ORIG. RUSSIAN: EFFECTS OF CROSS-SECTION RESONANCE STRUCTURE ON FISSIONABLE NUCLEI

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• Collection: General CIA Records
• Document Number (FOIA) /ESDN (CREST): CIA-RDP88-00904R000100110005-4
• Release Decision: RIPPUB
• Original Classification: U
• Document Page Count: 17
• Document Creation Date: December 22, 2016
• Document Release Date: August 26, 2009
• Sequence Number: 5
• Publication Date: May 1, 1964
• Content Type: STUDY

 Approved For Release 2009/08/26: CIA-RDP88-00904R000100110005-4
Third United Nations
International Conference
on the Peaceful Uses
of Atomic Energy
Confidential until official release during Conference
A/CONF.28/P/362a
USSR
May 1964
original: RUSSIAN
L.F.Zhorherun, A.K,.Krnel.n, G1.1.l'llndov, I.P.Sndikov, V.A.Tsrabanko,
A.A.Choi.~ynhav -
Beryllium and beryllia are of int,,rest In the nuclear engineering as construction mnte-
r?nla of rrtactors of various types duo to their good moderative properties, weak ther?mo1 neut-
ron absorption and fast noutron mult.lplication in the reaction lie' t(n,;'n), ilhyafcal properties
of beryllium and beryllln determining, dlffunt..n2 moderation, scattering and nultiplteatIon of
noutrons have been ntudlod for a few yoars in the Kurchatov Institute of Atomic Enervy (IAN).
The main results are briefly preuonted In the report.
In a, .lltion, the fast neuil;ron multiplication date obtained from the analysis of the criti-
cal assomblies in the Institute of E:nerFeticn of Academy of Science BSSIH are presented.
I.F.7hozherun, I.P.Uadikov, V.A.Terabanko,A.A.Chernynhov
(The Kurchotov Institute of Atomic FnerFT)
1. Effect of bpryll.tu microstructure and t;omperaturn on thermal neutron
scattering eronti-section
acett:rtu,.
The mierocryutallyne structure can essentially influence on the moderativo and
properties of boryllia clue to the affect of size and orientation of crystal grains on tha
scattering croon-uection 6S . It in known that with the increasing of the grain at:.a 0&
decreases due to the extinction effect= their advntageous orientation (texture) which can s -
pear in prcuring or pressing out of Boo articles can cause the anisotropy of 6S . To make cle-
ar how much those effects are to be taken into account when calculating the reactors of P'?0
moderator, the total croarr-section dt (6T-1 = es for BeO) wee meaertred with the ohoppor for
four samples with various grain size (see Fig.I). Sample I consisted of the plates I.2x7x.1 r:;&
produced by pressing out, sample 2-of the rods 324x23 mm produced by pressing, sample 5u?i Ir
of the disco 30 mm in diameter, 3 mm thick produced by pressing out and sample 4- of the discs
38 mm in diameter, 3 mm thick produced by cold pressing. The microstructure analysis of the sa-
mples, carried out by Yu.G.Digaltnev and V.I.Kuohakov, showed the all samples are cloned pecked
crystallite of irregular polyliodron form. The grain sizes are shown In Fig.1, the moan size wed
determined as a square root of an average area of a grain in a microsection photoltraph. In
different measurements the sample thickness varied between 3.2 g/cm2 and 5.6 g/om .
Under given experimental conditions the energy reeolutioa was between 4 and 10% In the
range 0.03-0.1 ev. To observe the anoootropy of 6 two series of measurements have been done
with namples I and 2, the neutron beam being fallen both in parallel and normally to the di-
rections of pressing or pressing out (Fig.2).
It is seen from these figurres that at :small energy (0,005-0.2 cv) the diffrrenco in
is 40% for the samples with the grain nl.zcrl 8" and 29Jt. : it may cause If -e..hn ngc of the rage spectrum scattering length X?S or the square diffusion length t!ri" (see Table 1 ). The ex-
tinction effect does not practically ?nfluerca on ri?_ if the grain sine .. IO)r..
