzed the production technology of several thousand chemical products and developed "closed systems"
on this basis. A large number of absorbers were proposed for air purification, the most interesting being
a Multiventuri scrubber for trapping dust and a fountain scrubber made by Steiler (GFR), for removing NO,
HC1, and HBr from air at D = 1 m, Hst = 0.6 m 1000 m3/h. The quality of purification is monitored by moni-
toring and measuring instruments which were well represented at the exhibition.
Translated from Atomnaya Energiya, Vol.42, No.1, pp.68-69, January, 1977.
This material is protected by copyright registered in the name 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 $7.50.
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Wastewater from plants of various companies is purified according to a scheme incorporating concen-
tration by precipitation, ion exchange or flotation, and filtration and subsequent combustion of the precipitates.
This is the scheme by which the BASF company (GFR) operates an installation with a throughput of 106?m3/day
for the purification of effluents from the company plants in two cities - Ludwigshafen and Friedentahl. For
the first operations the companies usually employ standard equipment, and various designs of special-purpose
circuits are proposed for combustion. Ion exchange is ensured by ion-exchange resins of helium and macro-
porous structure, the assortment of which runs to more than 150 brands. An interesting continuously operat-
ing installation for effluent purification with activated carbon is produced by the Chiyeda Company (Japan).
Sorption is by means of a pseudoliquefied layer of carbon flowing through a plate column; the carbon is regen-
erated thermally. There also is an evaporation apparatus of special design which ensures distillation purifi-
cation of water by a factor of 106 to 107.
It should be noted that all companies are striving to build apparatuses with the largest possible capacity.
Thus, methods are being developed for ensuring high-grade mixing while increasing the volume of reaction
vessels to 200 m3. For this purpose, several mixers are to be installed in a reaction vessel, at times of
different designs, the assumption being that a lower mixing speed imparted uniformly throughout apparatus
cross section yields a greater effect than does a centralized high-speed mixer. Various types of mixers and
densities of arrangement are proposed for reaction vessels operating at temperatures up to 250?C and pres-
sures up to 15 atm. Reaction vessels for mixing thick pulps and other viscous media were shown at the exhi-
bition.
For liquid-liquid systems there are flow-type reaction vessels, most often horizontal, appropriate for
highly viscous media (up to 1017 cp) with worm conveyor and so-called static mixers, i.e., tubes with special
immobile elements, ensuring contact of the fluids with viscosity ratios of 1:1 to 1:106 cp (the Kenix Company,
USA). Heat exchange can also be carried out in these mixers at an efficiency five times that generally accep-
ted, owing to those elements. Such mixer elements are used in vertical reaction vessels for liquid-gas sys-
tems.
A variety of extractors was presented at the exhibition, the difference from previous years being that
only columns with an auxiliary energy supply were displayed. These were of the following types: rotary-plate
(Louva, Switzerland), pulsating vibrating (Montzl, GFR; Robatelle, France) with sieve-plate and filled (Rasch-
ig rings) attachments. The Robatelle and Podbilnyak companies, which are famous for their extractors,,
confined themselves to folders about them; Robatelle displayed a pulsating column and announced that such
a column measuring 1 m in diameter had been built for the nuclear fuel reprocessing plant in Marcoule.' The
Montzl folders described a sieve-plate pulsating column with a diameter of 2.5 m and a capacity of up to 100
m3. Louva displayed an asymmetric rotary-plate extractor which was a model of a column with a 1.8-m di-
ameter and 45-m3 capacity. Only one (glass) mixer- settler for pilot plants (Quickfit) was shown. For purely eco-.
nomic considerations, the company representatives recommend mixer- settlers only for processes with fewtheoret-
ical stages (3-4).
Among the large number of precipitator centrifuges on show at the exhibition attention was attracted by
direct-flow auger-feed centrigutes with hollow rotor, purifying discharge water at a rate up to 120 m3/h as
well as program-controlled mechanized centrifuges. Five companies use pulsation or vibration to unload the
precipitates.
The numerous filters, pumps, and equipment for loading and unloading solid materials and pulps were
not distinguished by any particular novelties.
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Much attention has been devoted in recent years to a comparatively new approach to solving problems
of controlled thermonuclear fusion, inertial plasma confinement. The basic idea consists in heating a small
granule of thermonuclear fuel (target) instantaneously with powerful energy sources to' thermonuclear temper-
ature, upon which fusion proceeds while the target disintegrates. This approach has become possible because
of the considerable progress made in the construction of high-power lasers and high-current electron accelera-
tors. A distinction is made between laser and electronic thermonuclear fusion, respectively.
A meeting of experts, organized in Dubna July 19-23, 1976, by IAEA in conjunction with the State Com-
mittee for Atomic Energy of the USSR, was devoted to a discussion of the state of work on inertial plasma con-
finement and consideration of the prospects of research in this area. Taking part in the meeting were experts
from the USSR, the USA, Japan, France, Great Britain, and GFR. The IAEA was represented by the Deputy
Director General, I. S. Zheludev, and the Scientific Secretary, J. Philips. The opening session was attended
by the Vice Chairman of the State for Atomic Energy of the USSR, I. G. Morozov.
