Title Page
 Table of Contents
 List of Tables
 List of Figures
 Description of the problem
 Measurement of neutron spectra
 Description of apparatus
 Results of integral spectrum...
 Results of differential spectrum...
 Results, conclusions and recom...
 Biographical sketch

Title: Neutron spectrum measurements in heterogeneous media
Full Citation
Permanent Link: http://ufdc.ufl.edu/UF00097943/00001
 Material Information
Title: Neutron spectrum measurements in heterogeneous media
Physical Description: xii, 132 leaves : illus. ; 28 cm.
Language: English
Creator: Salah, Sagid, 1932-
Publication Date: 1964
Copyright Date: 1964
Subject: Neutrons -- Spectra   ( lcsh )
Neutrons -- Measurement   ( lcsh )
Nuclear Engineering Sciences thesis Ph. D   ( lcsh )
Dissertations, Academic -- Nuclear Engineering Sciences -- UF   ( lcsh )
Genre: bibliography   ( marcgt )
non-fiction   ( marcgt )
Thesis: Thesis - University of Florida.
Bibliography: Bibliography: leaves 127-131.
Additional Physical Form: Also available on World Wide Web
General Note: Manuscript copy.
General Note: Vita.
 Record Information
Bibliographic ID: UF00097943
Volume ID: VID00001
Source Institution: University of Florida
Holding Location: University of Florida
Rights Management: All rights reserved by the source institution and holding location.
Resource Identifier: alephbibnum - 000565757
oclc - 13579150
notis - ACZ2176


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Table of Contents
    Title Page
        Page i
        Page ii
        Page iii
    Table of Contents
        Page iv
    List of Tables
        Page v
    List of Figures
        Page vi
        Page vii
        Page viii
        Page ix
        Page x
        Page xi
        Page xii
    Description of the problem
        Page 1
        Page 2
    Measurement of neutron spectra
        Page 3
        Page 4
        Page 5
        Page 6
        Page 7
        Page 8
        Page 9
        Page 10
        Page 11
        Page 12
        Page 13
        Page 14
        Page 15
        Page 16
        Page 17
        Page 18
        Page 19
        Page 20
        Page 21
        Page 22
        Page 23
        Page 24
        Page 25
        Page 26
        Page 27
        Page 28
    Description of apparatus
        Page 29
        Page 30
        Page 31
        Page 32
        Page 33
        Page 34
        Page 35
        Page 36
        Page 37
        Page 38
        Page 39
        Page 40
        Page 41
        Page 42
        Page 43
        Page 44
        Page 45
        Page 46
    Results of integral spectrum measurements
        Page 47
        Page 48
        Page 49
        Page 50
        Page 51
        Page 52
        Page 53
        Page 54
        Page 55
        Page 56
        Page 57
        Page 58
        Page 59
        Page 60
        Page 61
        Page 62
        Page 63
        Page 64
        Page 65
        Page 66
        Page 67
        Page 68
        Page 69
        Page 70
        Page 71
        Page 72
        Page 73
        Page 74
        Page 75
        Page 76
        Page 77
        Page 78
        Page 79
        Page 80
        Page 81
        Page 82
        Page 83
        Page 84
        Page 85
        Page 86
        Page 87
        Page 88
        Page 89
    Results of differential spectrum measurements
        Page 90
        Page 91
        Page 92
        Page 93
        Page 94
        Page 95
        Page 96
        Page 97
        Page 98
        Page 99
        Page 100
        Page 101
        Page 102
        Page 103
        Page 104
        Page 105
        Page 106
    Results, conclusions and recommendations
        Page 107
        Page 108
        Page 109
        Page 110
        Page 111
        Page 112
        Page 113
        Page 114
        Page 115
        Page 116
        Page 117
        Page 118
        Page 119
        Page 120
        Page 121
        Page 122
        Page 123
        Page 124
        Page 125
        Page 126
        Page 127
        Page 128
        Page 129
        Page 130
        Page 131
    Biographical sketch
        Page 132
        Page 133
        Page 134
Full Text







December, 1964

.,.Kr 'Jli'LElr'1Eh T3

i;,e a lthror would l il e t;, tha.- r;i i? per'i'-,sr

c:r-mittec, .pF.e:-l liv n- i' th-eri. supcr.'ii.r, lr. T. F.

Pi krirn-cr fl'or ra-i.; pat iernc, ad.'..c .i,.E ecai oura,emer.t

Jurinr, tlh c',urs: :.f the 4orl':. le 4OUI C l j al s. likae TO

c:rnvie h i1 gratitr u e t.5 .r. '1. F,. l'alton, mener r or

his 5upervi ;or,. :Cormi tte, ifr iil itn. arra-ngrmentr Itr,

Dr. 'J. ,ric_ rief o f I' ai Ridg ':arso,ar La.:Cra or',',

to V's tr the Lab..ratory ur. eCr "." pF ri.:iFpati:.n c:-n:r .ac

in order to consult .itr r tr.c e there .r-on r:,- u.3 i ,an.

cori;truct inr of tre ir.ur Erci ai f rac:i:r sp 'ctr.areter.

P-se autlh r roul 1 also li've r; .'pri3 ;-i.; cratsi-

tude to ir E. O. llan .f ia Page .A dtiorna Lar.c:r-

to.', for ris relpfij c ugge ti.n:r, and de .ron;.Lrrat :r o

rhe ope-rari: r, rl-of t a,. Piag cr.,';t-l ;-pe trometer.

Also, tre a 1 i r joul. 11i' to a :ri'.'c ,iiny tier.. tor

L'r. L. ail -.r of Brokha '.'lrti oral Lab:.ractor,, for

ris.- r ilpfaui uggest i rOn an. for sending telue print; fr

tr -C ,onstrucricn o.f tne collimator anr to Dr. '.1 J.

rrtur o*f the Irnternat onal Institute ofr 'jucl'ar 7.:i nrcc

ard Eng;ineerin., at Arianr.e Jat;ionai Latc.ratory,' for seriair.,

omea drarinaps of tre cr-,ri al spectrore:er with a cop,. of

the e'xerimrntal 'Jr!ite-up.

The aij of Dr. L. E. 'rri ter, Dean :.' Tr. Gra uate

-r.iol. l.n ,r.'e:ro t, o r Fioriao a r.j ,r. io .- rt E. lnri r1 ,

tn S i comiiL t tee ei r e an Ile. ia f Ti :'e .-epartmcar.t -.f

u: lear [ri rin e rirg,: for :* tair. r.g the r.-':e ; ;ar, f r.in s

.itr l wrcr, to -.ur':a? th'e 'mair ger arinc s iSte-n f the*

;E.:tro,-M Cere w'ia- .,er m cr a ; ira e reic a= .

Ais, .u:n ;r rit tJle ji idue [Dr. F. E. ..irnarl a;a

or J.lI, F'. Lrur-h of J a For.t ae IlenouJr' Irnc.

-aariran Piver LaLt:rator,', Ai-en, _otn Ciirolina for

imalkini the TIHEPrI : ca i"cjiat' ir. for tr.e eometrie. ise

LI-. t6 -Lcriticai riaCtir.

Tre eaitnor 4-'JlJ i1de t.o 'ar.a cr.,e D i.'s;or oft

a,1 ..1Cl r i II3at:i ari TtrairsnFin LU. .A. .- 'aslirctor,

D. c. for tre !,ar3 r:f t ri natural 'raniiYii sl.i 3 an I

b 0.r Aiso, r. 'woil lik .e to cori -,' tis gratiCtilde to

re Laarran F .'ver 'Cpe'ratt iriE ,: iffi:e, IJ. A. E. Aif err,

*i.tr, ar iina f:r the loar. of natural *rariji' sev;,?rnt r .

Tne arnthr ii jeepiv. ir*n c. tce to. Mr. L. D.

E u t erCr i id F,. actor .'upe r'.'isor, ari lr t. L. T'-w-.Cet.

for pat icrt ly rnr .r.r, thne irT marn' tinmea afrer norm-al

wcork:ir ric.ur:; to Mr. .;. w. rogie f)r ni nelp iin rne

ornstrujtriorn of tri tcnpcrature ccrtrol JInit; to Mr.

F. A. Primo and t'r. rl. H. loos anr mair, o.tners for the

C:-ri t ruction of apparatia .

Finally.', thr' autrn-r wouii ii, e to express r1is

sircer gracit;tul e ,j to fisi arara 3'.'l.a for nr sugg sionsr

ar. r, lp irn utting inro fi f ilorm in and vpirg this rhesis.


.: ,ll ril JL E,'El :ilT . . . . . . . . . i

LI T -F T LL . . . . . . .

LIu T ..r F FE . . . . . . . . .

AB .TT.CT ................ ..... .

i. LCE : FTiTi- [i :F TMH Fr- bLEL- . . . .

iI. 'IfE. UF r !Mr;T Er iCilTPC i -P CTP.RA . . .

III. Ej: 1''l 0iiAl ,0 1 At'F.i Tu . . .. . . ;:

I'.'. FELJLT: ",*F I rTLJft-.L FCi:';, .'TFT
MLA.LIFErII.IT . ... . ........ .

PEt LT' .:.F C. ITFr EPCI TI L :E; T; RU'1
M1A i- i PL rL:JT . . . . . . ... '. -

'I. PLE I.LT :, "* rJ iiL .i-i 'I .N 11' t C:.: l' lll 'TI l_. L,

A. EITH'):,D OF CAL-.ILATI'-, t ,1 ""' . . 1 1

p. T LH TIHERilM. C,'DE, . . . . . . .

TH F:E iPR F' CAL LATTIi E .. ..... L

D,. PlC.: 'O T CALCULATI'I-'li . . . . .. .

E. PF ':'P f.L T': U'L L UFT' .A ;:i.iIF E _Fl'R
THE ,IECFITI'AL A.-.EI L' ..... . . .... .1

LI T Or FEVEFE.IICL'. . . . . ... . . .

ii :'i' A HI .EPTCI.L : l . .. . . . . .

I. 1 : T T'.- P,. ELL

T I: ra- f' n-r

'.1 r,.r'.a :rer ri tL: .? : r .' .t ti r
I-._t ._ .r . . . . . . 1

S. T l f : .-r" f r 'iffer-,;

S.. rr I w 1 1 t a E .It . .'

,r a l F .. . . . . . . i
' _, r L 1 e--. r I -. . . . . . . . :
'.. oi :. -a',, i =' ,r r: F :.r u rF aJ.r
L .i1" 1 ..-:.-orr-cr l -.t ir;ei . . '

.. Lu ,N',d L, ."r,, z.h : ., a T . .r
En er y -- I1 .7. .. I-

-. : i;.r 3il 3 A.:ti .'L Ci 3 tII I i -i' '
S:, l t i r, . .. . . . . . 1'

.' A 1' ,"T fadn, in A4.u- aou' -: ut i .- ;.',

... hFati: .r tr,_ At '' I AL- rer in 1:, R'm.
L.i' Liter . . . . . -. . ''r

-.' 3.t.: I',' ti .:.r, Fa-' tait r s f- : r ui.FTF ,:'r_ . ,''

:. .1 :.-,l:-ar n1 :f tr, e :lIri e t- E. ff-.:c .'-
'i-u r.,':r, T_ -LrFstlr r. a Jr, t L.:ili . 11.

.1 [r _-r '.' 'r,, fc, r I, 'I- .. C:.al:u t 'r "i ir

FLirre ase

:'.1 :,crtvi ti r, ,'ria ,ecr i.n:-n . . . . .

S a it-rat '. :ur. e -r . . . 12

p. r, of Fiflectr l . . . . .

1.1 "in g C i'r atr t . . . . i

3.1 : : .f Eff ect i.m ure . . . 31

3. biffra.ct:.or. e.:trcme-nr r in C[ r. aticr . j3

S3. DI.tc t.r .rm .- trn l cc.nJ c.llin- tor . .