The preset' ce of texturo in the hexagonal Boo lattice aooma to be observed In the beat -4y
from neutron t voi reflection on the planes being normal or parallel to the --n.xi:; of the or;, n?
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tat element;trey eolI I.e. ('ruin the reflect;ionu in whIt:I, tlm fIr Fit. two 111dexo0 or the last one
are equal to zero. The antuotropy or 45~ In obverved Irum the c?,nflnutlon on the plane (110)
at E = 0.012 ov (two inserts on fLg,..') an rnru:hlnl; ;'1it~ of the I-rtrtlnl or 'I't of the moonurod
rro
Cross-sections. little valune of thin uroo:t-ooottonn hl and ton00n uhuw the advonrnrooue orien-
tation of the crynts.l (;rains by a-'oxiu of thn nlo:nontnry cell in direction of ltr.enuing out and
normally to the pre:rnint; dtrnt-lotr, it' the noutnin betun in iturmtI or parellei to the pronuing
out or pros:tini di.rect.tonn. For other reflectIwo, the itifi ronec+ In 6.j and Q:;., 1f it is,
does not exceed the menneurement; erlorn. Thtru, the rtnlootrupy of (j4 Is mime Ii and its influen-
ce on G may be not lected.
In the ranKe 1-10 ev where atom bindle(; in the crystal lattice darn not effect on mcatte-
ring the measured value of li { is constant ttnd egwtIa I0?)).15 burn I'?T a I I the ;+rrmplon.
The t;ompcraturo dependence. of dit ir: of Importance for the unlrnttntion of the temperatu-
re reactivity coefficient. In Fig..,) the mt?tunreaunut, results of (Ztf ,rrc, shown for the nemple
of advantah;eons grain ei zes 10-.10,),1. at 'I' floe; 13w; 15t tp?K. In Fig.4 the tompt,ruturo
dependence of o~t (E) for some on,ergios t.a plotted on will no that: of 0f and (46 avers(;ed
over the Maxwelliou spectrum (at the M'uhr'trr l t.rnperutura TH T 4 1l)u"Il) and obta ua,d from
Fig. 3.
The measured results reveal Mint with the oamplo hentlm;' 1) thu 1tr'?slr.lon of Prna,g maxima
are shifted towards lest, onorgioa in accordance with the tamp+erotar(1 oxipnnnlon; ;') thtt voluo
of the maxima docruasea; 3) the value of tit incrnanotl, the rroator it will be 011, 11-0 the
neutron oner[,ry E is. At E70.15 evtt6 )hf and ((6'., P have w minimum near 't"-1100 K t,hioh
can be explained by the oompotition of two proceuuosr rit'creuulnf, of the coherent cl.nntic .wnt.-
tering and increasing; of the coherent inelastic one with tho temperature i-ncrt:alai. di ace 1If-
gen and beryl lilt) In BoO are anisotropic rend the Incoh.-rent acettnrln.t; in tie do i',ndint; on the
spin is small, the measured C,~ can in prtict.ically divided only In two termer the. olrrutit: end
inelastic coherent scattering cross-nectiun, t in ma tiny due to the latter at 1; - 0.0035 ov.
The change of (t with the tompuroturo in the ronl;e :"X1-1500?K can lead to the d(ncronulut;
of LI by about 217,8.
The sample density was 2.BO-2.65 [Jcm3, I.e. it woo loon than the theorel.icnl vat uo
3?04 g/em3. Therefore the quest;icm appeared whethor the ncatterine In :.,mall an;;les, crtttnrd by
the refraction and the diffraction of the neutron wavent at the boundaries botwenn uuhnt;rnce
and air in the sample pores, effects oil the moosured (k:,4. the r+tt.l.itlonnl meamirornontn on Its')
sample in the form of the fine-grained Bunt showed that the ucnttoring? in nninll anglen am be
neglected.