A survey of the US program up to the year 2000 on inertial confinement was presented by L. Quillian
(ERDA). Research on laser thermodynamic fusion is being conducted in the USA by the Lawrence Livermore
Laboratory, the Los Alamos Science Laboratory, the KMS-Fusion laboratories, Rochester 'University, and
other scientific centers. A laser fusion board has been organized to coordinate the work in the ERDA. Accord-
ing to the long-term program, it is expected that a reaction with a positive efficiency will be achieved in the
1980's and a demonstration reactor will be built in the 1990's. The main research up to 1986 will be based on
multichannel neodymium lasers. At the same time, it is proposed to develop the technique of high-power gas
lasers, primarily of the CO2 type, since neodymium lasers have a low efficiency and their active elements have
a short lifetime. Much hope is put in new types of lasers. The long-term program envisages close coopera-
tion between research establishments and industry.
A paper by L. Boose (Los Alamos Laboratory) considered questions of the commercial use of lasers in
controlled thermonuclear fusion. Since an energy amplification of more than 100 is impracticable, it is be-
lieved that the efficiency of a laser used in a reactor should be no less than. 20%. Lasers of the carbon dioxide,
chemical, atomic-oxygen, excimer, and iodine types seem to hold out the most promise. The Los Alamos
Laboratory intends to construct a high-power CO2 laser with an energy of 105 J for demonstration experiments
in 1979.
The results and prospects of work on laser-produced fusion at the Livermore Laboratory was taken up
in a paper by C. Hendrix. The Laboratory specializes in neodymium lasers. Construction is now under way
of a powerful 20-channel machine, dubbed Shiva, with a pulse energy of 105 J and an output of 25 TW and it is
scheduled to come into service in 1978-1979. Demonstration experiments are planned for the early 1980's.
The KMS-Fusion laboratories (paper by F. Meier) recently conducted experiments to ascertain the nature
of the neutron radiation from quasispherical targets with the aid of corpuscular methods of diagnosis. The pa-
per presented a conclusion about the thermal character of the fusion reaction. The laboratories have developed
a new method of measuring the laser energy injected into a spherical target by using a spherical calorimeter.
The injected energy is 10% of the laser energy.
The foremost US laboratories have now attained an integrated output of 107 neutrons in a pulse during
irradiation of quasispherical targets. Much attention is being paid to designs of multilayer targets.
Translated from Atomnaya Energiya, Vol.42, No.1, pp.69-70, January, 1977.
This material is protected by copyright registered in the name 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 $7.50.
80
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The Scindia Laboratory is the leader in the domain of electronic thermonuclear fusion. In two papers,
J. Jonas, who is heading the work, reported on the equipment being used, on the experimental and theoretical
results, and on future plans. An undoubted virtue of electronic beams, as compared to laser beams, is the
high efficiency of electronic accelerators (50% as against several per cent). However, there are problems
of transporting and focusing the beam on the target. The American program is based on the use of self-
focusing of the beam in a diode in two-sided irradiation of the target. Since a thermonuclear microexplosion
occurs inside the diode, small targets must be used. The problem of obtaining short pulses arises in this
connection. Experiments on irradiation of targets are now being performed at powers of up to 1012 W and
pulse duration of up to about 20 nsec (Hydra and Proto machines). The yield of 107_108 neutrons per pulse is
evidently of nonthermonuclear origin. Demonstration experiments are to be carried out in the early 1980's at
a power of 1014 W. For the purpose, an electronic accelerator, the EBFA-I (4.1013 W), is under construction
and the EBFA-II (1014 W) is under development.
The Japanese program of work on inertial plasma confinement was presented in papers by Ch. Yamanaka,
S. Nakaya, and K. Niu. The main research institutions are the universities of Osaka, Nagoya, and Tokyo.
There are two projects: the Gekko project, based on the use of high-power neodymium lasers, and the Lekko
project, based on electro-ionization CO2 lasers. At the present time, research is being conducted on the
Gekko-II machine (neodymium laser with 150-J beam, pulse duration 3 nsec, and flux density up to 1016 W/cm2)
and the Lekko machine (CO2 laser, 200 J, 1 nsec, 1014 W/cm2). The researchers are studying the absorbed
and reflected energy, the spectral composition, the electron temperature, and the energy spectrum of the ions.
A threshold of parametric instabilities was established at 1010-1011 W/cm2 for the CO2 laser. Experiments
have begun on the compression of shell targets with laser radiation and the interaction of electron beams with
plasma and metal foil.
In France, work on laser-produced thermonuclear fusion is also under way in several laboratories. The
meeting heard a paper on the Research Center at Limay (paper by A. Bequiarian). Experiments on the inter-
action of laser radiation with matter are being conducted on the facilities M-3 (CO2 laser, 10 J, 1.7 nsec) and
C-G (neodymium laser, 100-1000 J, 0.1 nsec). A laser is being built with disk modules to operate in the ultra-
short-pulse mode at an output of 1 TW. A great deal of attention is being paid to increasing the radiation con-
trast and improving the diagnostic means.
A paper by Z. Witkowski (Garching, GFR) discussed problems relating to the use of high-power lasers
for thermonuclear fusion. A high-power iodine laser with an energy pulse of 200 J and 2-nsec duration is
under construction in Garching. Flash-tube pumping of such lasers ensures good duplication of the radiation
parameters. Increasing the radiation contrast remains an unresolved problem. Research on laser-produced
plasma with the neodymium laser is being carried out in parallel.
The laboratories in Garching and Limay have recorded a very high coefficient of reflection of laser radia-
tion from plasma (up to 30-50%), which is at variance with measurements made in other laboratories.
