THE SOVIET JOURNAL OF ATOMIC ENERGY VOL. 4 NO. 1

• Document Type: CREST
• Collection: General CIA Records
• Document Number (FOIA) /ESDN (CREST): CIA-RDP10-02196R000100010001-2
• Release Decision: RIFPUB
• Original Classification: K
• Document Page Count: 157
• Document Creation Date: January 4, 2017
• Document Release Date: September 13, 2013
• Sequence Number: 1
• Publication Date: January 1, 1958
• Content Type: REPORT

Declassified and Approved For Release 2013/09/13: CIA-RDP10-02196R000100010001-2
ro1.1,sso. 1
THE SOVIET JOURNAL OF
jan. 1958
OMIC ENERGY
ATOMI1a5f
1-lepr1151
TRANSLATED FROM RUSSIAN
CONSULTANTS BUREAU, INC.
Declassified and Approved For Release 2013/09/13: CIA-RDP10-02196R000100010001-2
Declassified and Approved For Release 2013/09/13: CIA-RDP10-02196R000100010001-2
NUCLEAR REACTIONS. IN. LIGHT NUCLEI.
IN ENGLISH TRANSLATION ?
Supplement No. 5, 1957 Soviet Journal of Atomic Energy
Ten Papers describing in detail (with diagrams of-all apparatus),, important experi-
ments by the Academy of Sciences, USSR, 1951-1955. Mainly concerned with meas-
urements of the total and differential cross sections and product angular distributions
in interactions involving isotopes of light elements many of which are- of interest in
connection with' thermonuclear fusion reactions. Makes detailed comparisons of all
available experimental data: discusses errors and means of avoiding them; refers ex-
tensively to Soviet and non-Soviet literature.
CONTENTS: Determination of the total cross sections' for the D(d,n)He3
e""' reaction in the energy range 20-220 key; Investigation of ? the DD reaction
in the deuteron-energy range 0.20-1.75 Mev; The D-D- -reaction in the deu-
.teron-energy range 100-1000 key; Measurements of the yields and effective
cross sections of the D(f,n)He4 and D(d,p)T reactions using thick targets of
heavy ice; Measurement of the effective cross section for the E,i(t,n)He4
reac-
tion in the deuteron-energy range 40-730 key; Total effective cross section of
' tritium for neutrons with energies of 2.5 and 14 Mev; Measurement of the
effective cross section for the Li6 (n,d) reaction for 2.5 Mev neutrons; Total
'effective cross sections for Li6 and Lii, for neutrons with energies of 2:5 and '
14 Mev; Effective cross section for the Be6(n,d)He6 reaction; Specific stop-
ping power of 150-1100 Mev in nickel. --English translation, 71 pages,,$15.00
For subscribers to our translation of the 1957 Soviet Journal of Atomic Energy
_ _ - only $10.00
*
ACOUSTICS AND ULTRASONICS.
RUSSIAN-ENGLISH GLOSSARY _
10,000 Russian terms. Covers acoustics, ultrasonics electro-acoustics, with emphasis
on the rapidly growing field of ultrasonics. Terms selected from-thousands of pages
of the most recent issues of Soviet physics and engineering journals, especially the
Journal of Acoustics, the Journal of Technical Physics, and Radio-Engineering, as
well as from Russian acoustics texts. Russian equivafents are also provided for
? tetins selected from the following: IRE Standards; the International Dictionary of
Physics and Electronics; the Russian translation of L. Bergman's "Ultra?onics
Theory". 23 page index of Russian-English _equivalents for names commonly found
in acoustics and ultrasonics literature. , 193 pages, only, $10.09
This is the lateSt in a series of 8 specialized glossaries being published prelimi-_
nary to publication; in 1959, of our Russian-English Physics Dictionary,
- which will be compreheniive, authoritatiYe, permanently bound. Pre-publica-
tion subscribers to the Dictionary also receive each of the 8 glossaries upon
, publication all for only $50.00 ?
Write for free catalogs -fully describing the Dictionary and 8 glossaries, as
well as our current Russian-English translation-publishing .program,
. ,
Consuitants Bureau's translation by bilingual scientists. Clear feproduc-
tion by multilith process from IBM "cold type", (except glossaries,
which are varityped), including all diagrammatic and tabularfnaterial;
books staple bound in durable paper covers.
CONSULTANTS BUREAU,? INC.
227 W. 17th St., NEW YORK 11, N. Y.
Declassified and Approved For Release 2013/09/13: CIA-RDP10-02196R000100010001-2
Declassified and Approved For Release 2013/09/13: CIA-RDP10-02196R000100010001-2
vol 4 no. 1
jan. 1958
THE SOVIET JOURNAL OF
ATOMIC ENERGY
ATOMNAIA ENERGIIA
A publication of the Academy of Sciences of the USSR
Year and issue of first translation:
volume .4 number 1, january 195'6
TRANSLATED FROM RUSSIAN
Annual Subscription $75.00
Single Issue 20.00
Declassified and Approved For Release 2013/09/13: CIA-RDP10-02196R000100010001-2
Declassified and Approved For Release 2013/09/13: CIA-RDP10-02196R000100010001-2
EDITORIAL BOARD
OF
ATOMNAIA ENERGIIA
A. I. Alikhanov, A. A. Bochvar, V. S. Emel'ianov, V. S. Fursov,
V. F. Kalinin, G. V. Kurdiumov, A. V. Lebedinskii, LI. Novikov
(Editor-in-Chief),V.V.Semenov (Executive Secretary),V.I.Veksler,
A. P. Vinogradov, N. A. Vlasov ( Assistant Editor-in-Chief ).,
Copyright 1958
CONSULTANTS BUREAU, INC.
227 W. 17th St., NEW YORK II, N.Y.
Printed tin the United State)?
Note: The sale of photostatic copies of any portion of
this copyright translation is expressly prohibited by the
copyright owners. A complete copy of any article in the
issue may be purchased from the publisher for $ 12.50.
Declassified and Approved For Release 2013/09/13: CIA-RDP10-02196R000100010001-2
Declassified and Approved For Release 2013/09/13: CIA-RDP10-02196R000100010001-2
7-RAY SPECTRA FROM THE RADIATION CAPTURE OF NEUTRONS
FOR EVEN-EVEN RADIATING NUCLEI WITH ROTATIONAL LEVELS
L. V. Groshev, A. M. Demidov, V. N. Lutsenko
and V. I. Pelekhov
Using a magnetic Compton spectrometer, we measured the spectra of the 7-rays
arising from the capture of thermal neutrons by nuclei of gadolinium, erbium, hafnium,
dysprosium and tantalum in the energy range 0.3-9 Mev. We determined the energies
and the intensities of the y-lines. For the first three elements, the radiating nuclei are
the even-even nuclei 64G46, 64Gdr, 68Erit and 72Hf1g, which have rotational structural
levels close to the ground state. The peculiarity of the spectra of these nuclei is the
presence of a group of closely placed intense 7-lines with energies of 1 Mev. These
lines are absent in the case of even-odd (for example, 66Dyl9r) and odd-odd
radiating nuclei (for example, 73 Tag:). The peculiarities of the 7-ray spectra noted
are due to the structure of the lower nuclear levels.
The present work is a continuation of previous investigations by the authors on the spectra of 7-rays,
arising during the capture of neutrons by atomic nuclei. The measurements were carried out with a magnetic
Compton spectrometer in the energy range 0.3-9 Mev on the RFT reactor of the Academy of Sciences of the
USSR. The experimental conditions and method of measurement and processing of data obtained were described
previously [1].
In the spectrum of 7-rays from the radiation capture of neutrons by the nuclei of a heavy element which?
does not lie close to the magic numbers, the main part of the 7-transitions from a spectrum which is not res-
olvable by our apparatus [1]. In measuring the spectra of these elements, we observed that in a case where the
radiating nucleus was even-even and had a system of rotational levels close to the ground state (90 N 112),
the 7-ray spectrum had a sharply expressed peculiarity. This lay in the fact that on the background of the con-
tinuous spectrum, there was a group of closely placed intense lines with energies of 1 Mev. In the case of
even - odd and odd-odd nuclei, this peculiarity was not present.
It is regrettable that even-even nuclei with rotational levels are formed in the (n, y) reaction only in an
extremely limited number of cases. We were able to measure the 7-ray spectra for only four such nuclei,
namely 64,Gdig, 64G458, 68Erin and 72HfRe . For comparison we obtained spectra for even-odd (66DAS5) and
odd - odd (T3Tafg) radiating nuclei. Below we present and discuss the results we obtained.
Gadolinium
The spectrum of the 7-rays, emitted during the absorption of thermal neutrons by gadolinium, was meas-
ured both for the natural mixture of isotopes and for the isotopes Gd' 55 and Gd157. In the first case the sample
irradiated consisted of 1.8 g of gadolinium oxide, deposited on five discs of thin aluminum foil, 60 mm in dia-
meter. The discs were placed at a distance of 2.5 cm from each other inside a graphite container, which was
placed in a channel in the thermal column of the reactor. The samples of separated isotopes consisted respec-
tively of 30 and 50 mg of the oxides of GdI55 and Gd157.
1
Declassified and Approved For Release 2013/09/13: CIA-RDP10-02196R000100010001-2
Declassified and Approved For Release 2013/09/13: CIA-RDP10-02196R000100010001-2
Fig. 1. Experimental 7-ray spectrum of Gd203-
TABLE 1
Some Data on Gadolinium Isotopes
Isotope
(target)
Content in
natural mix-
ture, %
Isotopic absorp-
tion cross sec -
tion, barns
Contribution
to total
thermal neu-
tron absorp-
tion cross gec
tion,*
Content in
sample en-
riched in
Gdia,
Content in
sample en-
riched in
Gd155, %
Gd152
0.20
Gd164
2.15
Gd155
14.8
Gd15?
20.6
GO"
15.7
Gd158
24.8
Gdm
21.8
6.4 Mev.
A corrected 7-ray spectrum for a sample of Gd203 is shown in Figure 4. On it, the 7-ray energy in Mev
and the value of Hp in oe.cm is plotted along the abscissa. The value of v (E)Hp ? 10-4 [1] is given along the
ordinate, where the value V (E) equals the number of 7-quanta emitted per neutron capture for a unit interval
of 7-ray energy (1 Mev).
The energies and intensities of the 7-lines in spectra obtained in the present work and also by other authors
are given in Table 2. The intensities of the lines are expressed in the numbers of 7-quanta per 100 neutron cap-
tures. They were determined by normalization of the emitted energy to the neutron binding energy. The y -
lines given in Table 2 for natural gadolinium and the isotopes Gd158 and Gd' 58 are responsible for 11, 9 and 12%
respectively, of the total energy radiated by these nuclei.
Comparison of the spectra given shows that the lines 2-7* in the spectrum of the natural mixture of isotopes
belong to the isotope Gd158. To the isotope Gd158 evidently belongs line 1, which is absent in the spectrum of
Gd158, and probably line 8. Actually, in the Gd158 spectrum, the latter lies practically within the limits of stat-
Declassified and Approved For Release 2013/09/13: CIA-RDP10-02196R000100010001-2
Declassified and Approved For Release 2013/09/13: CIA-RDP10-02196R000100010001-2
TABLE 2
Energies and Intensities of Gadolinium y -rays
Results of this work
Results. of other work
Kinsey and
Bartholomew
Bartholomew [4)
Skliarevskii, et al.
[5]
et. a1[6]
Church.
1411abe4macher
j
Fenster-
et al_ [RI
designation of
7-lines
Isotopes irradiated
isotope
irradiated
Gd (natural
mix- 1
ture of isotopes) I
Gd158
Gal"
ET
I. ?
E.,. ?E.,
,
/..
E Y
Mev
Mev
Mev
Mev
Mev
Ey
Mev
I..
E.
F
Mev
I"
E Y
Mev
7.78+0.05
0.03
.7
7.33+0.03
0.17
?
?
7.33+0.03
1
7-36+0.05
0.03
2
6.74+0-01
2.1
6-74+0.01
3,7
6.74+0.03
0-4
6.73+0.03
0.5
3
6.44+0-03
0-5
6-4410-03
0,4
6.44+0.03"
1.3
6.41+0.04
0.2
4
5.8610.02
0.6
5.88+0.03
1,8
?
?
5.87+0.04
0.2
,5
5-63+0.03
0.8
5.62+0.03
1,3
?
?
5.61+0.04
0.3
p**
?5.2
?
?5.2
?
?
7
4.93+0.02
0.8
4.92+0-04
0,8
?
?
8
4.30+0-04
0.5
?
?
?4.3
?
9
1.32+0.02
2
1.33?0.02
2
?
?
/0
1.26+0.02
4
1.26+0-02
3
1.24+0.02
9
1/
1,180+0.015
10
1-185+0.015
9
1.17+0.02
15
1.16+0.04
12
1.12+0.02
8
1.110+0.015
8
?
?
12a
?
?
?
?
1.06+0.02
6
13
14
0.96+0.02
0.91+0.02
11
8
0.96+0.02
0.900+0.015
13
8
(0.9610.02)
7
0.95+0.03
15
0.78+0.02
3
0.78+0.02
5
16
(0.69+0.02)
1
17
(0.64+0.02)
2
-
0.65+0.02
18
0.55+0.02
3
0.196
34****
Gd156
0.196
0.1987
0.20+0.01
0.183
29****
Gd158
0.179
0.1817
0.087
50****
Gd156
0.088
0.0888
0-079
53****
Gd158
0.079
0.0791
?Investigation_ of y-rays emitted during the capture of resonance neutrons.
**Intensity in quanta per 100 neutron captures.
**? Unresolved group lines.
****Intensity of transition taking into account conversion.
Declassified and Approved For Release 2013/09/13: CIA-RDP10-02196R000100010001-2
Declassified and Approved For Release 2013/09/13: CIA-RDP10-02196R000100010001-2
istical error, which must be quite large here (the low statistical accuracy of measurement for the Gd156 spectrum
was due to the fact that a small amount of material was used). Line 3 is found in the spectra of both isotopes.
We cannot exclude the possibility that line 2 in the Gd 156 spectrum may be explained by the presence of small
traces of the isotopeGd157 in the sample of Gd'.
A group of intense peaks with energies of ???? 1 Mev were found in the spectra of both Gd156 and Gd'. Due
to the greater neutron absorption in Gd157, all the clearly separated peaks in the spectrum of the natural mixture
of isotopes (peaks 9-15) were shown in the spectrum of Gd'. The energies of the lines 10, 11 and 13, found in
the spectrum of Gd156, within the limits of error, agreed with the energies of the corresponding lines in the GPIs
spectrum. The line 12a in the Gd156 spectrum was not separated in the spectrum of the natural mixture of iso-
topes due to its low intensity. We were not able to assign the low intensity lines 16-18 to a definite isotope.
We did not detect the line with an energy of 7;78 Mev and an intensity of 0.03 quanta, found by Kinsey and
Bartholomew [4]. If this line was present in our spectrum, its intensity was less than 0.02 quanta per 100 captures.
The energies of the 7-rays we found agree well with the data of Kinsey and Bartholomew. However, there is a
discrepancy in the intensities. The reason for this discrepancy was not clear to us. In our measurements, the inten-
sities of the 7-rays may be high due to neglecting the conversion of 7-rays and also the presence of 7-rays with
energies less than 0.03 Mev. In the case of gadolinium, the increase due to this should not exceed 8%.
Erbium
The sample irradiated was 30 g of erbium oxide with the natural isotopic composition.
In Table 3 we give data on the stable isotopes of erbium and the neutron binding energies for the product-
nuclei. The total thermal neutron absorption cross section for the natural mixtures of erbium isotopes' equals
(166 ? 16) barns. The contribution to it from the separate isotopes is practically unknown. At out request,
V. V. Skliarevskii measured the spectrum of the 7-rays from the capture of thermal neutrons by erbium in the
low energy range using a scintillation spectrometer. It was shown that in the radiating isotope of erbium, there
was a system of rotational levels, characteristic of an even-even nucleus with a number of neutrons between 90
and 112. Thus the probability of a transition from the first to the second excited states, allowing for internal
No. of coincidences in 10 min.
0
i0000
Hp,oe ? cm
Fig. 5. Experimental 7-ray spectrum of Er203.
*Line 7 in the 7-ray spectrum of Gd158 was obtained after subtraction of the line with energy 4.95 Mev, emitted by C"
which is formed bythe absorption of neuirons by the graphite container.
6
Declassified and Approved For Release 2013/09/13: CIA-RDP10-02196R000100010001-2
Declassified and Approved For Release 2013/09/13: CIA-RDP10-02196R000100010001-2
TABLE 3
Some Data on Erbium Isotopes
Content in the
Isotopic absorption
Contribution to the
Neutron binding energy in the
Isotope (target)
natural mixture,%
cross section, barns
totalthermalab-
sorptioncross sec-
product-nucleus, Mev
measured [2]
calculated*"
?don, %
Erin
0.136
6.9
Eri84
1.56
6.6
Eri.8
33.4
6.46?0-056
6.3
E0437
22.0
7.76?0-056
7.5
Erio
27.1
2.0?0.4***
0.3
5.a
Era"
14.9
9+2***
0.8
5.6
* ?a =(166 ? 16) barns.
**Calculated by Weizsacker's formula [3].
***Activation cross section.
TABLE 4
Energies and Intensities of Erbium y-rays
Results of this work
Results of other work
Fenstermacher et al. [11]
Skliarevskii1 et al. [5]
Dzhelepov
et al, [11]
?designation
of y-lines
E..
Mev
1..
Ey
Mev
r..
Ey
Mev
E.
Mev
pe
/
6.680?0?015
0.9
2
6.202?0.015
1.3
3
6.07?0.03
0.5
4
5.88?0.03
0.6
6
5.73?0-04
0.4
6
5.34?0-03
1
7
4.77?0.035
0.6
8
4.66?0.03
1
9
4.42?0.045
0.6
/0***
-4.1
//***
-1.9
12***
-1,3
13
1.01?0.02
3
14
0.94?0-02
5
15
0.828?0.01
36
0.82?0.02
16
0.736?0.015
10
0.73?0.02
17
0?64?0.02
4
0.28?0.01
5
0.185
82****
0.188?0.01
-50
0.082
85****
0.0798
*Investigation of y-rays from resonance capture of neutrons.
**Intensity in quanta per 100 neutron captures.
***Unresolved group of lines.
****Intensity taking into account conversion.
7
Declassified and Approved For Release 2013/09/13: CIA-RDP10-02196R000100010001-2
Declassified and Approved For Release 2013/09/13: CIA-RDP10-02196R000100010001-2
2.5
a.
2
1.5
0.5
10 000
2171100 Hp,oe.cni
1
Fig. 6. Corrected 7-ray spectrum of Er203.
Mev
conversions, amounted to 80 7-quanta per 100 neutron captures. In the capture of neutrons by erbium, it is
possible to form only a single even-even isotope, namely Er168. From this we concluded that the main contribu-
tion to the absorption of neutrons by erbium was from the single odd isotope Erla. Therefore, the main part
of the erbium.7-ray spectrum must be ascribed to Er168.
The experimental and corrected 7-ray spectra of erbium are shown in Figures 5 and 6. The energies of
the erbium 7-ray spectrum are given in Table 4. There, we give the results of measurements by other authors
for the low energy range. The intensities of the lines in numbers of 7-quanta per 100 neutron captures given in
the table were obtained by normalization using the following formula [1]:
'Max
E,v (Er) dE, (7.76.0.8+ 6.3.0,2) Mev
- 3
where 7.76 Mev is the neutron binding energy of Er168 and 6.? Mev is the average binding energy taken for the
rest of the isotopes. The erbium 7-lines, given in Table 4, are responsible for about 10% of the energy radiated
by the sample.
Hafnium
In the measurements with hafnium, 85 g of hafnium oxide Hf02 was used as the radiation sample. Data
on the isotopes of hafnium are given in Table 5. The total thermal neutron absorption cross section for hafnium
equals (115 ? 15) barns. The data given in the table indicates that the 7-radiation accompanying the absorption
of thermal neutrons by the natural mixture of hafnium isotopes would mainly belong to Hfin 70 %) and partly
to Hen(? 20%). The rest of the isotopes would make a comparatively small contribution.
8
Declassified and Approved For Release 2013/09/13: CIA-RDP10-02196R000100010001-2
Declassified and Approved For Release 2013/09/13: CIA-RDP10-02196R000100010001-2
TABLE 5
Some Data on Hafnium Isotopes
Isotope
(target)
Content in the
natural mixture, To
Isotopic absorption
cross section,
barns
Contribution toth
total thermal neu-
tron absorption
cross section, To *
Deutron binding energy in the
product-nucleus, Mev
measured
calculated "
Hf174
HP"
Hf177
11f178
llf179
Hfiso
0.18
5,2
18.4
27.1
13.8
35.4
1500+1000
15+15
380+30
75+10
65+15
13_+15
2,4
0.7
65.4
19
8,3
4,2
6.70+0.09 [10]
6.28+0.056 121
7.55+0.056 12]
6.52+0.12 [10]
6.18+0.056 121
7.32+0.056 [2]
6.4
7.9
5.4
* aa = (115 t 15) barns.
**Calculated byWeizsacker's formula [3].
idences in 1
-600
400
200
a
4 5 Ey ,Mev
Hf
7.6
10000
Fig. 7. Experimental y-ray spectrum of Hf02.