2. Study of thermal neutron diffusion In Lwry) Lion and
beryllia
The diffusion parameters of Be and Be0 were utudiod by meanu of the pulue c;' thud with the
linear accelerator of IiE. The method. :is in (mown, is to measure the dnmplinr; coofficirnl;
04_ of the neutron density in the moderator block with time end to analytic con:+e'luently the
dependence of e. upon the block geometry parameter B21
4 (I)
where acv is the absorption velocity, D and C are the cooffir,ionta of diffueit, t rand diffu-
sion cooling respectively.
The coefficient ~.L was measured for 30 beryll irtm blocks iii; B2 = 0.005'-0.11 cm 2 end for
27 beryllia blocks at B` 0.004-0.095 cm -2 (nee Fi);.5). The average Be density in blocks was
1.79 g/em3, that of BeO - 2.79 s1cm3. The measurements of o(- for much great numbor of the
blocks allowed to obtain the more accurate di.ffuoion parnmotere (see Table II) than those In
[2-8J .
The all experimental values of the cot!ffi'lunt D for Be, including the ones T-Able 11,
coincide within the measurement errors; for BoO the difference is considerably hie;hcr
the error. For the coefficient C the data are in ngrnempnt for Roo but as for Be there is
- 2 -
0
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no such agreement.
The study of the cause of the experimertal data dispersion for D and 0 showed that it may
be essentially connected with the possible dif-!'orcaoi of the crystal structure of the materi-
als under investigation. Thus the estimated osiculatlone of D and 0 for BaO using the above e>~64
for the samples with the grain sizes 8JL and 29 J/, , .ve the values of D within 10% and the va-
luae of 0 within 60%. The effect of the term with lit' in Bq, I in negligible as it to aeon from
the additional analysis of measurements by moans of the computer.
In C9] for the explanation of the dispersion of 0 it was indicated on the neutron trap
effect which must result in dependence of,L.. upon the meaaurome''t conditions for email blocks
(the neutron source power, the background level etc.). Our attempts to detect this dependence
for the Be block of 20 cm3 when the oouree power changes 10 times and the background level does
3 times failed (Fig.6).
The value of C measured give some Information on the neutron slowing-down ii-ix the ther-
mal equilibrium ,,.ndicating the decrease of the mean logarithmic snowy beat In Be and Be0
approximately 4-5 times. 5
3. Measurement of moderation length in Be up to 1.46 or
and 0.3 or
The slowing-down density q(r,&,.) was measured in the rectangular prism 801'90,.145 on, The
U23S converter, irradiated by the neutron beam of the rpncctor thermal column, nerved an a neut-
ron source= the indium foils in cadmiun filters were used on the neutron detectors at 1.46 ov1
the small plutonium chamber in the filter with mixture of samarium and gadolinium oxidon [10]
was the detector at energy 0.3 ov. The moserxroment reoulta are presented in Fig./ (for In) and
In Fi6.8 (for Pu chamber) .
The measurements by means of t!,e Pu chamber wore carried out in each point under the 1ul-
lowing conditions:
1) the chamber was surrounded by the filter of 0.125 g/cm2 Um and 0.04 f-,/cm2Gd (ft ?m)1
(id
2) the chamber was surrounded by the filter of 0.125 g/om2 Bm, 0.0r1 /Cm` Gd and 0.358/era Gd
(bSmGdCd) i
3) the chamber without filters (N).
The neutron flux of 0.5 ev was obtained no the difference of the first two meaeuromento
00.3 = NUmGd - NSmGdCd1 and the thermal neutron flux Pr?= N - (1-T)-l N3mGd, whore T is the
transmission of the resonance neutrons by the filter. Sm+Od. The inaccuracy of the value T, de-
termined from the cr:lculation, effects niightly on Tr , since N.SmQd 4- N.
The curve,, for 9)a.,and 9r (Fig.11) at distances Z..>60 cm from the source are parallel.
It implies nt such distances the density of the slowing-down neutrons of 0.3 or in negli-
gibly small in comparison with the density of neutrons of the same energy in the ostablished
Maxwelllan spectrum. Using the ratio Y'p,l ]rT = (6.58?0.1).10-3 at distances 't> 60 cm one can
obtain the slowing-down density qO .3 from the total flux 90; .