According to brief communications by T. Allen (Great Britain) and M. White (Rutherford Laboratory,
Great Britain) practically no work on inertial plasma. confinement is being done in Great Britain and lasers
are used largely to heat plasmas in magnetic traps.
The work done in the USSR on laser-produced thermodynamic fusion was presented in papers by G. V.
Sklizkov (P. N. Lebedev Physics Institute of the Academy of Sciences of the USSR) and M. I. Pergament (I. V.
Kurchatov Institute of Atomic Energy). The Soviet Union has been first on many fundamental problems in this
area, such as the idea of laser-produced thermodynamic fusion obtaining the first neutrons, observation of
compression of targets, and maximum reflection coefficient in targets. At present, research is being conduc-
ted on the machines Kalmar, Flora, Delfin, and Mishen with a beam of 100-1000 J (neodymium lasers). A
project is being developed for an energy of 104 J, at which attempts can be made to obtain a positive energy
output in the target.
The results and prospects of research on electron-produced thermonuclear fusion in the USSR were dis-
cussed in papers by L. I. Rudakov, V. P. Smirnov, S. D. Fanchenko (I. V. Kurchatov Institute) and M. P.
Svin'in (D. M. Efremov Scientific Institute of Experimental Atomic Physics). In contrast to the American
program, the Soviet program is based on the technique of generating a long-duration pulse of 100 nsec. Cal-
culations show that if an energy of 3-5 MJ is injected into the outer shell of the target, a thermonuclear reac-
tion ensues with an energy output that is 10-100 times the beam energy. To prevent the destruction of the ac-
celerator by the energy from the thermonuclear microexplosion, the target should be at a distance of several
meters. This entails a problem of how to transport the beam to the target. A project is being developed for
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a 1014-W accelerator of modular design for demonstration experiments. Simulation experiments carried out
on the accelerator Ural (beam energy 1 kJ) confirm the promise held out by this method. A great achieve-
ment has been the obtaining of the first thermonuclear neutrons 3.106 in a pulse, during irradiation of a
quasispherical target in the accelerator Triton (1.5 kJ, 30 nsec). Research on focusing and transporting
beams and the interaction with targets is being conducted on the new Kalmar and Angara-1 accelerators at
an energy current density of up to (5-10) ? 1012 W/cm2.
During a visit to the I. V. Kurchatov Institute. of Atomic Energy and the P. N. Lebedev Institute the
foreign delegates to the meeting had an opportunity to become familiar with the equipment being used.
The results of the meeting show that some countries have long-term scientific programs for solving the
problems of controlled thermonuclear fusion on the basis of inertial plasma confinement. The important
experimental and theoretical results obtained thus far give reason to hope that within the next 5 to 10 years a
thermonuclear reaction with a positive energy output will be achieved.
THIRD SESSION OF SOVIET-AMERICAN COORDINATING
In accordance with the program of exchange between the USSR and the USA in the domain of controlled
thermonuclear fusion (CTF) the Soviet-American Coordinating Commission held its third session in Moscow
July 1-3, 1976. The session considered the state of the art and the prospects for the development of work
in the USA and the USSR on CTF, the results of the collaboration in 1975 were summed up, the program of
cooperation for 1976 was made more detailed, and a draft program for 1977 was drawn up.
In the course of the exchange of opinions it was noted that in the year since the last session, significant
results had been achieved, giving rise to optimism among the scientists engaged in work on the resolution of
the problem. In the first place, note should be taken of the relatively large energy time of plasma confinement
(^?60 msec) in the Soviet tokamak T-10 and the record temperature of the ionic component of plasma (^-2 keV)
in the tokamak TFR in Fontenay-au-Roses (France), successful experiments on heating plasma by injection
of neutral beams of ^?300 kW on the American tokamak ORMAC, a marked increase in the parameter nr in ex-
periments in the open magnetic trap 2XPB in the Lawrence Livermore Laboratory (USA). In the area of in-
jection designs for CTF, work has proceeded successfully on the construction of powerful injectors of neutral
beams, on the development of a technique for heating plasma in tokamaks with gyrotron generators, and on
the development of new superconducting cables and structural materials for thermonuclear systems.
The heads of the thermonuclear centers, M. Gottleib (Princeton), J. Clark (Oak Ridge), T. Fowler
(Livermore), and F. Ribby (Los Alamos) reported on the state of research on the principal experimental
thermonuclear machines of the USA.
Research has proceeded successfully on systems of the tokamak system. Work on the PLT machine,
put in service at Princeton at the end of 1975, has produced a steady-state discharge with a current of up to
600 kA in a 35-kGlongitudinal magnetic field. The mean plasma density was 3.1013 cm-3, the electron tem-
perature was 2 keV, and the energy lifetime was -40 psec. Experiments are to be started with a magnetic
field of 50 kG. The first PLT injector (40 kW, 25 A) is to come into service at the end of 1976, and experi-
ments with all four injectors with a total injection power of 2-3 MW are envisaged for March 1977. With the
power of the injected neutral beam increased to 300 kW, plasma with an ion temperature significantly above
the electron temperature (1500 and 660 eV, respectively) was obtained on the tokamak ORMAC (Oak Ridge).
Translated from Atomnaya Energiya, Vol.42, No.1, pp. 71-72, January, 1977.
This material is protected by copyright registered in the name 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 $7.50.