3 .'. T Lle.ati r. . . .. .. . . . :

3. Top .' of t :e iit-:riti l Latr ic . u

.'" "i i:, ,f tr i r'- r ar tor .r.,. . . . :

.1 rilj' ir.jn F 2 *,,1 i 1 in. t 1 r. i ;:
r 'i . . . . . . . I.i

4L. Lu Tr .erz; i Tnrrcugh I.i- aI . . .

4. I /.1 'Can i t. tal .-te:t: r i il) r . . .

4. 'l "ormal :-. Ll, tm ,.: i t it e in .i "it
Fill- n ith j', c I M -: i2 Ir I :. o luticnr z . .

U.5 IJ)lrna lL eJ Lu'1 A.: tr t ie r AlI :ar-
FilleJ 'I tlh Aj :.u L,1:' .Oliuticn: . :

N.i'. h:-rmaiz-d l i r i rziteI ir. Al an
Fi l ,: i th A iue. !' E olut .n . .

." cr,-,a i ze J s : n lPr J'j:t .A:Mi 'iti .es
in Al C: r. 11Fil 3 ith .' P ec - C0
i uti n: 1 . . . . . . . .

Li r ,F FIr: ..1PE'

LIST OF FIGURES (continued)

Figure Page

4.8 Lu177/Lu176m Ratios in B203 Solutions . 62

4.9 Comparison of Normalized THERMOS Flux . 63

'. in Fr;. t ;.on o.f :.:tl .'tin: DO -t tors in
J.rT R ,:or . . . . . .. .. . t

.i- Tr '. r; s T rI .I,,in li FT i r '-.re . . . .

'<.1 u HC:ti. i t.' Li ;trr uti.:ri frr Marl.. '.-
Natural 'I F u.i Ui rn 1l.' c ti . .

i.' Lu Ac., ' Lie r t -r.ji.:rl for 'iar 'l-
jd At .r a 1-1 Ftu w r i ~ : i rt:. . . .

4.1" Pu Act c .' 'i St .i,'i: n for Mir, '-

I: tur i 1 Fu : .i: .:~ Fit . . .

'.1': u r i .i. Li.trat.u ".ri f.r r' r I arV-
ca r .-- '. t jrs i I Fu Fitr cu. cm. . r. .

-4. Lu ,Cti .'it L' itri ut i -r f r I i'r' I ar
r' r1 '.-I l3t.,jral F.ai il . in ~- : r.1 .

,-, i ,Lu ,:, i .' t 'L1,= trit-,t i' nr, f r r'.ar i ar l
'. i i. fuel .' r I ; i: r t r .i :.. . . .
ili.2 rk lo 'f -i l r'. -'. It . lit

'i.ir .u F: rom rt-ir r .:r-i r r, r rl. r' I an ral
,4.2' Ai F'il r I.. a I .I i ir

I.I *j Ir. .:I-; Fa *C.: ... .... .. . ......... .-.

F.. 'lot of A Al e", r .'T T ar. ':1 utF.
LDi ; t ar*-*. Fr- rTi L r.-r 'a l rirF in I ari
riar'. .- lat urai 1.1 Fuel .*i th I c. f ctcr. A4

Di 5 ar.:- Froi, C,.'er, r I.ii f r.* liar' I arl
'art. ''-b 'laturai '. Fu- 1 Jitri. c: m 'il :r, t

LI7T OF FrIGuPEE j t conrtire.j

figure Pa.e

4. 4 A* ial Cli; tribj tio.n of rlux in tr.e
T, o Foot Tank T.l=in Ha lrk I and MarP .-E
!litural IU F el i wi cr. Pi irch . . 8

.2': ai'i al Di ribujtior of Flux in rn-. T .:
Foot T i. using ar.k -R l:Iat.ral
Fuel lth r, cm Pirt n . . . . . '

.2E 4 l ['1ii rlri ,uti of Flux in tn, Tiwo
Foot a-nir r.1n= ri,ark V.-l a t.,ral '.1
Fuel Jirn i 4. cm Pit. . . .. .

?' A'ial ['istriC.'utior of Flux in. tre-
TwD FT.oot .an:. Using irt .. . . .

5.1 rletrin of Alignm-ienr of tr, Diffraction
-pqetrormeter . . . . . . .

2. Po:kin C.~rv. of :.'1 'i ( 20.I . . . .

5. Po: ing 'tar e f LiF (111 . . . .

.4 'Fein Beam li-lurron p.e rjrin From i Cenrter
of FTR Core Usinr I.iF ( 111) ,.r,'tal . *'

5.5 Pati -f Hax,. 11 ran iist riljt ion an i
t-.e ExpFerTrimntal pe.trtct l, at To
Di ffercnt Teri;eratuires . . . ... 10

i.E Experi rencta and THELF.lr-I I"pe :t a sirn;
lark .,'- Natural u Fuel itro 2 .cm, PiN r, 10.3

.' Lxpcrimen:tal ani T1"HrF.'OR r:ectra Usiriv
llarn. I and. Mark V-B Natural 1Il Fuel
With 22 :1m Pir c . . . . . .. . ..i4

x ExpF.rimen ical an, THEPI M': M peccr.a Lusi .i
Mark '.'-r natural 1- Fuel Witt j .' .:mi Pt:n l.jn

Experimrnta anrid :rrec:a.d THEPrIOL ;e :cra
l.'sing ilark I in3 larlk '/-5 sltural 1 Fuel
'i r. :: :r Pitcn . . . . . .. i

.i Unit Call -_ a Lat .:t c . . . . . 11ie

'.'I 1

Abstract of Dissertation Presented to the Graduate Council
in Partial Fulfillment of the Requirements for the
Degree of Doctor of Philosophy



Sagid Salah

December, 1964

Chairman: Dr. Thomas F. Parkinson
Major Department: Nuclear Engineering

In this investigation neutron spectra were

measured both integrally and differentially and then

compared with theoretical calculations. Measurements

were made in highly absorbing media in the University

of Florida Training Reactor (UFTR) thermal column, in

the UFTR core and in the subcritical assembly sitting on

top of the graphite pedestal of the UFTR. The subcritical

assembly contained some typical D20-moderated natural

uranium lattices.

Precise knowledge of the neutron spectrum in a

heterogeneous medium makes it possible to optimize the

neutron economy. This is true because fuel elements in

a reactor have varying cross sections for different energy

neutrons. By proper choice of the fuel-to-moderator ratio

and t geometry an.J composition of fuel clements, optimum

,'ie of nrciutror9 can !e attained for maximum, fuel burn-up

.,ti-t trie .a- ine t cncr.'er;iio ratio.

In tre trer-n.l column of t e ..F'TP, rernmal neutron

spectra were neasurej integraiiv usinr activation letectora

.sucl as AP.17, L'1 Lu1 Lu16 and P. i The detectors

Lil?' enJ P, ". 9 rnave icw-l ingr atvs:rption resonances,

anereas Au1 ard Lul n rave a l:v ac-sorprirn, cr.'s:- section

for neutron cr-loa L.'1 e.'. fin: dO te ccor .r, sh ar.

abstrp ion cr3os 3 _:tlon trat i steeper tnan i v. Te-,

mrcuarimenr jr ir mi d' in a atainl-ss steel rod, a n turai

uraniuri ;lat arn, in an 'i1 cr.n fiiild l it', c.orated water

and results -re inrt rpre tei u irs'iin,; J tcctC' forri ilat .rr.

In a nat rural urarniurm slar. the effective neutron

temperature cnanr,- frcn teai center to me o, uts e Doojrar;

of -he siat was or-tair.nd mv meIjsurir. the .jci'itv ratio-

of Lu1"6 ard u1 '. In stainless Teell rd, tr,?e -'r-spel al

-effect i'e neutror trmperarure crane waI mea-Icaudr-3 Uiinge

Pu' and Lu5T activaticn detectors aria trner, re rartos

of activitieE to trn- ic:l t.'iTi of 1 a ar.sorr-rc -je-re


The i T's t,'p of mEsasureTenTss i4re mrad:e in ar Al

can filled with different concern rat or. r '. Tnrse

results were crompares witr TIILPHE'. caiculations3 r,noever,

due to the ari i tr :, orf trh e < ir.i-,ni. our:- :nr t .ns=,

agreement was poor.

The effective neutron tempe ratur- arni tre epitr.rmal

index, rVT/To, were measured t. ..3inr activati:rion etectorc

in the UFTR core between the rtw fu.1 b*ox- in tre Nortr-

South center line. The result of tr,- effrcti'.e neutron

temperature measurement was cnr.parer l iitr. tne oC'en-Dam

differential spectrum and fou-a to in g o:-. a;rement.

A crystal diffraction 3pectromretr for differ.rnteia

spectrum measurements in the .j?:rtl:i:.i asemDrl/ wbs. dued.

For these measurements, the total fficien:, ci nce raariine

for different Bragg's angle wa3 firsr octine. t.' taKirn a

neutron beam with known spectrum o fut of the abt.:rLt-i:l

tank. The tank, 24 in, in diameter anr 66 in. lonc, was

filled with D20 and rested on to; of tne irsprit. pezscital

of the UFTR. The neutron spe:trr.. out of tri .cie lim Jas

measured at two different temp~;rtur . re ratio: of ter

two spectra were plotted with the ratioe :.f tn :aic'iatiiorn

and found to be in good agreement.

The neutron spectrum oat of the .-t.:ritrcal a;embtly

was measured for two different laric-e pI'c.e;; u3ing MarP i

and Mark V-B natural U fuel elementrs irn -. A neutron .-te

was extracted from the cell boundar/ anr from tre center of

the cell for each of the three iatt:ic arrangement. The

results were compared with the trne:retl:aJ spe:tra :alc.latec

with tre THEPRH13 code and founl to be in excellentt agreement.

irtegral measr r mert rere alc'-. i:ma inr trie ur-
tial 17 a A e ex
critical s;Ln cr1i a ru e rdetctrI. r ine experimental

.ictivation measLre-Serits were compared 'Jitn tre THiEPHi'.

calculations and 'ere also four.i to Lb ir, excellernt

agre cc nt .

Finaii, tihe cffecti'.'e neutron temperature charge

in a unit cell for four U-D.O lattice arrangements wer-

r.easurej differentiall-. ani integrall' and comrare.3 w.tr

nhe tneoreti.cal calculations. ine results ,ere in goo.j



LL.:.hIF[ I [ OJ; F Ti FFj. LEML

iJ -tror s;ictruT iT, .a iu -.r, c 'i. ero,-ne-js

n- i 3i ar. importare c fcr a ral ri It :rns: i' fior

S., a udt iari .,rf trr u tifrIal ut l :atic n factor f ar.1

rr1e r- err, a i r ro-Juj t io fa:toz r,; for ti-.- :al-

c'lirt on f r j :.aC. r f'u.l :.: le i ; (.? f cr -o' .ar i-i.:r.

.-iftlI', ,uLt L arou;- : i .u at or, of rn rneutror, ;.ec r urm;

ar.a ( '' r F r' tr. gre.ji:t. i n o f 3I-- :e rat : in a .iipL ,

rin .3:i nr c. tc-r ni rn eutra-r c r rgy i; r ric:.jE i.

Fr~r ;- ir : nc. lc 1ej cf trni rne4tron -;ectr'um itn

a .er',rc-g r-.-.; re iuh- .iI- mi- it r- iir.i c. tI Oitimiz-E

tie rn~utrc.r. c: r:.mT,. I'ris i.- tr'Ijc Li7c d jais, fue l

-.lereint it n r a recta or r.avy '.'-ryvtrg ro. ; t c or,.r for

ttfftrinr enr rg' ni--utrorn;. '3 i propF.r ic-r:.a of tne

fu.? -t--i o .-i o3ratior rat ic arna tirc geometr.,, arna ccuipo: L -

fr. cf f-1 tCene-rt, opticu- aE- of n:uEtroras caJr

,t: iLadnr,c for m.axuimm fu -uel aur r-up ai rni r.Lgi i Cl:

ccOne'Tra;i-r rat ic. Iri mry .ae e nc, ci-ntrroi ing tih

i1kdagi pe':tr4m, frTc a a : dtcr core to i 3 air-l forn'.,

tir, Taoxiiurr, coJon- ri ionr ratio in true j.lar.i -t riaterial

rill be realized. T : fol.lowi becajie 1i.3 anj In i32

w~,icn are tr.e usual fhrt ile oiarnet material for nuclear

reacrors, r.ave r rir. resonarnces for ncirrc.r *:apturc ar

3.d ev ari. 2'-2 ev, re pectiv-1y,. in oraer to pre-

dicrt tre ;~acia i and siecrral di- ribution of neutrons

trenorericaily, trie bera.v.ior 3f reutr-nsr in the rneter.-

gen-eous m~iia miust t-e wull understood.

ir. Tri i inve t, igation, the neutron spectrum -wa;

neasurIed torr integrally (1) an a ifieretntially ( and

trier :o.iipared wirrn rre:re iL.:al calcuiartions (3 S, i .