From Figs.7, 8 it is teen that at distances 't !L, 30 cm from the nourco the slowing-down
density in approximated by the expression Cj,~ t~ ^ e- -Z1/4zvith 't -110f2 cm2 at F?L =1.46 ev
and with 'V =91.5 '-' 2.5 cm2 at t L = 0.3 ev. At 'i 30 em the oxp.,euuion 7 ~t) ti 2 Q t/'tis
valid with A = 7.27?0.10 cm at E 2 = 1.xrb ov and 0.3 ev1 this expression presents evident-
ly the density of the first collisions. Over the whole region of measurements (7,&90 cm) the
where T, hitrm 2, 'c.? =1?r0cm?, v 265cID 2
I'1 0.0666, P, 0.30'x', P 0.027 at E.,, = 1.46 ev
P.1 = 0.541 , 1'? = 0.4}t.utron nlowlnr;-'lowu in Be and BeO below the threshold of Be9(n, 2n),
Bo9(n,.,i,) and 016(n,?.) reactions. This annwnlition is approximately true, an at E > 4 May
6rv,n. is nearly constant, and at E 4 11ev the collision densities in Be and Boo are similar.
Asa moult = 1'34 was obtained. Hence Ktic0 = ?1.08?0.023.
it, 6C 4.61.
B. CONTRIBUTION OF FAST 11'F1 CTB ON Be TO THE 4lULTIPLICATION
COEFFI3IENT OF B:'.RTI,I,IUM AU0EMBhIF6
A.K.Krasin, G.I.Plindov,
'Vito Inntituto of Enorgetirs of Academy of Rcienoeo
113";H
It is of interest to take into account the effect of (n,2n) and (n,*?) reactions on Be
on critical masnoa and sizes of physical beryllium assemblies and to separate the contribution
of fast effect inl?o the multiplication coefficient.
For title purpose 10--group constants for beryllium were obtained. The Be (n,2n) reaction
has considered as inelastic scattering lending to an additional neutron. The croua-sections of
(n,2n) and (n,,4.) reactions wore taken in from [16-22] and 123,251 , respectively.
For verification of constants obtained the neutron age of fission spectrum and fast-nout-
ron multiplication coefficient in infinite homogeneous beryllium medium wore culoulatod. The
evaluated neutron al;e `C = 79 cm2 and the value of fact neutron multiplication coefficient
KBe - 1.0137 were obtained, which are in a good agreement with the data [ 26] and with theore-
tical ortimutiono [ 27,281 , reupectively.
With these con::tante the multiplication coefficientts,, calculated maaaeo
in multi-group andcticfdi-ion
mensions of physical a;;oemblias, deucribod in [ 29] ,
i-raland with
approximation, taking into uecount the reactions Be (n,2n) and Be (n, d )
no account of them ("b"-case). The contribution of the fast effect on Be wee defined as a dif-
ference of the multiplication coefficients, calculated with the account of Be(n,2n) and Be
(n, d ) reactions or without it.
The results of calculations are shown in Table V. 1 t; is soon from Table V that the value
of the fast effect on 9-10% Be is somewhat less, than the value 12?4% given earlier for the
same assemblies [29] , but is within the experimental errors. Since the fast effect on Be
was calculated in multigroup theory, the value of the present work seems more preferable.
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X. N.Z. 102OPY9, H.f1.CaAkicoB, A.A.11bpm4vjC31. rllrnlt L3, 250 (1962);
N.1.Jeaopyg, H.I.Ca 1ROB, B.A.Tape6enr;r' , /.A ATOWIall inept'nu L3, 258 (I962);
H.O. o opvu. A'routten v1Oprwift
;rnlp;~n, N.(1.CaANlcoa, B.A.TapH68nbtto,
A.A.9epliinuoB. ATOMHeH BneprRfl 1 485 (i9%)'3, 1 ;'.yomoryn. ATOVIIOH aneprnn , 505 (I960);
N.T.1exopyn. ATONIIan aueprI 16, Hey'uHNO npogecco eoue11neul1H
110ATpoHOB B 00PRA HH H o14ICN k!eT0,rO1f. HO onybnHttoBono. OcnODUHO peaynb-
TtJTH A'0icn47lWBOUTOtt Ha AeNeBclcot Itoni apai; voi.