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TABLE 1. Parameters of US Tokamaks
Machine (laboratory)
R,cmI
a,cm I
B,kG
I,kA
Commissioning, designation
ISX, Oak Ridge
90
25
18
150
February, 1977, study of contaminants
ALCATOR -B/C, MIT
64
17
100/140
800/1200
December, 1977, high-8 experiments
February, 1978, plasma of noncircular
DOUBLET-III, GeneralAtom-
140
45x 150
26
5000
cross section
is
ORMAC-V, Oak Ridge
92
30
40
800
April, 1911; powerful injection (2 MW)
RDH, Princeton
145
47
25
500
April, 1978, divertor
It was intended to increase the injection power to 500 kW by the end of 1976. The tokamak ALCATOR at MIT
produced a record plasma density (5.1014 cm-3) in a 75-kG magnetic field. After modernization of the machine
experiments are to begin with a magnetic field of - 90 kG. A project is being developed for the reconstruction
of the machine, envisaging a subsequent increase in the toroidal field to 100 kG (ALCATOR-B), and then
even to 140 kG (ALCATOR-C). Elliptical and doublet configurations of the plasma pinch were obtained on the
machine DOUBLET-IIA (a tokamak of noncircular cross section, General Atomic). It was shown that the elon-
gated plasma configuration makes it possible to obtain a large discharge current at the same toroidal field.
However, the advantages of elongated configurations are not convincing as yet. The parameters of the new
US tokamaks are listed in Table 1.
Considerable progress has been noted in the field of open magnetic traps. A combination of a cold gas
stream and cold plasma with intense injection of high-energy neutrals enabled high values of /3 (^?0.7) to be ob-
tained on the machine 2XPB (Livermore). At an injection of 225 equiv. the plasma produced had a density of
1.2.1014 cm-3 with an ion temperature of 9 keV and nT - 1011 cm-3 'sec. Experiments with large-dimension
plasma with a long pulse duration were proposed for the end of 1976. Moreover, it was decided to extend the
open-trap work and, in particular, to begin construction of a huge machine, the MH, designed to.obtain nT =
1012 cm-3?sec at a plasma density of 1014 cm-3 and an ion temperature of 50 keV.
No noteworthy successes were achieved in experiments with high p systems. Research continued on im-
proving the stability of plasma in the machine SCILLAC. Vertical stabilization of the plasma pinch was achieved
with a system of feedbacks. Attempts are being undertaken to ensure horizontal stability by using profiled dis-
charge chambers.
The head of the American delegation E. Kintner (ERDA), reported on the elaboration of a long-range US
program on CTF, up to and including construction of a commercial thermonuclear power plant. The ultimate
goal of the national program is to incorporate thermonuclear power into the overall energy balance of the USA
early into the next century. The program is divided into three successive phases:
1. The immediate tasks up to 1985: obtaining plasma with reactor parameters and study its behavior,
and realizing the D-T reaction with positive energy output in the TFTR testing tokamak-reactor.
2. Development of the first energy systems by 1990: obtaining electrical powers of more than 10 MW
in one or two experimental reactors.
3. Solution of the problem as a whole by the year 2000: constructing the prototype of a commercial
thermonuclear reactor with an electrical output of no less than 500 MW for demonstrating the technical feasi-
bility, economic advisability, and radiation safety of commercial thermonuclear power.
The program has been based on systems of the tokamak type. Open traps as well as pulsed systems
based on lasers and relativistic electron beams may be competitive. The total cost of the program (up to the
year 2000) is estimated at 14.5 billion dollars. Along with the gradual construction of the principal thermo-
nuclear machines and reactors the program envisages provision of the engineering means for the problem. In
particular, it provides for the construction of powerful sources of 14-MeV neutrons, as well as an engineering
testing reactor ETR for thoroughly testing structural materials under loads corresponding to those in commer-
cial thermonuclear power reactors.
In discussing the results of the cooperation in 1975 and 1976, the commission noted the successful ful-
filment of the agreed programs, bringing unquestionable benefit to both parties. Soviet and American special-
ists participated in the initial experiments on the PLT and T-10. Fruitful discussions were held during work-
ing meetings on the problems of divertors, open traps, contaminants, etc. Joint computational work was done
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on computers and a number of joint papers and articles were published. A program of exchanges in 1977
that was agreed upon envisages 32 joint undertakings (experimental and theoretical research, development
and testing of elements of demonstration thermonuclear reactors, and joint investigations on the engineer-
ing problems of controlled thermonuclear fusion). The commission found it desirable to organize an ex-
change of apparatus and equipment and, in connection with this, to standardize some assemblies of the ex-
perimental installations. The prepared program will be presented for approval by the Soviet-American
Mixed Commission on the Peaceful Uses of Atomic Energy.
After the session, the American delegation visited the I. V. Kurchatov Institute of Atomic Energy, the
P. N. Lebedev Institute of Physics, the A. F. Ioffe Physicotechnical Institute and the D. V. Efremov Scientif-
ic-Research Institute of Experimental Atomic Physics where they became acquainted with research on CTF
and plasma physics as well as with the organization of the design and construction of large-scale thermo-
nuclear systems.
The traditional annual conference Neutrino-76, devoted to the problems of neutrino physics, was held
in the small West German town of Aachen from June 8 to 12, 1976. More than 350 representatives of labora-
tories throughout the world participated in the work of the conference. The agenda covered not only neutrino
research but also included some major aspects of present-day physics, new particles.