Meas remni iii -''ere carried our in a hiigr.ly

ab;orling iMela.un i1 the rUniv.'rsit ,' of Fiorida iTrininc

Paicor uL'TR) rnermal column, ir the 'rTR :ore, anr it

the iub:zri tiial asse.erLly sitting orn tp o. trne ;-.rapir

p-Jesrai of ri. UFTR. Ti;e ub:rritcal a;sermbi con-

sairi.. oe typical [.,3-moaerated natural uranium


Uirnerlirneo nruirers in parentnesI s refer c. o he List
of Reference;.

':APTLE ii

-A !t. L I OLIiT ':F F "IL 'JT P]"':j I "E ,'T F..

rIt r: :2jCt .: ri

Ai- early at i- i, rI:utri:r. iit ffri:t ~on .

:r,'at ii e r At. ri r al a su 3gg. t L,-] L i- ia -er 1.L

ain experimTirii : a ily ir I on r. ra t- Lit I, iL L r, rini Preiu erK k7)

anJ i., itc li anr] .' -ers ( :. Ui -ing F.a-b e sour:, s,

triee experi r ltnt pr-.? triear r,-ijcroria .-ij r ie i fra cc ,

L it tn-y --re : no r 1-ac r ,- l to or t rain rU r.:-crir-7mdt :

rineutr.i-i: -u-ie r: .r, -r nirie:: ,.r tr,- 3ou'rc. -.

nO. r aft- the -'..-?lopm- r ir tr e .-uc 'iear rcact:.r,

rniutrori i -ere, 3,. 1 i c. li in great qiUanr i anrd ri-u ror,

1iffraccion -pe:r*: r;.- errs -ere DuLi at Arg-rinre (i, 1 .,

i'a' F.1 lg- i ', CraiK -.1'.er, *'ara.aia j ar-ell,

rngiarn (ii) ar.i i-- r-e. .1c' at. r Me t r-, t It.

:f-f ig ~: E TCrn ii' d a- re aevelopel ( 'l, L). ArOaut tr e

Sii -. vT rr;crc ri i et.cnOs cif reutro n nFI:trum dr al, 1i

-Ir iiCrlc-ti Cmy d' Jm C (r i* Cdm C L- 1 e-r al. I

ari ii I gnii ara T rrn cli ffe (18). 1 r :e (ii) and 13 e i 20

.a l co- 'ru 3 li tgr.t ri. tri- uu jcz ct.

An earl:" theoretical treatment of the spectral

nardening ess carried our n:, Plass (ii), .ho assumed

neutrons of eacr energy diffused independently without

energy interchange. Later models were develop..p to

calculate neutron -pectra cy the u e of free nyfrogen

arnd found hbydro,=n scattering kernel (2., -3).

One of the better me.ho's for calculating the

Pace and energy dependent flux in a unit cell was

developed tb HonecK (.4, ?i) for rH0 and D0-,TOioerated

syvsems; it is described in Apperdix II. Re-ently

at tAPL, GolIman (C.) constru-ted a scattering la-

based on Nelvin'- model, and agreement ith trhe

experimental results using iZI.> is excellent. At

General Atomics, Younr (27) has measured neutron spectra

using a pulse nign-currenr electron linear accelerator

in H C', C:I and C 6H6 mocerators poisoned with B, Sm, Er

Cd and also D.0 (28). Heasurea spectra were compared

with DSE (5) transport-tneory caicilations utilizing

the Dound hydrogen scattering model for water. Earlier,

Beyster (2') measure neutron spectra in pure and

poisoned H,O, iH2.n, and ZrH using the pulsing technique

and compared it with jS'l calculations.

litigrai 11ltnoa

ini r,- 3" -ur -i. lr.t of ri cutcrcr. rit. rh -, E:rt u11 nir

L.a im-c- :)f- f itt tec'.:rIn .Ie r a crystal ;i ;pec ror m ze er

rju.irs tr,'e e xtra:ti ior of a re.-'ucr .-.rI ru iam ro

recat: r i ti: icn i s i ifficu l t t. -io for ,iore

an i fei. r.epr eertat i s posite ir.. h-c.ier rE;

u. Lri, ract i E icr, 3tec .ars, ;leDctru-i cr.iriges trirougriut

cr-i cI ii mi, IL. mUippiJ Out ( gooa-i ispd:i a

r s: luE icr c O ain J -itr. mirnimai c ii p rtur.at 1 :.ri)

Tr.e u:u1i ea.ri[ertai t crir..i ue rfor o-er. ing

tr e Spe- trat :_iarge ir. 3 urit c: il of a rLa:tcr ir.i .l

apping trne itivit/ rari; of r-sonan:- ani 1 .' crIos

-?cticn IJeector For triii type of mTesureUnCr- various;

y '-i of -'t c toru arI uLImmaar l in: ? ri T it* .1. Ir

iFigure :.1 ru- .:ros q e :.ic.nr of tre i aLs3oro.er Lu1

arin re rsc-rarince ac.iorter Lul i.6 ) 3are gaon. sis.

incl-uli -i in tne figure are tin croi ;n:cioni-l fcr aLi D

i j1) ar3.1 FP ( ). tli a l li a-r ne-.utronr i istr :.zi 0or

in tnie ttnrual r-aergr; rl gicrn i t i .r. average tEitmperaura-

of 2'ii. is i ro-n in -re Bar-e figure.

by ir crt ioin of figure 2.1, it is seen trl ,

as tr.e leaxeiiiar.n 3sritj;ion shift; to rnigrer energies,

tne riti1 of r? act.'ioties of L! ard Lu 7' will

increase 3ir; trIe r.acticr, rat- is prcportrionrai to tne

integral of tne in'utrr.r, flux times; tn iL.-sorpticn *ross

-iction ( i3)

.10 1-

Enerr.',, ev.

Figure 2.L. Activation Cross Sections






- I -.

Z I j


- '


r. c .-. .

44 -

'S Z 1 I

'2 -'

E L t i
L t
i r. r
'S I



-7 ..~





- ~ J


in well-moderated media with low absorption,

(e.g., D.l, H,1-, C, Be) far away from neutron sources

and t.ouar3aries, me spectrum approaches a Maxsellian

diitrirution witn the. average temperature corresponding

to the temperature of tne medium. 4ren these weil-

thermalized neutron eiter a nighly at.sorbirg medium

(e.g., a fuel element nwich nas a 1/v absorption cross

sectionn, lowei energy neutrons are preferEntially

absorbed, resulting in a gardeningg" of the energy,

spectrum within trh fuel.

ine activation results were interprecea ct

using rne WeEtcotr formulations t23). Trig r.erhod applied

to .aell-moderated sy'srer aucn as tri UF.i. In a reactor

;pectrum, effective cross 3;ctions are given as

3 = Jo (g*ras) (2..)


0 = effective cross -ection

o = cross section at v = 2200.1 ni/ec

r = relative intensity/ of the blowing
down spectrum (or epitnermal indes'

g,s functions of the neutron temperature, T

The values of g and a are tabulated (35) fcr various

nuclides. For 1iv absoruers g = 1 and s = '. Using

this notation, the CJ ratio for a very tnin detector

is gi-.en as:

g + rs
Red rs + -2-

K To (2.2)

where 1/K is approximately the density fraction of

epithermal neutrons transmitted by the Cd (34). The

factor 1/K varies with the thickness of the Cd filter

and is tabulated in the literature (34). For 1/v

absorbers g = 1 and equation (2.2) becomes

1 + rs
Rcd = ---
rs + (2.3
K (2.3:'

Rearranging this equation gives:

1 1
o s(To/T) (Rcd-1) + Rcd/K (2.')

T',ere fore, :',, usinr ver, thr n sr terctor i, t-e factor

r ca" r. Ieasljre .

ror *ear.acora wirr appreciac-le -"lf aesorprtL:r,

eiUacrion ( 12.) :e:orme, 3 l0

z, h e-
r i-- -
S (FP -li ) r I. -R )
-,1 C'e.I ( ,.

Gth :rhnermal reutror self nshiel-irm factor,

r = resonance self snieldir,, factor,

F Cj transmission for resonance flux,

,i = fraction of resonance acti.artion belo,
Co cutoff,

h = thermal transmisr.ion of Cd filter.

In order to measure the effective temperature

of the tnermal rneurons, the activity ratio: of Lul17

and Lui 'm were measured. ihe activity ratios of tnaee

isotopes at position x wlth respect to a standard

position a is expressed as

[A17 ( r. )176 '

J L(q + rsil7 1 '.

[AImj [(g ),

SEquation (C.6' i? for ver; dilute J-tector3, Jriere
resonance anr thermal self abDorption is negligible.

F, aisu.jmirn, 1 and r 1, ana1 30ol-irg for C

r.n- following relati.ronnip ii oDtainred:

(g rsa
[ -1ra r11
x -

J*- r, ;)l (2.n

For r = : (i.e., ro epitrn rnal neutrori ) qquat.i. (2.7)

reduce; to

[E6 : F :z P[g17 )s (.

The effecrti, neutron temperature for gR.6 (teperature

ir.JeK ,of Lu17') S oDTairne. from Figure .2 ( .

If r +: m ce [(I + r E ll mux t be evalusatd.

For Lul = 1 an r. r' is a r-,measrable val.ije .it-

jilute fails.

\ 1 Io r Gso r

*' This equation takes into account tre self-shielaing
of resonance neutrons.

Mir. iMB.64


I '.


CALcuA.AfTl vfLU.



1 0

2000 30 4.0 00 w0. 10 %G 00 000
SPKCTIAL Ira ,*3 r

figure 2.2. Calioration Curve for 9176

is ai o Jdeterrmind exp.crim.ntall.'. Tnen using the values

1of g17 ani ', giver, bt Westcott (~ ', .orrrectej values

tf g176 and S, are obtained by trial an- error. The
effective neutron temperature It found from tre value

of Gl-6 lsee Figure 2.:).

An alternative metrCod of evalo.ating r\ T/.' is

to irr-diate two tIi.ctors and express their activation

ratio- as fcllous:

L( g,Stn r ^ '

Ab gL( G r' ra ,' )a

or rearranging

[g"h r TT 5 G i]
Sh o r x
X a R' 1 / X---
x S
th r. r'To sn s rx (2.10)

s is determined from the Cd ratio of one of tne detectors.

Solving for r, T/T0 in equation (2.10), the following is


R' Xs(gGthb (gGth)a

r\ T T, :
(e G Ir R'. r )b
o r or .11)

Lif feren iai methodd


Tri time-of-flight Metrioo utilizes a mechanical

rotor with narrow slits rallea a chopper (37) or a

pulsed accelerator to produce Dur;cs of neutronr witr

a time duration depending on the speed of the rotor or

accelerator pulsing system. Tne Dursts of neutrons travel

trough an e.acarted tuDe to a Dank of detectors. The

energies of neutrons are determined o. electronically

measuring tme time it takes for neutrons to travel from

the sourcee to the detectors.

Usually cnoppers are classified as slow and

fast. Slow choppers give bursts of about 20 u sec.

duration whereas the burst of a fast cnopper is on

the order of 1 u sec. Unlike crystal spectrometers

whicn produce monoenergetic neutrons, croppers select

certain velocitv neutrons out of heterogeneous beams.

