ORIG. RUSSIAN: INVESTIGATION ON SYSTEM WITH ZIRCONIUM HYDRIDE MODERATOR

• Document Type: CREST
• Collection: General CIA Records
• Document Number (FOIA) /ESDN (CREST): CIA-RDP88-00904R000100110009-0
• Release Decision: RIPPUB
• Original Classification: U
• Document Page Count: 17
• Document Creation Date: December 22, 2016
• Document Release Date: August 26, 2009
• Sequence Number: 9
• Publication Date: May 1, 1964
• Content Type: STUDY

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of Atomic Ener9Y
A~CONF . 28/P/361
USSR
l,~~y 19 64
Uri~inal: RUSSIAN
Confidential until official release during Conference
Investigation on System with Zirconium Hydride
Moderator
N.N. Ponomarev-Stepnoi, O,N. Smirnov, R.V.Kuleva
Results of an _investigation on physical characteristics
of critical assemblies with zirconium hydride moderator
and 90~ uranium enrichment are described. The cr. itcal systems
with different reflectors and without were studied. The
measurements were fulfilled_with assemblies of different re-
1.Construction and materials of assemblies.
The physical assemblies with ZrHn and U-235 with or
without reflector were of a rectangular parallelepiped
form. The assemblies had a plane heterogenoue structure:,
fuel and moderator sheets being placed horizontally one by
one. The opportunities of change of core composition, as-
sembly dimensions, operating and safety systems were fore-
seen in construction. The sssembly dimensions may be varied
from 200 x 200 mm2 to 500 ~ 600 mm2 with height up to 800 mm.
Controlling rods moved in duralumin slits 10 x 100 mm2,with
wall thickness of channel 1 mm. There were two plane rods
of safety system, made of Cd, and one of steel for slow
compensating, used in experiments. Fig. 1 shows a general
view of the experimental arrangement.
The fuel elements of planes kind consist of a core and
a coating (1) . ~ core comprises a chemical mixture of CF2
and U308, with 90~ uranium enrichmenti;. A coating is made of
CF2 film. The average dimensions of the fuel elements are
100 x 100 x 0.5 mm3, with content of U30g 1.85 g and CF2
about 11.75 grameo The fuel elementswere put together in
the operating magazines, constitution and number of them
depending on the experiment.
from 120 t~ 500.
lative concentrations >^ -~5 , changed within a range
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~~, Third United Nations
International Conference
on the Peaceful Uses
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Two kinds of ZrHn moderator lumps were used in the
experiments. One was of rectangular parallelepiped form
50 x 50 x 10 mm3 with densii:y x.84 g cm`s and atomic ratio
H. = 1,86. Another was of a prism form with height: 6 mm and
'Lr
length 50 mm, density 4.95 g cm 3 and atomic ratio H a 1.91
~Zr
The lumps of Be (100x50x10 mm3), Be0 (100x50x1.5 mm3)
and ZrHn were used ae~ reflectors.
2. Experimental results.
Two aeries of axperiments with ZrHn systems were made.
The assemblies with thick berillium reflectors ~~lere~ studied
first, the moderator lumps of rectangular ;parallelepiped
(atomic ratio ~, ~ 1.86) being used. Characteristics of
the aesemblleaZr and critical heights measured are given in
Table I ;see Fig. 2 also). The thicknesses of the two side
reflectors in assemblies Nos 3,4 and 5 wer? 150 mm, 100 mm
and 50 mm respectively. The thicknes? of two other ref-
lectors was constant and equal 150 mm. In Fig. 2 a criti-
cal height and a critical mas? of U-235 are plotted agains ~
the side reflector thickness. The conclusion follower from
the curves, that a use of Be reflector thickneee~ more than
120 * 150 maz is not reasonable for the similar assemblies.
In assemblies Noe 3 and 6 the concentratioim PS was cn?1-
stant and equal 280.
One fourth layer reactivity was measured for the ~.~ssem-
blisa Noe 2 and 3. "Ones fourth layer" comprises fuel, ~node-
rator and reflector in quantities 1 of full content of
these materials in the upper layer of~an assembly, ~, reac-
tivity was measured by using the grad~.~ated compensating rod.
The results are summarized in Table 2.
~ contribution of the upper face reflector (thickness;
of Be 53 mm) to the reactivity was measured the pulse neut-
ron source being used slid the result was found to be equal
0.0145 ?0.0057. The spatial neutron dietri but ion in the re-
actor as a whole and in the cell was studied oy In a,ctiva-
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tion metho3. The results fcs the assembly Na 1 are ehoMa
in Fig.3? The thermal neutron distribution in the fuel was
measured by r?gistration of fission products, accumulated
in the fuel elementea.