20000 Hp,oe?cm
The experimental and corrected y-ray spectra of Hf02 are shown in Figures 7 and 8.
The energies and intensities of the y-lines of the Hf02 spectrum obtained in this work are given in Table 6.
There we also give the results of measurements by other authors in the low energy region. The y-lines given in
Table 6 are responsible for about 12% of the energy radiated by the hafnium nuclei during their capture of thermal
neutrons.
9
Declassified and Approved For Release 2013/09/13: CIA-RDP10-02196R000100010001-2
Declassified and Approved For Release 2013/09/13: CIA-RDP10-02196R000100010001-2
0.5
Dyserosium
Fig. 8. Corrected y-ray spectrum of Hf02.
The irradiated sample was 1.8 g of Dy203, deposited as a thin layer on three discs of thin aluminum foil.
Data on the isotopes of dysprosium are given in Table 7. The total absorption cross section of the natural mixture
of dysprosium isotopes equals (1100 ? 150) barns. Comparison of this with the activation cross section of Dy164
shows that the capture of neutrons by Dy'64 amounts to approximately 70% and, consequently, the greater part of
the y-rays belong to Dy165. The thermal neutron absorption cross sections of the other dysprosium isotopes were
unknown to us.
The neutron binding energy of the Dy165 nucleus has not been measured experimentally as yet. In the last
column of Table 7 we give the binding energy calculated by Weizsacker'sformula [3]. For Dy165 it equals 5.8
Mev. We also used this value in determining the )'-line intensities in y-quanta per 100 neutron captures.
The experimental and corrected y-ray spectra of dysprosium are given in Figures 9 and 10. The energies
and intensities of the dysprosium y-lines are given in Table 8. The y-rays given account for 17% of the energy
emitted by the nucleus, i. e., somewhat more than in the case of an even-even nucleus.
Tantalum
The sample was 425 g of metallic tantalum. The experimental and corrected y-ray spectra of tantalum
are given in Figures 11 and 12. The energies and intensities of the y-lines are given in Table 9. They agree well
with the results of Bartholomew and Kinsey [17], except for the intensity of the y-line with an energy of 6.04 Mev.
The reason for the discrepancy in this case was not clear to us. As in the work of Bartholomew and Kinsey, the
half-width of the peak at an energy of 6.04 Mev which we obtained exceeds the standard value. Though we,
too, resolved this peak into two components (lines 1 and 2), in Table 9 we give the total intensity of these lines,
since the ratio of their intensities could not be determined sufficiently reliably.
10
Declassified and Approved For Release 2013/09/13: CIA-RDP10-02196R000100010001-2
Declassified and Approved For Release 2013/09/13: CIA-RDP10-02196R000100010001-2
TABLE 6
Energies and Intensities of Hafnium y-rays
Results of this work
Skliarevskii
[5]
Results of other work
et al.
Sharf-Gold- iHeydenberg,
haber et al. fremnier[13]
[12]
Sunyar [14]
Bockelman
et al. [15)*
aiiigna-
rion of y-
' lines
?
"1.
Mev
/..
E..
M ev
1"
Ey .
MeV
E Y
Mev
F
,y
Mev
E
Mev
-
-
1
6.39 -f0.04
0-5
2
6.14 .-?-0,02
1
4
5.73010.012
3.6
4
5.49 ?0.03
1.2
5
5.34 ?0.03
? 1
6
4.92 10.03
0.5
7
4.80 +0.045
0.4
8
4.54 10:04
0.2
9
4.38510.015
1.6 -
10
1.41510.015
1.2
11
1..33910.015
5
12
1.30 10.02
3
13
1.22010.015
7
14
1.180+0.015
9
15
1.090?0.015
6
0.501
0.4436
0.3324
0-3310.01
0.213
66***
0.216
.0.2210.01
0.092
71***
0.0933
0.090
0.093 ;
0.090?0.005
0.0576
*Investigation of y-rays from resonance absorption of neutrons.
**Intensity in quanta per 100 neutron captures.
***Intensity taking into account conversion.
TABLE 7
Some Data on Dysprosium Isotopes
Isotope
(target)
Dy158
Dy158
Content in
natural mixture
To
0.0524
0.0902
Isotopic absorption cross sec-
tion, barns
Contribution to
total thermal
neutron absorp-
tion cross sec-
tion*, To
Neutron binding
product-nucleus.
measured [2]
energy in
Mev
calculated ???
7.0
6.(3
Dy180
2.294
6.4110.056
6.4
Dy181.?
18.88
8.17?0,050
7.7
Dy1132
25.53
6.2710.056
6.0
Dy103
24.97
7.63?0.056
7.4
Dy104
28.18
510120. 1.3 min.**
2100+300. Tvz-.--2.4 hrs. ,*
67
5.8
*0 a =(l100 150) barns.
**Activation cross section.
***Calculated by Weizsacker's formula [3].
11
Declassified and Approved For Release 2013/09/13: CIA-RDP10-02196R000100010001-2
12
Declassified and Approved For Release 2013/09/13: CIA-RDP10-02196R000100010001-2
No. of coincidences in 10 min.
ZOO
too
2
IC
45
4
Dy
Fig. 9. Experimental y-ray spectrum of Dy203.
3
2 .3 4 5 6 Er, Mev
Fig. 10. Corrected y-ray spectrum of Dy203.
Declassified and Approved For Release 2013/09/13: CIA-RDP10-02196R000100010001-2
Declassified and Approved For Release 2013/09/13: CIA-RDP10-02196R000100010001-2
300
5 Er,
Mev
a182
*
?
0
200
100 Annih.
to boo
Fig. 11. Experimental 7-ray spectrum of Tana.
TABLE 8
Energies and Intensities of dysoprosium 7-rays
Results of this work
idam
20 000 Hp, oe.crn
Tantalum has one stable isotope ,Ta181. The
neutron binding energy in the Ta182 nucleus formed
equals 6.03 ? 0.15 Mev [18]. Line 1 probably corres-
ponds to a transition between the initial and the ground
Results of other work
states. Almost nothing is known about the excited levels
Skliarevskii Gibdon, of Ta182.
et al. [5] Meuhlhause
16
designa-
tion of Er
7-lines Mev
I.
Ey
Mev
I.
Mev
1 587 +0.02 0.26
2 5.580=1-0.015 5.9
3 5.15 +0.02 2.7
4.05 ?004 0-5
5 4.10 ?0.025 1.2
6 3-48 ?0.03 1.6
7 3.14?0.03 1-3
8 3.04 ?0.03 1 . 9
9 2.86 +0.03 2.1
10 2.74 ?0.025 3.9
11 0.42 ?0-02 4
0.180
0.104
0.078
21**
49**
16**
0.188
0.108
0.080
*Intensity in quanta per 100 neutron captures.
**Intensity taking into account conversion.
DISCUSSION OF RESULTS
From the spectra given above it is obvious that
in the case of heavy nuclei that are not situated near
to the magic numbers, the main part of the 7-transi-
tions forms the unresolvable part of the spectrum, due
to the closeness of the levels in these nuclei. On both
sides of the continuous spectrum, a series of peaks sepa-
rates out. The peaks in the high energy region corres-
pond to 7-transitions from the initial state, produced
by the capture of a neutron, to lower nuclear levels.
In contrast to light nuclei, here the separate lines, as
a rule, have a low intensity: 1 quantum per 100
neutron captures. The lines situated on the initial part
of the continuous spectrum correspond to transitions
between the lower levels.
13
Declassified and Approved For Release 2013/09/13: CIA-RDP10-02196R000100010001-2
Declassified and Approved For Release 2013/09/13: CIA-RDP10-02196R000100010001-2
0.75
?
05
025
10 000
20 000 H ,oe ? cm
f82
Ta
2
6 El, IvIev
Fig. 12. Corrected y-ray spectrum of Ta182.
TABLE 9 From the spectra of Gd158. Gd 158 and Hf178, it is
very clear that in these cases in the low energy region
1 Mev) there are groups of closely placed intense
lines. Their total.intensity is about 50 quanta per 100
neutron captures. Apparently, a similar picture is found
in the case of erbium. However, the latter example is
less convincing as here the distribution of the thermal
neutron absorption between the isotopes has not been
Energies and Intensities of Tantalum y-Rays
Results of this work
Results of other work
Bartholomew and Skliarevskii
Kinsey [17] let al. (5)
0
.0
4'8
BY Ey
Mev
?
Mev Mev unequivocally established.
I* I*
1 6.04?0-02
2 5.94?0.03
3 5.80? 0.03
4 5.54?0.03
5 5.36?0.03
6 5.24?0.03
7 4.99?0.03
8 4.83?0.03
} 1.8
0.3
0.4
0.3
0.8
0.4
1.2
6.07?0.03
0.7
5.78? 0.05
0.3
5.57?0.03
0.3
5.38? 0.03
0.3
5.21?0.03
0.5
5.05?0.03
0.5
4.84?0.03
1
The lower states of all the even-even nuclei
Mentioned have the characteristics 0+, 2+, 4+ and
energies of 0,-. 80 and 300 key. Transitions between
these levels always have high intensity. With our
apparatus we were unable to measure y-rays of such
low energies; however, they were readily observed by
the luminescence method [5].
0.272 70 To return to the even-even radiating nuclei
0.170 22
0-133 30 which interest us, it is notable that for the intense lines
0.107 15.2 lying in the region of 1 Mev, the difference in their
energies, in many cases, agrees quite well with the spac-
ing between the levels of the rotation bands of the ground
state (Table 10 for Gcl158 and Gd158). From this we can
*Intensity in quanta per 100 neutron captures. conclude that the group of intense lines with energies
of about 1 Mev correspond to transitions into the ground
state and the rotation levels closest to it.* In its turn,
this forces one to admit that in these nuclei there must exist a small number of heavily populated levels in the
region of 1 Mev. From this, however, it does not follow that the nucleus is obliged to have a low density of
levels in this energy region. A small number of levels with a high capacity may also appear in the presence of
*The high intensity of the 7-transitions considered also indicates that these 7-lines correspond to transitions
between lower nuclear levels.
14
Declassified and Approved For Release 2013/09/13: CIA-RDP10-02196R000100010001-2
Declassified and Approved For Release 2013/09/13: CIA-RDP10-02196R000100010001-2
TABLE 10
Energy Differences of the 7-Lines of the Radiating Isotopes Gd1S8 and Gd188
od158
Goss
designation
of 7-line,
energy of
)'-line,
key
difference
in energy of
7-lines",
key
level spacing,
key
designation
of 7-line,
energy of
y-line, key
difference
in energy of
y-lines*'
key
level spacing,
key
9
10
1320
1260
60+20
80
(Ground state ?
second ex-
cited)
/0
11
1240
1170
70+30
89
(Ground state-
second ex-
cited)
/0
11
1260
1180
80+20
//
12a
1170
1060
110+30
11
12
1180
1120
60+20
12a
13
1060
960
100+30
9
12
1320
1120
200+20180+30
180
(First excited-
second ex-
cited)
/0
12a
1240
1060
198
(First excited ?
second ex-
cited)
12
13
1120
960
160+20
11
13
1170
960
210+30
*The differences in energy of the 7-lines were determined from the positions of the tops of the corresponding
peaks.
a high level density if they belong to bands of collective excitation. In this case we would observe an agglomera-
tion of transitions into the ground states of the bands of collective excitation at energies of 1 Mev, if the proba-
bility of transition between the levels of this band and the levels of the bands with equal or close projections of
total angular moment (K) on the axis of symmetry of the nucleus, was much greater than the probability of a
transition to the level of the first rotational band (K = 0). Apparently, transitions from the ground state bands to
levels of the first rotational band also result in the appearance of intense peaks in the region of,- 1 Mev in our
spectra.
In particular, such a picture was observed in the scheme of 7-transitions for the 74141 nucleus (Fig. 13
taken from paper [19]), which also belongs to the category of nuclei considered and has been thoroughly exam-
ined in investigating the 0-decay of Ta182. Alaga et al., [20], in considering this scheme, came to the conclu-
sion that in this nucleus there were bands of collective excitation at energies of ??? 1 Mev. Apparently, there is
a similar picture in the case of the even-even radiating nuclei Gd, Gd, Er188 and Hf178 which we investigated.
To confirm this picture it is necessary to perform measurements on the 7-ray spectra in the region of
0-2 Mev with considerably greater accuracy than was possible with our apparatus. Such measurements would
make it clear whether there were present in these nuclei the comparatively intense 7-rays, which may be assigned
to transitions in higher bands of collective excitation.
As Figures 9 and 11 show, in even-odd and odd-odd radiating nuclei, lying in the same range of
yalues of N, groups of intense lines in the energy region of 1 Mev are completely absent. This is due to the
fact that in even- odd and particularly in odd - odd nuclei, even at excitation energies of 0.3-0.5 Mev
there is a high density of levels, belonging to the different configurations. Under these conditions, during the
radiation of the nucleus the most strongly populated are the lowest of its levels, between which the transitions
are such that they cannot be recorded by the apparatus we used.
15
Declassified and Approved For Release 2013/09/13: CIA-RDP10-02196R000100010001-2
Declassified and Approved For Release 2013/09/13: CIA-RDP10-02196R000100010001-2
1600
331,77
1500
1400
152,41
266,06
275,37-
709 70
1300 577
Is(36
1200
110
W000
0
.0? 800
c$3,
700
600
500
900
40
300 329,36
20
7.70 10409
0
171452
72205
El
253 09 55,71 01-
1.11
tyff_
141461),
(4
(2
33,30(E7)
(2
1313) E
5 12222 1231 1155 1003 $27?
(2 042) 041.22) (531
14
37 li 7;! 1713 1722 950
(M3) 4E3 41+E2 6)
?
?
219 17
E
09
4 ? v
4 ?
24
Fig. 13. Scheme of 7-transitions of the W2 nucleus.
TABLE 11
Characteristics of the Initial States of Gd156, GP and Hf118
arget-nucleus Radiating
roduct-nucleus
spin and evenness
of ground state
spin and evenness
of initial state
Gd'55
Gd151
HP
3/2 - [21]
3/2 - [21]
7/2 - [22]
GP'
Gd163
H0.78
1-; 2-
1-; 2-
3-; 4-
We should nota a series of circumstances concerning high energy transitions from the initial state, pro-
duced by the capture of a neutron. In Table 11 we give the moments and the evenness for the ground states of
the irradiated nuclei and the initial states of the radiating nuclei. As has already been shown, the final nuclei
in all cases have a system of rotation levels with characteristics 0+, 2+, 4+, close to the ground state. There-
fore, in Gd156, Gd151 and Hem El-transitions are able to go to several of these levels. However, according to
our measurements, intensity of such transitions is insignificantly small. Thus for Gd158 it does not exceed 0.02
quanta per 100 neutron captures and in the case of HP the limit of the value is 0.01. This can be explained
by the following circumstances. A number of authors (see for example [23] ) have shown that the coupling energy
16
Declassified and Approved For Release 2013/09/13: CIA-RDP10-02196R000100010001-2
Declassified and Approved For Release 2013/09/13: CIA-RDP10-02196R000100010001-2
7,87-.
1,40
126
120
),11
Cd '?8
8,46--
1,24
1.17
,..,
0,26 11 I ,t 4' 0287
008
d 2' 0089 1
0" 6
2 3 12 13 10 If 9 12 jr f 12o 10
/214 ff
Fig. 14. Scheme of y-transitions of the Gd'59 and Gd156
II
13
7, 76
;80
1,28
1,08
4'
2'
0,265
0,080
0
0"
Er?
T-2
71/2-032 ? sec
Fig. 15. Scheme of y-transitions of the
nuclei. Er nucleus.
of the nucleons is greater the greater their orbital spin moments / . Consequently, we may assume that the
even-even nuclei in the ground states have final neutrons with high values of / (for Gd, GditiB and Hims, in
all probability, 1 = 3 [24]). Therefore, the El-transitions considered will be associated with large changes in
1 for a neutron, which can considerably reduce their probability.
For the even-even nuclei we investigated, almost nothing is known on the excited states, besides the levels
of the lower rotational band. Therefore, it is impossible to construct reliable schemes of y-transitions for them.
However, using the interpretation of the group of intense lines given above, we can suggest the schemes of y-
transitions for the nuclei Gd158 and Gd, given in Figure 14. They are naturally not unequivocal and can only
illustrate the character of the transitions in the even-even nuclei considered.
After this article had been written, a report [25] appeared on the results of investigation of the decay
168 1< capture Tm > Er168. y-Rays were observed with energies 0.0804; 0,0999; 0.185; 0.199; 0.247; 0.448;
0.720 and 0.810 Mev. In the work it was assumed that in Er168 there were excited levels with energies of 0.080;
0.265; 1.080; 1.28 Mev (metastable level with T112 = 0.12 u sec) and 1.80 Mev. Several of the y-lines measured
by us fit well into this scheme of levels (Fig. 15).
We should note that in the study of different 8-decaying substances, in a number ofcases schemes of levels
were obtained for even-even nuclei, reminiscent of the schemes in Figures 14 and 15. This is so, for example,
in the case of 62SMI52, 64Gd154 and 94PU238 [26].
Received August 31, 1957
17
Declassified and Approved For Release 2013/09/13: CIA-RDP10-02196R000100010001-2
Declassified and Approved For Release 2013/09/13: CIA-RDP10-02196R000100010001-2
LITERATURE CITED
[1] L. V. Groshev, B. P. Ad'iasevich and A. M. Demidov, "Physical Investigations. ? Report of Soviet Dele-
gation at the International Conference on Peaceful Uses of Atomic Energy (Acad. Sci. USSR Press, 1955) P. 252;
Acad. Sc!. USSR Session on the Peaceful Uses of Atomic Energy (Meeting of Phys.-math. Div.) (Acad. Sc!. USSR
Press, 1955)p. 270.
[2] W. H. Johnson, private communication.
[3] E. Fermi, Nuclear Physics [Russian translation] (IL. 1951) p. 16.
[4] B. B. Kinsey and G. A. Bartholomew, Can. J. Phys. 31, 1051 (1953).
[5] V. V. Skliarevskii, E. P. Stepanov and B. A. Obiniakov, J. Atomic Energy (USSR) 4, 1, 22 (1958)
[present issue, translation page 19.]
[6] L. V. Groshev, A. M. Demidov and V. A. Naidenov, Izv. AN SSSR (in press).
[7] E. L. Church and M. Goldhaber, F'hys. Rev. 95, 626A (1954).
[8] C. A. Fenstermacher, T. E. Springer and H. L. Schultz, Bull. Am. Phys. Soc., Ser. II 2, 218 (1957).
[9] B. S. Dzhelepov, B. K. Preobrazhenskii and K. Ia. Gromov, Izv. AN SSSR (in press).
[10] R. Tobin and J. McElhinney, Bull. Am. Phys. Soc., Ser. II 1, 340 (1956).
[11] C. A. Fenstermacher, R. L. Hickok and H. L. Schultz, Bull. Am. Phys. Soc., Ser. II 2, 41 (1957).
[12] J. W. Mihelich, G. Scharf-Goldhaber and M. McKeown, Phys. Rev. 94, 794A (1954).
[13] N. P. Heyderburg and G. M. Temmer, Phys. Rev. 100, 150 (1955).
[14] A. W. Sunyar, Phys. Rev. 95, 626A (1954).
[15] C. K. Bockelman, C. A. Fenstermacher and J. E. Draper, Bull. Am. Phys. Soc., Ser. II 2. 41 (1957).
[16] C. T. Hibdon and C. 0. Muehlhause, Phys. Rev. 88, 943 (1952).
[17] G. A. Bartoholomew and B. B. Kinsey, Can. J. Phys. 31, 1025 (1953).
[18] J. A. Harvey, Phys. Rev. 81, 353 (1951).
[19] J. J. Murray, F. Boehm, P. Marrnier and J. W. M. DuMond, Phys. Rev. 97, 1007 (1955).
[20] G. Alaga, K. Alder, A. Bohr and B. Mottelson, Kong. Danske. Vidensk. Selsk., Mat.-fis. Medd. 29,
No. 9 (1955).
[21] W. Low, Phys. Rev. 103, 1309 (1956); D. R. Speck, Phys. Rev. 101, 1725 (1956).
[22] D. R. Speck and F. A. Jenkins, Phys. Rev. 101, 1831 (1956).
[23] J. M. Blatt and V. F. Weisskopf, Theoretical Nuclear Physics [Russian translation] (IL, 1954) p. 598.
[24] M. G. Mayer and J. H. Jensen, Elementary Theory of Nuclear Shell Structure (1955) p. '74.
[25] K. P. Jacob and J. W. Michelich, Bull. Am. Phys. Soc., Ser. 11 2, 260 (1957).
[26] B. S. Dzhelepov and L. K. Peker, Decay Schemes of Radioactive Isotopes [in Russian] (Izd. AN SSSR,
Moscow-Leningrad, 1957).
18
Declassified and Approved For Release 2013/09/13: CIA-RDP10-02196R000100010001-2
Declassified and Approved For Release 2013/09/13: CIA-RDP10-02196R000100010001-2
INVESTIGATION OF THE 7-RAYS ACCOMPANYING THERMAL-
NEUTRON CAPTURE BY CERTAIN RARE-EARTH NUCLEI
V. V. Skliarevskii, E. P. Stepanov and B. A. Obiniakov
Using a scintillation spectrometer measurements have been made of the
spectra of 7-rays accompanying thermal-neutron capture in a number of nuclei.