2. A.B.AtITOHOB H Ap. B xuNre "(Dnuivicotcr-e RccnegovolIHH" MOCKB8, N34-BO All CCCP, 1955, crp.158
(ItotcnaAli COBOTCK.Acnorauini He ueziLyHapo,111o11 1COH~opeHtUHn 1`10 MHpUOUy ac11071T000e11nn aToutrog
anoprHH. I[eHOBa, 1955).
S. E.Qarpbel, P.Stoleon. ORNL, 2076 (1956).
4. T.Komoto, F.Kloveretrom. Pranu.Amer.Nuol.Soc., 1, 94 (1958),
5. G.do auenuro and E.G.Ullvor. Nuol.Soi.Abetr. 1 , ?1059 (1959); Nucl.Gc1. I F'ng.,ti,
195 (1959); Proo. of Syn,ponium Vienna, 17-20 & tober, 1960, p.500.
6. S.D.f.Iyonger, O.3.Mani, R.Raclanna and N.Umakanth Proc.Ind.Acnd.sc?i., IU.V, B A, 265
(1957).
7. L.S.Kothary, P.G.Khubchandnr, p, Hoact. 13ci.and Toobnul., :15, 30 (1961 ).
8. K.W.Ueeman, Nucl. Sci.Abotr., 11, 140) (196:').
9. G. de ilaussure. Nucl.2c1o and Irig., 12, 43, (1962).
10. 11.4'.it:c copyu, H.I1.Ca,11t1toU, ii.A.4epinomOH "IIIH(opu 11 T XIBIno a1ICnopnueHT8" No 3, 4,3 (I902).
II. P.Ilenoist at al. 1loiutup No 1192, HIK~ACTUBj,11HN11 T1,; nltltet 110 BTOpyA urxAyneponllyu Holitle-
peHIIHIO n0 MHpNOMy 11aIlonh'OM Htia BTOMl1Ol1 JHCprHH (F(!IU'Ba119`,)f)').
12. G.A.Joanon, A.J.Goodjuhn and N.F.Winker. Nucl.:3ci.ancl L'ng., 1j, 171 (1062).
I3. 8.I'.j~iAbicH11, B.I1.r:1TaJ111H8, A'rOM11a11 'HCpiHH, 10, 5 (1961).
14. 1{,CHttrB4, J1.Koxapa. Tpyian Il?- ;poll MJJ1yuapoAno8 KoH~,~eponu;iM no urapHu'4y Hc,110 3on8HHq
OTOMHCP eiieprHH. X.OHOBa, 1)58 P. H3dpalIHIJe A01MJJpl HHOCTplIlIIJx yvr,lyx, T.2,
ATOM'',13113T, MOCI1BO, 195?).
15. ]1, :.XbK7AzC, P.b.ulBepit. ATni1C 1109TPOIIIIUX CO4o11H11. HfAUHHe BTO9OC. ATn-4113AAT, Mo(:I(Bo, 1959.
16. )(.b3. IiCt{1'pow1NO HCCJio onOHHH Ha HAepHk1X I(OTnOX, CTp.I6I. l13A.HHO(,'TpoIIH0 n1lTOpoTypu,
!,iocic1. n, 1954.
17. H.Itie#, Nucl. "ci.and Eng., 10, 83 (1961).
18. J.S.Marion, J.S.Lovin and L.Cranborg Fhye.Rev., 114,(1959) p.1584.
19. G.J.Ficaher,I'hye. Rev. 108, 99 (1957).
20. J.R.Beysher, R.L.Henlcol, R.A.Noblee and J.M.Kiuter. Phys.Rev., ,je, 1;'16 (195x5),
21. U.f'.;syOOB, H.C.llcoo)teB, B.M.Mopo3. CGopHHK "1Ie8TponHan 41318HH8" 1OC8TOUHBnnT, I..196I.
22, W,r. Rccll, M. Mo:Gregov and R. Booth. 19tye.ltev., 110, 1392 (1958).