Tnre energy res slut ion of a cnoppEr ic Ja.cri'ced

t.y tl eq'jat ion ( i

3E b t :
= -0.0''- r + --
E T, ". 12 -

aJfl'C rI

LAE urcert.air.ty ir erergv,

E = enT er, of cne nutrorn,

at = ur certairat, inr flight Tlrie per m eter,

= fli r,C p.atr, meters,

.m uncertairtv ir, fi nrit patr.

For a flit c.-opper, tr-e second term i rnligule

rJ tre reoolution r-eiuCes to th.i fir.t term. Letter

energy/ r5es)litior i o-.btarn ed atn lon er flirt pacti-.

A list of re- lclt ions coletner 1ith flignt paths for

.3xfifeiar choppers is limited tb, Arnaer=.or ( '.. Multi-

creannre analysis deTrrminres tre irernsities of neijtror,

in different ererg, irnerals.

1.wi crnoppers car. ie conrstructej muc r more

sasili than tne fast cr-oppert.. Tr i; is Jue to cre fact

treat for the former, c nopping is ac:'ompiil-he.d atrn thin

layer; of Cd, whereas it takes marn irchea of pFlasci anr

steel for fast cn:ppera ( ').

An alternate methoJ for reasuring neutron energy'

spectra (40) is the tie-of-flight mertoo with a pulsed

source. The advantage cof this metnod are: (1) the

fuel elements get low irradiation, n'1 the rotor cut-

off function ,does nor have to be Jeatrmined, and (I)

Dy the use of tne chopper and pulsed source, t.e neuatraor

spectrum as a function of slowing dor.n time can be


Crystal Spectromerer

The jue of crv6til jiffractic.n spectrometer. for

detecting monochromatic neutrons has ceean investigate

Dy man'. autnors (9, 10, ul-471. ; fraction is a

scattering process. A regularly arranged series of atoms

of a cr.,stal will Ecatttr the neutron a res in all

directions, buc ordl in particular directions will

scattered waves te in phase and reinforce eacr. other to

form a diffracted beam. The atoms of a crystal are

arranged periodicaliv in parallel planes, so that in

gEneral scattered waves are out of phase except in a

few directions where reinforcement takes pla.:i.

Tr.e diffraction process applies to X-rays a;

well as to neutrons. The fundamental difference between

the two is that <-rays are scattered .'y tne orbiting

electrons, unere aE rhe neutrons are .cattere tb the

nuclei of the atom. For this reason, the X-ray

-:acttring amplitzude i proporrt.onal to ten atori.

nuririer i"f mne eie irm.nt, w ni le tr neutron scattering

arpii tuJd :-rio a relativ.el ,' small *Jr Lar. ion wi,

atomicT nurri r.

Jren neutronr frrom collimator impirnge on a

crytFl piano of a single crvstai at an angle, u, onri,

neutron: of o-nc enerp', are Jiifracte.1 in trhe 2irectior

of tren angle 2'. Tncrefore, the :cr-',-st l srd tne

ietector rust mairtrain an angle ratio of Mne-rnalf ir

orJer to trail norenergeti. nretror .

rr.e diffraction of .tre neutronr :earim penri on

tre lattice pia:ing in :r-e r, saal. Tnhi space .'aries

japn-ring on trh *:r'sal. material anil cn tre crystal

axi; along rnicrn it i.:- cr ir.e conerent :attering of

neutron from trhe ruc-?i of atomsi in a s*inpie crystal

Ic proi.duJ a morochromatic neutron betiam n is po.'erniJ

tre familiar tragg's relation:

n = 2, rin (c.1 )


.3 = lattice spacirg,

n order,

I = aave lent ,

= g.glarcing angle.

In energy terms, tnis relarai nsiip becomes:

Fcv) i n .' r ; E

inere k i3 a constant for ca:h latti-:e spacing.

Tiale 2.:' glves a liis of cr-,tail with e. and the

Jetectsole energv at 1'.



(2. I" )

Crvstals x. 10 ( ev Energ,, (evl

-u (1ll) 71 E.s:

Na Cl (200) 2.S 8.4

Al (1i 11 3.76 12.2

Ge ,111 1.?2 6.22

LiF (111) j.6L 1i .25

From equaior, (:.14) it can be seen rrat the

nigher order inrerferencr will c due to neutrons with

energy n- times trn lowest .rdier. Aleo, there 1 inter-

ference due to the mosaic spread of the cr.3tal.

Mosaic Structure

In order to know the energy of diffracted

neutrons at different angles, it is necessary to know

the distance between the atomic planes of the crystal.

The distance depends on the direction in which the

crystal is cut and also on the crystal material. If

the crystal were perfect, neutrons of a single energy

would be diffracted at any given angle. However, all

real single crystals have a mosaic structure, that is,

they possess structural imperfections which break up

the arrangement of atoms into a number of small blocks,

each slightly disoriented from one another. This

mosaic structure causes the diffracted neutrons to

have a spread of energies at any angle.

Higher Order Diffraction

Also, i-cor-jing to equation (2.14), there are

higher order neutrons diffracted at -acr, angle. The

ratio of the second order to firir order neutron

detected in the cam can De .rLtter, s (&6s :

f(!) (E. tE) S(E:)r,-E w*-',n r,(E,
'2. n.1 ni)



i .i )L)

Fn= .(n=-, E)

(*(E) is aa4unei to Ce 1/E
for energy greater than 0.4 e..')

(ratio of the detector efficiency"
for second ana firnt order neutrons)

1 E)3 co9[ (4fE, n=?)jAe(LE)

2 (E) .Cfoa e(E, n l)]J Le( )

2 .16)


w (4 E) rL r=I
ww (L1 r
w(l, nfl)

o(E) = n

(w(E) i tre fraction
of reflected Deam trans-
rittse by collimating
sysE ter)

(r(E) 5i reflectivity
of tre crystal plane
use )

In equation 2.16) cos[d(uE, nri2 ] : cos [a(E, n:l)J.

ani let a = CE) wricr red.ices the energy band
trar e to (E detector to
transmitred to the detector to

a(L) = o,
L .

. .17)

where c = 4

ri.e rrf'ict; i ".t" of a crvs a ri for rieutrcn. is

gi.'en I; equation i ll) of -olm ( ) for tre La.je C eia

-A tcan li*1
r.' = exrp'.-2H' '. -A r

1J (2.18)


exp(-:M' = DEcr-Wal er temperat ure
correct ion factor

r "rmiaic ipr'a of tr e cr,'stai

A = p;rDd-ct of the inr-ear dt-lorp ion
coefficient and the patr iengtn
in crvytal

E. 3 -
( 2 r, 3

t trhickne-s .f cr' tal

'i reciprocai of tr, unit cill

r = crystal trurcture factor

The [Leb,,e-,aler teimFeratjure c;rrecrion factor

a:cournt; for the reduction in intensity of the Praeg

reflecriorn dJe to tre rhermal motion of trie strci: in

tre lattice, hr, ere

M ( T,( T ( .lil
mL i, 6 J

= xdx
( J -x
0 e'x1 ( 20)


HlI L= Deobe or cnaracteristic temperature
of tne crystal

h,k Planck's and ialtzmann's constant

a r nuclear mass

T = temperature of tre cr/3tal in degrees
:e lvin

jince the factors in equation (.'.1) cannot be

calculated accuratel, it is easier to obtain an open

beam count rate of L and 4E. Tr.e ratio 13:

c:unt (rE1
f-(L) -- = o(E)E(E)o(E) U(E (r))
count (E) nl n=(E i n


Equation (2.21) is a good approximation obcause the

second order contamination is usually on the orier of

a few per cent, unless the first order energy is be1loi

tne Maxi-llian peak. Now, o(E)ni is

aE(n=i, 4E) 4E ''cos[( (4E, n=i)]a, (4E)
L(Ern=, E E cos--C, n-)J(- ) (2.2)
Eirn=l, E) E cos[i(E, nr l)]a> (E) (2.22)

wrc re

co* f .(L .n=i)]

.:O [,(E, n a)]

3( E)r= i -- o a r 4-.? )

.,~(E r ( fE) term in terms of f' L', .: expre:aeJ as:

r(EE) -

r F : f ( E )

: lir,.-. i ( )r, i = 1, h.-nr,
r'Fl .'wE'

r( L) .
f = f.') 1:: ------ f (E) ("L''

Tri re f rc. u- inr tre C al :i ate i value *f F(' I f(F

car te eiTimatiJ.

i re F.rnningr .r E tfecr

whern a neutrcrn ;rpectrrurm wa: ineasiurcd usLirng a

cr-.'tal 3p:etrja.rter ar.d correct iron wer- made, manr,

large lxps were fc-nIr (2, 5j-5) insarea of trie irrootr

i'ectiruim idaracteriktic o)f a :Baxweilliar, *jistriDutic

or neutron veilocitie friac fluc tuat i.rs are due to

Eraig reiiection of nr.u-ror s from reflecting plane;

otinr inan that usel to obtain tne rmono.n romatic Deam.

Tnii rerlecttion is best .Expla;i=-j by the use orf the

reciprocal lattici ano sneare re flcti.:. conceptE (iS

and ti .,ectr)r rotation as outlined in App-n.jix III.

Figure 2 nemo3nstrates multiple reflec-icn by

miia3 of th ap3nerF off reflect ion, where tne radiLu of

tne 3phere is 1.' ; it 1i center-;: on tne cryscal at C,

arin passes thr.r u n cie origin of thii r-eciprc al l attice

at 0. For ar in.:io-er. direction CO, reflection occurs

in tr~h .ir-ectin CP 1if Eii r.e :iprc.cal iatti:e vector

', tcrmir.nates at F en rte Ftnere. iupposi a 5econr

re:iFrc:al letri:e sectorr r; terminate at :, on the

ipere trlenr re flect i.:n :.f rte same t.ave length ;.:cUrs

1t rhe drecion Co. fa:king C as tie orignL of tnr

reciprocal iieti:e an: CQ ar : he i:icidelnt direction,

firtnrer r rlectioi :orr.e;ponring to nte victor r', i

rc.si",le. Trhe dcu 'i refl-ection Dy .a.i of r' and r

giveI a re-'suiant in tie sam ie ir.crion and at tne same

wa. 'e len ith a s a re f l i i on tr, rojug in:e rl r,

* r tre 11iller indieC; of the Flanes ire related cy:

ri : r 4 1 KL 2 3' 1 i 3 ( '

irTe .jDobl reflection can occur wiErn ar. reciprocal la tice

point ', ii or t.ne sprere, wrere Q is n:r necessarily



- -- -4-i~.n _Ci~cinI

F gt' E i .3. Sphere : f ReftLc:i.:n

F. ff l ct i re :t i,.rn

located coplanar .itll C, u, and P. Finally, it should

be noted trar Whern nultlple Sraeg reflection occ.rs

for firat order reflection, it also occurs for rnigner

order reflection at the same angle of inciden.e.


:inr:e reflecrl.it ie3 for NaCi an- be have deen

c:alcuiated ('9), a iaCl :ry 3 al cut along the ( 20'L'

plan was u:-ed. Tr. 3i 3ada'.ntage of tiis .:ry'stai is

that tne seconj order contamination tec:ome: s ery large

at law energies (e.;., = S., per -ent at L = .0u cv).

In orler to rdu:e this i =Seor..: orJer contaminat,-.n,

3 cr,.:ail trn :-upFre.p ed sec rnd orfer refie.ctivit.

must L- used, LIT (1il1 is su.-n a crystal. Tn,

suppression or secor3 crrcr refiectior, : .ue to the

oppcsire sigr of acattr.rLrn frorM S.ucci ,ile plain (1:).

Thrre are sOme dJiajvantace, in u.ing LFi

:ry'tais. Tnese ar.: tih lattice. psraimters are

uncertain t55), tie .diffiu e .a.:kgrcunJ :atternln s1

fairiv nigr, single cr,'stalz are hard to ottairn aal

suppres-;ion of ;ec.rn order in n-r .,ery e r- r [F (il )'

F k2 :*:1 1.97].