A number of intense lines have been found below 300 key in the 7-ray
spectra for thermal-neutron capture in europium, gadolinium, dysprosium,
holmium, erbium, thulium, hafnium and tantalum. Lines corresponding to
4+ 2+ and 2+-4 0+ transitions between rotational levels of Er168 and Hf178
were found in the erbium and hafnium spectra. The intensity of these transitions
corresponds to 0.5-0.8 photons per capture event.
Using a scintillation spectrometer with a NaI(T1) crystal (3.0 cm in diameter, 1.2 cm thick) measurements
have been made of the 7-rays accompanying thermal-neutron capture in europium, gadolinium, dysprosium,
holmium, erbium, thulium, and tantalum, in the energy region below 300 key. A diagram of the experimental
arrangement is shown in Figure 1. The work was carried out using the neutron beam from the RFT reactor of
the Academy of Sciences, USSR. The pulse heights were measured in a 30-channel analyzer. The energy dis-
crimination of the spectrometer was 15 percent for the 320 key 7-rays from Cr51 and 20 percent for the 102 key
7-rays from Gd153.
To determine the intensities of the capture 7-rays (the number of photons per capture event) a compari-
son was made of the areas of the photo-peaks for the 7-rays being studied and the 480-key 7-rays formed in
the BH(n, ct)Li7 reaction in a boron target. The yield for these 7-rays was taken as .0.93. This method of deter-
mining the intensities of capture 7-rays was first used in [1].
As is apparent from Figures 2-4, the photo-peaks which appear in the spectra are found in a rather continuous
distribution; part of the effect is due to the background (amounting to 5-30 percent of this distribution, depend-
ing on the target) but the main contribution is that of pulses produced by the harder capture 7-rays from the
target.
Because of this continuous distribution it is difficult to determine the areas of the photo-peaks. Thus,
additional measurements of the spectra were carried out in which lead or tin filters were placed between the
target and the crystal; these filters absorbed a known fraction of the 7-rays being measured and the areas of
the photo-peaks were then determined from the differences in the spectra measured with and without the filter.
Since the filters have virtually no effect on the background, the differences in these spectra are completely
determined by the radiation being studied.
In some cases the measurements in which the absorbers were used made it possible to establish the presence
of 7-ray peaks which remained unnoticed when the simple spectra were taken. This effect is illustrated in the
europium spectrum (Fig. 5).
19
Declassified and Approved For Release 2013/09/13: CIA-RDP10-02196R000100010001-2
Declassified and Approved For Release 2013/09/13: CIA-RDP10-02196R000100010001-2
Fig. 1. Diagram of the experiment. 1) Neutron beam;
2) target; 3) boron absorber; 4) crystal; 5) type "C"
1600
15 1200
800
400
0
ti.
0
x-ray klradiatiod
267
i
Er spec-
trUm
? without absorber
? absorber 36u ? Sn
900 A
a02
4
tas
f86
key
I82

2:_t_____?
o
0.85
?
i82
.
kev
.
.._
10 20 30
Analyzer channel
40
photomultiplier; 6) lead shield; 7) absorber (0.3 mm Fig. 2. Erbium spectrum. The proposed level scheme
of tantalum plus 0.5 mm of tin plus 0.2 mm of copper) for Er165 is shown. Figures near the arrows on the level
for attenuating the x-ray, K-radiation from lead; scheme indicate the intensity of the transition.
8) collimator; 9) boron collimator.
2400
I I Hf epectrur
i
without absorbk
-Absorber 12011 Sri-
066 4. 9000 11 Pb
213 key-
s key
20 40
Analyzer channel
Fig. 3. Hafnium spectrum. The proposed level
scheme for Hem is shown.
60
The dependence of spectrometer efficiency
on 7-ray energy was computed in the usual way
[2]. The ratio of the number of pulses at the photo-
peak to the total number of pulses produced by the 7-rays, which is required for these calculations, was measured
using a number of sources of monochromatic 7-rays with energies of 102 key (Gd'), 145 key (Ce141), 320 key
(Cr51), 480 key (the 315(n, a)Li7 reaction) and 662 kev.(Cs137).
The targets were powders of the oxides, pressed into aluminum containers 20 mm in diameter and 0.3 mm
thick. The background spectrum was measured with an empty aluminum container.
4000
??-I
a)
13200
g tau
?
x-ray k-ra-
diatiolt
I i I
283
.
262
I
1
?111
I
1129
87
.
0.34
79
0,52 (149
? 0
?
iske
, 0
V Hey Gd
.
6d .
II
I
183 key
I toskev
4-11
?
?
,t
li
G ,s7
d
'1
i
/
0
4 .
l?
4
0
20 40
Analyzer channel
60
Fig. 4. Gadolinium spectrum. The solid line corres-
ponds to the y-rays emitted by the Gd155 target, the
dotted line corresponds to the Gd157 target. The level
schemes proposed for the isotopes Gd 156 and Gd191
formed in neutron capture are shown. The figures near
the arrows on the level diagram indicate the intensity
of the transition.
20
Declassified and Approved For Release 2013/09/13: CIA-RDP10-02196R000100010001-2
Declassified and Approved For Release 2013/09/13: CIA-RDP10-02196R000100010001-2
1600
74)1200
0
800
0 40
0
Ix-ray. on -
adtati
Resolution of
erence for
with. nd wit
the diff-
curv -
out aisorl
s
II
400
200
?Ike
93 ke
I
II$3
ke
+
' -s.'
--'
111
A20
nak
30
.
?
40 50
without absorber
bsorber 360
S
I
Eu spectru
0 20 40 50
Analyzer channel
Fig. 5. Europium spectrum. On the 93-key line is
shown the unresolved line at 71 key which can be
separated graphically as shown in the insert.
er
As a rough check on the purity of the targets
each target was used in a measurement of the total
thermal-neutron cross section using the transmission
method with a boron target as a detector; the 7-
rays from this target were measured with the scin-
tillation spectrometer. The results of these measure-
ments indicated that the materials being investi-
gated had no significant contamination.
Results of the Measurements
Erbium. The way in which each isotope
contributes to the capture cross section in erbium
is known. In the spectrum obtained in the present
work (Fig. 2) the 7-ray lines at 82 and 185 key
are particularly pronounced. The energy ratio for
these lines is in good agreement with the energy
ratio for rotational levels of an even-even nucleus.
The corresponding energy-level scheme is shown
in Figure 2. The high intensity of these lines (the
number of photons per capture event), computed
from the total neutron capture cross section in erbium, indicates that the main contribution to the thermal-
neutron capture cross section in a natural mixture of erbium isotopes is due to Er167 ? the only erbium isotope which
can form an even-even nucleus in neutron capture. The first rotational level is known from experiments on 7-
rays in Coulomb excitation [3]. The value of 79 key for the first level obtained in this work is in good agreement
with the present value. The present results for the second level are in agreement with those of [4] in which
188-key 7-rays were found with an intensity of approximately 0.5.
Hafnium. The main contribution to the thermal-neutron capture cross section in hafnium is due to Hfin.
In the capture neutron 7-ray spectrum for hafnium (Fig. 3) the line at 92 key corresponds to a transition from the
first rotational level in HP, known from Coulomb excitation experiments [3]. The 213-key line corresponds
to a transition from the second rotational level in Hen to the first; however, a significant contribution may also
be due to the 215-key 7-rays emitted in the isomeric transition in Hf179 with a half-life of 20 sec. The Contri-
bution of the isomeric transition was determined by measuring the spectrum from the hafnium target immediately
after the neutron beam was cut off and was found to be 20 percent of the total intensity of the 213-1ev line.
These data confirm the results of [5] in which lines at 90, 220 and 330 key were found in the 7-ray spec-
trum accompanying capture of resonance neutrons.
Gadolinium. In References [6] and [7], in which studies were made of the spectra of internal conversion
electrons for 7-rays accompanying thermal-neutron capture in gadolinium,it was established that there are 79
and 180 key 7-rays corresponding to the Gd157(n, y) Gd 158 reaction and 89 and 196-key 7-rays corresponding to
the Gd155(n, y)Gd156 reaction.
The measurement of the yields of these 7-rays was carried out in different isotopes in the present case.
In the G(1155 target the content of the isotope being studied was 97.3 percent while in the Gd'57 target this figure
was 91.4 percent. The spectra for these targets are shown in Figure 4.
In erbium and hafnium we carried ,out measurements of the y ? 7-coincidences which indicated that the
7-rays corresponding to the proposed transition 4+ ?4. 2+ and 2 + -4. 0 + in the even-even nuclei Er168 and Hf'"
are actually emitted in cascade fashion.
A general feature of capture 7-rays emitted by even-even isotopes of erbium, hafnium and gadolinium is
the high intensity of the 4 + --> 2+ and 2+ ?> 0+ transitions ;;it follows that a considerable fraction of the transi-
tions from the higher levels go to the 4+ level.
21
Declassified and Approved For Release 2013/09/13: CIA-RDP10-02196R000100010001-2
Declassified and Approved For Release 2013/09/13: CIA-RDP10-02196R000100010001-2
Isotope emitting
the 7-ray
Energy of the
7-ray, key
Intensity of the y-
ray (number of
photons per neutron
capture event)7v7
Multipolarity
of the trans-
ition
aK
ct
Intensity of the
transition v =
= v7(1 + ocK + al)
Er168
82
0.18
E2
1.6
2.1
0.85
185
0.64
E2
0.20
0.084
0.82
Hfin
92
0.19
E2
1.0
1.7
0.71
213
0.55
E2
0.13
0.07
0.66
58
Gd'
79
0.104
E2
2.0
2.05
0.53
183
0.22
E2
0.22
0.09
0.29
Gd156
87
0.137
E2
1.37
1.25
0.50
196
0.277
E2
0.17
0.054
0.34
D y165
78
0.028
M1
4.1
0.68
0.16
104
0.018
E3
3.4
22.6
0.49**
180
0.16
E2
0.22
0.1
0.21
E052
72
0.044
90
0.20
Ho168
121
0.20
142
0.31
Ta182
107
0.152
133
0.30
170
0.22
272
0.7
Turf?
150
0.073
* v for Er168 is computed for a total neutron capture cross section in erbium a = 166 barns. In all the other
cases the isotope cross sections are used [11].
**This value of the intensity for the isomeric transition with a half-life of 1.3 min actually represents a frac-
tion of the cross section for the production of Dy165 m in the total neutron capture cross section for Dy164. In
Reference [12] a value of 0.7 was obtained for this fraction.
In the neutron capture 7-ray spectrum of dysprosium there are lines corresponding to the well-known
transition between the lowest levels of Dy165 [8]. A number of rather intense lines appearing in the capture 7-
ray spectrum of europium, holmium, thulium and tantalum correspond to transitions between the lower levels
of the odd-odd nuclei Eu152, Ho168, Tul" and`Ta182. The presently-available data are still insufficient for establish-
ing the scheme for the lowest levels in these nuclei.
The energies and intensities of the 7-rays are given in the table.
The accuracy in the determination of the energies and yields of the 7-rays is 2-3 percent and 20-30 per-
cent,respectively. In view of the high values of the conversion coefficients, the accuracy in the determination
of which is small, the total intensities of transitions with energies greater than 100 key are obtained with an
accuracy of approximately 40 percent. The conversion coefficients for the K- and L-shells were taken from the
tables in [9] and [10].
The authors are indebted to Academician I. V. Kurchatov for his interest in the work and to Professor
L. V. Groshev, V. M. Strutinskii and D. P. Grechukhin for a number of valuable comments and Professor I. A.
Zaozerskii for kindly furnishing the rare-earth samples.
We wish to express our gratitude to G. P. Mel'nikov for providing reliable operation of the electronic
apparatus.
22
Received August 8, 1957
Declassified and Approved For Release 2013/09/13: CIA-RDP10-02196R000100010001-2
Declassified and Approved For Release 2013/09/13: CIA-RDP10-02196R000100010001-2
LITERATURE CITED
[1] I. V. Estulin, L. F. Kalinkin and A. S. Melioranskii, J. Exptli-Theoret. Phys. (USSR) 31, 886 (1956). *
[2] K. Liden, and N. Starfelt, Ark. f. Fys. 7, 428 (1954).
[3] N. P. Heydenburg and G. M. Temmer, Phys. Rev. 100, 150 (1955).
[4] C. A. FenstermacherR. L..Hickok and H. L Schultz, Bull. Am. Phys. Soc., Ser. II 2, 41 (1957).
[5] C. K. Bockelman, C. A. Fenstermacher and J. E. Draper, Bull. Am. Phys. Soc. 'Ser. 11 2, 41 (1957).
[6] E. L. Church and M. Goldhaber, Phys. Rev. 95, 626 (1954).
[7] L. V. Groshev, A. M. Demidov and V. A. Naidenov, Report to the Seventh All-Union Conference on
Nuclear Spectroscopy (Leningrad, 1957).
[8] B. S. Dzhelepov and L. K. Peker, Decay Schemes for Radioactive Isotopes,**(Izd. AN SSSR,
Leningrad, 1957).
[9] L. A. Shy and I. M. Band, Tables of Internal Conversion Coefficients for Gamma Radiation, Part I,**
azd. AN SSSR, Moscow-Leningrad, 1956).
[10] G. F. Dranitsyna, Internal Conversion Coefficients for Subshells (Izd. AN SSSR, Moscow-
Leningrad, 1957).
[11] D. J. Hughes, Pile Neutron Research*** (IL, 1954).
[12] G. Weber, Z. f. Naturforschung 9a, 115 (1954).
*See English translation.
**In Russian.
***Russian translation.
23
Declassified and Approved For Release 2013/09/13: CIA-RDP10-02196R000100010001-2
Declassified and Approved For Release 2013/09/13: CIA-RDP10-02196R000100010001-2
Declassified and Approved For Release 2013/09/13: CIA-RDP10-02196R000100010001-2
Declassified and Approved For Release 2013/09/13: CIA-RDP10-02196R000100010001-2
NUCLEAR INFORMATION OBTAINABLE FROM LOW ENERGY
NEUTRON SPECTROSCOPY
D. J. Hughes
(Brookhaven National Laboratory, Upton, L. I., New York)
The results of measurements of thermal-neutron cross sections, level distri-
butions in the resonance region, Fn /D ratios, and determinations of the effective
nuclear radius from potential:scattering of slow neutrons are considered.
A discrepancy in the results of measurements of the thermal-neutron fission
cross section in U235 is noted. The distribution of levels exhibits a deficiency in
small spacings as compared with a random distribution, i. e., there seems to be
a "repulsion" of levels. The dependence of r?n ID on atomic number A is non-
monotonic, in accordance with the complex-potential model of the nucleus;
however there is a considerable discrepancy between the experimental data and
theory for atomic numbers in the neighborhood of 100. The effective radius de-
termined from potential scattering of slow neutrons indicates a nonmonotonic
dependence on A, in agreement with the model of a semi-transparent nucleus
with smeared-out edges.
In discussing nuclear information obtained from neutron experiments I feel somewhat squeezed in two
directions. On one hand, in view of the papers of Bethe, Wheeler, Wigner, and others, it would be presumptuous
of me to talk about the nuclear theory that has been developed on the basis of the experimental cross sections.
On the other hand it wouldn't be quite right to talk about the experimental techniques, considering the many
reports on these that we are to hear. What I do wish to talk about, therefore, is this narrow region into which I
am squeezed ? the treatment of the experimental data as it passes out of the realm of measurement to become
the basis for nuclear theory. I am glad to be thus limited ,for I can concentrate on what seems to me an import-
ant matter, that is, how to make the nuclear data good enough so that it can be legitimately and safely used by
theoreticians.
The material of this conference divides rather neatly into two parts, low energy and high energy, but in
a sense other than energy there is a marked difference between these two categories. The high energy work is
quite difficult, I think, compared to the low energy work; as a result there are a lot more data available in
the latter region. If you will merely glance at the abstracts you will notice that most of those concerning low
energy deal with a lot of numbers, such as parameters of various isotopes, and so on, whereas many of the high
energy papers discuss the developing experimental techniques.
In the low energy field we are in a spot where many instruments are running steadily, turning out data
night and day. In fact, one of the papers this afternoon, by Malkonian, will deal with the problem of what we
will do with all this data pouring out of thousand-channel analyzers all over the world. Now the point that I
want to emphasize strongly is that, faced with this great accumulation of our own data, we do have a certain
*Report to the International Conference on the Interaction of Neutrons with Nuclei held at Columbia University
in September, 1957. (A report on the conference is given on page 125 of this issue.
25
Declassified and Approved For Release 2013/09/13: CIA-RDP10-02196R000100010001-2
Declassified and Approved For Release 2013/09/13: CIA-RDP10-02196R000100010001-2
responsibility. In his introductory talk, President Kirk considered the social responsibility of scientists, and now
I want to add another that we experimentalists have ? to see that the numbers we turn over to the theoreticians
are good. Bethe has shown that the problem of dealing with these numbers in nuclear and reaction theory is
extremely great even if the theoreticians can trust them completely. But if the theoretician must in addition
decide whether the numbers are good or not, and how to correct them if not, the task is almost impossible.
So in the time I have available, let me consider a few cases for which we do have quite a lot of informa-
tion but where we have to be very careful, probably more careful than we have been in the past, in producing
valid sets of data for use in constructing and testing nuclear models. I shall begin by mentioning very briefly
some thermal neutron cross sections, at the low energy end of the resonance region, just to remind you that there
still are such things that require careful work. Then I'll talk a bit about the question of the level spacing dis-
tribution, which was already considered briefly by Bethe, followed by the strength function, and finally the
question of potential scattering and its relation to the nuclear radius.
Thermal Cross Section:s
On the thermal cross sections, which I'm putting in here primarily to remind us that we're not through
with these supposedly well-known standards, let us look at one of the most outstanding thermal cross sections that
have given difficulty, the cross section of boron. Some ten years ago, everyone believed that the thermal cross
section of boron was 703 barns, and when some measurements indicated that perhaps it was about 730, these
were thought to be unbelievable. But as most of you know, the thermal cross section of boron has now crept up
to 755, and we are not absolutely sure it has stopped. We think it has stopped at 755, but I would not bet on it
with very high odds. I am sure that you are thinking that it is a very simple thing to measure and we certainly
should know it well. My own feeling is that the present value will not change much, but it certainly has required
much careful recent work to establish it.
The other thermal cross section that has been the subject of much work is that of Uz35, primarily its fission
cross section. True, you can hardly think of a cross section more fundamental to the whole atomic energy busi-
ness than the fission cross section of 05. A few years ago we all believed that the fission cross section of U45
was 550 barns, the total absorption 650, and capture was 100. Well, since that time, the fission cross section has
crawled up from 550 to 582 10 barns, and it looks as if it's going to break 600 soon. So again you say it is
easy, it is just a relatively straight-forward, simple measurement, and we have lots of velocity selectors. But
it has gone up during these years, and it's the sort of thing, in a way, of which physicists throughout the world
should be a little ashamed and not rest until things are better stabilized. Stability certainly hasn't been attained
at present; several careful measurements recently have given values of 555, 579, and 606 barns, each accurate
to about one percent. On my recent rip to Europe, I discussed this discrepancy at every laboratory I visited, and
I hope that I got some measurements started in various countries throughout the world. Perhaps a year from now
we can say that this cross section has stopped changing, just the way that we now feel that boron has stopped.
Level Spacing Distribution
With this brief reminder that there still is work to be done on the fundamental standard cross sections, I
will go ahead to something that is of more recent interest and has more direct relationship to nuclear structure.
This is the matter of the spacing distribution of individual levels in a nuclide, and again it is a good example of
the necessity of great care in treatment of experimental details. It was noticed a year or so ago that levels in
U238 occurred with surprising regularity, and for a short time it seemed that the neutron resonances occurred every
18 volts, almost without exception. This result at least stimulated further work and it soon turned out the levels
were hardly that regular. Whether they were completely random or not was not clear from the available data,
however.
Recently, there has been increasing evidence that there is a deficiency of small spacings, the "level re-
pulsion" effect. I would like to review briefly some results that J. A. Harvey and I have obtained during the
last few months. A moment's reflection will make you realize that there are many reasons why the observed
distribution of level spacings is not correct. Of course, when levels are very close together they cannot be re-
solved and some small spacings will be missed. However, in correcting for this effect it is necessary to study the
question of possible correlation between the spacing of two levels and the size of the levels, given by their
neutron widths F.
26
Declassified and Approved For Release 2013/09/13: CIA-RDP10-02196R000100010001-2
Declassified and Approved For Release 2013/09/13: CIA-RDP10-02196R000100010001-2
We all know that the On ID ratio is something that doesn't vary widely from nuclide to nuclide, but
this ratio applies to the average On and the average spacing D. But what if there is a correlation between the
individual D's, that is local spacing, S, and the individual r?11 ? In fact, a literal interpretation ot the usual
derivation of the rn ID ratio would lead one to suspect a local correlation. If this is true, levels close together
will be small, hence the loss of small spacings would be more serious than it would be for no correlation. Thus
even before the correction to the experimental spacings can be begun, it is necessary to investigate a possible
On and D correlation on a local scale.