New Particles. It is precisely in this area that there have been extremely rapid developments in the
preceding year. Up to the time of the previous conference individual facts pointed (indirectly, it is true) to
the existence of particles which possess a new quantum number, "charm. " The results most statistically
secure were those from an experiment executed with electronic equipment on the 400-GeV accelerator of the
E. Fermi National Laboratory (FNL) in the USA. The Harvard- Pennsylvania-Wi sconsi n- FN L group (USA)
discovered events with two muons in the finite state
v+N -- ?-+}e++ X.
Analysis of their characteristics provided evidence in favor of the hypothesis about the formation of charmed
particles with subsequent semileptonic decay
v+N -. t-4-aO,>+X
In the hypothesis under discussion, D and F mesons (in the language of quarks, the states (cn) and (ca), i.e.,
with "open" charm) are the most probable candidates for charmed particles. The addition of this family to the
family of 0 mesons, states with "latent" charm (cc), recorded earlier in a+e- collisions and pN interactions
gave great weight to the arguments in favor of the "reality" of the c quark. Muon-pair production is observed
at an energy of Ev s 30 GeV. The fraction of the total cross section for neutrino interaction per charmed-par-
ticle production multiplied by the relative probability of decay via the semileptonic channel was estimated at
pt- 1%. Unresolved questions remained, however. In particular, why, at the expected value of 1.8-2.0 GeV
for the D- and F-meson mass, is the effect of muon-pair production observed at such a high energy? Are there
among the hadrons accompanying the dimuon, strange particles predicted by the four-quark model? Why do we
not see the formation of D and F mesons in a+e- annihilation?
Intensive work in these areas has been done in all the major accelerator centers in the world. An ITEF-
IFVE (Institute of Theoretical and Experimental Physics, Institute of High-Energy Physics) group (USSR) in-
vestigated muon-pair production with the aid of a detector and the spark chambers of the 70-GeV Serpukhov
Translated from Atomnaya Energiya, Vol.42, No.1, pp.72-74, January, 1977.
This material is protected by copyright registered in the name 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 $7.50.
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accelerator. It was found that in the neutrino-energy range from 10 to 30 GeV dimuons are produced at the
same level of cross section as recorded in the Fermi National Laboratory. This gives evidence in favor of a
value of ^-2 GeV for the mass of the charmed particles. Interesting results were obtained from searches
for another type of lepton pairs, pe, which were carried out with large bubble chambers at CERN and the FNL.
The choice of the pair pe as an object of the search was methodologically obvious since bubble chambers with
a heavy filling enable electrons (positrons) to be recorded with a high degree of accuracy. In addition, in these
instruments it is possible to study the vertices of interactions in detail. In the Gargamel chamber in CERN
16 events with p-e+... of the finite state (with an expectation background of 7 ?2.5 events) were found in a
beam, and three of them were of the type ?-e+V?... (with a background of 1.12 ?0.5). The cross section
proved to be smaller by a factor of 20 than in Serpukhov and the FNL. But this is explained if it is considered
that the energy range in the experiment was E = 3-8 GeV. At such an energy threshold effects have a consid-
erable influence. Not much later, experiments began on the 15-foot FNL chamber, filled with a neon-hydro-
gen mixture (20% Ne-80% H2). The Berke ley-Wisc onsin-C E RN group found 15 events of the type ?-e+.. .
among - 5000 neutrino interactions with an energy of s 5 GeV and 11 of these were accompanied by V?. As is
seen from the data of the two experiments, there is a correlated production of strange particles together with
a lepton pair. In the latter experiment, the number of strange particles is as yet too high. The mean number
of K mesons accompanying the lepton pair calculated with the isotopic ratios, from the number of neutral K
mesons detected, was (Nk) ~_ 3.6-4, which is approximately double the theoretical expectations.
For the present, the mechanism of the production of lepton pairs in an antineutrino beam remains un-
clear. They were observed with approximately the same intensity as in a neutrino beam, only in the FNL
electronic apparatus mentioned earlier. Neither the ITEF-IFVE group working with the Serpukhov accelera-
tor nor the Michigan-FNL-ITEF-IFVE group, analyzing photographs of vN interactions in the 15-foot cham-
ber, has thus far succeeded in finding lepton pairs at the level of 1%. of the total cross section.
The culmination of this section of the conference was a report by the Stanford accelerator group (USA)
which is engaged in a search for new particles in colliding a+e- beams. This group has detected "narrow"
states (width less than the instrumental resolution, F < 40 MeV) in the systems K?7F and K7rT Tr:Y with an
effective mass of 1.86 GeV. The production cross section is several per cent of the total annihilation cross
section in argon and has a threshold at ^-4 GeV. Since in a+e- collisions charmed states should be produced
associatively, it is important what accompanies each of them. No partner of the same mass was observed in
the spectrum of the recoil mass, but a partner with a mass of 2-2.15 GeV was clearly seen. The results do
not yet have an exhaustive explanation. The variants
with the subsequent decay D* --D + ir, are working hypotheses.
One more experimental fact pointing to the production of charmed particles in a+e- collisions has been
obtained on collision rings in DESY (GFR). According to provisional data individual electrons, accompanied
on average by five or six hadrons, were found to be created at a level of several per cent of the total cross
section beginning from an energy of ^-4 GeV. The most natural explanation of the effect is that of associative
production of charmed particles with one of them subsequently decaying via semilepton channel D - e + ve +..
and the other, via the hadron channel. To date, 22 such cases have been recorded.