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 3 312 202 464 150 150 - 7
q. 312 202 q~93 100 150 .. 7
5 312 202 611 50 150 ~ 7
6 312 202 540 150 15U --
10 15.8 1.450.018 18 There is upper Be
-0.018 reflector
10 15.8 1.456+0.018 18 gef = 0.985;
-O.Q7.8 subcriticality
measured by
pulse method
10 17.0 1.623+0.020 18
-0.020
10 16.9 1.722+0022 18
-0.022
20 34.0 1.917+0.024 17.5
-0.024
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Critical Parameters of ABSembliee with Reflector
~~+'Core dimen- Thickness of Number Thick- Dimen- Tempe-
sions, ~n Be reflec- f$~1 ne$s of eion U-23~, ratur~
o
H
f k
1.86 o
g
tor. mm. elements Zr
A~[ ~ H
d~ d d~ in mega- mm cell,
~ Zlne ~
1 312 202 548 150 150 53 5
2 312 202 548 150 150 ~- 5
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 Critical Parameters of ,seembliee without Reflector
Table 3
Abe
Core dimensions,
Ce~.l c ra~teristice
ae-
cm
Num er o is see a is -
Content of U-235,
sem-(parallelepiped )
fuel elm of ZrH Q neee,
kg
bly a ~ H
mente in X1.,1, mm
magazine
7
51.5
50.5
34.4
12
12
19.0
7.077+0.113
~'
-0.088
8
51.5
50.6
36.2
12
18
25.0
5.703+0.087
-o , o7i
9:
51.7
50.6
43.8
12
24
31.4
5.782+0.100
-0.072
10
51.2
50.6
35.3
8
6
11.0
8.248+0.136
-0.103
11
51.6
50.6
33.8
8
12
16.8
5.349+0.067
-0.067
12
51.5
50.7
6j.0
8
24
30.0
6.019+0.075
-0.075
13
51.6
50.5
51.3
4
6
8.6
4.904+0.061
-0.061
14
51.6
50.6
46.0
4
12
15.0
4.194+0.052
-0.052
^
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Table 4
NQ
assembly 8 11 12 13 14
Rcd 10.2 9.9 13.7 7.0 12.0
P" 257 254 503 2571 525
J?r
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Characteristics of assemblies without reflector and
influence of tY~ reflector upon the critical dimensions were
studied in the second aeries of the experiments. Zirconium
hydride moderator with atomic ratio FI: ~ 1 91 was used in
the assemblies of p p
parallels i ed r form (see Table 3).
The critical dimensions were determined for different con-
centration ~s withi n a range: 130 t 500. The critical
mass and height of an assembly are plotted against the
PH
value Pr in Fig. 4. The material parameter depending
on number of fuel elements in tYn layer t}iicknesa is
shown in Fig. 5 for two concentrations: P 256 and
516. Typical thermal neutron distribution for the layer
thickness of the reactor is shocv~n in Fig. 6. The measure-
ments were fulfilled with the assembly N4~ T2.
Cadmium ratio Rcd for U~`35 in the moderator is given
in Tabls 4. Fig.7 gives a comparison of Be, Be0 and
ZrHi~86 reflector effectivenese~. The gain factor 1.8 of
critical mass is resulted for Be and Be0 reflector with
t~~ickness 120 t 150 mm in comparison with ZrH reflector.
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R
R
Z
--
Rv
,o
v
~
a
~
I
x
0
-
- _
- -- I ._.._-
-- --
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- -- - -
- --
---
~--
I
I
I
i
'i
--
fi
-
-
-
~~
-
-
t
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~J ~.
,~ ~ /
~~~` 2
~
~,~
~-.~i
~
~~
i
~
~~
,
_
~
-o--
~ ~
n=
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n-
n_ti
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/,y
/, 3
/, 2
/,O
0,9
O,d
~~
~
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a
L
1~ig. 5?
361
/2 /1
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/D
8
6
Fig. 6.
3b1
13
t3~
Be0
,7zNr,~
~
,,..
i
i
i
2
/0
/2
/y
/6
X
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Figurer Inscriptions
Fig. 1. General view of assembly with zirconium
hydride moderator
Fig. 2. Critical mesa and critical height ofl assembly
versus eideE reflector thicknea~
G-~35- critical mesa, kg
H -critical height, em
X -reflector thicknesa~
Fig. 3. Thermal neutron distribution and cadmium ratio
in assembly NQ1
I - core; II -reflector
{d - relative thermal neutron flea
Rcd- cadmium rP-tio by In
x -distance t;. the edge of assembly, cm
Fig.4. Critical massy and critical height for composition
Solid curves -critical mass; broken curves -
critical height of assembly
G235_ critical mass, kg
H - critical height, cm
Cap" - concentration
PS
n - number of fuel elements in layer thickness
Fig. 5. Material parameter versus n. -number of
fuel elements in layer thickness
2
~ -material parameter, 1
cm
n -number of fuel elements
C ps - concentration
15
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Fig. 6. Thermal neutron distribution in reactor cell.
(A3sembly Noll)
I -fuel; II -moderator (ZrH1.91)
~ -thermal neutron flux, relative unite
x -distance from center of cell, mm
Fig. 7. Effectiveness of Be, BeO, ZrHl.86
Solid curves -measurements with assembly Na14;
Broken curves -assembly N~13
S -Physical gain factor in reactor dimensions, cm.
x -Reflector thickness., cm.
361
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