We have investigated this matter reasonably carefully, with the results shown in Figure 1. Here we have
plotted, for a number of zero-spin target nuclides, the number of cases in which we find particular ratios of r?n/S
to the average, or r?, /D. If r?n /S is a local phenomena, all these points should be clustered about unity, but
in contrast a continuous distribution is seen. The theoretical curve is based on a Porter-Thomas distribution of
r?n , a distribution of spacings that I will show you in a minute or two, and an assumption of no'correlation be -
tween individual rn? and S. Since it looks as if this agreement is reasonably good, we can conclude that width-
to-spacing is not a local correlation.
7
7 5
g 4
1 I
Vf1Xj5/2
? U234,6.8 h292
0
5
Fig. 1. Experimental ratios of the "local" rn?/S to
the average value for zero-spin nuclides, together with
a computed curve based on the assumption of no local
correlation.
It is then possible to go ahead and investigate
the observed spacing distributions. Figure 2 is the dis-
tribution for the zero spin target nuclides U334, U236,
U238 and Th22, for which there is no difficulty of the
presence of two spin states. ?The triangles are the
experimental points, and the correction increases the
number of small spacings. This correction is an ex-
tremely complicated one to make. We're quite sure
we have made it correctly, and are also quite sure
we can't explain it to anybody. However, as soon as
we decide how to explain it, we are going to publish
this work. In Figure 2 the results are compared with
an exponential curve, corresponding to a random dis-
tribution, and the disagreement is not really very
great. There does seem to be deficiency of small
spacings, however. -In Figure 3, the same data are
shown compared with a distribution that is simply a
convenient algebraic expression, 4xe-2x. It is seen
that here the correction is smaller than in Figure 2,
and the corrected results definitely show a repulsion
effect, agreeing reasonably well with the curve.
Since there are only a few available even-even
nuclei, the statistics are poor in Figures 2 and 3. ,But,
having a reasonable distribution established, we can now look at the case of two spin states combined, the non-
zero spin target nuclides, where we have much more data. Figure 4 shows the case of odd nuclei in which there
are the two spin states. Here the statistical error is smaller, but the distributions do not differ as much from ex-
ponential as for the zero-spin cases. This is simply because two nonrandom distributions, one for each spin state,
produce a distribution more nearly random when combined. Here the experimental results are shown with the
theoretical curve based on the expression shown in Figure 4. Also shown in Figure 4 by the solid line is an ex-
pression suggested by Wigner at the Oak Ridge conference in the fall of 1956. Actually the points agree reason-
ably well with either curve and definitely show a repulsion effect.
We are looking forward very much to hearing what Wigner will have to say later in this conference on
the theoretical side of the level spacing distribution. Experimentally we believe quite firmly now in the repul-
sion effect, a deficiency of small level spacings relative to a random distribution
Strength Function,
Here again is an example that shows how careful we must be in presenting the experimental data. The
experimental points from a number of laboratories are shown in Figure 5. They show the wavelike characteristics
27
Declassified and Approved For Release 2013/09/13: CIA-RDP10-02196R000100010001-2
Declassified and Approved For Release 2013/09/13: CIA-RDP10-02196R000100010001-2
40
36
32
18
24
20
16
12
8
4
A Observed
0 Corrected
Q
40 e-1
-
z-S/D
Fig. 2. Comparison of the observed and corrected
level spacing distributions for zero-spin nuclides,
with a random distribution (the exponential curve).
2
-30
Fig. 4. Comparison of the observed and corrected
level spacing distributions for nuclides of non-zero
spin with curves representing the combination of
both spin states. The dashed curve is based on the
curve of Figure 3 for a single spin state and the
solid curve on the Wigner distribution.
adjusting the parameters of the theory to get better
for the theoreticians to answer, however.
0
36
32
78
24
t 20
16
Fig. 3. Comparison of the observed and corrected
level spacing distributions for zero-spin nuclides with
a distribution showing repulsion at small spacings.
expected from the cloudy 'crystal ball model, but the
disagreement at certain atomic weights is quite large,
particularly around atomic weight 100, where the
experimental points are low by about a factor of 5.
The theoretical curves in Figure 5 are based on a
diffuse-edge nucleus of parameters shown, but without
the effect of the aspherical nuclear shape. Some recent
calculations of Chase and Willets, to be presented
later at this conference, improve the agreement above
A =420.
There will be other papers on the experimental
side of this question later in the conference, and also
several theoretical papers. The question that naturally
occurs, in the light of all this activity, is how far is it
profitable to push this kind of comparison. Certainly
the experimental points can be improved, but it's not
easy, and the question is how many years of our lives
should we spend improving experimental data, that is,
how much will be learned about nuclear structure by
and better agreement. I think that is mainly a question
Potential Scattering and the Nuclear Radius
My last example of the kind of work that requires great care to get answers that mean anything, concerns
the matter of potential scattering and the nuclear radius. Here there are important points on both the experimen-
tal and the theoretical sides. There are rather fundamental theoretical questions concerning the nature of the
potential scattering. What is the real meaning of the statement that potential scattering is the value of the cross
section that occurs between resonances? Obviously, the scattering will be affected by the nearby resonances,
but the question is how many resonances are nearby. Must you subtract the effect of five or ten resonances on
either side of the point in question, or several thousand ? Again, if the analysis of performed at a second point,
say a kilovolt away from the first,will the same result be obtained ? Thus the very question of what meaning is
there to the term potential scattering is an important one.
28
Declassified and Approved For Release 2013/09/13: CIA-RDP10-02196R000100010001-2
Declassified and Approved For Release 2013/09/13: CIA-RDP10-02196R000100010001-2
rri
Spiherical nucleus
ors N nspherical nucleus
V, = 42 Mev
- 0.08 -
- 1.35 ? 13' 13 cm
trod - 1.65
0.10
0 01
, 0
I Brookhaven
?
a Duke University
0 University of Wisconsin
? Argonne National Lab.
ic)
2 (r-R)
1-f elp
A_
40
' '
12 0 16 0
L
''
200 240 280 A
Fig. 5. Experimental values of the n /D ratio, or strength function, and the optical model values for spherical
and nonspherical nuclei.
On the experimental side, the related question is one of the correct procedure for obtaining the potential
scattering. If we simply look at the cross section at low energy, we shall get very misleading results. For a
long time it was thought that the potential scattering of U8, for example, was about 8 barns, because if capture
is subtracted from the total cross section at low energy, what is left is a rather flat cross section with a value of
about 8 barns. If this value is substituted into the expression a = 41r R2, a small R is obtained, which definitely
pot
disagrees with other data.
The results of a much more correct method is shown in Figure 6, the open circles of which show the total
cross section of U238 in the region 20 to 80 ev. It is possible to correct the cross section at any point for the effect
of the resonances, primarily the resonance-potential interference. It can be done quite accurately because the
parameters of the levels are well known. When the correction is made the closed circles represent the cross
section with resonances removed. The resulting cross section is now very flat with energy at a value of 10.7
barns, much higher than the 8 barns obtained from the cross section near zero energy. Also, the potential scatter-
ing cross sections do seem to have a definite meaning, for the same result is obtained at one key neutron energy.
Thus the potential scattering as obtained by removing a small number of resonances is constant for energy changes
for a key or so.
Now the interesting question of the relationship of this potential scattering to nuclear structure can be considered.
In Figure 7 Are shown theoretical curves and recent results obtained at Brookhaven, by methods to be described
29
Declassified and Approved For Release 2013/09/13: CIA-RDP10-02196R000100010001-2
Declassified and Approved For Release 2013/09/13: CIA-RDP10-02196R000100010001-2
020 25 30 35 40 45 50 55 60 65
Energy, ev
70 75 80
Fig. 6. The total cross section of U232 as observed (open circles) and after correction for the effect of resonances
(closed circles). The corrected curve is the potential scattering.
in more detail by Seth later at this conference. The smooth curve labelled r0A2/3 is based on an ro = 1.35 x
X 10-13 cm and gives the distance to the half-way point of the potential, as shown in the inset. The cloudy
crystal ball model with the constants listed (assuming a spherical shape) gives the curve that oscillates about the
smooth line. This curve gives R', where 411" (R!)2 is the potential scattering of slow neutrons. The experimental
points seem to verify the predictions of the cloudy crystal ball, except in the region of highly deformed nuclei,
A about 140 to 240. These results are similar to Figure 5 for the strength function, where the verification of the
model was reasonably good. Again, as for Figure 5, the agreement is made much better when the aspherical
shape is included, as given by Chase and Willets' calculation,to be reported later in this conference.
However, these results can be used for another purpose in addition to verifying the optical model, that is,
to obtain a value for R. Here we definitely need help from the theoreticians in the interpretation. The points
oscillate about the smooth line, which is based on an 1.0 of 1.35.10-13 cm. The dependence on the model'
actually is not very great, so we can think of these results as determinations of R, hence ro. In order words, the
results give an r0 of 1.35, and we must consider to what extent that answer is dependent on the constants of the
model. In Figure 5, the position of the maxima is determined by KR, where K is the wave number of the neutron
in the nucleus and R is the nuclear radius. Stated in another way, the position of the maxima is determined by
the well depth V, times the radius squared. Similarly, the angular distribution of neutron or proton scattering is
determined by this same quantity, VR2. R is not obtained separately from the V.
However, in the potential scattering work we get R without knowledge of V. The reason is that the places
where the theoretical curve crosses the roAl /3 line are determined by VR2, but VR2 is obtained from the strength
function results of Figure 5. In other words, the points at which the nucleus acts like a black nucleus (R'.= R)
are fixed by the strength function results, so that tells us how to obtain R from the results of Figure 7. For in-
'stance, the strength function results show that at A near 110 the cross section is 47r R2 , and we thus get a value
of R, which leads to ro = 1.35.10-13 cm. Now this, of course, gives the radius of the potential well felt by the
neutrons, not the matter distribution. Around A = 180, it is difficult to use the results to get an accurate value
of ro because of the large effect of the aspherical nuclear shape. However, as already pointed out, this region
is useful to verify the computed effect of the aspherical shape on the potential scattering. Howeveroat lower A,
near 120 where nuclei are spherical, the combination of this work together with the strength function results
can be used to get a good value of the radius of the potential.
30
Declassified and Approved For Release 2013/09/13: CIA-RDP10-02196R000100010001-2
Declassified and Approved For Release 2013/09/13: CIA-RDP10-02196R000100010001-2
10
9
8
7
6
5
4
2
Spherical
nucleus
?
?
?
Nonspherical
radius
.00
V0=42 Mev
.=0,08
ro= 1,35. f0-1? cm
d 1.16./0-13 C111
41.
11=-10
2 r-R
exp
i
TO 40 60 80 100 120 140 160 180 200 220 Z40 260
Fig. 7. Measured values of the effective radius R', compared with the optical model calculations for spherical
and nonspherical nuclei. A curve for the nuclear radius R is also shown.
The topics considered here are only a few examples of matters where really hard work and careful atten-
tion to details is very important. The work is certainly not finished; in spite of all the thousand-channel analysers
there still remains much to be done. Actually, some phases have hardly started ; here in my opinion the two
outstanding ones are the study of capture gamma rays as a function of neutron energy, and the whole host of
effects as function of level spin. As so few spins have been determined, the whole field of the dependence of
radiation widths, fission width, etc., on spin remains to be investigated.
Received December 12, 1957
31
Declassified and Approved For Release 2013/09/13: CIA-RDP10-02196R000100010001-2
Declassified and Approved For Release 2013/09/13: CIA-RDP10-02196R000100010001-2
INVESTIGATION? OF THE STRUCTURAL CHANGES TAKING PLACE
IN A URANIUM-MOLYBDENUM ALLOY UNDER THE ACTION OF
NEUTRON IRRADIATION
S. T. Konobeevskii, N. F. Pravdiuk, K. P. Dubrovin, B. M. Levitskii,
L. D. Panteleev and V. M. Golianov
An alloy of uranium with 9 wt.% molybdenum Was subjected to neutron irratiation,
after which the electrical resistivity was measured and the structure studied by x-ray
and microposcopic analysis. Preliminary heat treatment allowed specimens to be
obtained with an a + y' eutectoid structure having various grain sizes. It was established
that the rate of diffusion leading to homogenization under the action of irradiation in
annealed specimens is inversely proportional to the square of the grain size (the period
of the lamellar eutectoid). In a homogeneous specimen (y-phase) irradiation causes a
change in properties and structure which rapidly (in 2-4 hours) attains a limiting value,
which is explained as being due to radiation annealing. Disordering was found in the
y'-phase, with a transition to the cubic lattice which took place under the influence of
irradiation during the first hours of exposure.
All these phenomena are satisfactorily accounted for on the basis of the theory
previously developed [2], although the magnitudes of the thermal-spike region and of
the energy liberated in it, equal respectively to 2.5 ? 1.0-11 cc and approximately 2 Mev,
are less than were determined in [2].
An alloy of uranium with 9To molybdenum can exist in two states at room temperature. On the not-too-
slow cooling of this alloy from temperatures above 600?C, the high-temperature 7-phase is retained in it,
taking the form of a homogeneous solid solution of molybdenum in uranium. The homogeneous state appears
to be metastable at low temperatures. Annealing the alloy in the temperature range 350-550?C causes decom-
position of the solid solution into a eutectoid mixture of lamellae of a-uranium and the intermetallic compound
y'. As has been shown, the compound y' is an ordered solid solution whose composition corresponds to the formula
U2Mo. The reverse transformation of, eutectoid into y-phise takes place 9.n heating in the temperature range
590-610?C.
In previous work [1] it was shown that while specimens of the homogeneUs alloy retain their phase compos-
ition on irradiation, specimens of the heteroianeous alloy show partial or complete homogenization after irradi-
i ?
ation. Such a transformation from one state to another was revealed by a sharp change in the electrical resisti-
vity, temperature coefficient of electrical resistivity, density and hardness of the -heterogeneous alloy after its
Irradiation and was definitely confirmed by x-ray structural analysis.
A theoretical explanation of the observed phenomenon was given in (2], in which it was shown that the
transformation of the heterogeneous state into the homogeneous during irradiation can be regarded as the result
of unusual diffusion caused by intermingling of the atoms of the alloy in microvolumes of the specimen due to
slowing down of the fission products. The concentration of molybdenum at any point-of the specimen (x) must
vary during irradiation in accordance with the following relationship:
33
Declassified and Approved For Release 2013/09/13: CIA-RDP10-02196R000100010001-2
Declassified and Approved For Release 2013/09/13: CIA-RDP10-02196R000100010001-2
? ti=oo
27m e -4712:2 D1
c=c l
[ 1 1 1 ?X s in "a cos
uta ?F
ri=
(1)
where a is the width of the lamellae of the y-phase; X is the period of alternation of the lamellae (the total
width of the lamellae); t is the irradiation time; D is the diffusion coefficient. The value of D can also be
found theoretically from the expression for "thermal spikes":*
D=-1.16.10-18(;)1s w,
(2)
where E is the energy (in key) expended by the fission products in mixing the atoms of the alloy in the micro-
volume; T is the minimum temperature (in ?K) at which the intermingling of the atoms in the microvolume of
the alloys can be observed; W is the specific heat (in watts) evolved by 1 g of alloy during irradiation.
The theoretical value of the diffusion coefficient (2) can be compared with the value (1) obtained from a
study of the rate of homogenization of the alloy. From this a parameter E/T is found. It follows from (1) that
the homogenization time must be proportional to the square of the period of the eutectoid (the thickness of the
double layer a +y'), which in [2] was provisionally taken as equal to 111. For this value of X a value was
obtained for E/T of about 9 key/?C and for E (taking the lowest temperature of homogenization T as equ'al to
2000"C ) of about 18 Mev. This estimate, judging from the present work, was too high.
In [3] a study was made of the action of irradiation on alloys of uranium with 9, 10.5 and 12 weight %
molybdenum and with 10 weight 010 niobium. The authors arrived at the conclusion that in all these alloys
irradiation gives rise to a transformation of the heterogeneous structure to the homogeneous one and gave an
explanation which had the same basis as that presented above.
In the present work, designed to verify the theoretical relationship between the rate of diffusion and the
period of the eutectoid structure, a study was made of the transformation of the heterogeneous structure of the
uranium alloy containing 9 weight "7o molybdenum into the homogeneous structure in relation to the size of the
eutectoid lamellae and also to the amount of irradiation. Varying degrees of dispersion of the eutectoid were
?
obtained by annealing specimens of the alloy at various temperatures.
Material
The alloy of uranium with 9 weight 010 molybdenum was prepared by melting under vacuum in an induction
furnace (chemical analysis of the alloy gave 9.05 weight 10 molbydenum). Ingots of the alloy were reduced by
hot and cold rolling to a thickness of 0.1 mm. From such thin sheets specimens were cut for measuring the
electrical resistivity. The same specimens were subsequently used for the x-ray investigations.
Heat Treatment
All the specimens were given a homogenizing anneal for 3 hours at 1000?C. Annealing was carried out
in a quartz tube in a vacuum ,of 1-5. 10" mm Hg. After the 3-hour anneal the quartz tube containing the spe-
cimens was cooled in air. Some of the specimens after such heat treatment were used to study the effect of
irradiation on the properties of the alloy in the y-solid-solution state. The remainder of the specimens were
used for obtaining eutectoid structures of various lamellar sizes by annealing at temperatures from 550 to 400?C
(Table 1).
Annealing was carried out in evacuated quartz capsules (the vacuum before sealing off was 10" mm Hg).
After annealing, the specimens in the capsules were cooled in air. The period of holding at each temperature
was determined from the C-curves (Fig. 1) previously obtained for this alloy. Curve I corresponds to the begin-
ning of decomposition of the y-phase and Curve U to the end. The extent of transformation of the y-phase was
determined by measuring the electrical resistivity (R) and the temperature coefficient of electrical resistivity
*This terminology does not agree completely with that in the English literature, in which "thermal spikes" differ
from "displacement spikes" postulated by Brinkman.
34
Declassified and Approved For Release 2013/09/13: CIA-RDP10-02196R000100010001-2
Declassified and Approved For Release 2013/09/13: CIA-RDP10-02196R000100010001-2
(a) of each specimen after annealing. Such a check showed that all the specimens were completely transformed
into the heterogeneous state with the exception of specimen No. 5, which had been annealed at 400?C for 700
hours. Judging by the values of R and a for the annealed specimen No. 5, it was concluded that decomposition
in it had proceeded to the extent of approximately 84 percent.
TABLE 1
Characteristics of the Specimens of Uranium ? 9 weight %Molybdenum Alloy Studied
Specimen No.
Condition
Heat treatment
Mean period of
eutectoid, microns
Remarks
temp.,?C
time, hrs.
1
Quenched (homo-
geneous)
1000
3
?
?
2
Annealed (eutectoid )
550
1000
1.0
?
3
" "
500
100
0.3
?
4
" "
450
100
0.16
?
5
" "
400
700
0.1
Decomposed 84%
550
-500
0.450
C
10 too
time, hours
4,
Fig. 1. C-curves for uranium ? 9 weight % molybdenum
alloy.
Irradiation
Irradiation was carried out in the RFT reactor in a neutron flux of 2.1013 neutrons/cm2. sec. Before irra-
diation the specimens were firmly gripped between the two halves of a magnesium cone, which were then pressed
into the conical aperture of an aluminum container. The container was hermetically sealed with a lid and placed
at the bottom of an aluminum tube, surrounded by water in the reactor, the temperature of which did not exceed
50?C. Calculation and an experiment carried out previously on the direct measurement of the temperature of
an alloy specimen during irradiation made it possible to assume that the temperature of the specimens did not
exceed 100?C during irradiation. After irradiation, which lasted from 1 hour to 35 days, the container was re-
moved from the reactor and opened remotely: Before measurements were begun, the specimens-were allowed
to give off radiation for a month.
35
Declassified and Approved For Release 2013/09/13: CIA-RDP10-02196R000100010001-2
Declassified and Approved For Release 2013/09/13: CIA-RDP10-02196R000100010001-2
Measurement of the Electrical Properties
The transition of the heterogeneous structure to the homogeneous on irradiation was followed by measuring
the electrical resistivity of alloy specimens of dimensions 0.1 - 2-50 mm. In view of the comparatively small
radioactivity of the specimens after irradiation, all measurements were carried out after local protection on a
potentiometric instrument of the type UPI 3/3. Before and after irradiation the specimens were placed in the
same holder, in which the potential knife-edges made contact with the specimen in the same places. Duplicate
measurements showed that the maximum scatter did not exceed ? 0.1%. During the measurements the holder
with the Specimen in it was thermostatically controlled in a bath filled with carbon tetrachloride. The temper-
ature of the bath was measured with a mercury thermometer to an accuracy of 0.1?C. The electrical resistivity
of each specimen was determined at two temperatures (at approximately 20? and 70?C) and from the results
obtained the temperature coefficient of electrical resistivity was calculated. The relationship between the vari-
ation in electrical properties of the alloy and its structure can be seen from the graph (Fig. 2). The electrical
resistivity of a heterogeneous alloy increased with rise in temperature. Its temperature coefficieneof electrical
resistivity in the range 20-100?C was 1.15-10-3 per degree.
Cooling
100 200 300 400 500 MO
Temperature,T
Fig. 2. Change in electrical resistivity of a
heterogeneous specimen on heating and cooling.
quantities were measured with an accuracy of
17,000.