23. P.11..;te1 on and E.C.Campbeil, Phya.Rcv., 106, 1252 (1957)-
24. M,E.Fiar,tat and F.L.Ribe. 22, 80 (1953).
2i. R.Nuso aid T.W.Bonner. Nucl.Phys.,U, 122 (1961).
2.5 {,Iilart.ipo. MnTepnantJ KOMNCCHH no OTOMHOH allapCNR CILIA. 8nrpirue petfTOI'I4,
27. K.C.Xines and J.R.Pollard, Journ.of Nucl.Energy, Part A-B, 16, 7 (1962)
28. P.G.Alino, F.E.Novu.k and B.Wolfo. Nucl.Sci.and Eng., Z, N? 4, betters (196)).
29. A,I{,Kpocon, F. P.7(yy6ovcio;R, M.I1.IolutoB, 1).10.Pnaoicon P. l(,I'oH4alvn, A.P.I(au.ioe,
B.7, B. B.BOFHnOB, P.8.HHIOTHH, A.f1.Coll 4C111c00. i' f~UXAyll3po }i0ll 1(0111K'j'Ci33031 nO HcHnnh3r?,,.,
111A 7Toi.o;oll oirnprHH B MHpnw.x ItenAx,(I AC1ione ( ). IlOxnan 2I46.
3620., -7-
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1.46 (In)
0.3 (Pu)
0.178 (Cd)
0.0976 (8m)
Transfer length.
.4.z
cm
Diffusion timee a
maec
Abaorptim
cross section etc at
2200 m/aeo
Value of d and aver.igod ovo.r the
Mazwellian spectrum at the nuutrun temperature T. = 390'K
262411
(1.24.013)? 105
(3.61110.20-105
21.8{1.0
1.50+0.01 6
3.82-0.017
174,16
(1.56?0.01)-105
(4.12-0.27)'105
X9.9?1.0
1.88-0.020
5.75-'0.020
c n c+a s on.
= 0.1 FL
7.2
7.5?1
9.3
9.5?1
15.7
17.5?1
19.2
26;2
20.4
4013
26.3
5143
27.6
73?5
34.8
6815
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4a, 1.0396
4.b 0.9447
5a 1.0431
5b 0.9503
6a 1.0420
6b 0.9508
37.9
48.4
34.7
4N4. 6
34.3
45.3
28.9
36.5
25.8
32.5
23.9
30.0
9.5?1 9,211 .5
27?2 103.4'1.9
5113 112.1'2.1
6914 ) 117.7`'.4
122.5'2.9
40.4 4.8 5.46 0.1016
37.5 5.02 5.86 0.0997
36.5
6.10
6.66
0.0971
31.5
2.78
3.31
0.0949
28.4
2.79
3.36
0.0928
26.2
2.85
3.42
0.0912
Approv
2MeV-1.46eY
2 VeV - 0.3 eV
2 MeV -0.178eV
2 Me! - 0.13 eV
514?)
40?3
'17.5?1
2 MeY - 0.0976 eV 73?5
2 Met - (0.07-0.045)eV
(0.07-0.045) - 0.05 eV
135
185?20
?) It is calculated using the obtained values of
the energy range 0.3 - 0.0976 ev.
Re3zp Mcal
an kg
Calculation results of Raff' oriticai s:zee,
critical maswjes and fast effect on Be
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3 2 .1 4 5 0 789IU 2 l 5 67D9'U 2 J r 5 67897'
10" _ 3 4 5 679910'' E ,,
Fig.1. Total cross section 6~ for the BeO samples of various
crystal grain sizes; sample 1 (o): grain sizes = 4-23u. , ave-
rage size = 8p , advantageous sizes = 10-15,i L 7 2(.V,):
sizes = 9-60.,R,, average one 29,u. , advantageous one = 4Q,cc. ;
3 (?) : sizes = 5-37,u- , average one = 13 p- , advantageous
ones = 10-20,u. ; 4 (x) : sizes are large than ones of I and
are less than ones of 3, average size = 14,Y_ .