Jse of Ge ani -i cr'y tals, .nuC: rie ianmond

stru:ture, i .verv favorac e iecauz-, f:.r tre (111) plane,

t-.e e-ond order ;. ) vanishmi completely, in fact,

it has been shown (56) that at 0.015 ev, the higher order

contamination of a Ge (111) crystal is only 2.5 per cent.

Use of a quartz filter also reduces the higher order

contamination considerably (57).

Transmission of Reflected Beam Through Filters

Transmission of a neutron beam through a filter

can be expressed as:

T = T1 + T2X2 + T33 + (2.


Ti = transmission of neutrons at
energy Ei

Xi = fraction of neutrons at energy

The sum of the fractions of neutrons must add up to

one (EXi = 1). By use of absorbers such as Au, Cd,

Sm, Ag, Rh, In etc., neutrons with certain energies

can be suppressed. These absorbers ri.' a large re -nanr;

and'or a l'v cro's section. For instance, for a l'v

3Lruler, jupprfi.:3;.- i r r n- fir.r *:.r.ir o,; per crr n

si-.i.re- s Trn :E:OnrJ orl-r L ?I,) i;.r .:.- t. T ri T r ; ,

the rr,:,i-is;i3 cn ,'rC .j i s a v. ery j:2rf ore for

r-oilutin .of ae r'stnl1 sp.,:tro.re-r regie::in ; cntr

rmc.si.: s3 r-'i of cnr. :ry;ial is 3ei;r-e.sij a; ( i:


Tre arctul reclu:ton ;I determined v. plc.tting tnh rockir.n

curi'.? or different angle. Tne roci-ng curve is ot-

tain 0., counring 3iffractre. r neurons with a stationar.,'

j-ate:ctor and t rot r, ig or rockiing tI :r.'sal to

.JifrferenTr anfl1 Thie maximum of trhe 3i tritution

c*:rre F ;cii t. tne positior, D rnere the j.-tector and .:r,'tal

planr. are aliEned. iTn; widtn of t-e; pear at narf-

rma'imuium is= ual to al trn: .nrgy spread, of th- sy3stm.

the ain advantage of a crv.Ctal spectromiter

:rompare. to rne time-of-fllghr marni-l in rne Ic. ernrg.,

range i n tntrl te area of tne ctrm at tre ,je cctor is

quite n5mall. A diffraction spe:tromrletr car cover the

ererg:' range, from J0.0l trc e.', whereas, it is

difficult Co cover rnii energy range t.ir one cn:pper.

The *3isadJvantag-g of a crystal -spectrometer are: (1)

tin reflectri.,it varies in.'ersel as t ire neuron enrg'.y;

(2) th-e .ontrisuticn of the nigner c.rOr aiffraction

increarSe3 teid t e Maxweiiiar pea'., anl.; ( ) tie

sFectrof.ter detector i: lc;ser to the r-actor than rth

tire-:f-flight de tecors, resulting in a nigner bacgrcuiud.

.i-tiTLpl III

[ ,' C. F ii J ,: F .,-F P A e lT ,lK

*' i .lmTi .: r

in c..ll.LiT titrtr i-a Etraras tr rroir. r .a r :rar ei,

ran intren.,it Jecrea.ec very raF l.,,. Tper force it

is ie.:essar, to pri.ae srd- ral cl i Lasrt r.g ctarn1. JB id

r.,, .- ie, hr-rr cr :nar nrail ra: tc ie re 4 ired r sj mall

arguLar .iverrr -rc. Tris trYe of .-oiil tai :,r i; call e

a o.iiar coliriator i'i.

l-.llar :oLlirmator was cor.i trcte frcr, si- gr.t

: tan irlesi -r el tri '. .0. t Li. trin:, L. li. wiiJe

ar, 1 "i ir. L.:.r'g. :.ta;ile_- sitc i roa *:-.re-5igrtra of

,a icrac uar Jicre 2 sd foar scfaraii ig tn-g tri[ .

Tr'i coiiiir.atc r iwa trier, i ri i rted i.',toi a .a- 1 rei; : i-ot

1 in. x 1..5 in. x A3 in. r, a 3 ir. Jiae m eter .JaoJer,

c:.iirjr; cthe :cl Limrtcr wir ri.la 1 r, the Sl.;i t.y

friction.. I~r cc liIeratr -'a trh-n 3ipp g d int a

Dail rg L-atr of paraffin in, '-i r ,, ai;,i v.sd tr

t* ira-Z ( :i- T is procedjure gai a tr rii, coaT of

''i.- oir tri, -E urface .;f the .:ollicr.ating piste; it

order to eliminate the secornlar.', 3:atterkng from ti',

ill;. Trne a.ngular Jiv;rgen:e of this collimator ie

1..0 mnirnjte; oe -ection cf the -oiilimacor is shoin

il Figure 1.

ileutron: etraring the collimator propagpte in

four oiff.rcnt (a1',: (1) Jirect tranqsmis ,crn (2)

mirrl or reflection (.r) tranam: ion through tie

oliiimat:r .alis, arn (u) res:attering ty cne walis.

rne-e 'ffe:ts are r.owa considered in txrrn.

For dire-t transmission wiftn an isotropic

sOuirce on one ernd, ccrnier a narrow slit itr rhi-:.nIesi

T, uidth 4, and length L, as h.rown in rFiure 3.1.

Th'r rumtr of neutron em ierging from t.,e

.;ollimator rer unit widtl .i1 founr from the relation (.-"'

a 1 T
'l(neutrns .': sec) = J
o a' L3?ec- 6

S t TIJ( L tsn 6) i3.1I

wt ce r -

CiL tan 6) = lire aour:e eiemenr

-I T3(L tan A) m source sirergth pF2r unit
'" soliJ ais gle


_T -. ,

F r i I I i.01E "'-- I L r.ari.r C : 1 ,r

IT [


--- T

H- .

__~ _
i ------- CI

F ,z ,r ? ',. 1z -. ., r.-, E f -. -r e r.: -

L2 ec' : Jdiranr.e from emitting
elemenr a(L tan e) to the

0 = angle from the emitting
element to the receptor in
radia ns

On integratir.n equation (3.1 the following ra;ult s


rlineutr.nscc sec) = ---- a
-" L o .2)

DEividirn born sides of equation. (3.2) y th Eliicness I,

a reitriornhip between me direct inlet and outlet

3caler flux IF obtained aj folloW2a:

." L ( .)

Tne intensLt,; of rhe neutron bteam emerging from

tne collimator ouldl be a triangular functicn if the

coliiti ator were perfe-.r;

I (.) = I [1 e,a] ( )


I(s) = integrity a3 a function of angle *

I = maximum intensity in the center of
tne collimator axis

a i. r tri ar gI v* .iari e fr.io -a r. *a. Lu- to

imiu rf :tr .1- rr. :-Diimar or an-1 trme fi.rit- train;-

mi lo o1 lieutr.crS errrn.ugr. trc ..all tris rri rnguiar

urti; ri r rr15 t i r c r r Er 'a3'j 5i r. rtri u iricr.

r'-. r a ir ia3arl appr ma1ii-.r or e u ti rra ( 3. : iS


E lrt a tual *eA;'ieril tal se -up t di

sour..e i l.'Cat 3 soiTi di tar:e L.,aC, tre *:cl 1 at*ir

irliet ti-re tfori ari drpjrc*-Lcmtt rl- 1ati:ri-r must L,

jerJi C-d r : l trie -srai-r fiux *,omiri, Iout cf tr-n

:. I i TEtor a r i tr,, sr:ali r flu j-,' r;I, e c 5.u. r:-e. ghFain ,

a; :um r.e d r.?e :.ur: ,c i; itrF .'pL: a ~n c n i.JI r til'. t,-r c

ritucror.i nii:n ar; inn tea 3ir c.t ly. Firure 3 .L s j'- i

S ari i tre .. il tri iird trr r tr, rr:- c f tre scur r e

L ter-I? d N r.; E c lImator cJt l t ...r cr. ; a -pr .x im a eI

rect aIular irn hali.

re ixpr- lsoi.r: for and w a r' a; f:ciiows:

14, ,J*; C i.E


'o' iimagir, that t j-e .ollimaror ii of thick~neas T

4i.tr, .: air, l' rgth (Li L2). Using equatio. (3.3),

trer relate ionMhip for [r-. out ~. EC.alr fluix for this

coll niatr 15 :

r'(nsutrors'cm; sec~

T Q e

Sirxce ,the act ~Ja area of the

is TI' rarner thar 7 -'.j- an

the oucletr caier flux using

as follc.s :

w *T
4( reutrors.'cm' sec) e

outlet colmiTair g s.it

approximat. expressing for

cqutic .n r i. ) is bitir] d

\f9 exp(-( Q' )J*'] d

e x p. do_

( 3. 8

whe r

l/2(T T)
Ar = rc *s n

S- Arc sin L(r 'L;J

( 3.7)

Tle rc-t al refle-. tion of nclrr:.-ns L tr.< wall

cf trhe c.:.ii mat.:r can aier .:rt Tr, i.,eutr.r n ;.ectrum.j

u-icc a refl-ticn .a. first repcrt-r- t Firmi an.d "irn

( i. i'- c:ritr. ai anrgl. for su;n r f'icction t (o i-'.

I Na n)
1I S. i .1 ang Bi ,

g nutro i -at L'rc.tr.

I : cume .r of atoms ;' i in tra s.atterring
me Iajl

"a' : a rage .jnr- renrt sca trying lcngtr

l a.i. .-.r i( ". si c. tr.at there r tic. e l angl i.; .iv

funrc: .:.- ri.-iutr-r n e*n rg.,. In tHm i reljati.o r.ip f.or

trie crt.cial angle, "a' can r'e either poiti ,e -:r

n-gatrir *.penrin; orn trie -:atterurg material. For

inrtarnce rnarc.ger as, r -i i a.'c c:dattring lengTrn,

r,,iile cartocr ras a p :.ti'e .'al e. Lxplri'ert-r,3 ha'.'

Le';n 1.erfc.rmirel sing neutron mirrors irt, .,ariouls rir,.:r.-

carlc.ri (i.t ) arn] it .a3 four that -. t c *i..mes zero for

a rat ri f m 'C 1. '- i.e., trhe negari .- sc. at er ,ng

1Angtri of h i equal.ji t -: r pt ciit ive value e of C. Th rr-

f;re, if trie cc-llimat:r wilE rnave a ,alui c.f li .

larger tr.r an .'S, [.tal reiflec:t in- carrot occur.

*.:cort'ngl;, 1 ti-. s urface c.f tsr, co.lli ,Mator .alls -aS

cc'atel -itlr a trrn ioat *oa paraffin r i ni:r, d'ain, g anr

ii. ratio of approximaTs ly ahoulJ elininiat the

otcal reflection, of neutrons. 7nhi type of collimaror

has Deer. constr.uctr previously (64b with a thin film

of polyerhyince.

The probarlitty of direct transmisrn io.n through

the 'jali of tre Coilimator without absc.rption or

scattering is expressed as A where t is the

tOtai cross section of the wall materLal anJ. z is the

path length of tne neutrors through the walls. L..e

:hough the aLeorption of ateel is not rign, this

proabiliity is very;' mall since sar neutrons whicr the

steel aso.O's, will pass through it at very smial angise.

nTus, the neutrorn patr length in steel is relatively

long, and tranrmi3sion through the wall is negligile

compare.J to the iarect transmission.

Calculations have oeen maJe (:t for th. trans-

nissi:n of neutrons 'F rescattering in the walls of a

similar collimator. For this calculation, this co,-

trit'tiorn from rescatteri-ng was founi tc be less than

one-nailf per cent of the total rransnri ted intensity

witn neglLgible effect upon the angular Jistriburion.

The description above state that the neutrons

emerging from the collimator come predominantly from

Jirect transmission. A calculation -wa made for rhe

ratio of o.,o for the =cperiramntal ert-ip and was founr

t be ie uai to ".14 x 10" .