Curves showing the relationship between the electrical resistivity of the alloy specimens and the amount
of irradiation are given in Figure 5. Curve 1 is drawn for the homogeneous specimen No. 1 and Curves 2-5 for
specimens Nos. 2-5, which were annealed before irradiation at temperatures of 550, 500, 450 and 400e C,res-
pectively (see Table 1).
As can be seen from Figure 5, the change in electrical resistivity of any alloy takes place in two stages.
At the beginning of irradiation, during approximately the first 2 hours, a sharp increase in electrical resistivity
takes place in all the alloys. During further irradiation the increase in resistivity of the homogeneous specimen
rapidly falls off and reaches saturation after approximately 4 hours irradiation. The electrical resistivity of hetero-
geneous specimens, after a similar sharp rise, increases gradually during further irradiation. The maximum increase
in resistivity for the homogeneous specimen was equal to approximately 4.5%, while for heterogeneous specimens
it was about 70/o at this stage. We may note that in this first stage the change in electrical resistivity of hetero-
geneous specimens does not depend on the degree of dispersion of the eutectoid and is approximately the same
for all specimens.
The heterogeneous alloy transforms to the homogeneous
state at temperatures of 590-610?C. During this transition
the electrical resistivity \of the alloy decreases by approxi-
mately 4%. Cooling the alloy at a rate of 3?C per minute
does not lead to the reverse transition to the heterogeneous
state, and the y-phase is retained down to room tempera-
ture. As can be seen from the graph, the temperature
coefficient of the homogeneous alloy in the range 20-100?C
is almost zero, and its electrical resistivity at normal tem-
perature is approximately 28% greater than the resistivity
of the heterogeneous alloy.
Figure 3 shows a typical microstructure of the eutec-
toid consisting of alternate lamellae of a- and y'-phase.
The degree of dispersion of the eutectoid or the size of
the lamellae depends on the annealing temperature.
Figure 4 shows the relationship between the total
width of the lamellae of the a + y'-phases (the period of
alternation) and the annealing temperature. As can be
seen from the graph, this value, is equal to approximately
0.111 if the specimens were annealed at 400?C and of the
order of 111 for specimens annealed at 550?C. Such small
0.0511 with the electron microscope at a magnification of
36
Declassified and Approved For Release 2013/09/13: CIA-RDP10-02196R000100010001-2
Declassified and Approved For Release 2013/09/13: CIA-RDP10-02196R000100010001-2
550
Fig. 3. Microstructure of uranium 9 weight %
molybdenum alloy after heating at 550?C for
1000 hours (x 17,000).
25
20
15
10
_
----------
?
5a
.?
/5
--
/
/
1
r
?
R
.5.
....
t hrs..._
1 1 ___
Time of holding, hours
Fig. 5. Dependence of electrical resistivity of speci-
mens of uranium ? 9 weight %molybdenum alloy on
time of holding during irradiation in a flux of 2.1013
neutrons/cm2- sec.
(a +
y')
a. 450
400
*
0.2 0.4 0.6 0.8 1.0
Period X, microns
Fig. 4. Width of lamellae of the a + y'-phases in
relation to the annealing temperature.
eutectoid, is transformed into the homogeneous
The second stage is characterized by the fact
that the electrical resistivity of the homogeneous
specimen remains constant, while that of the hetero-
geneous specimens increases, the rate of increase
depending to a considerable extent on the degree
of dispersion of the eutectoid. From the curves
presented it can be seen that the higher the anneal-
ing temperature of the specimens, and consequently
the greater the size of the lamellae in the eutec-
toid, the more slowly the electrical resistivity of
the alloy specimens increases. It may be assumed
that such a change in the electrical resistivity
depends on the transformation of the heterogeneous
structure to the homogeneous during irradiation.
This conclusion is confirmed by the curves showing
the change in the temperature coefficient of elec-
trical resistivity of the heterogeneous specimens
during irradiation, which are presented in Figure 6.
On increasing the amount of irradiation the tem-
perature coefficient of resistivity of all the hetero-
geneous specimens decreases, approximating to
zero. The temperature coefficient of resistivity of
the specimen annealed to 400?C and having a finely
dispersed eutectoid decreased to zero after irradi-
ation for 400 hours, which corresponds to practi-
cally complete homogeneity.
Specimen No. 4 approaches the homogeneous
state only after holding for 1000 hours. As can be
seen from the curves in Figures 5 and 6, specimen
No. 2, the structure of which consists of a coarse
condition very slowly during irradiation.
Figure 5 shows that the increase in electrical resistivity of specimen No. 4 after irradiation for 1000 hours
37
Declassified and Approved For Release 2013/09/13: CIA-RDP10-02196R000100010001-2
Declassified and Approved For Release 2013/09/13: CIA-RDP10-02196R000100010001-2
is greater than that of specimen No. 5. This can be explained by the fact that specimen No. 5, as has already
been noted, did not attain complete heterogeneity during annealing at 400?C.
The broken line 5a in Figure 5 shows the assumed course of the curve for specimen No. 5 if this specimen
had been completely heterogeneous before irradiation.,
4

100 ZOO 300 400 500 600 700 800 500 1000
Time of holding, houts
Fig. 6: Change in the temperature coefficient of electrical
resistivity of heterogeneous specimens in relation to the time
of holding during irradiation in a flux of 2.1P neutrons per
cm2 ? sec.
During irradiation of the alloy there takes place on the one hand a change in the concentration of molyb-
denum in the a- and y'- lamellae and on the other a change in the relative amounts of the a- and y-phases.
It is difficult to estimate the separate effects of these factors on the electrical resistivity of the alloy. However
for our purposes this is not necessary, since all the specimens are similar to one another in the initial state and
remain so throughout the whole process of homogenization, differing only in the period of the structure and con-
sequently in the time required to attain corresponding states.
Hence if we draw a horizontal straight line on Figure 5 it will cut the curves showing the change of elec-
trical resistivity in points whose abscissae will correspond to the irradiation times necessary for the attainment
of identical (corresponding) states. As can be seen from Expression (1), this time must be inversely proportional
to the square of the period of alternation A. We will draw two horizontal straight lines: one through the point
corresponding to AR/R = 9% and the second through the point corresponding to 1112/12 = 15%. The times sought
are equal to 6, 20, 50 and 280 hours respectively for specimens No. 5, 4, 3 and 2 (AR/R,= 9%) and 38, 125 and
385 hours for specimens No. 5, 4 and 3 (&12/12. = 15%). The first times bear the following relation to one another
1 :3.33:8.35:46.7, that is they are related as the squares of the numbers).:1.82: 2.89:6.83. The relationship
for the second three times of irradiation is 1:3.29:10.1 or as the squares of the numbers 1:1.82:3.19. As can
be seen from Figure 4, the values of A for specimens No. 5, 4, 3 and 2 are in the ratio 0.8:1.6:3:10. Thus the
experimental results on the whole confirm well the theory put forward that the amount of irradiation is inversely
proportional to the square of the period of alternation of the eutectoid lamellae in the heterogeneous alloy.
Theoretical Discussion
As was shown in [2], the coefficient of radiation diffusion, can be expressed as
D ? ? -1-v2 (Az)2,
38
(3)
Declassified and Approved For Release 2013/09/13: CIA-RDP10-02196R000100010001-2
Declassified and Approved For Release 2013/09/13: CIA-RDP10-02196R000100010001-2
where N is the number of acts of fission in unit volume: v is the volume of a thermal spike, and (Liz)2 is the
mean square of the linear dimensions of a thermal spike, which with a correction for the superposition of thermal
spikes can be expressed as
2
?3r2==0.257e/s,
from which, having substituted for N,
AT = 3.1.101.opw,
where W is the specific thermal emission expressed in w/g, we obtain
D= 0.0332.1010w/ow.
Having substituted for the density p its value for a homogeneous alloy p = 17.4 we finally obtain
D 0.577 .1.0"elaW
The experimental value of D can be found from the equation
470
-X2- Dt= In 11.2.
(4)
This formula is obtained from the requirement of tenfold diminution in the first harmonic of decay in the Fourier
series for the concentration of molybdenum in the eutectoid consisting of alternate lamellae of uranium and the
intermetallic compound U2Mo..
Finally we obtain for v
ks
0.20.10-" ? W 5.3 watts.
t '
Expressing A in microns and t in hours, We have
v M2.10-15(2-I )8/5
From this, ,using data given in [2], it is also possible to obtain
--= 0.471 ( )34 ,
where E is expressed in Mev and A in microns. Using experimental data from this paper we can obtain values
of v and E/T x 2000 (Table 2).
Let us return now to the variation in electrical resistivity of the homogeneous specimen No. 1 during irra-
diation. The observed increase in electrical resistivity of the y-phase can also be explained by the existence of
thermal spikes. The volume of metal constituting a thermal spike is similar to an annealed zone in which pre-
viously existing defects in the crystal lattice have partially disappeared. The state of the metal after such a
thermal spike is characterized by a certain completely determined concentration of defects which define the
properties. As long as all the metal has not passed through the thermal-spike condition, defects will accumulate
in it and will lead to a corresponding increase in the electrical resistivity. However, as soon as the whole volume
of the specimen has passed through the thermal-spike condition, further irradiation can give rise to no new
changes of state, and from that moment the electrical resistivity of the specimen will not vary.
39
Declassified and Approved For Release 2013/09/13: CIA-RDP10-02196R000100010001-2
Declassified and Approved For Release 2013/09/13: CIA-RDP10-02196R000100010001-2
In this particular case no attention is paid to the effect of the accumulation of fission fragments (as impuri-
ties) on the change of properties of the alloy in view of the fact that their concentration, as calculation shows;
should not exceed 10-259..
On the basis of these assumptions it is easy to determine the volume of a thermal spike from the rate of
change of a property of the homogeneous specimen, that is by another method which does not depend on previous
calculation ? from the rate of diffusion of the heterogenized alloy.
TABLE 2
Values of v and E/T x 2000
Specimen No.
X, micron
t 1 hr
v ? 1017,,cc
E/T x 2000, Mev
5 (annealed at
400?C)
0,1
250
2.58
2.16
4 (annealed at
450?C)
0.16
840
2.18
1.90
Mean
2.38
2.08
TABLE 3
Mean Value of the Volume of the Thermal-Spike Region
Volume of region,
cc
Radius of spherical
cavity, cm
From diffusion data
2.38 ? 10-17
1.78.10-6
From annealing data for the
homogeneous phase
6.28.10-17
2.46 ? 10-6
dV
The rate of increase of volume (V) which has passed through the thermal-spike state, ? ,,is proportional
dt
to the volume of the thermal spike v and the number of fissions (per sec) in the specimen N and also to the
volume (1 ? V) which has not passed through the thermal-spike state. Thus
Integrating this equation,we find
dV
? V)Nv.
V =1? e?Ntg.
With Nvt = 1, approximately 63% of the total volume of the specimen passes through the thermal-spike condition.
The maximum increase in the electrical resistivity of the homogeneous specimen on irradiation (see Fig. 5) is
equal to 4.5 %. If it is assumed that the electrical resistivity increases in proportion to the volume of metal
which has passed through the thermal-spike condition, then after time 1/(Nv) = r the electrical resistivity of
the homogeneous specimen should increase by 4.5. 0.63 = 2.8%. From the curve showing the change of electrical
resistivity of the homogeneous specimen on irradiation, it is possible to determine directly the time T and,
knowing N, to calculate the volume .of a thermal spike.
40
Declassified and Approved For Release 2013/09/13: CIA-RDP10-02196R000100010001-2
Declassified and Approved For Release 2013/09/13: CIA-RDP10-02196R000100010001-2
If it is assumed that on each act of fission 200 Mev is liberated, then the number of fissions N expressed
in terms of the specific heat evolution W (in watts per 1 g of alloy) is:
N 3.1. 1O10I/17p 2.95.1012,
where p is the density of the alloy, equal to 17.4 g/cc, and W = 5.3 w/g. From Figure 5 it can be seen that the
electrical resistivity of the homogeneous alloy increases by 2.8% after 1.5 hours. From this it follows that
v=7v-;=6.28.10-" ems.
The volume of a thermal spike as calculated from diffusion data and that calculated from the increase in
electrical resistivity in the homogeneous y-phase differ somewhat (Table 3), but they appear to be of the same
order. The somewhat larger volume of the thermal-spike region in the second case is easy to understand, since
complete atomic relaxation clearly requires a lower temperature than that required for the complete interming-
ling of the atoms essential for the appearance of radiation diffusion.
It can readily be seen that if this temperature is assumed to be 800-900?C instead of 2000?C as was taken
above for complete intermingling, then the energy expended in a thermal spike and for the case of annealing in
the homogeneous phase is of the same order as that in [2], i. e., about 2 Mev. Thus the sum total of these data
shows conclusively enough that in the thermal-spike region the expenditure of energy is of the order of 1-2%
of the total energy of fission.
X-Ray Data
An x-ray investigation by the method described in [4] fully confirms the conclusions reached above on
the basis of electrical-resistivity measurements of irradiated specimens.
In Figures 7-13 are presented the x-radio-
grams of the specimens investigated, drawn through
r0000 points at every 6'. On the ordinate are plotted
the mean values (of three measurements) of the
number of impulses of the counter for a period of
72 seconds, while on the abscissa are the double
Bragg angles 'read off from the spectrometer scale.
t" 9000
Figure 7 gives the initial reading of the radioactive
(a. specimen; the remaining figures give, for con- ?
? venience of comparison, the structure lines after
o. deduction of the radioactive background. (Indices
?-? 6000 of the lines are shown on the diagrams.) The accur-
acy of determination of the position of the lines is
about 0.02?, which for the range of Bragg angles
considered corresponds to a possible error Ad/d =
= 0.001.
35 36
Fig. 7. X-radiogram of a heterogeneous specimen'of
uranium ? 9 weight 07 molybdenum alloy after irradi-
ation for 1000 hours in a flux of 2.1013 neutrons/cm2
sec.
The results of measuring the x-radiograms
are given in Table 4. From the x-ray data the
following conclusions may be drawn:
1. Quenching the uranium ? 9 weight %
molybdenum alloy from 1000?C gives the pure
y-phase with a parameter a = 3.408 kX. The
half width of the (110) line is equal to 0.14?
(Fig. 8).
41
Declassified and Approved For Release 2013/09/13: CIA-RDP10-02196R000100010001-2
Declassified and Approved For Release 2013/09/13: CIA-RDP10-02196R000100010001-2
Fig. 8. X-radiogram of the homogeneous specimen
before irradiation (quenched from 1000?C). r is the
position of the (110 ) y maximum for the homogeneous
specimen.
t0001
110
021 002
tio
013
35
36
37
38
Fig. 9. X-radiogram of a heterogeneous specimen
before irradiation (annealed at 450?C for 100 hrs).
3000
C?3
g. 2000
0.
4.4
1000
2.
110 021 002
35 36 37
110
110 013
t
38 286
Fig. 10. X-radiogram of heterogeneous specimen
No. 2 after irradiation. r is the position of the (110))'
line for the homogeneous specimen.
1000
CN1
?r) 2000
0..
4.)
o f 000
1f0 021 002
34 35 36 37 38 29?
Fig. 11. X-radiogram of heterogeneous specimen
No. 3 after irragliation. r is the position of maximum
of the (110)y line for the homogeneous specimen.
29? 2, Annealing at 450?C for 1000 hours leads
to a heterogeneous structure consisting of the a-
phase, characterized on the x-radiogram by the
triplet (110-021-002), and the y'-doublet (110-
013). The ratio of the areas of the triplet and the
y'-doublet equals 0.87 (Fig. 9).
3. Irradiating a heterogeneous specimen for 1000 hours leads to varying results, depending on the tempera-
ture of the preceding heterogenizing anneal and consequently on the grain size or period of the lamellar (a + y')
eutectoid.
42
Declassified and Approved For Release 2013/09/13: CIA-RDP10-02196R000100010001-2
Declassified and Approved For Release 2013/09/13: CIA-RDP10-02196R000100010001-2
4. In specimen No. 2, which has the largest eutectoid period in the initial state, only an insignificant
decrease in the amount of a-phase is observed after irradiation for 1000 hours (Fig. 10 and Table 4). At the
same time the amount of y'-phase decreased markedly and a new (110)y line appeared, occupying a position
corresponding approximately to the center of gravity of the (110-013) doublet of the y'-phase. The new (110)y
line is asymmetric with an asymmetry index of 1.85. The half width of the (110)y line is 0.33?, i. e., it is con-
siderably greater than the half width of the corresponding line of the y-phase in an alloy normally treated and
quenched from 1000?C (0.14?).
5. In specimen No. 3 the amount of a-phase decreased. The ratio + 17, is in this case
I + I + I
Y Y
equal to 0.35, compared with 0.45 for the previous case. The deviation A 0 in the position of the line from the
"normal" position for the 9% solid solution also decreased. The asymmetry index and the half width of the line
decreased too.
6. The changes proceed in the same direction on the x-radiograms of specimens No. 4 and 5. In specimen
No. 5 we observe the almost complete disappearance of the a-phase and the second component of the (110-013)7'
doublet; the position of the (110)y line coincides almost exactly with the position of this line on the x-radio-
gram of the quenched 9010 specimen (Fig. 13). The line has the normal width and symmetry.
Fig. 12. X-radiogram of heterogeneous specimen
No. 4 after irradiation. r is the position of the ?
maximum of the (110) y line for the homogeneous
specimen.
? 3000
U
ra
ca.
fr) 2000
0
z t000
95 36 37 38
28
Fig. 13. X-radiogram of heterogeneous specimen
No. 5 after irradiation. r is the position of the
maximum of the (110)y line for the homogeneous
specimen.
The partial weakening of the a-phase lines in specimens No. 2, 3 and 4 and their almost complete dis-
appearance in specimen No. 5 correspond exactly to the "recovery" of the electrical resistivity in these specimens,
which varies with the different degrees of dispersion of the (a + y') eutectoid.
Special interest attaches to the fact that, in agreement with the x-ray data, the appearance of the cubic
y-phase precedes homogenization. It may be assumed from this that the y-phase is formed in the first place at
the expense of the direct transformation of the tetragonal phase to the cubic phase under the influence of irradi-
ation. First of all the lattice parameter of the 7-phase formed in the limiting case in the absence of appreciable
diffusion (specimen No. 2) corresponds almost exactly to the parameter of the solid solution with a composition
corresponding to the stoichiometric ratio for the y'-phase (the compound U2M0). Since the tetragonal character
43
Declassified and Approved For Release 2013/09/13: CIA-RDP10-02196R000100010001-2
Declassified and Approved For Release 2013/09/13: CIA-RDP10-02196R000100010001-2
of the y'-phase lattice is only a consequence of the ordered arrangement, it is natural to assume that irradiation
first causes disordering in the y'-phase (the compound U2Mo has a layer structure) and that this gives rise to the
transformation ofthe lattice from tetragonal to cubic.
TABLE 4
Data from Measurement on the X-Radiograms of Irradiated Specimens
Specimen -
number
Initial state
4 ?
relative
.
Position of (110) y
Tine
Half-
width of
cti 0) y
B .
.44
Index of
asYm -
metry of
(11,0) y
, 1
,?a+i , .,-i
00
A00
2
Annealed 1000 hr at 550?C
800
0.45
18.80
0.20
0-33
1.85
3
Annealed 100 hr at 500?C
645
0.35
18.71
0.11
0.31
1.50
4
Annealed 100 lir at 450?C
440
0.25
18.66
0.06
0.27
1.25
Annealed 700 hr at 400?C
160
0.10
18.62
0.02
0.18
1.10
I
Quenched from 1000?C
0
0
18.60
0
0.14
1.00
"I a is the area of the a-phase triplet (110-021-002). For a specimen annealed at 450?C and not irradiated,
= 980 conventional units.
**ly is the area of the y-phase (110) line; Iy-phase (110) and (013) lines.
Further change consists in slower diffusion, leading to a reduction in the molybdenum content in the y-
phase and to an increase in the amount of y-phase at the expense of the disappearing a-phase. The variation
in the y-phase parameter for specimens with different initial dispersions of the eutectoid confirms this conclusion,
already reached above from observations of the intensity of the a-phase lines. All this agrees entirely with the
conclusions reached on the basis of the electrical-resistivity measurements. Of course it would be desirable to
verify these conclusions by observing on an x-ray photograph the changes in a single specimen subjected to vary-
ing amounts of irradiation, though this is difficult to carry out in practice. It appears to us that the series of
specimens differing in the rate at which diffusion takes place in them also gives a very clear picture of the sub-
sequent stages of the transformation and consequently corresponds to the progress of the radiation homogeniza-
tion process with time.
The rapid disordering of the y'- phase is the result of the action of thermal spikes, which mix up the atoms
of the ordered compound and transform it into a disordered solid solution. This process must be completed in a
time comparable with that required for the whole volume occupied by the ordered phase to pass through the
thermal-spike state.
We have seen above that in the initial state of irradiation a rather sharp rise in electrical resistivity occurs
both in the homogeneous (quenched) state and in the heterogeneous (annealed) state. Moreover, it is found that
the initial jump in the electrical resistivity for the heterogeneous specimens is approximately 1.5 times greater
than that for the homogeneous specimen and is practically identical for the various heterogeneous specimens.