Charged Currents. Investigations in the given area have recently been quite orderly. Refinements were
made in the date on the total cross sections and structural functions over a wide energy interval, from 2 to 100
GeV. Much information came from groups working on the 15-foot chamber. In the range up to ^-30 GeV it was
found that the interaction cross sections for neutrino and antineutrinos grow linearly with the energy and their
ratio is constant, TUN/TVN - 1/3. The numerous differential relations are in fairly good agreement with each
other and do not display noticeable deviations (within 10-15%) from the predictions of the simple parton model.
At first, such a tendency was observed at high energies as well. However, the Harvard-Pennsylvania-Wis-
consin-FNL group found an anomaly in the distribution of the FN interaction with respect to the scaling vari-
able y (the relative fraction of energy transferred from the antineutrino to hadrons). Analyzing the data, they
arrived at the conclusion that from -40 GeV the ratio of cross sections a N/TVN begins to deviate from 1/3
and grows to 0.72 ?0.15 at Ev = 100 GeV. With less statistical reliability this result was confirmed by the Cali-
fornia Institute of Technology - FNL group (USA) engaged in research on the electronic installation of the FNL
accelerator. What is this? Violation of scaling, excitation of a quark-antiquark "sea, " or a new type of inter-
action? Each of these hypotheses requires close study.
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Neutral Currents. Since 1973, when they were discovered in "Gargamel," neutral currents have become
the object of heightened interest on the part of both theoreticians and experimenters. Widespread currency
was gained by the Weinberg-Salam model which has a single free parameter, the Weinberg angle, directly re-
lated to the mass of the intermediate boson. Experimentally, the representations were verified in both the in-
clusive channel and the exclusive channel
v(v)-{-N -,v(v)-X,
v(v) - p -- v(v)+P,
v (v)-e - v (-v) J- e-.
Experiments performed by CERN and the FNL in 1975-1976 established that parity is violated in neutral
currents. The ratio of the inclusive cross sections was measured in the energy range from 2 to 40 GeV and
found to be Qvc/QVC 0.5 ?0.2. This value corresponds to a V-0.8 A interaction. Using a segmented scin-
tillation calorimeter with drift chambers with a total mass of 33 tons, Brookhaven Laboratory (USA) studied
the process of neutrino (antineutrino) scattering on a proton. About 20 cases were recorded in each of these
reactions. The value of o- (vp - vp)/Q (vp -- vp) = 0.35 ? 0.2. The Raines-Hare group (USA), who for many
years investigated the scattering of electron antineutrinos on an electron with the aid of a beam of antineutrinos
from a reactor were the first to report observation of the effect. The difference found from the V-A theory
(by four standard deviations) speaks of a contribution by neutral currents. A "pure" process brought about by
neutral currents is the scattering of a muon neutrino (antineutrino) on an electron. To the three events found
earlier in an antineutrino beam in Gargamel were added 19 v?e events (background 2.9 events) and 25 v?e
events (background 11.8), recorded in the CERN spark-chamber installation by the Aachen-Padua group (GFR-
Italy). The data of all the experimenters, analyzed within the framework of the Weinberg-Salam model, give
an "average" value of sin20W 1/3 for the parameter.
The conference heard several original papers whose subject matter is marginal, as it were, to the prin-
cipal directions. A case in point is an experiment recently performed in the ITEF to obtain a more exact value
for the mass of the electron neutrino. A new lower limit of in 35 eV was fixed. Of the theoretical papers,
mention could be made of new approaches to the study of the properties of neutral currents via the effects of
the nonconservation of parity in atomic physics.
The conference yielded many interesting results which to a considerable extent reflect the wide thrust
of investigations in theis area of physics. The next conference has been planned for the summer of 1977 in
the USSR.
SECOND SEMINAR ON MOSSBAUER SPECTROSCOPY
At their second seminar on Mossbauer spectroscopy, held in Munich (GFR) June 16-26,1976, Soviet and GFR
scientists considered the following topics: relaxation effects, hyperfine interactions in magnetics, experimental
techniques, hydrogen in metals, coherent effects, and the application of the Mossbauer effect in biology.
V. D. Gorobchenko (USSR) expounded the elements of the theory developed jointly with A. M. Afanas'ev
concerning the time-dependent M6ssbauer emission spectra in nonequilibrium systems. The formulas ob-
tained enable experimental spectra to be correctly analyzed when the state of the electron shell of the Moss-
bauer atom experiences relaxation variations as a result of a previous decay.
W. Wagner (GFR) reported on the experimental study of the kinetics of the processes of radiative after-
effect using the example of the transitions of the ions Eu2+ zc~ Eu3+ formed after the decay of 153Gd by electron
Translated from Atomnaya Energiya, Vol.42, No.1, pp.74-75, January, 1977.
This material is protected by copyright registered in the name 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 $7.50.
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conversion. The Gorobchenko-Afanas'ev theory was used successfully to evaluate the relaxation time. Two
other papers on this subject demonstrated the broad possibilities of Mossbauer spectroscopy in the study of
relaxation processes.