Iall a ] Li (1 r, t 3a J we ,3j

for tr,- i e ;a-er imei L lmer, or: of [, )ri c ry' t.3a

. r- 1 1 o n. < i. x in.r

Trlie ,.or.i etter Lorsi' tI 5f sad ple rKacl.-e it%

a c:r .c.t l holder, an erv, or, Ari:rli :.-, e,,C-'or,. col .at r

i,-.] :ei ector 5r, el. jre- a.t acr, s.r tr.e earir.

,:-rm Trse gearir-g .t-n i1 in a ca31 alumifilfu D;x,

ar.] K .*:i e, mo.veJ mTauaii or electr nir i Figir

3.:1 irn s ru. c r,; al ; p:tror.t.- r ir. c.O erar3i n 3r t3

or rr ijr *r i': cf Florine Trar-nr.; $--3:or (ifliP..

ITre .:r, tai rol.Jer i, mr, e from a re:tar.-ular al mi.j 'J.T.

LO i X t L t', enrji 4-e.. n i tn rsi : e .: r" ital fit .

Tr.i DOx 1 a3 a cr a 1to O n *:r', t til Ll.e rl-, r..n of

,a t ai r.i :I c- l ro 3 ir. Ji amete. r.

neir 3e or &i [ i iiel i s tt a t to 1 re i 1 r -M t'r

a *co*1i im acor aj i; ;r)o r. ,n der. ai r. Fi lure 3. Tre

r. .ov.:er r.t of the cr'/y cal r,:ijer an the ]etI.ect:r arm car,

: These :r,-. tale were otrtaned from irie tironrrw
r.Ti al ,c.-mp.an. 193' L. 'tr r tre z Cle ..iar.
t '.rio.

** Picrer Lip lar.ar i. ffra torn Ter, 11 'l :.o. 3:27.


FicurE i.j. 1% r r a -r i or, : er irmeer In OpF~ra t io



-. I



I __________

ibe performed separat,.,ly or at an angle ratio of 1."'.

Trre i:.2 mo'.'ement is carried out at .'-ry nign preci iaon

Ly rmeans of Jormi gear in tne macnir,e. Taj odometer&

are attached to the box where tne angular pFosioias of

the crystal and tne detector can oe read to 1. 1).utn off

a degree.

.J:'curor De:erction ystein

Ine detector used for these measur'emrinE ia

1/3J in. diaaeter, 4r per cent e 1 enricned -F3

counter within pressure of :6 cm 1ig. The lerngn of the

tune is 1i. 3,u in. long with 1i' j3/ In. of senaiti.'e

lengt;; it nas a ceramic eni injdow." The center of

the plateau for tr.is detector was found to be u8,'0 vol~a

using tne existing cabis The length of the plateau

'4aa about 4ji v. wir.n change of siLope Co one per :ent

per 10iC' volt-.

The efficiency. of En- jeteitor for iffEtr ,nt

energy ieutrona 'as not calculated Lucause it wa:

Jeterminei experimentall/. Ineareticaiiy, efficiency

.arn Be calculated from tmh following relatior.niii ("):

E = 1 ea p -N> : 1 ) (3.1i )

n* Tio Jtector was supplied Dy Reuter-'3tokes
Electronic Components, Inc., Model Io. FPC--li5.


N = number of atoms per cm3 in the

x = length of the counter

C = numerical constant which gives the
1/v slope of the Bl0(n,a) Li7
cross section

E = energy.

With the BF3 counter, a Radiation Counter

Laboratory (RCL) decade scaler, preamplifier and linear

amplifier (model numbers 2032, 20200 and 20100,

respectively) were used. In addition, Atomic Instru-

ment Company regulated high voltage supply, Model 319,

was used.

The Subcritical Assembly

A subcritical tank made from 6061 Al, 24 in.

diameter and 60 in. long and wrapped with .030 in.

thick Cd, was placed on top of the graphite pedestal

of the UFTR. A grid made from the same type of Al was

placed in the tank, so that the fuel eimerint could be

arranged in a hexagonal pattern with lattice pitches

of 14.7 and 22 cm.

Figure 3.5 shows the location of the tank in

the UFTR, and Figure 3.6 shows the top view of the

lattice arrangements in the subcritical assembly.





1* r

. '. .

'' '

; /

* I



r, 7



Figure 3.6. Top View of the Subcritical Lattice

The pl ane Zourc-e of th-e rnautroin3 cnrters tr -J surcr.tlca

,eml'.' from the LcottoC face of t.re ranP. There is

a proximatr:: l.4 ,n. of moderator betw6.-r the grid ana

rnre cotton of tr e tank.

Two t:.peB r-f riacurai urarniumrt fali. eierents were

useI for tr.he experiinent : Marr V-8 snd ilarr I. Iari:

V-B is anr ar ralar t.':pe of eiem-rent 2.ES ir.. c. :. anr

i. I n. 1. i anrj 6 *i .: in. long. larr I is a ;oliJ

fuIel lenert one in. in aiamater ran 3 i. ;n. long.

There were :ix fuel eilmern, in -ar, tJbLe. Tnre rcieracor-

to-fuJ volume: ri ratio ',' If( arj p. c.ne ar- li3s1

in laLte 3.1.



Pitcr (ci) Mark V-. F.ojs Mars I F.-.ds Vmi''f

:.0 0 : 73.?

1 i 1 ii

I1). d i 0 '. -

14.' l i. 4. '5

:c-im oif t:- pjret aier of tre IbiJcrt ical

a:-seLnly 1 latticaL us ing tth BUir'SC.'T C'o i ( b ) ier

calcul ate an art listed in ApF:rndix IV. A prop-sal

for performing experiments in the subcritical assembly

utilizing the UFTR as a plane source is outlined in

Appendix E. The critical rod position of the reactor

'was checked after the installation of the subcritical

assembly as outlined in the proposal. No coupling

between the UFTR and the subcritical assembly was found.

At. i .'iE.iO. 0 rI.-.I :tor; i -tC u;. r i rt kir- r a

,Tieasur-mr.nrt_ anrJ :r ;rai .:iffr' r. ra, *e.:. rromei t r for

i iff-renrrial ,i'i.ii ur-lii-:rit For coiipsrisnc.r f ex i-ri-

-:.-tal r.;- ilts3 Mi : t i i tr- Dr..*, t IF-P '.i.: I arJ Ci'FiP

i :.,:Od; r .s ,jW3 .

i-o fi.. k lo r.iTt rej-it re I-.re tr aerr.td into

tr. [rnk a t tr D-0 :ould [t r,atei. A :r;rstant

itmpc raure inr tir tan ii mainrair. d / f rne u,3e of a

t-ErIerat.jrt :orntrol unic -hin Jti liJed four tr,.rmo-

:o-iples. .ijo, a rtirrer rAilF T.:. p a urnfprm

te.-pe rature trrougr, ut tr,- rank. A :-il i-: -f rii

s- -up. ir. lir tar. i s sr, n r in Fir r gur- J. '.

Tr1 r,. r.ir .ge, .:.-,r.: r-,i -,f tri, [ -. w,is iE[arnrar --J t.;

u_-i of the; ili J lu: -ar ignr r.ti: Fis er,.::e i -quic.,Tert L..

:-: 'J.i r : : :r:.. ", C :-,.:c. :tr '.:; lir -,-rt .a, '-. r,-.

T:. c_= .-1.r,5' per cent,

Triri.k are i-, u r. J3 il3:e ri c-f rhrc Jr1ni eCrB t of
i;ridj tieii:tr r'eparrm-rT f-r TmaKin tpri; ietermi.-atior.

Fiuee M of



aEr r. m me

re r

.- Collimator Tjioe




The first integral measurements were made in

the UFTR core and thermal column where there were few fast

neutrons (66). The spacial hardening of the thermal

neutrons in highly absorbing media was observed.

Then, the spectral hardening in a subcritical exponential

facility which uses the graphite pedestal of the UFTR

as a neutron source was measured specially using

differential and integral methods and results were

compared with theoretical calculations (4).

For integral measurements of the neutron spectrum,

various types of activation detectors were used. All of

the detectors fell into two categories: either they

had a 1/v absorption cross section or they had a large

low-lying absorption resonance.


;i.easuroeenrt in th.a Thermal Coluirnn

tainlej areel z Pod

Integral iieasiuremerts *ere made in a stanie-lss

steel rod one in. Jiameter and i .; in. long and in a

urariurm slat : in. x In. x 1.'I in. fPa.ai noles

).'j)' in. diameter and 1/. in. J-eep were Jrille.1 in

tre stainices steel pin holder 6.5 in. from me en.i.

iii; -.as done by cutting the :tainiess reel roJ into

two piece;. Tnese noles -l ielJ 4ir.e .etecror;. Fr te

uranium llaL, aicrectr-D. were -,ni.al.:hed in Letrien tre TJ

f:.-is u icr.. were in. A .' in. :n .0). in. Ilea ;ure-ents

were made :4 in. from the east endc of tne thermal colurin

cf r;te UFiF. At trPi: position, the ratri of rj-ermal to

epitnermal flux is approximately- i1,1. i(ii. Therefore,

the contric ti n iof tre ep i therr.al neutrons is rie&iigiole

and e iuation( ) a im usia d,recrty to nme.au re ii- crantge

in effi-cciv;e neutron temperature.

ui7 17 i64
Fot these measurlmenti Lu L ,

.1, and P4 r d.tuctors wur e Led. TIr detecCtors

.,ere fabricated in tre form of wires J..03j0 in. diamterr

containing 10 per cent by weig .r of the activarnt in an

Al marrix, except for trn Au wires, whicr, iare 0.L00~ in.

in diameter. The fir:t miea3iremTint wer. malej in rne

SPrelainar-. res.ul; gi -en in JL-713, Vcl. II,
pages j3E -: ( 1-1 .

stainileJs :-t; ro.J u: ing nr Eural Lu-Al .ire..' A few

n.hurs after irradi at on, Lu16m an Lu ac ivit ie

.,ere co'-rtel fi.'e r.imie using s scintillatic, counterr.'

ALco.u four da,'G later, after tre Lu 1 E acti.viy rtad

3.:a;/l Cout, fi'e mcr i --t r st f counts e.sre Eta Ker of tre

LuLI acri .iti:S. Tiie total *:I rnt rate for eacn t irT

.i3 at least 1.,'00 .:ojrnt TrIe procedure for obtain-

ing the averarc normali;ze activities of trie ruo

inocopes ani tneir raieos is ou a ine irn Appenalx A.

Pu-Al wire; werr calibrated b, measuring their

nart ral gia.-ia acti.'zies h.ese res were then

Lrra3Iatej in a stailnie: artEl re] ani garrumas from

tne [issis n fragments Lwere count- 1 : ''. Tre Pul

and DL.' wires were aic. irradiated in trte stainlis

steel pin rnold-r. Tie corrected activities from all the

deti ct.--rs are l15tei in 'aLle 4.l. The activities rf

tr,e '.' atio;rLers, the Lul?? an tri-e Pu:39 fission pro-

J.:uct w-re eac.rh itftej to the BeEsell function, I i r r)

and are plotted on rigure 4.1. ire ration of fitted

c jr'e fo.,r ,Lul ? l.'% absorber) and (Pu- .'1,'. aosorLUe )

* Intural Lu contains 2.6 per cent Lu1'' rl
;7.4. per cent L.1 5

Eaird,-Atoromc, Inc., Gamma Spectr.-meCter, Model No. 810.

* '. A:tiviieC of P, -'3 m ars act ivities of ene fission
fragmrnt ; of Pu-'I

Io ll. ir)
. Aui9" act.
Lui '' art. Io(O.980r)
Lul7 act.
S Fu 33 act.