In the light of the x-ray data presented here it is obvious that the additional increase in the electrical resistivity
of the heterogeneous specimens is connected with the disordering of the y'-phase which occurs in all the hetero-
geneous specimens. This disordering proceeds simultaneously with the accumulation of primary defects caused
44
Declassified and Approved For Release 2013/09/13 : CIA-RDP10-02196R000100010001-2
Declassified and Approved For Release 2013/09/13: CIA-RDP10-02196R000100010001-2
by acts of fission. Consequently there is a certain limit to the accumulation of defects at which the creation of
defects is balanced by radiation annealing. Under the conditions of our experiment both processes ? disordering
and accumulation of defects ? come to an end after 2-4 hours, after which there follows a further slow change
in the ratio of the amounts of the a- and y-phases, due to radiation diffusion and depending mainly on the length
of the diffusion path.
SUMMARY
The sum total of the data relating to the electrical resistivity, and structure of the uranium-molybdenum
alloy indicates the part played by thermal spikes, i. e., regions of great retardation of fission fragments, in the
change of properties of fissile material under the action of neutron irradiation. It has been established that:
1) thermal spikes are the cause of radiation annealing which leads to rapid saturation of the properties of the
y-phase under conditions of irradiation; 2) in compounds of the ordered-solid-solution type, such as the I/1-
phase, thermal spikes cause rapid disordering; 3) the intermingling of the atoms in the region of a thermal
spike is the cause of the interdiffusion of uranium and molybdenum atoms which produces homogenization of the
initially heterogeneous structure.
The theoretically predicted relationship between the diffusion rate and the square of the period of the hetero-
geneous structure has been fully confirmed. It appears possible to deduce the values of the fundamental parameters
of a thermal spike ? the volume of the spike and the energy dissipated in it ? from independent experiments,
one relating to the homogeneous state and the other to the heterogeneous state. A number of unsolved problems
still remain in connection with the role of thermal spikes in rhombic a-uranium, where, as is well known,
spontaneouS"growth" phenomena occur and where the saturation of properties which takes place in the cubic
y-phase apparently is not observed.
Further experimental and theoretical studies are required to solve these problems.
LITERATURE CITED
[1] S. T. Konobeevskii, N. F. Pravdiuk and V. I. Kutaitsev, Investigations in the Fields of Geology, Chemistry
and Metallurgy (Report by the Soviet Delegation to the International Conference on the Peaceful Uses of Atomic
Energy) [in Russian] (Izd. AN SSSR, 1955), p. 263.
[2] S. T. Konobeevskii, J. Atomic Energy (USSR) No. 2, 63 (1956).*
[3] M. L. Bleiberg, L. J. Jones and B. Lustman, J. Appl. Phys. 27, 11, 1270 (1956).
[4] N. F. Pravdiuk, Investigations in the Fields of Geology, Chemistry and Metallurgy (Report by the Soviet
Delegation to the International Conference on the Peaceful Uses of Atomic Energy) [in Russian] (Izd. AN SSSR,
1955), p. 165.
*Original Russian pagination. See C. B. Translation.
45
Declassified and Approved For Release 2013/09/13: CIA-RDP10-02196R000100010001-2
Declassified and Approved For Release 2013/09/13: CIA-RDP10-02196R000100010001-2
SPECIAL FINE-GRAINED EMULSION FOR NUCLEAR RESEARCH
N. A. Perfilov, N. P. Novikova and E. I. Prokof'eva
A method has been found for manufacturing special high-uniformity fine-grained
emulsions with a most probable size of 0.04-0.0811 for the microcrystals . A method of
potentiometric controlof the emulsification process is presented which provides good
reproducibility of the emulsions. Depending on the purpose of the research, using this
method it is possible to fabricate special fine-grained emulsions for detection of
charged particles with any sensitivity? from fragments up to relativistic particles ? with
track densities of 60 grains/100u of particle range.
INTRODUCTION
As the dimensions of the microcrystals in a nuclear emulsion are reduced a considerable improvement in
the resolving power of the emulsion in detection of charged particles of different types and energy becomes
possible. The charged particle encounters a microcrystal of the emulsion and in interacting transfers part of its
energy to the electrons. A certain number of electrons from the bound state may be transferred to the conduction
level and create conditions for the formation of an exposure center at the microcrystal. The higher the specific
energy loss of the particle the higher, will be the probability for formation of a development center, all other
conditions being equal.
In the interaction of a fast particle with the electrons a certain number of electrons may receive energy
sufficient to cause them to move beyond the boundaries of the microcrystal and allow development in a neighbor-
ing crystal. The smaller the dimensions of the microcrystal the more important will be this effect in forming
the track of the charged particle. The effective use of S-electrons with small energies leads to improved res-
olving power in fine-grained emulsions. In addition to the improved resolving power, fine-grained emulsions
make it possible to measure with high accuracy the angles between particle tracks in nuclear disintegrations and
multiple scattering of a single particle. With a reduction in the dimensions of the microcrystals of the emulsion
the change in the nature of the background due to x-rays and 7-rays makes the scanning of the emulsion easier.
In general, emulsions for nuclear research have a most probable diameter (ranging from 0.2-0.3 u ) for
the undeveloped crystals. In 1949 we were able to obtain emulsions with a most probable diameter lying between
0.04 and 0.08 p. for the silver-bromide microcrystals, that is, a grain dimension apprOximately 5 times smaller
than usual. In the course of the last several years development work has been carried out on improving the
synthesis of the emulsions and increasing their sensitivity. The present paper is devoted to a report of the results
which have been obtained.
Principles of Fabricating the Special Fine-Grained Emulsion
In investigating the effect of the proportions of potassium bromide and silver nitrate on the size of the
microcrystals in the photographic emulsion and its sensitivity in detecting fast Charged particles by a method in
which three solutions were used [1], an interesting fact was observed [2]. If the synthesis of the photographic
emulsion is carried out with a small excess of silver nitrate (beyond the equivalent amount of potassium bromide)
maintaining the indicated proportion throughout emulsification, up to the time at which cooling takes place, a
photographic emulsion which is very fine-grained and uniform in crystal size is obtained; this emulsion can
detect charged particles.
47
Declassified and Approved For Release 2013/09/13: CIA-RDP10-02196R000100010001-2
Declassified and Approved For Release 2013/09/13: CIA-RDP10-02196R000100010001-2
_7
,q mon
_
KNICT3
+ 6v ?
0
KCL
Hq2 C 2
Pt
Ng
Fig. 1. Potentiometer circuit.
The most important stage in the fabrication of the photoemulsion is the emulsification process; the proper
method is determined by the type of emulsion. To monitor the emulsification process we have used a potentio-
metric method [3] which allows continuous high-accuracy control of the proportion between the numbers of
bromine ions and silver ions in the emulsion. In Figure 1 is shown a diagram of the potentiometer circuit. In
the tank marked 3, containing a gelatin solution, there is a silver electrode and electrolytic cells with calomel
elements. The circuit is connected to a PPTV-1 potentiometer and a 6-volt source. Above the tank there are
two burettes containing a 60 percent solution of silver nitrate 1 and a 40 percent solution of potassium bromide
with various additives 2. During emulsification the solutions are continuously dripped from burettes 1 and 2
into the tank 3 where they are mixed with the gelatin by a mechanical stirrer. The emulsification time is deter-
mined by the amount of obtained emulsion. For 100 ml of liquid emulsion this quantity is approximately 18
minutes. During emulsification a continuous measurement is made of the potential (with respect to the calomel
element) of the emulsion being formed. By regulating the rate at which the solutions are introduced the potential
can be changed positively or negatively. Using the known relation for the potential of the saturated solution
of silver bromide the emulsification can be carried out under conditions of equivalence or with an excess of
bromine ions or silver ions. This method of preparation makes it possible to obtain emulsions with standard
characteristics.
Sensitivity in Detection of Charged Particles
To classify them in terms of sensitivity to charged particles, photoemulsions can be divided into three
types, differing only in the contents of a small number of additives and the method of sensitization.
Type 1. Low-sensitivity emulsions "P-9, fragment'" are capable of detecting particles with high specific
ionization losses: multiply charged fragment ions, a-particles with energies from 20 to 30 Mev, and protons
with energies from 1-2 Mev.
Because of the fine-grains in emulsions of this type it is possible to distinguish visually between fragment
tracks and tracks produced by a-particles and protons. For illustration, in Figure 2 are shown microphotographs
of tracks produced by fragments of uranium fission and tracks of a-particles from natural radioactive uranium (a);
48
Declassified and Approved For Release 2013/09/13: CIA-RDP10-02196R000100010001-2
Declassified and Approved For Release 2013/09/13: CIA-RDP10-02196R000100010001-2
a
Fig. 2. a)Microphotograph of tracks of fission
fragments and a-particles in "P-9, fragment"
emulsion ( x 1000); b) microphotograph of
tracks of fragments flying apart in opposite
directions (x 2500).
in addition there are microphotographs of tracks produced
by fragments flying apart in opposite directions (b). In
Figure 3 are shown the results obtained by photometry of
tracks of light fragments and heavy fragments in uranium
fission. A photometer makes it possible to determine the
point at which the fission occurs (by using the break in
darkening density). It should be noted that a trained ob-
server can determine this point without the help of a
photometer. Plates fabricated from "P-9, fragment"
emulsion have been used for a long time in studying fission
processes associated with slow neutrons. They are also
suitable for the detection of multiply charged ions (frag-
ments) against a background of a large number of a-
particles when the oxidation method is used [4].
Type II. The sensitivity of "P-9, sensitive" emul-
sions is such as to allow detection of protons with energies
of approximately 50 Mev. In contrast with the "P-9,
fragment" emulsion they are subjected to a second develop-
ment, before which the sensitizer is introduced. Films
made from "P-9, sensitive" emulsions are used in studying
nuclear reactions involving protons with energies of 600
Mev. To observe a significant number of tracks per unit
surface we are limited to that sensitivity for which the
primary protons do not register; thus tracks due to these
latter particles do not complicate the scanning. Under
these conditions the products of the nuclear reaction (a-
particles of virtually all energies, which may appear at
a given primary-proton energy and protons with energies
up to 50 Mev) can be observed; .it is also possible to measure
their energy. In Figure 4 are shown microphotographs of
meson tracks produced in 1r Il-decay (a) detected in
emulsions of this type and tracks produced by nitrogen
ions with energies of approximately 60 Mev (b). To show
the resolving power, in Figure 5 are shown curves of the
darkening density as a function of range* for various
charged particles in this emulsion.
Range, pi
Fig. 3. Photometry of tracks of light (1) and heavy (h) fragments
in uranium fission. Ib) photomultiplier current in measuring the
background near the track; It) photomultiplier current in the
measurement of given particle track.
"For the last 5011 of range.
49
Declassified and Approved For Release 2013/09/13: CIA-RDP10-02196R000100010001-2
Declassified and Approved For Release 2013/09/13: CIA-RDP10-02196R000100010001-2
Fig.4. a)Microphotograph of meson tracks from fr ? Il-decay in "P-9, sensitive" emulsion; b) micro-
. photograph" of tracks of nitrogen ions with energies of approximately 60 Mev in a "P-9,sensitive"
emulsion.
In "P-9, fragment" emulsions and"P-9, sensitiv,e" emulsions the concentration by weight of the crystals
in a dry layer is (84 ? 1)1c. with respect to the weight of gelatin. The shrinkage factor is 2.5 f 0.1. The stopping
power of a dry photo layer is about the same as the stopping power of a C-2 Ilford emulsion. In Figure 6 is shown
a particle size distribution for the microcrystals in a P-9 emulsion. The most probable dimensions for the micro-
crystals are approximately 0.08, 0.06 and 0.04 is.
Because of the small dimensions of the microcrystals the plate is transparent to the long-wave part of the
visible spectrum. In Figure 7 are shown values of the attenuation coefficient* for emulsions with crystal dimen-
sions of 0.08 and 0.06 I as a function of the light wave length. It follows from Curves I and II that to attenuate
radiation at a wave length of 800 mil by a factor of e a layer of thickness of approximately 25-100P is required.
In principle the small attentuation for the long-wave part of the visible spectrum yields the possibility of observ-
ing particle tracks in the layer without fixing. A Microphotograph of a-particle tracks (Fig. 8) was obtained in
a plate with an emulsion thickness of 100 il , developed after exposure to a-particles without subsequent dissolv-
ing and removal of silver bromide from the layer. Better results are obtained with smaller microcrystals of silver
bromide; however, as the dimensions of the crystals are reduced the sensitivity to charged particles characterized
by small specific ionizing losses is also reduced.
*The measurements of the attenuation coefficient were made by P. M. Valov.
50
Declassified and Approved For Release 2013/09/13: CIA-RDP10-02196R000100010001-2
Declassified and Approved For Release 2013/09/13: CIA-RDP10-02196R000100010001-2
Darkening density
0.5
0.4
0.2
0.1
{ He:
tf
0 10 20 30 40 50 60
Range in emulsion, II
Fig. 5. Darkening density as a function of range
of various charged particles.
sct
g
"6
70
60
50
30
20
10
1
1
1
i
i
,
I
?1,
?
"f
0 0.02
0,04
0.06
0.08
0.10
0.12
Grain diameter, ?
Fig. 6. Curve showing the size distribution of silver
bromide microcrystals in P-9 emulsion. I, II, III are
curves for emulsions with the same ratio of silver
bromide and gelatin but with different amounts of
potassium iodide added.
3200
2800
g 2 400
?000
cd
4- /600
:rd 1200
(3)
1:1
'....
..-9 ' ;1
.._9 -
.g.
4, .. ..,-.,. 0
0,.., .o
0 (.) 0 T.1
Concentration of
HC204 ion in the
equilibrium sob-
tion, mole/liter
Concentration of
free Pu +3 ions, To
Conc. of the complex
ion(Pu (C204)2] in
solution, %
Conc. of the complex
ion (Pu(HC204)11
in solution, 0/0
K.' .101?
1.
K Y.1011
1
from
exptl.
data
from
average
value of
K1
-
7.21
9.86
15.1
22.4
52.1
57.6
63.3
83.4
from
exptl.
data
from the
average -
value of
IV!
1
1.47
1.55
1.60
1 73
180
1.90
2.00
2.35
2.40
2.50
2.65
6.45.10-5
8.80.10-5
1.07.10-5
1.72.10'5
2.22.10-5
3.11.10-5
4..35.10-5
1.24.10-4
1.43.10-4
1.i6.10-4
2.72.10-i
1,46.10-3
1.61 .10-3
1.79.10-3
2.13.10-3
2.34.10-3
2.61.10-3
2-89.10-3
3.69.10-3
3.80.10-3
3.92.10-3
4.06.10-3
25.7
24.4
23.0
17.3
14.2
11,1
8.4
2.4
2.0
1.3
0.8
-
-
-
6.8
12.8
16.1
19.2
52.7
56.4
68,6
78,2
10.1
14.6
19.6
32.7
-
-
-
-
_
-
_
10.2
14.4
20.7
31.2
37.4
45.1
51.4
38.9
36.6
26.9 .
19.0
-
-
-
7.5
5.5
6.7
8.3
7.0
7.2
6.6
7.6
average
7.1.10'?
1.15
1.12
1.20
1.09
-
_
-
-
-
average
1.14X
x10-n
59
Declassified and Approved For Release 2013/09/13: CIA-RDP10-02196R000100010001-2
Declassified and Approved For Release 2013/09/13: CIA-RDP10-02196R000100010001-2
where N expresses the total concentration of other
complex ions in the solution. A graph of the rela-
cpu +3
100 tion between log .N and the logarithm of the
equilibrium concentration of C204-2 ion in the pH
range from 1.7 to 2.7 is shown in Figure 3. All the
0 points obtained fall on a line with a slope equal to 2.
Thus at pH > 1.7, a mixture of the two complex ions
70 [Pu(C204)2]- and [Pu(HC204)4f is formed. The value
of the instability constant of the complex ion
60 [Pu(C204)2]- in this pH range was calculated by Equa-
tion (14), where
90
80
50
40
.41
u 90
0 f.2 13 1.6 1.8 2,0 Z2 Z4 2.6 2.8 10 3.2 pm
Fig. 4. Effect of solution pH on the concentration
of Pu+3 ions. I) Pea; II) [Pu(C204)2r; III)
[Pu (HC204)4r
The constants Kit and Kui correspond to complete
cPu* a c2C2012
The results of calculating the instability constants and
concentrations of the complex ions and also the data
used in the calculation are summarized in Table 2.
The relation between the concentration of these ions
and the pH of the solution is shown in Figure 4.
As Table 2 shows, the instability constant of the
complex ion [Pu(C204)2] has a constant value over
the whole pH range. Consequently, in a solution at
pH > 1.7, a mixture of the complex ions [Pu(C204)21-
and [Pu(HC204)4)- is formed, having K'i = 7.1.10?
and K"1 = 1.1.10-II, respectively.
decomposition of the complex ions by the equations:
[Pu (C204)21- Pu" 2C20-4.2,
[Pu (1-1C204)41- Pu" ? 4HC20;. (16)
(15)
If there are two or more complex ions with unknown values of Ki present in the solution at the same time,
then using Equations (11) and (12), obtained for several experimental points of the curve (see Fig. 1), we can
always obtain a system of equations where the number of unknowns equals the number of; equations. By solving
such a system, we obtain all values of u, m and K1. Such a problem may always be solved readily by the
method of least squares (15), We should note that the value of Ki for the complex ion [Pu(C204)2], found by
the ion-exchange method, agrees quite satisfactorily with the value of this constant, obtained by a solution
method ,[1]. The corresponding instability constants equal 4.9 .10-" (from solution data) and 7.1 .10-" (ion?
exchange method), Some of the deviation in the values given may be explained by the different ionic strengths
of the solutions, used for determining the instability constant by these two methods.
The eornplex tons with a large number of oxalate groups, which we found previously at pH RI 8, were not
found in this case as all the experiments were carried out in the pH range 1.4-3.0. As Figure 1 shows, the method
we chose does not allow investigations at higher pH values. This problem may be solved by using an anionite.
Received August 15, 1957
LITERATURE CITED
r11 A. P. Oel'man, N. N. Matorina and A. I. Moskvin, J, AtOrritc Energy (USSR) 3, 10, 306 (1967).*
(2] 0, A. Kniazev, V. V. FOnlin and Q. I. Zakharov-Nartsissov, J. Inorg. Chem?; (USSR) 1, 2, 342 (1956).
Original Russian pagination. Bee C.13, Translation.
60
Declassified and Approved For Release 2013/09/13: CIA-RDP10-02196R000100010001-2
Declassified and Approved For Release 2013/09/13: CIA-RDP10-02196R000100010001-2
[3] V. V. Fomin and V, V. Sin`kovskii, J. Inorg. Chem. (USSR) 1, 10, 2316. (1956).
[4] V. V. Fomin, L. N. Fedotova, V. V. Sin'kovskii and M. A. Andreeva, J. Phys. Chem.(USSR) 29, 2052(1955).
[5] S. Froneus, Acta Chem. Scand. 5, 859 (1951).
[6] J. Schubert, J. Phys. Coll. Chem. 52, 340 (1948).
[71 J. Schubert, E. R. Russel and L. S. Mayer, J. Biol. Chem. 185, 387 (1940).
[8] S. Ju. Elovich, and N. N. Matorina, J. Phys. Chern. (USSR) 30, 383 (1956).
[9] L. I. Tikhonova and M. M. Seniavin, J. Inorg. Chem. (USSR) 2, 1, 74 (1957).
[10] V. I. Paramonova and B. V. Kolychev, J. Inorg. Chem. (USSR) 1, 8, 1896 (1956).
[11] V. I. Paramonova and A. S. Voevodskii, J. Inorg. Chem.(USSR) 1, 8, 1905 (1956).
[12] I. A. Korshunov. L. P. Pochinailo and V. M. Tikhomirova, J. Inorg. Chem. (USSR) 2, 1,68. (1957).
[13] E. B. Trostianskaia, N. P. Losev and A. S. Tevlina, Prog. Chem. (USSR) 26, 1, 69 (1955).
[14] B. P. Nikol'skii and V. I. Paramonova, Prog. Chem. (USSR) 8, 1535 (1939).
[15] K. B. Iatsimirskii, J. Phys. Chew .(USSR) 25, 475 (1956).
61
Declassified and Approved For Release 2013/09/13: CIA-RDP10-02196R000100010001-2
Declassified and Approved For Release 2013/09/13: CIA-RDP10-02196R000100010001-2
POLAROGRAPHIC INVESTIGATION OF COMPLEX PLUTONIUM OXALATES
V. V. Fomin, S. P. Vorob'ev and M. A. Andreeva
The composition and stability of complex ions of tri- and tetravalent plutonium
in oxalate solutions were investigated polarographically.
The complexes Pu(C204)4-4 (preponderant amount) and Pu(C204)4-5 were formed
in solutions of potassium oxalate with pH 3.5-6. Under these conditions, Pu +4 gave a
well expressed reverse reaction wave, suitable for the quantitative polarographic deter-
mination of plutonium. The oxidation-reduction potential of this reaction in 1M
potassium oxalate was equal to 0.205v (relative to a saturated calomel electrode at a
temperature of 25? C). Two Pu +4 complexes were simultaneously present in solutions
at pH 6-8.
From data on the solubility of Pu(C204)3, we determined the instability constants
of the complex oxalate ions Pu(C204)3-3 and Pu(C204)4-5, and from the polarographic
data those for Pu(C204)4-4 ions:
K
KPu Pu (C204)4-5= 2.4.10-12 (C204);3 =2.2
. ? 10-11. K
?Pu (c204);4 =33?10-28.