The results of investigations of a new effect, induced magnetic ordering in antiferromagnetics, were
presented in a paper by S. S. Yakimov (USSR). Using YFeO3 as an illustration, it was shown that in a
"skewed" antiferromagnetic an external magnetic field of 10 kOe sets up a magnetic structure in the temper-
ature range above the magnetic transformation point. New technical capabilities of Mossbauer spectroscopy
were discussed by Yu. V. Baldokhin (USSR). The use of radio-frequency (rf) pumping during a Mossbauer
experiment makes it possible to obtain such dynamic characteristics of magnetics as the rf-magnetostriction
and rf-mobility of domain boundaries.
Experimental techniques were of greatest interest to the Soviet participants in the seminar. In his pa-
per, M. Calvius (GFR) reviewed the helium cryostats and superconducting solenoids that the Mossbauer Insti-
tute at the Technical University of Munich (TUM) has for work in transmission geometry. He reported on a
system ensuring high pressure at low temperatures. The pressure on the sample reaches 100 kbar and the
temperature can be brought down to 1.6?K. The pressure is of a quasi hydrostatic nature; boron carbide is
used as the material for the pole pieces.
The institute has an original cryostat for research on amorphous thin films sputtered right in it at a low
temperature. It is coupled to a high-vacuum system providing a vacuum of up to 10-7. The lowest temperature
0.035?K, is produced by a cryostat in which the absorber is right in a mixing chamber containing 3He/4He. The
cryostat is provided with a 50-kOe solenoid.
The experimental equipment described in the papers was shown in the laboratories.
West German scientists presented several papers concerning investigations on metal matrices with
hydrogen impurities. Nuclei of 57Fe, 181Ta, 197Au, and 237Np were used in the investigations.
In the review paper "Mossbauer spectroscopy of metal-hydrogen systems," G. Bortmann (GFR) pre-
sented data obtained to date in the TU1\I. Among the most interesting were the abrupt variations in the iso-
meric shift and hyperfine field observed in iron nuclei and iron-nickel and iron-palladium alloys with com-
paratively small (several at. 9) variations in the hydrogen impurities. This result is related to the redistribu-
tion of the electron density in the crystal lattice (because the electrons of the matrix atoms are attracted to
hydrogen atoms).
Data on the influence of hydrogen on the isomeric shift and the width of the Mossbauer line of 181Ta nuclei
were discussed (A. Heidemann, GFR). Two results are particularly noteworthy: 1) as the hydrogen concentra-
tion grows to 0.17 at. % the Mossbauer line of 181Ta nuclei is broadened (five-fold) and shifts towards higher
energies (from 1 to 10 mm/sec); 2) as the temperature rises (230-400?K), there is a sharp decrease in the
hydrogen-induced line broadening so that when 400?K is reached the line has narrowed down to the width char-
acteristic of pure tantalum. This is explained by the effect of fluctuations in the local fields (produced in tan-
talum nuclei by hydrogen atoms and their being averaged when the temperature rises.
The results are of undoubted interest since they are essentially the first experimental demonstration of
the dynamic narrowing of a Mossbauer line owing to thermal diffusion of an impurity.
Great interest among the participants of the seminar was aroused by papers delivered by R. Mossbauer
(France) and V. I. Gol'danskii (USSR). R. Mossbauer presented a review of the basic principles of the inter-
action of gamma radiation with a solid, after a detailed consideration of the theory of coherent effects during
scattering of resonance gamma radiation by ideal single crystals, developed in the works of the Soviet scien-
tists Yu. M. Kagan and A. M. Afanas'ev. In his paper, V. I. Gol'danskii (USSR) dealt with the possibility of
employing the effect of inverse electron conversion, i. e. , the transfer of energy to the electron shell of a
nucleus in order to pump the energy level of isomers with laser pulses. He gave estimates for 235mU from
which it follows that 103 excited nuc lei can be obtained as the result of a single laser pulse with an energy of -10 J.
F. Parak (GFR) devoted his paper to research on the phase problem by using interference of nuclear
and Rayleigh scattering. In particular, analysis of protein by this method has a number of important advan-
tages over the method of isomorphic substitution now in use. The difficulty in determining the phase arises
from the low activity of the Mossbauer source in comparison with x-ray sources.
The seminar proved to be extremely productive because of the full scientific program, discussions,
and personal meetings. The next seminar is proposed for Moscow in 1977.
87
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BIBLIOGRAPHY
PROBLEMS OF THE METROLOGY OF
IONIZING RADIATION*
Reviewed by M. V. Kazarnovskii
To solve many problems of applied nuclear physics there is a need of sufficiently exact and reliable
estimates of fluxes of penetrating radiation (neutrons and gamma rays) in various inhomogenous and nonsta-
tionary media from pulsed and stationary sources. In the process it is often necessary to take account of
effects accompanying radiation transfer. Such problems arise, for example, in designing shielding for nuclear-
engineering installations and spacecraft and in predicting processes which accompany nuclear explosions for
peaceful purposes, as well as in connection with some geo- and biophysical problems. A number of such prob-
lems are considered in the compilation under review. It consists of two parts.
The first part is devoted strictly to the metrology of penetrating radiation: the metrological aspect of the
estimation of the results of cross sections of nuclear reactions and standard methods of calculating fluxes of
neutrons and secondary gamma rays, as well as other secondary effects. Here, in the first place, note should
be taken of the new system of nuclear constants for calculating the field of neutrons and the secondary effects
they produce in air. This system was obtained on the basis of an analysis of the present-day level of experi-
mental error in nuclear data; this analysis is carried out in the first five papers.