1I1 0(6.8r i

- c

1.11 '

--_ I .' i r



0. 1.0 1.5
Pa'Jiu c m
Figure .1. Flux grr'.' erei and Ratio of Lu1
Lul .ann3 Pu 3j .'Au 'I in i in.
Ttanirc CSteei Rca


- -, S

* -'~~r-- - S S

-T ~


~ -

- - - -~



Tr .' T
-. .-. r -f

are rabulaste in Tdarl 4. togeCrier r.wh the cianre

in affecti.,e neutron tr,-.perature from the outer surface.

to tr, c *nter line of rhr. stainl~sa steal ro J using

taiuJated' g factor:. TreF ratios show trat rnt

actii'.'t ratio 'Lui'/ I/Iv adcsorerL is more sernsitive

t c Th j- aect rT, i 5nift in igil,'gr an3 ort -igng gmdia than

the (Pu23:'-, ao.-or-.mr) ratio.

Llrarnium :las

Lu wiri- werei placed terwesrc uJraniun foils as

sri.~ri in Figure t.'.anr the uraniiuu foils l ere posI iionl .J

.n a slot in a graprl.ite Diocki Tr.e corrcied, arct i.i e-

.f Lu I' at Lu 1 ttoget-i r.r ,' th ir, i r ratio ar- p ot1t F.

orn tr c.' ottom of TEurc 4.. and tabuiatre. ir Table 4. ).

Trie djta in. t-hi mdi3 umT jere i terpret .- it t rrn of

f fe :riv- rineutron t perature using p: 'iat on (.'.d

C'- ratios ..r-rr measured irnide andi oursiJe of Lie iJ

las arr, it as3 found tr-at trrie ;orricution of epi-

irn rmal rneutrrion to tre Lu a:tiv.itie- ai i neglipible.

Trhe effctv.'e rneutrcr, terampi nature crrarnga in trie s.ian

"ja foun-d to b 'j.4 0 1 u-ing tabulated g


___ ___ ___ ___ /

't~ilrls il
I' 'fl I~
' ~ J ....~.cc.



K ; .



I a .j a .

rig.re 4.. L. TraveraI, IhrOUgn U-Sl1dD

,I ,

I 1



j, i

T4ELL 4.2


[Lu 77 .,'v Ab'OPiEi ] A:TI'.'ITI[L'

(Pu2j33,j, absorber)
Radius i ( 30rrI (1.0lj r)'

fLull7 ,l.'v a: e orDer)
I (. 8Cr) I ( l.L10 ,r)'

j. 0' 1. 30 1.0 '

0. 0 '" 0. 9 7

,-I .1 .', ? 9 t 9 t -

1. U 0. 7,, 1 93 2

1, ".'0 0,. 96'* 0, '-1 "
1 7 ,0.-' 7 .t 770.

S Trie

S TreI

Srand.ar.J aevii. onr :.f Tret3e value e
les& tran 1'.

cnarge in neutron temperature using
'ifferen ratio- were:

"TLuli ~ 26.4 f J .[C

p,.2j :3 '0.)1 lu. C


Lu 1 AND Lu176 A "" .. ril 1: A il TiHEIf.

Pc Itio: (cmJ A A17A" A1 .'A

0' 5 1.1300 1.l. 0u.95'

0. 1' i.0 a 1i.0 69 0.9 0 6
.i1. i .. 'i. 00 '0J
-0. i' 1 i i. 00 1 ' i4 ." 0.9 3'rj
J.5' 15 1.1 ) 1.15 4 '.91
-0.:55 l.IiJ60 1.160 1.93

s" rim.atea2 tarniarJ aelviation is
less itar.n 1 *r *:crEt.

A: rivat ions in U 1 i' -o urion

Tne sp.etral hardenrng in an Ai *:ai filled with

s.i c Icus scl.jiion of r ., asi measureJ using activation

-litectors. T.ne IJ taii l f the Al can iI 3r.c.un in

figure ..

The. Al can, fille wuicr aqueous E -0 solutions,

was pia-eJ :14 a frc rim ti east -idJ o-f the thermal

columni anr irra-iatwil for ten minutes. Thn flux at tne

centerr of trie an ai.4 approximately 4 A i) neurror;.'crm

sec. Trirei .ilffer-s r 503 solutiois were use. as

follows: orainar.r tap water, I grams s 03.'1 iter, ani

11' grams 3 0, 'ilter. Tr e Maxwillian. averaged absorption

Section AA\

3.5" S
3' -

'4 11.1 I.

9',j A P rod


riRi~re 4.3. Al I~n Ui~h r.1,e De~aectr HlOlder

cross sections for these concentrations Jrr-e u.tl Darrn,

2.609 barns and 4.496 barns, respectively Tre jc~d .EorP

used for these measurements were Dy164, Lu', Lui

Au197 and Pu239

Normalized activities of the five Jerector: are

listed in Table 4.4 and plotted in Figure- "..-'.'. Ti.e

ratios of Al77/A176m are listed in Table .5: aniJ .Lttr.

in Figure 4.8.

In order to compare the measured a:t.'irie 'Jitri

theoretical values, calculations were male using rti,

THERMOS Code (4). The results of the cal.uiaronea gave

the neutron density and flux per unit volu-me for tnirrt;

energy groups at different space positions n.ar- aiio tr,

activities of Dy164, Pu239, Lu176, Au197 ein L1 i-. Tih

calculated activities of 1/v absorbers ?ere found. to et

almost identical to the calculated neutioro flu,; tnere-

fore, experimentally measured activities fr;m trae 1,.

absorvers were compared with the calculars. neutron

fluxes. The results are plotted on Figure ". Tnr.e

is some difference between the two which ,. arrricut-l

to the inability to mock-up the axial feei of cner -odjr:ei

in the THERMOS code.* The axial feed of r.- ;ourceB

makes it anisotropic wheres; the THERMOE *:,ee sseum;-

isotropic scattering of tr,- sources. The trnecrerical

fi, < -alk. ir the H 0 medium a few mm. n ir,.i e tii. Al



r r

0.i" i, g thd n i) e

l.u g- -- -n- lt

AI Po. B2,, bi s.ion uAi cani:
. L ..-.. .__ ,___ .. L. .. . ..... 4.....- ... c :--_,u i -... .

DL'itance Fr--m Center of Can inm)

Figure 4.<. iNormali:ed Luit'n ActLvir I in
Al Can i.lled d.irr Aqueous B.33 Sol.. lon.;



I :-'

0" -- --.


-.C---" fi(tandard Leviation
les6m tnan it)

AL R.. E.." sEolut L ---U Al car,
, I .. .. .

1 : 3 4 5

instancee Frcm Center :ci Car (cm|

Figure '.:.. tJcrmalizeiJ Lu 17' Activities ir Al Can
Filled With Arueou- B.O3, Solutions



gm -a l r
I!. i-

i.or 3' '
M /
o a I

10 gm B., 3'liter

u ..
(Standiara 'eviati n
1e tha an lb1

alJ o ..------. iO. solution ----. Al Can

u.. -----. ... .-...
1 2 3 .

ristarce From Center of Car, (cm)

Figure 4.. N. f;rmralized Tr,164 A.ctivities in Al Can
Fill-J Withn Aqueous b C'. Solutilcri


11:1 gnm b ., la ter

i -arn.Jara Die li.a3t 1on
1..53 thin 1)

" --- ----0 soutior _--..Al Carn

lirt anc frr m Ci-r er of -'rn ..-m

Figure 4.7. tJorrm lized Fission F'r:.odu Acti/ities
ir. Al :an Fill-d. with; Aquec.u 8; ,

i -

u .0

** l1ter
- ted curve
f.tted curve

Al +.. VI* 'G a d B 2 .1 + A L + C.r- C.
,, A I+ H, a i i r.c I 4 A t

r cLI1 7 LU1 7. Rat L 1.
6 7 ;ol~tions
2 3

L1 '


1. 4

1. 2



< 0.8

:a I

0.6r 5 gm B203/liter

S210 gm B 2O3/1iter

i O(Standard Deviation
1 less than 1%)


r.0 / less than Can1
0 Ro -------3 solution AI CanI

1 2 3
Distance From Center of -:an (cm)

Figure '. .*mg ril .n of Nornmaii:ze. IHLPMi'." Flux

i.lr LL 4.4


B E Detector6

Grams' s m) Lu ?" .u1 r,,,I"* ul?7 Pu1 3'

: .6 0.5 0 7 0. 5955 0.,636 0. 386 0.. I2
S 1 .6 '.ijt9 '."066 ------ .t 73 u.t. ii
7 ;. 4. . 7 4 I) ~, 76 :< 0, 741 0 7 3 74
3.1 0.i')6 0. 8 3 1 0 910: 0.8)1
i 4 -.45 1. l ?nl j i l0 0l 0. 67 l. 74.1 0.73l

5.0') 0.2774 O 9 .2743 : 0.; 6 'l. 3ob8
5.0 ]O l i2 : 1 7 .l 3 17 0. 16i 3
.0 2.6 u l.] i j 3 5. It. 1 i ) 3.' 1
..' 3. i]. '8i u. 7 0, 4i 0. 7229 '. 83.3
5.1 i 1 l. ) 0 1 j. I i-10 0 I .00'.') l 0 0u00

1l .' 0.6 0.1S 8 .i 78 0.157 8. j C. i .1714
1J.)i 1.E :I 1. 1 21) 4 .; 7 0. o .,; '
10.i' .6 i. 372~5 23t, i 3t 6 0. 39 :
i0.0 j.i l.7171 0. 4j) I i.7u0t 1 0.6E 0- U.'33 8
10.0 4 5 1 .00 1j0 1.000) 1.11) J0 1.0u

LatimateJ stani.ari deviartia r less than ii..


s' ''is1 7E .rIpL: I: A:'iuEc'LIS L'I.*

Ditrince from
,'entf.r (cm) LIg,: Water '.gm'liter i'igm literal

r) (, 1 .. 6 'l 4 .'. I ,,'l'. :

l.t i. 0 i{ ,liil5 i l 9

.1 1 1 7: 1.0 1.0

3. 1.' : 8 1.0 1 i d

4. 5 1. 0 1 s.r 00i 1. 00 )0

Estimated staralar. deviation less than I .

can, ana trhs is --lie.ed to t- due to tre external

sour-e conjitionr. Ine rarios of A1',','v at2orber for

exp-rimentai ani theoretical calculations are listed

rn Tabie 4.o. The theoretical spectra are softer than

the experimnntai valueS and again, thiS is due to the

THEPRM, source :onadtions.

-A L.'EL 4.6

FATI:' 'r A 1 'v AB:, IFnT.P I N 10 gm. b-,. LI .LR

Distan:e ( cr m i teore t i a i Experimeirtal

0.6 1i.0 63 1.1191
16 1. 3:U0 i.i05
".6 1.0> 1., i 3
3.0 0. 99i 1i.0331

*, .50 i. 00'i1 i, 0

: standardd ieviat ion less thrn 1 p r cent.

in order to duplicate tne source conditions

imposed t the TIILPWI' Co3-, an atrrtept aas made to

perfor.i, an experiment L', placing the Ai caan filled with

c.orated watrr in rne center of tne UFT-i. However, with

.nnl one gram of ;j'.OIliter, te exce-ss reactivity of

the reactor was not *nr.,ugh to override rne poisoning

effect. Therefore, tr e onlr way this experiment :an re

performed properly. is to provide sufficient reactci.it.

ro override tnt B. 3 aLsorptlon.

Measurements n tr,.e Ur'F Coic

In order to measure tne 3picii d-p:rn.-rce -f

the effective neutron temperature .-.r tr, r'. 'T,

factor in the UFTR core, Lu -r:i ani ver: tnhin Au

foils were irradiated. The Au f(cls .wer mia-e u~ril,

Au resinate solution,' which oa appiil tEc Ine -urfi:e

of an Al foil and then baked Ilo.l; in an electric cv-er

for about 45 minutes until tre tcimpirature ra.crine

9000 C. The baking process vlarllii:j tr.e crgani-:

material in the film of resinate -.ltlr: n ar lifrt a

thin film of Au on the surfac- of r't .,i f.il. TI-

maximum thickness of the Au film a.i nrr .ore train

0.5 microns. This was determane t,. cimiaring tln

activities of Au foils of kn.:. an r. s nrjr.nr tr icne;s.e

in a known flux. Since the iif-aL-orption i:

negligible for a Au foil wi-' t'i-;i re ;f u.S micron;

(68), it was correct to assjme tinat titii- oils ir

infinitely dilute. Activities: frcim rru~ mpiJrite 3 r

found to be negligible. Ac.:jr-at-e *eir n of tr.le

thin Au foils was practical. i.ipc .Li e; tnr f.re,

the same foils were used to mreaure rnme bre and tre

Cd covered activities. This pr'-?e ::.rre:re foir Jacinr

* Supplied by the Hanovia Cnimi.:ai and :1arfacturrn
Company, East Newark, Ne. J-r=~c.