The reports on the existence of oxalate complexes of trivalent plutonium are contradictory RI By spec-
trophotometry and solubility determination, W. Reas (2) established the existence of the Pu +4 ions PuC204+,
Pu(C204)2, Pu(C204)3-2 and found the corresponding stability constants; he also showed the existence of
Pu (C20414-4 ions. There are references (1) to unpublished polarographic investigations of oxalate complexes
of Pu +4, but the results are not given.
The authors of this article investigated polarographically the complex ion formation of tri- and tetravalent
plutonium with oxalate ion at concentrations of the latter from 10-3 to 1.2 M. The work was carried out on a
V-301 polarograph, which automatically recorded the curves of current strength against voltage. A dropping
mercury electrode acted as the cathode; the anode was a saturated calomel electrode (sce). 0.01% of gelatin
was added to the solution to suppress the maxima. The experiments were carried out at 25 ? 0.1?C. Purified
argon was passed for 20 minutes through the solution in the electrolyzer to remove dissolved oxygen. The argon
was freed from oxygen by passing through a tube, containing copper filings heated to 700?C, two bottles with a
solution of divalent chromium, a bottle with water and an empty flask to trap splashes. The polarogram of the
background (potassium oxalate), after the passage of argon, contained no waves up to the liberation of hydrogen.
The correction for the resistance of the system (electrafyLer, intermediate bridge, calomel electrode and leads)
was found, as usual, by determining the value of the half-wave potential under the same conditions, but with a
different plutonium concentration in the solution, using a ratio of 1:16.
Potassium oxalate was used as the complex forming salt as its solubility is considerably greater than that
of the sodium or ammonium salts; this made it possible to investigate the complex plutonium oxalates over a
wider range of oxalate ion concentrations.
Solutions of potassium oxalate and oxalic acid were mixed together to investigate the effect of pH of the
medium on complex formation. Before taking quantitative measurements, we proved the reversibility of the
electrode reaction Pu +4 Pu +3 in an oxalic acid solution. In addition, we compared the half-wave potentials
63
Declassified and Approved For Release 2013/09/13: CIA-RDP10-02196R000100010001-2
Declassified and Approved For Release 2013/09/13: CIA-RDP10-02196R000100010001-2
for continuous recording of curves and for plotting separate points (the electrode was maintained for 3 minutes
at each value of the applied emf for plotting the curves by points). Waves from the same solutions continuously
recorded and plotted as separate points, did not differ greatly in half-wave potentials or in wave height. The
half-wave potential obtained by plotting points was'0.094-0.005v more negative than the half-wave potential
from continuous recording, with a measurement error of 0.002v. This, apparently, is explained by the fact
that the equilibrium at the electrode surface is not established immediately between the oxidized and reduced
forms of plutonium ions. The concentration of the oxalate ions was calculated by the equation
ZC204 = [C20;]+[HC20'4] + [H2C04] (1)
(where EC204 is the analytical oxalate concentration) Using the known concentration of hydrogen ions and
the ionization constant of oxalic acid (K1 = 5.9 ? 10-2; K2 = 6.4.10-5) [3]. The relation of the ionization con-
stant of oxalic acid and the constant of the complex ions to the ionic strength of the solution was not considered.
The usual methods for the polarographic investigation of complex formation were used [4]-[7].
Experimental Results and Discussion
We first plotted polarograms of the solutions, containing tetravalent plutonium and oxalate ions at differ-
ent concentrations and with various solution pHs. The values of the half-wave potentials and wave heights are
given in Table 1 and one of the polarograms is shown in Figure 1.
? am
2
0.2
0.4
0,6 E,
Fig. 1. Polarogram of Pu +4 in an oxalic acid solu-
tion at pH = 7.89.
TABLE 1
The Effect of Concentration of C201 Ions and pH of the
Medium on the Complex Formation of Pu +4 and Pu +3
(Total Oxalate Concentration ? 1N, Concentration of
Pu +4 6.5 ? 10-1M)
Conc. Wave height' Half-wave
Lc29:1tiam
tr equiv/lite ps potential
pH of solu-
tion
1.000
1.60
?0.193
7.89
1.000
? 1.83
?0.192
7.04
0,997
1.94
?0,194
6.70
0.985
2.25
?0.193
6.03
0.918
2.29
?0.193
5.25
0.423
2.23
?0.195
4.06
0.098
? 2.24
?0.194
3.58
0,028
2.30
?0.178
2.97*
2.11
?0.144
2.25
The wave was displaced
1,50
considerably towards pos-
itive potentials.
*Precipitation of oxalic acid was observed in the last
A considerable displacement of the half- samples.
wave potential towards more negative values in
comparison with the oxidation-reduction potential
of Pu +4 and Pu +3 in a noncomplex-forming
medium [8] indicated the presence of stable plutonium complexes in the solution. It was established that only
one clearly expressed wave appeared on the polarogram at solution pHs of 3.5-6. Regardless of the sharp change
in the concentration of oxalate ions in this pH range, the half-wave potential remained the same (Table 1).
This indicates that the coordination numbers of Pu +4 and Pu +3 are equal. Two waves appear at pH 7.89.
According to our hypothesis, two complexes exist in oxalic acid solutions at pH 6-8 and an equilibrium is slowly
established between them, as with other elements [9]. The experiments carried out showed that at a pH close to
64
Declassified and Approved For Release 2013/09/13: CIA-RDP10-02196R000100010001-2
Declassified and Approved For Release 2013/09/13: CIA-RDP10-02196R000100010001-2
8 (Table 2)the ratio of the various complex ions changed considerably with time. A second wave appeared at
more negative values of the half-wave potential. A third wave with a half-wave potential of about- 0,30 v
appeared when cai ions were present in the alkaline tnedium (due to absorption of carbon dioxide from the
air and this was confirmed by experiments with K2CO3 added).
TABLE 2
The Height of the Pu +4 Wave with Ey2 = - 0.205v
the 1st and 9th Day After Preparing the Solutions
K2C204 con-
pH of the
Wave height
Wave height
centration
solutions
the 1st day
the 9th day
M
tia.mps
!lamps
0.10
8.08
3.42
2.22
0.23
8.50
3.38
2.36
0.49
8.63
3.34
2.71
0.75
8.68
3.46
2.61
1.01
872
8.37
2.93
1.14
8.72
3.38
301
TABLE 3
The Relation of Current Strength to Pu +4 Concentra-
tion in a Normal Potassium Oxalate Solution at pH 5.5
Wave height
Aamps
Half-wave
potential, v
Pu +4 concen-
tration, M
17.86
-0.195
8.10-4
9.40
-0.193
4.10-5
4.97
-0.197
2.10-4
2.63
-0.193'
1.10-5
1.94
-0.194
5.10-5
0.72
-0.198
2.5.10-5
0.44
-0.197
1.25.10-5
0.24
-0.197
6.25.10-5
The reversibility of the reduction of the Pu +4 complex ion may be proved by the basic polarographic
wave equation
0.059 i
E E112 -- log.
(2)
The various values of E and the corresponding magnitudes ofid of the wave were carefully measured
-
on the polarogram of Pu +4 in a 1M potassium oxalate solution at pH 5.5. Using them we plotted a graph of
E as a function of log.(Fig. 2). The experimental points lay on a straight line, whose slope was equal
d
to 0.063 v, which agrees well with the theoretical value for a = 1 and indicated that the reduction of Pu +4
complex ion at a mercury electrode proceeded with the participation of one electron, i. e., to Pu +3.
0
-05
,
,
i
0.053 v.1.1
IPA
I
1.0 (40
-0.10 -0.15 -0.20 -0.25 -0.30 -3.0
E . v
Fig. 2. Testing the reversibility of the reaction
Pu +4 in a 1M solution of K2C204 at
pH 5.5
-20 -1.0 ao +to
log A oa
Fig. 3. The relation of the half-wave potential
of Pu +4 reduction to the logarithm of the potassium
oxalate concentration.
65
Declassified and Approved For Release 2013/09/13: CIA-RDP10-02196R000100010001-2
Declassified and Approved For Release 2013/09/13: CIA-RDP10-02196R000100010001-2
Experiments showed that at a pH of the oxalic acid solutions of 3.5-6, the current strength during the
reduction was a linear function of the Pu +4 concentration (Table 3 and Fig. 3).
TABLE 4
Displacement of the Half-Wave Potential of p+4
Reduction in Relation to Potassium Oxalate Con-
centration; pH = 5.5
K2C204 con-
centration
Log of
K2C204 con-
Half-wave
potential, v
Kox
K d
re
_______Centration
1.10-3
?3.00
?0.069
2.27.10-17
440-2
?2.40
?0.118
1.36.10-'7
1.10-2
?200
?0.141
1.36.10-'7
2.2.10-2
?1.66
?0.164
1.22.10-17
4-6.10-2
?1.34
?0.188
1.00.10-"
9.4.10-2
?1.03
?0 197
1.47.10-17
3.10-1
?0.52
?0.201
4.10.10-17
5.10-1
?0.30
?0.200
7.95.10-'7
7.10-1
?0.16
?0.198
1.1310-12
1.00
?0.00
?0.1E9
142.10i6
1.20
+0.08
?0.201
1.5340-16
4.0
- 40
6.0
-40
-20 -1.0 00
lag A', oa
Fig. 4. Graph of the relation of the Pu +3 oxalate
concentration to the logarithm of the oxalate ion con-
centration. ????) according to data in Table 5; xx )
according to data in Table 6.
Considering the reversibility of the reaction examined, the good reproducibility of the wave and the small
value and constancy of the half-wave potential, this electrode reaction may be used under chosen conditions for
the quantitative polarographic determination of plutonium. Using the equation for the half-wave potential
E112 = E0? 0,05g
910 Dox 0,a059 (p q)logCx,
a pred.
(3)
one can determine the formal oxidation-reduction potential of Pu +4 / Pu +3 in a 1 M K2C204 solution, if
Dox +4
is taken as $11. As shown by Figure 2, the half-wave potential of Pu reduction in a 1M potassium
Dred
oxalate solution, relative to a sce at 25?C, was equal to ? 0.205 v.
Determination of the Instability Constants of Oxalate Complexes of Tri- and Tetra-
valent Plutonium
Using the equation
Eg logl(TKoxi-
0.059
a (p? q)log C x,
a ec
(4)
0 0
where Ec = (EA +4
v is the potential of a system containing K2C204 and Pu ; Es = (E112 )s is the potential of a
) c
noncomplex-forming system containing Pu +4, the ratio of the instability constants Ko x and Kred may be found.
As (E1/2 )s is a constant value, then Equation (4) is also a linear equation and therefore the difference in
the coordination numbers 2 and q may be determined by the tangent of the slope of the line:
66
AE112 = K ? ylogCx,
Declassified and Approved For Release 2013/09/13: CIA-RDP10-02196R000100010001-2
Declassified and Approved For Release 2013/09/13: CIA-RDP10-02196R000100010001-2
where
A.Ei/2-= (Ei/2)2? (E1/2)3; K = ?*?5910? ic?x
a ?Kred.
0.059
= a (1)? q) an a.
The values of the half-wave potentials were found from polarograms, plotted for different concentrations of
potassium oxalate and a solution pH of 5.5 (Table 4).
In the range of potassium oxalate concentrations 10-3 ? 1. 10-1 M, the difference in the coordination
numbers was equal to 1. It follows from the data in Table 4 that in this region the ratio of the instability
constants is equal to 1.5. 10-17.
The coordination numbers 2 and a equal each other in the range of potassium oxalate concentrations of
1 ? 10- - 1.2 M. In this case the ratio of the instability constants is equal to. 1.4 .1046. The increase in
the difference in the number of coordinated groups with a decrease in the concentration of C204" ions may be
explained only by a decrease in the coordination number for the complex Pu +3 compounds and the instability
constant of the complex ion with the lower number of coordinated groups is approximately 10 times greater
than the instability constant of the ion with the greater number of C204 groups.
Experiments carried out showed that if a precipitate of Pu +3 oxalate is introduced into a potassium oxalate
solution, it rapidly dissolves on stirring. The polarogram of such a solution shows only a cathode wave and, con-
sequently, the Pu +3 is oxidized to Pu +4. If dissolved oxygen is first removed from the oxalic acid solution,
and then the oxalate of trivalent plutonium is added, the polarogram of this solution shows an anode wave with
a half-wave potential of ?!0.197 v. Apparently, Pu +3 forms complexes in oxalic acid solutions, but they are very
rapidly oxidized by atmospheric oxygen. Our experiments also showed that even without dissolved oxygen in
the oxalic acid solutions, the Pu +3 is slowly oxidized, though this may be explained by an effect of the a-
radiation.
In order to find the instability constant of the Pu +3 complex, the solubility of the oxalate at various
potassium oxalate concentrations was determined. Trivalent plutonium: prepared by reduction with hydrogen
in the presence of platinized platinum [5], was added as a solution of the chloride to potassium oxalate solution
in a sufficient amount to precipitate plutonium oxalate.
It was assumed that in the precipitation, an equilibrium was rapidly established between the precipitate
and the solution. Polarograms were plotted immediately after the addition of the plutonium solution, then the
pH of the solutions were determined. The Pu 43 concentration was found from the polarograms as the ratio of
the difiusion coefficients of the oxalate complexes of Pu +4 and Pu +3 , found by measuring diffusion currents for
equal Pu +4 and Pu +3 concentrations, which was equal to
DPU" = 1.055.
Dru.4 .pu.,
Expressing the complex formation reaction in the form
PU2 (C204)3 ? 911201d [2Pu (C204)1-2x}sol
? ? 2x) C2061 -I-- 9H20,
we find the equilibrium constant of this reaction
K = K = [Pu (C204)1-212[C20]3-2x,
x=0, 1, 2, 3, 4, . . .
67
Declassified and Approved For Release 2013/09/13: CIA-RDP10-02196R000100010001-2
Declassified and Approved For Release 2013/09/13: CIA-RDP10-02196R000100010001-2
The solubility was determined by the concentration of complex ions in the solution
In this case
since
S = 2 [Pu (C204)!-21= E ic20;1:-1;,x ?
dlnS d ln S
[C 0 ] d ln S
d In [C20'.:] d [C201 ? 2 4 d 1C2071
[C2OT
?(---2").K
LI [C20]"2?x
1 NI 2
[C20:J312?X
3
[C20';i312?x
1 - ? Kx
vi K. 12 [c2(413/2--x
Ex?Kx 1= 3 no.).3-22
IC20D8/2?x 2 m [Pu(C204).3-21
K.
ah_x [Pu (C204)!--21.
[C2041
For the linear part of the solubility curve, which indicates the existence of one complex in the solution,
d ln S 3
d In [C201] T?x?
It follows from the experimental solubility curve (Fig. 4) that
d In S 62.5= 2 6
d ln [C2011 ? 23.5 '
Then x = 4.1, i. e., the coordination number found from the solubility curve for Pu +3 equals 4.
At potassium oxalate concentrations equal to 1-10- ? 1.2M, the coordination numbers for Pu +4 and
Pu +3 were equal, i. e., p = q = 4. At potassium oxalate concentrations less than 1 ? 10-1M only the number of
coordinated groups for Pu +3 in the oxalate solution changed, which as shown above, equalled 3.
The instability constant of the Pu +3 complex was calculated by the formula
_Lii,.)1, (c204
EC20112):1:
where r is the number of oxalate groups in a simple Pu +3 oxalate; L is the solubility product for a simple
Pu +3 oxalate.
68
Declassified and Approved For Release 2013/09/13: CIA-RDP10-02196R000100010001-2
Declassified and Approved For Release 2013/09/13: CIA-RDP10-02196R000100010001-2
TABLE 5
The Relation of the Solubility of Trivalent Plutonium
Oxalate to the Concentration of Potassium Oxalate
and the Value of the Instability Constant at q = 4.
Added
Solu-
Instability
IC2c2o,t
ion
Conc.
c204"
Conc.
Pu43
constant
M
pH
m
m
0.17
2.7
0.005
3.43.10-6
-
0.37
,
3.2
0.034
9.00.10-6
2.540-12
0.50
3.9
0.168
2.58-10-4
4.7.10-12
0.60
3-8
0.176
7.74.10-4
5.5.1042
0.78
3.9
0.263
5-06.10-2
7.3.10-12
0.87
4.2
0.435
2-3940-3
5.4.10-12
TABLE 6
The Relation of Pu +3 Oxalate Solubility to a Different
Potassium Oxalate Concentration (ionic strength of
solution ? = 3) and the Value of the Instability Con-
stant at q = 4.
Added
Solu-
Conc.
Conc.
Instability
K2c204
m
tion
pH
?
'2i-,i4"
pu.8
m
constant
0.35
3.9
0.117
0.3240-2
1.5.10 13
0.58
4.0
0.215
1.4040-3
1.6.10 12
0.70
4.0
0.264
1.80.10-3
2.1.10-12
0.83
4.1
0.363
2.70.10-3
3.1 10-12
0.95
4.1
0.420
3.2040-2
3.7 10-'2
Reas and Konnik (see paper [1]) calculated the solubility product
K _ [Ptt+92[112C20413.= 2.
1H+16 10-10
and found that it remained approximately constant when the hydrogen ion concentration was changed from
0.22 to 3.7 M. Using the dissociation constants given above for oxalic acid, we find that
[Pu+12[C20:] = Lp = 1.1.10-26.
Using this value for the solubility product, we calculated the instability constant of the ion Pu(C204)4-5, given
in Table 5. The actual value of the constant depended on the accuracy with which the solubility product had
been determined." ,Similar experiments were carried out with a constant ionic strength in the solutions, which
was maintained by adding potassium chloride (complex formation of Pu +3 with chlorine ion was disregarded in
the presence of oxalate). Furthermore, the oxalate ion concentration was chosen in such a way that one form
of complex ion would predominate in the solution (corresponding to the linear part in Fig. 4). However, even in
this case, there was some increase in the constant, apparently caused by a higher solubility value at low oxalate
ion concentrations, due to the presence of a complex with three coordinated groups.
The value of the ratio of instability constants of Pu +4 and Pu +3 oxalate complexes, equal to 1.4.1046,
was given above. Knowing the instability constant for Pu(C204)4-5, we may determine the instability constant
for the complex ion PU (C204)-44: Kpu(c200,-;4=2,4 X X10-12.1. ,4 ? 10-16=3,3 .10-'8, if we assume that
Kpu(c204)-4-5,= 2,4.10-12 (the average value of data in Table 6). The instability constant of the ion Pu(C204)3-3
equals 2.2.10'11.
Received August 29, 1957
LITERATURE CITED
[1] G. Seaborg and J. Katz, The Actinides (Foreign Lit. Press, 1955).
[2] W. H. Reas, The Transuranium Elements (McGraw-Hill, 1949). 4, 14B, I, 423.
*Remark added during correction. In the article by A. D. Gel'man et al., (see page 55 ) Lp was taken as equal
to 162 ? 1C25; therefore the constant K12 was approximately 15 times greater than the one given in our work.
69
Declassified and Approved For Release 2013/09/13: CIA-RDP10-02196R000100010001-2
70
Declassified and Approved For Release 2013/09/13: CIA-RDP10-02196R000100010001-2
[3] ?Beilsteins; Handbuch der Organischen Chemie 2, 477 (1942).
[4] I. M. Kolthoff and D. D. Lingane, Polarography,(Foreign Lit. Press, 1945).
[5] J. Heyrovsky and D. Ilkovic, Coll. Czech. Chem. Commun. 7, 198 (1935).
[6] M. Stackelberg and H. Freyhold,, Z. Elektrochem. 46, 120 (1940).
[7] J. J. Lingane, Chem. Rev. 29, 1 (1941).
[8] K. A. Kraus, The Transuranium Elernents,(McGraw,?Hill, 1949) 4, 14B, 1, 241.
[9] R. Brdicka, Coll. Czech. Chem. Commun. 2, 489, 545 (1930); 3, 396 (1931).
Declassified and Approved For Release 2013/09/13: CIA-RDP10-02196R000100010001-2
Declassified and Approved For Release 2013/09/13: CIA-RDP10-02196R000100010001-2
RADIOACTIVE DANGERS FROM CONTINUOUS ATOMIC BOMB TESTING
0. I. Leipunskii
The present article is a study of the hazards?from the global radioactive fallout
of continuous atomic bomb tests of 11 megaton TNT equivalent per year. The Sr90
concentration in the bones is calculated, as well as the number of incidences of leukemia
(blood cancer) and the number of cases of genetic damage. Calculations show that at
the end of the century the Sr90 concentration in vertebrae may be greater than the
offician maximum allowable concentration for a large segment of the population, and
that each year of continued testing increases by 44,000 the number of people in the world
burdened with hereditary disease and increases the incidence of leukemia by 29,000 cases.
1. Criteria of Danger
We shall consider the action of radioactive fallout from high-energy explosions, this fallout being carried
by air streams in the atmosphere and precipitating over the whole earth, so that atomic explosions affect the
whole population of the earth (we shall not consider the local fallout in the region of the explosion).
The radiation dose from radioactive fallout is not large. Thus the biological problems which arise in this
connection belong to the least investigated field of radiation medicine, namely the field of small chronic effects.
This problem is important because any harm that is done affects all of humanity without exception, threat-
ening to change the hygienic conditions under which mankind evolved.