Valuable results are given by A. M. Kovalenko and G. Ya. Trukhanov in a paper in which they present
a method of enhancing the efficiency of the Monte Carlo method substantially by using the 6-scattering formal
ism in calculating particle fluxes in nonstationary and inhomogeneous media, based on a special choice of the
form of the dependence of the total cross section on the coordinates and the time.
Three papers in this part are devoted to the further development of the so-called quasidiffusion method
of solving the kinetic equationl (employing the formalism of the integrated nucleus). These papers consider
the space-energy distribution of slow neutrons in homogeneous systems with plane and spherical symmetry.
It is demonstrated that the quasidiffusion solution of the kinetic equation can be used for a wide class of ther-
malization problems as a standard method, and also in metrologically securing the measurement of fields of
penetrating radiation and in evaluating the error of approximate methods. An important new physical result is
the calculation of the space-energy distribution of slow neutrons in an exponential atmosphere. Of particular
interest is a paper by G. G. Vilenskaya in which a solution is found to the model problem about the electro-
magnetic field excited in air by a nonstationary gamma-ray source on an ideally conducting plane.
The second part of the book is devoted to the physical processes which accompany the penetrating radia-
tion transfer in matter as well as metrological information which can be obtained from the data about these
processes. Particular attention should be drawn to a cycle of five papers examining the current problems in
the theory of declaration of particles in matter with quite general assumptions about the energy dependence of
the losses (provided that the mean energy loss per collision is small in comparison with its energy); an analytic
solution is given for a problem about the moderation of neutrons from a stationary source with allowance for
inelastic scattering; a study is made of the effect of weak absorption on the space-energy distribution of neutrons
from a pulsed source; there is a discussion of the evolution of a nonstationary neutron spectrum in the presence
of resonances in the absorption cross section; the elastic moderation of neutrons from a pulsed source in a
* Atomizdat, Moscow (1975).
t The nonlinear iterative method makes it possible to obtain a sufficiently exact solution of the complete kinet-
ic equation with a small number of iterations. This is achieved because part of the calculation is transferred
to the solution of a diffusion-type equation with a coordinate-dependent effective coefficient of diffusion (quasi-
diffusion), recalculated during each iteration.
Translated from Atomnaya Energiya, Vol.42, No.1, pp. 75-76, January, 1977.
This material is protected by copyright registered in the name 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 $7.50.
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heavy, weakly inhorriogeneous medium is examined; and an analysis is made of the. asymptotic behavior of the
solution of the stationary equation for neutron transport in an exponential atmosphere.
The remaining papers consider current problems associated with various electromagnetic effects in air
caused by the passage of penetrating radiation. In particular, they first examine in detail the reverse effect
of excited electromagnetic fields on the currents exciting them and discuss the processes of the generation of
electromagnetic fields by distributed systems of charges moving at the speed of light.
On the whole, the book is a serious scientific work devoted to current problems; it will undoubtedly be
of interest to a wide circle of specialists. However, in regard to the appropriateness of new publications of
a similar type, the following comment must be made about the editorial makeup of the book: papers devoted to
various aspects of one general subject have not been combined into one unit, thus resulting in too many repeti-
tions and making reading difficult.
E. G. Rakov, Yu. N. Tumanov,
Yu. P. Butylkin, A. A. Tsvetkov,
N. A. Beleshko, and E. P. Poroikov
ReviewedbyS.- S. Rodin and Y u. V. Smirnov
Recent years have been marked by major successes in the study of the chemistry of inorganic fluorides,
especially in connection with their use in the atomic industry.
Moreover, investigations on fluorides (especially of transuranium elements) have had a strong influence
on the development of many areas of inorganic chemistry, (ultramicrochemistry, crystal chemistry, and the
chemistry of coordination compounds) and many new areas of nuclear physics and chemistry. Fluoride com-
pounds hold pride of place in these investigations.
Many previously unknown fluorides have recently been synthesized and of these particular mention should
be made of fluorides of elements in the zero group of the periodic table; and the accuracy with which the physi-
cal and chemical constants of fluorides are measured has been increased noticeably. Fluorine compounds are
employed widely in many branches of technology. This makes it necessary to publish appropriate handbooks
to meet present-day needs.
The handbook under review is the result of a systematic search, compilation, and generalization of
numerous sources in the literature. It classifies and systematizes scattered data on the principal physico-
chemical properties of inorganic fluorides (about 850 compounds).
Six tables give the structural and x-ray characteristics of crystals, the temperatures and thermodynam-
ic parameters of materials in the standard state, vapor pressure and decomposition pressure, the molecular
constants of inorganic fluorides, and the thermodynamic functions at temperatures of up to 5000?K. An exten-
sive bibliography is given at the end of each table. The handbook has a formula index and the accepted single
numeration of materials, and it draws upon original publications to the end of 1973 (more than 1800 references)
and some handbook pulbications.
Despite the fact that the handbook is not exhaustive and that the tables in individual chapters are of a spe-
cific character, the goal set has been achieved: to generalize material on the principal physicochemical proper-
ties of the most common inorganic fluorides.
* N. P. Galkin (editor), Atomizdat, Moscow (1975).
Translated from Atomnaya Energiya, Vol.42, No.1, p .76, January, 1977.
This material is protected by copyright registered in the name 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 $7.50.
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The handbook is addressed to specialists of scientific institutions and enterprises of the atomic energy
and chemical industries as well as nonferrous metallurgy. It will also be extremely useful for teachers,
graduate students, and students.
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