12 I
10' 10? 10' f;
Fig.2. Total cross section for samples I and 2 produced by
extrusion (a) and pressing (b). The incident neutron beam is
parallel ,) and is normal to direction of extrusion and of
pres .ng (x). The partial cross sections for the reflection
from the plane (110) (see the insert) differ by 20-25?ro. The
solid line representsthe value of 6S calculated with the
assumption oz absence of the extinction and the account of
only elastic scattering.
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6, du PH
ao
o E opai,6 so cer scar.
3 4 5679910'
5,. ?
Fig* 4.l Total cross section for BeO vs temperature, and
C6 )' are averaged over the Maxw llian spectrum for neut-
_on temperature Tn = T + 1OO0KO
362 ti- - 11 -
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 Fig-5. Damping coefficient vs B2 for Be (a) and BeO(b).
The dots are the measurement results, the solid line
corresponds to parabola (see Eq. (1) and Table II).
Fig.6. Neutron density damping in Be block of 2O3cm3.
1 12 , 3 are various powers of a neutron source; 4-with
the large background level. The dotted line represents
the background plus the effect, the solid lines are ob-
tained after the substraction of the backgro-,=~I.
362 c..
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 Fig.7. Moderation density at; E = 1.46 eV for BeO in various
coordinates
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fl ,ann. eD.
17,75 27,75 37,75 47,75 57,75 67,75 77,7f
r, c..
W
Fig.8. Measurement results with Pu-chamber: (1) flux of 0.3 ev
neutrons 41(2) contribution of higher resonances;
(3) therma eutron flux Q ; (4) moderation density z at -
E = 0.3 ev. I - relative lit, II-g, cm
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 Approved For Release 2009/08/26: CIA-RDP88-00904R000100110005-4
Fig.9. Comparison of the slowing-
down densities at 0.3 ev(o) and
1.46 ev(s ).The solid and dotted
lines correspond the synthetic
nuclei of type (2) at E =0.3 ev
and 1.46 ev.
Fig.11. Expexiiental energy-time
distribution of slowing-down neut-
rons at E =0.3 ev in comparison
with the theoretical one. ~6 -ex-
periment for Be and BeO. The solid
and dotted lines correspond to voi s-
son distribution: N 8e `_ 42e -
a)
3
Fig.10. Measurement results of the
slowing-down time. 1,2 are the de-
tector counting rates N(t) of 0.3ev
neutrons in blocks of Be and BeO,
respectively; the inverse transmis-
sion l-4(:) of Cd(3,4),Sm (5 6) and
In(7,8) filters in Be and Be().
Fig. 12.Bxperimental arrangement
for studying of transmission thro-
ugh boron. 1-neutron collimator
with Cd and ByC; 2,3--filters; 4-
moderator block; 5-collimator sup-
port; 6-collimator holes; 7-BF -
counter; 8-shield of counters.3
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 Approved For Release 2009/08/26: CIA-RDP88-00904R000100110005-4
Pig.13. Trssion of boron filters for the Be block
60 cm ; I-filter 0.012 g/cm ; 2-filter 0.023 g/cx2;
-various measurement series.
Fig.14.Transaission of boron fl-
ters for Be0 block 70x8ax75 cat
I-transmission; II ,L1 sec.
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 Approved For Release 2009/08/26: CIA-RDP88-00904R000100110005-4
Fig.16. Ir tegral counting rate N vs -
the average neutron energy lossaE:
1 - Be layer; 2 - graphite layer;
3 - K Be N (e ) /Nc CA E ); 4 -gBe
with correction of hole effect in
spheres for the transmission of
neutron beam
Fig.17. Effect ofiE calculation
inaccuracy upon .Be. The calcu-
lation variants : 1 -with utiliza-
tion of cross-sections on 15% as
large in comparison with the
data r"15J; 2 - with utilization
of crow-sections,15; 3 - gBe
with the account of neutron ab-
sorption in a wood Sphere;
4 - with an assumption that6..,.,=c6
1 - Beryllium ]layer thickness',,
g/cm
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