.'ariatior. A:ti.'ir.v from the first irradiation 'was

au.tracted from the. acord using crue same foil for

L, rn irradiation;, cirn:e tr,- naif-life of Au i well

i.nown. iner LJ wires were 30) 'ils in dii mei r and Crn-

mained 1I] per *:nrt by ieinr of Lu.:,. The positions

where Lu wire; ina Au foila 3ere irrdiat-ej is showrn

Ir rFliure 4.i1. COn na:surement wa. made i r nrs-

nerntr of tnn fuiel cox.

Frcm r;,e result of r-e Au foil act ivations,

Jalue4 of r T'T were :alculate uSinrg qcijitior (. ''.

Ir tlis r ]i uatl. n, ao for Aj is kno.rn i, (E ani is

&pproximiaely u ual to 1 .5. From these caiijiated

.'al-e of r", I,; ther effective neutrc,' rsmperar ejr irn

the center of tre UTTFP. :cre was calcul atea ov trial and

error using equation (2.;). For these calculations

tatulatEd values of g an. 3' ere ue;i for L176. nhe

factor g for Lui isIs appr.oxiatii:/ one arnd the factor

SG'r ~as djeteriined exprim.nrtall .y cy rne use of Ca

ratios of Lul'', and by using r '. -cotained from

cne Au foil activator, togeth cr tri equatio (:.).

Ihe effective neutron temperature .as calculate to ce

-'.0 ;.9- C in tne center of ti e UIrNf uwen compared

to the reference point in the thermal column.

Ine numerical rereult for r'. T. T A'

A17Al9m 175 and (, s C are taculatcd
r. :1 .:a o r


Ie. /LL rltr I
ol wret restriew

Figure 4.10. Position of Activation Detectors
in UFTR Core

ir, Ta.le 4.7. In Figure 4.11, A 7?'7 '7 Fi3 and
r"' T';; are plo ted.

iHe:asurments in rte ;uD:rirnal Asssmbti

Integral mctauremenits .erE onae rJaiall.' 12.5

in. from tre bot torm 3f rre central fuie tuce because the

aiot in tie special llark. V-E fuel elemenci was locate.t

at ciis position. At T.ti ri ;rig t the axial Cd rario

nis reacrie.j a constant vala~ indicating spectral tequilir-

rium. An At foil nC.i.Jer was attnacri to i;ne tuDe at

t.i- heigr so trmat racial traverses co'iid :e Tak=dn to

the cell boundary ard Dc'.:r..

Bare a.nd co'.ereJ Lu anJ A.i frc s -ere irrad.i-

aced i- four different arranigeinmrt. using to lattice

Firches as 1_ l4stLc in 1 i:i J.l. Also, TlEF.I1103 anr

CEPTF. calculia.iona -ere nadl for nhese arranremirirs

ar, all n~e C~perienrtal anrJ heoretical results are

plotted ira Figuras .12 to .i9 for rthermal and epi-

thermal activities All the experi':.c atl results were

norrmaliied at tre cell ;Drdar.', ard tre dir.ectior. of

:ne traverse uwa equidistant ctctweer Seo fuel tuL.e3.

Au foils 0.001 in. tnis:K na 0.2 in. iameter werre u:ed

together 'itr. foils containing a 10 weight pr cent

pec.i.al unclal Mark V-5 and Mar,. i fel elements
wirrt sl:.ta for ictivatirzr detectors were LborrowJc
from tr, ie savannra Fiver uperat ions Office, Aliern,
Soutn Carolina.

15 10 5 0 5 10 1i 20
9-p) 1 4.4

Figure 4.11. Traverse Through UFTR Core



1. '




Epicadnmi u
(s.d. 1 1


.Al Al' Al
AI Al' Al
E. u I'l )

H 1 -! -_ Ii,
: 6 F 10 12

Distance From Center i cm

Figure .1. A Au A:tit'.itr Disrruutiion for rlark: V-B
Natural U Fuel Jitri 14.7 cm Pitclh

Thermos Curve
Norma.iized at
Cell Edge

C.- 11

.ub.ca Jnium

0. .4

1 I

j -J

*:r; i r ur. e-1
,r-' r 1 1',.ge

,11 Cell


A, 1 A! %I
-. ':. ,j-- i ` li ij

__ II L _l.._u i ..
S 6 I : 1;
Cis Tranrc From *rnter (:m)
Figure '. iJ. Lu Acti .i.,' Di trirutiorn f.cr Marar V-B
Natural U Fuel Wi -. 1w.7 c Fitc:h

ij 6


1.81 -



*uc U Smi 2 Ti

PaC 1i

- r'- .,


( .d. 1 6 i)

I" D;.C

_ 1 1 ... .

Distance From Center (cm)

Figure 4.14. Au Activity Distribation for Marb.
V-P rNtural U 'itrh 2; cm Pitcn

Trermo, 'Jirve
.crml i e 3 at
Cell Elge

1 i) 4

,., Lzi'

Tre rr.:' L C r' e
',rnal ie d at
Ce11 EL3ge

1.c.admi u
(9.a. : .711

R dis


1 --o- .. i-

Al -Al
Ai ,'

Epica.lmium x 10
(3.d. 3.S)

8 10 1: 14

List-nce From Center (-:mi
Figure ".15. Lu ActivLEt DistriSurtonr for MarK V-B
Natural U Fuel Witn 22 m Pitch

Trnermro Cur'.r .
NIrcrmalized i

Cel l


z jut..4adriiuirT

3. . 71)

E Epica miu rri x 1'

Al Al Ai *Al
i C0
.1 ECi0 u (J-. -.

6 11 1


EDistance From Cnerer (cm.'
Figure 4. 1. Au Actr .'itr Di trijburion for Marn I and.
HarK V-B Jarurai uj jael L tir 14.?7 cm Pitcn

Sri.rt|: ur u i

: l:l : 1


L u 3 l ui
*k' J. : ii

1 x F:'i: JTiurm

41 4 11i

.i "iI I
,! "-0 i2 i .

,st rance FrcirT. .enter .c -i

FipJr-. u.17. Lu .ct "i t',' LI'c riut C r, t c. r rarp: I
arl 'lark V'-3 IJa jrai 1I FIel JitrI
lu.' .m F tic r


Ihermos Cur.'e
Normalizel at
Cell Edge


s'jca miu
(...j. .


Al Al Al Al

Li h 0r[



. 3. 1.6't

.__ _-_ L..L .
S 4 6 A 10U 1 2

Cistance From Center (cm)
Fig 're ". 18. Au Ac.ti'.'it Distribuuornr for MarK I
and :lark V-R Narural IJ iT4n ;2 cm PLtch


-- -- r

i r rTTr,? ur
liorm asize.- at
Cell Ej,-e



1.0 h

E pi c almi u- m

Al Al Al
U E' -.1' i

6 10 12 14

Distance Trom Cente r (cml
Fimire .19. Lu Activit: [Listritut ion for Mar. I
and MarK V-B tlatural IU Witn :2 cm Pitch

S. C r



r-- I

i -, I
2 3

r J

*. r. ,


a r~ C = -

oi 0 & C. *



di:p-ril.on cf LJ..,' ini Ai. Tr1 latter were trie 0.01:.i

rh. rni, i .. r. a m. ans ret r. E*k[ i TE we re

:c.rr -e K-. f-ir E. r 3iatal .o ri f u x i i r5 t r n if.r cr,

iui-rit ii .s:cuor-ir fg to the relation:

S P r r ---

S = r.c c.rr. ct. j flu

i' = :orre ri flux

EL aTi r-..a 1 a K i 'iriec -cr- A eeAurmd u;rg 1.U.' 3i in.

a cov.r-s. Iiirefor a cur-off .:f .' :.' as- us3e for

'.ri THELJP : ;al:ui.atioiC..

;r. ai3itior, car- ansd Cd cojerei. traverses Fcre

milr as rlr l nfii it 3ilute Au foil tc. .'alujdare rhe

-r.ttr: irnai ir, e.J r in the unr t z l il for e cr. lattie.:

arranc.T eant ijing n ir. iJ~. rdat i:c of Lu a ri

Au effecci;v rieutrorT r:mpr uare at J Jffererr cell

po itr iton. wiere :alc.jiaced .L Iu in g equa'r.r (2.1 icr

a refererc:e tr.e neuct rcrn r-mprature at tre cill Dour,..ar/

*- e detr.eriLned y a i fferenclal nmetro.l in oraer to

d' err;,irs. trei efficti.- tenlf.:rature change in nte unir

c li. Tre results of treese aasaure.Ten t are plo cei on

Figure' 4. ". to L.:1. Also nrown ori Figurse '".2 to

.27 arc cre s
tne corresp lring -J ratios .




0 -
1 1

Ai Ai' Al
., : u D :'J

O I i 5 4 7 f ) 10 11
Distan,: From ,:erter (cm)

Figure 4. Flot of Al" 'A19i r'. To ar .:p
With Distance Fror, Center Using Marl: V''-
Natural U Fuel dirn 14.7 cm Pit.ct

I, IA1


1K _____ (___


S I A Ai

E a 9 10l

Figure ".21.

Di['scan -.c romri C rncer (cri.)

Flst of A ,i r I.T arin Cnp With
E'i- stance From C.rter Ulling Mark: '-B
iatural I.I i. n 1--' cii ,'itl h

1.0 L0

.9 .09

-.08 r





-- A177, "
A ~~



;1 Al Al' Ai

'j D i- "

I0 i 'i F
Distancrce from

D- j

L 7 6
centerr ( cm


Figure u. 2. Flot of A"' A19cl, r ".'r, and CdR Wri
Distance rrom C-;nte-r .iinrg Mark I and
Mark V- nJatural IU Fuei With 14. 7 cm Pitch

r 'i

I l I



S; r .1'4. -

- .1 **'1

r I .

Hrm n. 1 Ai .z1

i- I t i.r. Frc-cm sncter '.cm'
ict cf nir m '' ,- r 1T ,i-i C-3; 'Jitiri
ir ta r. i Frcrrn .- r.t-r i. i-. lIar 1 3rand
;ar -v ; ,tj r.31 1., Fu-: 1 w t:r c.. Pitchr



10 0
S7-rire 4erl Act Fvation


root lank Usin-g rak I an- Mar .'-B
I- iural Fe .itr ?? :m Pit r
--- ,:,i Pl ic, x ICo'-'


105 1 :- t

rigire i.2". Ax Foot ]ank l' sing rMark I ani Mark '.'-B
ltiiural U J uel r Jitr, 4,? .: P Pit.:r

S.TI- T r.a~ : i rc. r


*:, . I 0-r 1

[:1 [r r,-it l
'. -t1i 'at r -


F jrc .. .

1i 11 i lij
b n i r L) t i .:|T T
An. i D'i-,tribujt :'n tf fIux i tricn TIJ.
F.-c i ariI 1. Mair, '-E[ iJd urral I
Fu uli rt1 .- m F 1 t :ri

3 S

Thermal Act '.'at .ro

f i

1' Epittrermai
SActu Jat io'r

----- --

1 l

rF.;ure ;'c. 4i

- Ci Hai: 1'?


Sr, '* 1 t .

Height ( :r,.
ii f'liriblbj10i1 oif Frui ir. tree Two
ot Tanr: TJ;ir.A '"ria V-B Nratural U
l Wicr 14.' cm Pitch


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