A quantitative evaluation of the possible damage is necessary for practical conclusions. This evaluation
is complicated by the fact that the necessary data from the different fields of biology, biophysics, geophysics,
etc., are at present incomplete, often inexact, and sometimes even contradictory. As did a previous work on the
subject by the present author [3], this article attempts a quantitative approach to the problem of radioactive
fallout hazards, based on the available data.
An evaluation of the hazards of atomic explosions depends strongly on whether radiative effects have or
have not a threshold. If a threshold exists, the radiation below the biological threshold causes?no harmful effects.
If there is no threshold, then even small doses have some action.
The concept of the maximum allowable dose has been developed on the basis of peaceful work with radio-
active substances. According to practice which is officially recognized in all countries, radiation of the order
of the allowable norm may be generated without a health hazard. The concept of an allowable limit does in
fact indicate that a threshold is assumed, and the allowable limit itself is taken to correspond to the effective
threshold of the biological effects of radioactivity.
When radioactive substances are used in practice the organism is not irradiated uniformly, particularly
when a radioactive isotope enters the organism, so that it has been required that the radiation be no greater
than the allowable norm not only in the organism as a whole, but also in the particular organ, called the criti-
cal organ, in which the radiation is greatest. For instance, if Sr90 enters the organism, one may practically say
that only the bones in which the strontium is assimilated are subject to radiation, and that the radiation to the
rest of the organism is negligible.
71
Declassified and Approved For Release 2013/09/13: CIA-RDP10-02196R000100010001-2
Declassified and Approved For Release 2013/09/13: CIA-RDP10-02196R000100010001-2
Therefore the radiation dose due to strontium need be calculated only for the bones, and the bones (the
skeleton) are the critical organ. The critical organ may be small compared to the whole organ (for instance,
if radioactive iodine enters the system, the critical organ is the thyroid gland, whose weight is about 20 g).
Nevertheless, the dose to the critical organ, rather than the mean dose to the whole organism, is the official
measure of the radiation hazard.
Looked at in this way, the question of the danger of atomic explosions reduces to a determination of the
radiation dose to a critical organ, followed by a comparison of this dose with the offician allowable norm.
If the dose to the critical organ due to radioactive fallout from explosions is greater than the maximum allowable
dose, then atomic armament tests are inadmissible from the point of view of official criteria for the health and
safety of the population.
Since we are talking of world-wide effects of atomic explosions, it is clear that this dose should not be
greater than the maximum allowable, not only when averaged over all of mankind, but also in separate groups
of the population. In principle, not a single person should be subjected to radiation above the norm. This
requirement necessitates an investigation not only of the mean global radiation, but also the statistical devia-
tions from this mean.
One one-hundredth of one percent of the population is 250,000 persons. If, therefore, with a low mean
dose there is a probability of 0.01% that a fluctuation occurs in which the dose is a certain value above the
mean, this fluctuation will affect a large number of persons, namely several hundreds of thousands.
An evaluation of radiation hazards based on the allowable norm, or essentially based on the concept of a
threshold to the action of radiation, is convenient in practice, although it is approximate and hardly corresponds
to the physiological action of radiation. The available data show that in many cases it is doubtful that there
exists a threshold.
With respect to genetic effects (mutations) it may be considered established [1], that there is no threshold
and that ionizing radiation will have effects in arbitrary doses. It is quite probable that a similar statement is
true with respect to leukemia. *
In the absence of a threshold, the evaluation of the hazards of atomic explosions involves just the determi-
nation of the number of illnesses caused by the radiation dose from the products of an atomic explosion. This
necessitates knowing the relation between the number of illnesses and the dose. For most effects of radiation,
this relationship is not known. Data exists only for mutations and leukemia. In both of these cases it is assumed
that the probability of harmful effects is directly proportional to the radiation dose to the gonads (for mutations)
or to the bones (for leukemia). Further, there do exist evaluations of the proportionality constant.
By comparing the number of illnesses due to an explosion with the number of the same kind of illnesses
caused in other ways, one may judge how serious are the effects of atomic explosions when compared with other
factors causing similar illnesses. This does not, however, refute the fact that even the smallest explosion is
known to cause a certain number of hereditary and somatic diseases, and leads to serious injury to a definite
number of individuals.
The calculations presented below are based both on the assumption of a threshold (taking account of the
existing allowable radiation limit), and on the concept of nonthreshold effects.
*Leukemia is a serious illness of the blood, consisting of the unlimited multiplication of imperfect leucocytes,
and is always fatal. It is supposed that this disease is caused by mutations in the cells of bone marrow (2].
Genetic victims (mutants) are persons with illnesses due to damage to elements of the reproductive cells from
which the organism has developed. A characteristic property of such illnesses is their hereditary transmission
from parents to descendants. There exist about 500 illnesses of this type [1], such as hemophilia, dwarfism,
infantile idiocy, etc. From two to four percent of all births are burdened with genetic diseases, and ten to
twenty-five percent of these come from mutations caused by the natural radioactive background.
72
Declassified and Approved For Release 2013/09/13: CIA-RDP10-02196R000100010001-2
Declassified and Approved For Release 2013/09/13: CIA-RDP10-02196R000100010001-2
The calculations based on the allowable radiation norm considers (see Section 3) irradiation of the skeleton
by Sr90, since when long-lifetime fragments enter the organism, the critical organ is the skeleton, and the active
Isotope is Sr90. (One need consider only long-lifetime fragments, since the precipitation of the fragments from
the stratosphere takes years and all short-lifetime fragments, decay before they reach the earth.) Of the two long-
lifetime fragments,namely Sr 90 and Cs137, one need consider only Sr" in calculating the maximum allowable
dose to the critical organ. This is because this isotope is collected in the bones, and is eliminated from the
organism one hundred and fifty times more slowly than is Cs137, which enters the soft tissues. Its concentration in
the organism is therefore correspondingly greater than that of Cs137, whose action we may thus neglect. When
dealing with nonthreshold effects, one must account for Cs131 in calculating the gonad radiation dose and the
occurrence of mutations [3].
In calculating the dangers from the nonthreshold point of view, we shall deal with (see Section 4) the num-
ber of leukemia cases due to bone irradiation by Sr99 , C, and CsI37 (external radiation), and the number of
mutant births due to gonad radiation by Cs137 and C.
We give here the quantitative criteria for danger in the case of threshold (a) and nonthreshold (b) effects:
a) The allowable radiation of a critical organ in nonindustrial personnel is considered to be 5 mr/day,
or 1.8 r/year. This quantity is lower by a factor of ten than that for persons working in atomic industries (50
mr/day, or 18 r/year), and is ten times greater than the natural background (0.5 mr/day, or 0.18 r/year).
Whether there is any basis for the allowable dose is not clear. The norm for persons who work under conditions
of radiation would seem to be too high, as is indicated by the five year lower life expectancy for medical radio-
logists (according to British statistics). The simple division by ten of the norm for atomic industries, which leads
to the norm for the population as a whole, is quite arbitrary.
Thus the officially accepted allowable norm of 5 mr/day or 1.8 r/year cannot be considered to have
sufficient basis or to have been sufficiently analyzed and reconsidered. A natural norm is the natural background
of 0.18 r/year. Increments above the natural background which are no greater than those of natural fluctuations
(for instance, up to 0.3 mr/year as in some brick and concrete houses) are in all probability allowable.
b) As more accuracy is being attained in methods for recognizing the effects of radiation, data are being
collected which throw doubt on the concept of threshold effects. One of the important effects of small radiation
doses, namely harm to the genes and the occurrence of mutations, can take place even in a single act of ioni-
zation in the gene, and is therefore not a threshold effect. We may assume that there is likewise no threshold
for occurrence of leukemia.
The probabilities for mutation and occurrence of leukemia are proportional to the dose. The proportionality
constants are the following:
for leukemia [2]
for mutations [3]
2.10-6
year ? roentgen. person
cases
A mutants *
4.10'
r ? person
In addition to clearly defined diseases (leukemia, genetic illnesses, etc.) chronic radiation in small doses
may have a depressive effect on the organism, as in systematic nonobservance of hygienic rules. This may not
cause any definite disease, but may affect life expectancy, productivity, resistance to infections, etc. The
absence of any data which could be quantitatively dealt with restricts our calculations to only the two above-
mentioned effects of radiation. Thus the quantitative results on the effects of atomic explosions will be some-
what too low.
?According to other data this proportionality constant is several times greater [1, 3].
73
Declassified and Approved For Release 2013/09/13: CIA-RDP10-02196R000100010001-2
Declassified and Approved For Release 2013/09/13: CIA-RDP10-02196R000100010001-2
2. A Calculation of the Amount of Strontium which is Precipitated on the Earth
by Continuous Testing
a) The amount of strontium in the stratosphere. In high-energy bursts, fission fragments enter the stratos-
phere. According to Libby [4], the mean time the fragments spend in the stratosphere is ten years. The frag-
ments gradually leave the stratosphere, entering the troposphere (in all probability by turbulent diffusion), from
which they come to earth in the precipitation. The amount of strontium in the stratosphere is determined by
the rate at which it enters it, the rate of its radioactive decay, and the precipitation rate, so that we may write
dQ n Q Q
dt Tp T d (1)
1 Q
ip id ep
where Q is the amount of strontium in the stratosphere,* n is the amount of strontium entering the stratosphere
daily, Tp is the time constant for the precipitation of strontium from the stratosphere (Tp = 10 years); Td is
the half-life of strontium (Td = 40 years);
The equilibrium value of Q is
Tp. Td
Tep = r
T +Td 50
400
- 8 years;
Q. nTep(1 e-t/Tep)
(2)
Q0 = nTep (3)
(in eight years Q is 0.67 of its equilibrium value, and in sixteen years it is 0.87 of this value).
b) The amount of strontium on the earth N is given by the equation
dN Q N nT (1 ? e--tIT eP) N
dt Tp Td TP Td '
nT T
N =?' eP-SI- ( T ?T1 TTd,/Td +
7
P d ep
+
TeP- e -1IT )
--- ep
Td ? Ter,
from which we find that
nkP Tcl n ? 8.40
t?. N N c?
713 10
t= 20 yrs N =-Noo? 0.24 =-- 7,7n;
t =--- 48 yrs N =-- N ? 0.62 20n.
(4)
(4a)
(5)
*Here, as in the author's previous article PI the amount of radioisotope is expressed in units of megatons (Mt),
by which we mean the amount of isotope contained in the fission product of a burst whose energy is 1 Mt TNT
equivalent.
74
?
Declassified and Approved For Release 2013/09/13: CIA-RDP10-02196R000100010001-2
Declassified and Approved For Release 2013/09/13: CIA-RDP10-02196R000100010001-2
Let us evaluate n on the assumption that the powerful bursts that have taken place since 1952 have occurred
uniformly in time. From the data presented by Kulp and co-workers [4], at the end of 1955 (that is, after four
years) there was about 3.2 ?C /km2, which corresponds to precipitation from 10 Mt.
Setting N = 10 Mt and t = 4 years into Equation (4), we obtain
N 10 11 /
n = 0.88 = 0.88 = Mt" Yr'
The amount of precipitates on the earth corresponding to continuous uniform testing at the rate of 11 Mt/yr
is given in Table 1.
TABLE 1
t, years
n Mt
At the beginning of 1952
0
0
At the end of 1955
4
10
At the end of 1972
?20
84
At the end of 2000
?48
218
Equilibrium value
CO
352
3. An Evaluation of the Dangers from the Point of View of Official Norms
Official norms require that the dose to the critical organ be not greater than 1.8r/year. In the present
case the critical organ is the skeleton (or more exactly, certain definite bones of the skeleton; see below).
Thus an evaluation of the danger reduces to determining the dose rate from Srse to the bones and compar-
ing it with the allowable norm.
There are two ways to calculate the strontium dose to the bones. The first is based on the idea that the
strontium-calcium ratio in the bones is given by this ratio in the soil with discrimination factors taken into
account. These discrimination factors come into play as the strontium and calcium move on their biological
path from the soil to plants, from plants to food, from food to blood, and from blood to the bones.
Since strontium is not entirely equivalent to calcium in its chemical properties, the strontium-calcium
ratio decreases in each of the above-mentioned transitions.
Thus
( Sr \ ( Sr \
Ca }bone Ca )soil ?k 1k 2k 3k 4,
where k1 is the discrimination factor in the transition from soil to plants (k1 = 0.7); k2 is the discrimination
factor in the transition from plants to food (milk) (k2 = 0.125); k3 is the discrimination factor in the transition
from food to blood (k3 = 0.4); kg is the discrimination factor in the transition from blood to bone (l(4 = 0.33) [4].
The direct use of discrimination factors is complicated because they are not well known and because of
their great variation (in particular in the case of k1 and k2), as well as because of the variation in the concen-
tration of calcium and precipitated Sr" in the soil, the difficulty in accounting for the use of food from different
locations with different calcium concentrations in the soil, the nonuniform distribution of strontium through the
various parts of the skeleton, individual variations, etc. We shall therefore perform the calculation in a different
way, using more direct measurements of the strontium concentration in bones, as presented by Kulp and co-
workers [4], to determine the strontium in the bones (see Equation (8)). These data refer to the end of 1955,
when the precipitation on the whole earth corresponded to 10 Mt (see Table 1).
75
Declassified and Approved For Release 2013/09/13: CIA-RDP10-02196R000100010001-2
Declassified and Approved For Release 2013/09/13: CIA-RDP10-02196R000100010001-2
Kulp and co-workers [4] give values for the Sr" concentration at various locations and for various age
groups, and present world-wide averages.
In choosing Kulp's value for a (the Sr" concentration in Ei C/g Ca)* one should bear in mind the follow-
ing factsr
a) The world-wide average cannot be used without taking into the account the distribution.
The distribution in values of a reflects the superposition of all the factors listed above in their natural
combination (the distribution in the k coefficients, in homogeneity and precipitation, the distribution in the
Sr" and calcium concentration in the soil, various diets, individual susceptibilities, the spread in the concen-
tration in the various bones of the skeleton, etc.).
It was mentioned above that values of a which occur 0.01 percent of the time will give the Sr" concentra-
tion in hundreds of thousands of people. Therefore one must use not the mean values of a, but the largest values
which occur in a small but definite fraction of the population in the statistical distribution of a values. The
statistical sample in Kulp's work is not great, referring only to several hundred samples (taken over all age groups
and many locations on the earth), and therefore values of a which occur with a probability of 0.1 or 0.01 percent
cannot be calculated. At a given place, the spread in the a values is not great (about 50 percent).
In North America, there occurs a measurable number of cases (1.8 percent) in which the a Values are ten
times greater than the mean (Fig. 3 of [4]). Values of a five or more times as great as the mean occur 5.4
percent of the time, and those three or more times as great as the mean occur 11.4 percent of the time.
The distribution of a values (on the above-mentioned Fig. 3) is not gaussian, being asymmetric with a
large number of large deviations. Such a wide distribution is not obtained if samples are taken only from a res-
tricted area. This would seem to be a reflection of the world-wide statistical distribution in the strontium pre-
cipitation, the calcium content of the soil, variations in diet, and perhaps several other factors (such as indivi-
dual susceptibility, etc.).
One cannot say whether or not this statistical distribution can be used for the population of young children,
all of the calcium in whose organism contains some Sr". In any case, it is a fact that a significant part of the
population (about 1.8 percent according to Kulp's Fig. 3) has a Sr" concentration of 1.1 s. U. (with a mean value
of 0.11 s. u.).
In children the highest concentration is found in the ribs (for instance in Houston, Texas), the figures for
children up to four years being 2 to 2.5 s. u. (whereas the mean in Houston is 1.07 s. u.), and those for children
between four and nine being 1.6 to 1.2 s. u. (with a mean of 1.08 s. u.).
b) Kulp and co-workers [4] note the nonuniformity in the strontium distribution in different bones of the
skeleton (see Table 1 of [4]). In particular, they find that the Sr" concentration in ribs is twice as great as the
mean over the whole skeleton, and that the ,concentration in the spine is four times as gre'at. In Table 2 (column
1) we give the mean values over the whole skeleton as obtained from Table 2 of [4] (0.11 s. u. for all ages,
0.3 s. u. for ages 0-4, 0.4 s. u. for ages 0-4 in the United States). Therefore in the ribs and vertebrae the quan-
tities will be two and four times as great.
Columns 2 and 3 give the a values for ribs and vertebrae. They are obtained by multiplying the values
in Column 1 by two and by four, in agreement with Kulp's Table 1. The calculated values are given in paren-
theses.
If we are to proceed on the basis of a critical organ, which is officially accepted as valid, we must con-
sider not the skeleton as a whole to be the critical organ, but the vertebrae. We shall then use the figures we have
obtained for the vertebrae by means of the coefficients of Kulp's Table 1. These figures are those in the last
column of Table 2. As can be seen, the a value for the end of 1955 may be chosen as 4.4 s. IL, which occurs
in 1.8 percent of the cases investigated in North America.
* A Sr" concentration of 1 11PC /g Ca is called esunshineflor''Strontium unit," which we shall henceforth abbre-
viate s. U.
76
Declassified and Approved For Release 2013/09/13: CIA-RDP10-02196R000100010001-2
Declassified and Approved For Release 2013/09/13: CIA-RDP10-02196R000100010001-2
TABLE 2
Values of a (Sr" concentration in s. u.) the Fourth Year After the Start of
Powerful Explosions (end of 1955)
Average over
skeleton
Ribs
Vertebrae
World-wide mean for all ages
0.11
(0.22)
(0.44)
For 1.8 percent of the cases in
North America
1.1
(2.2)
(4.4)
World-wide mean for children up
to 4 years of age
0.3
(0.6)
(1.2)
U. S. A. mean for children up to
4 years of age
0.4
(0.8)
(1.6)
Highest value in Houston
(1)
2.0
(4.0)
The question of the reliability of the data presented by Kulp in his Table 1 has yet to be answered. It is
possible that the nonunifcirmity he notes in the strontium distribution may be of a kinetic origin? and that it may
become more homogeneous as time goes on. The authors note that in the interval from 3 hours to 125 days the
distribution pattern does not alter. Since the homogenization of the strontium concentration takes place not by
means of diffusion in the bones, but through the blood, it would seem that it should take a time of the order of
the biological elimination time of Sr". If this is true, theprocess of homogenization is equivalent to elimination
of strontium, and will be accounted for as eliminated from the part of the skeleton being considered in Equa-
tion (6), which gives the amount of strontium in the bone.
We shall use the following notation.
Amount of Sr" on the earth
Concentration of Sr" in the soil
(s is the concentration of strontium
in the soil in the precipitation of 1 Mt)
Concentration of Sr" in food
The amount of calcium in the food
entering the organism yearly
The food-bone discrimination factor
The strontium concentration in the
bones
The amount of calcium in the
skeleton
The strontium content in the
skeleton of an adult
The yearly hitake of Sr" by the bone
The amount of strontium in the bone
The effective time constant for
strontium elimination from the
bone
N,Mt
sN
b = sNk1k2 (s. u.)
Ca
C year
k3k4
a(t),s.
M(t),g
Mco = 1000 g
m = bck3k4 (s. u.)
q(t) = a (t) M(t), ILIAC
Td.Tb
Td - 11.3 years
Teb -
(Tb is the time constant for the elimi-
nation of Sr" from the organism, equal
to 15.3 years [5] )
In order to calculate the amount of Sr" in the bone, let us consider the equation
77
Declassified and Approved For Release 2013/09/13: CIA-RDP10-02196R000100010001-2
Declassified and Approved For Release 2013/09/13: CIA-RDP10-02196R000100010001-2
dq q
m ,
di T b
m = sNk1k2ck3k4= ve N (t) =
= vNo?( 1 40
e?t/40 e ?1/8 )
32 32
where u = sk1k2k3k4c( p PC /yr-Mt).
Integrating (6) with the initial condition q = 0 (at t = 0), we obtain
q = vNcoTeb? F (t) = qF (t),
(6)
(7)
where qe3 = v NcoTeb is the limiting value of the equilibrium concentration of the radioisotope in the organism,
and
112 read
F 0) (Tp?Tep)(Td ?Ted +
e?t/tep
(Td T1') (T Teb)
d?tiTeb [1 Tt2i
(Td ?Ted (Td ?
T2
+Td -
(Td --Tep)( ep?Teb) a
eb)
The radioisotope concentration in the critical organ is
(f) v N eoTebF (t)
a (t) =-- = ??C/g.
The dose rate P in the critical organ can be calculated from the formula
P (1) = a (t)?1.8 r/yr
aD
where ap is the concentration which gives a dose of 1.8 r/yr,
The dose in the critical organ is
where
78
1.8 r
D = P (t) dt ? M aD q (t)dt,
q (t)dt = eeTeb t
0
Ta __e?tad)
(Td Pep) (Td ?Teb)
(7')
(8)
(9)
(10)
T I
( ?etiep)
Teb (1
e?t/Teb)
x
+ ?
(Td ? Tep) (Td ?Teb)
T2d
x [
(
d?Tep)(Td ? b)
(11)
T2d
(Td
p) (TeP-7;:i)
?
Declassified and Approved For Release 2013/09/13: CIA-RDP10-02196R000100010001-2
Declassified and Approved For Release 2013/09/13: CIA-RDP10-02196R000100010001-2
Let us find the concentration a(t) by using the above formulas.
In order to avoid uncertainties related to the large distribution in the numerical values of the coefficients
s, k2, ks and 1