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IFISSION AQD SQhïïTÀQîl
5HBSÏS
SBB miVSBSlTÏ GF BQlfflAY
POS 5HS BE91SS OF
DOCTOR OP PHILOSOPHY
am cimm JAEÎ, M, SO.
DIVISION,ffiîaBHA ATOMIC RESEABCH CEHTBE,
BOtBAT
SEFSÜSMBEB, 1 9 7 1
» E Q L A B Ä T I Q
I hereby äsclaxe that the work »sported in this
tiiesio Is original end has not basa submitted by me to
any other university or Institution fer the områ ef any
other degree or diploma.
wam JAK)Student
I certify thi"t the above deolaxafiioa is correct
( 1.?. Pa-Miiiah)Seeearch Guide
~> (
i i
A C K B O W, 1 ff B. Q K M E Ë T
1 am highly indebted to &r. M.ï. feœaniah, ïïead» HaaioebemlstayDivision» Bhabha Atomic Recearch Centre, fox* hla invaluable guidanceana constant enoeuragomenfc during the entire course of this o tody»
îh© studies on the solvent extraction of em«riciara-241 «erecarried out by mo at the University of Lieg®, Belgiute» andergeneral direction of Prof, 6. Duyekaerts. I take thisto express my gratitude to Prof. 6. Bayckaorta for his kind permi.-asion to include this work as part of the thesis.
'i%- sincere tbanka axe dae to Dr. C.L. ia,o, £z. K* Kängan andDr. Satya. Ptakaeh for their help during tbe course of this etucSy. Iwiah to exiwess my tharfeo also to a l l those who extended their beetcooperation during this investigation.
X ara gratefUl to the Director» Bhabha Atomic Research Centre,f Bombay, for granting me permission to x-eglater as a research
student of the University of fio'sbay and allowing iss tc avail of a l lthe facil i t ies of the Centre»
Last» but not lofiat, I am gzatefal to tgy wife, Pushpa, »hoshared isueh responsibilIttoe of day to day life and thus gave encourage-zaent tlwou^iout the course of this »oik.
(U.C. Jain)
SYHOPSIS OF TSE 3HRSIS SUBMITS? (a TO 1ME
UKRBRSIfy OF BOîuBâY FOR THE DEGREE
OF1 Ph.D IS CHESI5ÏKY
I'iaae ef the student t Hera ChaM
t Dr. l.V* EaiTBniahof the guide
riacs of work
Ko. and date of registration
'?itle of the thesis
» Bhabha Atoraio Besearsh Centre,Trorabay, BomTjay-85 (AS)
» SiïïC/177 dated ï&y 5» 1966
« Kadiocnemical Studies of theiïeavy EleaeEta, Fission andSolution
'This thesis destrrfbee the investigations carried out on the
and solvent oxtmotion827 22?neutron-induced f iss ion of 'Ac, -'Ba ana241studies of Am using hi^x-molaculer-ws^Jit amine in different d i luents .
2» The f i s s ion étudies «exe carried «»it wife the objective of gett ing
an ineigbt into the trémie in maes distribution i n the heavy olenent227
xe^on» Fission of 'Ao »as coosidex^â particularly lnportani. l a thisconnection In view of the result» obtained by JKIföES sad FAIRSUA In
226'ih« ieutroa aai beliam ion f i s s ion of Pâ and e proposal mad» by themto explain the triple-peaked rcass distribution sn 3 » assmaption that
there i s & sharp transition froœ syna»trie node of f i s s ion to eisyosetrio
mode a s one passes fro* the f iss ioning nucleus aotlcioa to ttiorinnu I t
«as considered worthvhile to imrestigeta the neutron-indaeed f i s s i o n
of 'ào Bint» this should glv« cleaxly a triple-peaked raaas d l s t s i »
bution i f these m s suoh a strong dependenoe* Fission y ie lds «ere227determined in the reaetor no»tron-induced f i s s ion of Ae nslng Hie
'comparison nethod' and wnplflying radioeäsraioal techniques. As the
amount of 2 2 ' j \c available ma amll, the recoil oatohor teohniqoo «ss
used to conserve the torget natarJal. Since the f i s s ion oxoas-eeetion
Iv
ia alee small, fission yields for only twelve nuelldes could be deter-mined. Bcsrovex, sufficient mas»-yield data waa obtained in the troughregion and i t was found that these ie only a small third peak in thesymmetric raglan and i t is less than 1?6 of the total yields clearlyshowlRi' that there is no strong: dependence of the shape of the tsass-yield curve on the charge of the fissioning nucleus*
3. In view of the vary significant results that were obtained in227the fission of Ac, we wax» prompted to study the neutron-induced
fission of e t i l l lighter elensenta. Sadloia-223 was on» such isotope fortthieth an upper limit of fission croBs-aoction of about 100 barns wasreported. Eadiura-223 wae separated f roa Ac aid cheeked for purityby taking alpha spectrura. Carrier-free Ha «as evaporated in thematrix u&torfsl (ratterial used for retainteg fission products). A blackwan always prepared under Identical conditions and irradiatad» Radlo-etfcsmissal technique was used to aeparato and purify hl^i ylald fissionproducts like atron*iuia»91 * Preliminary experiments showed that only afew counts above backgsounS could be obtained* 'though the stadias wereinitiated with Hie idea of âater&ining the rn&ss-yiald curve for the fissionof this isotope, i t was found that the fission cross-section is too 1-flrto enable any detailed study and an upper limit of 700 milllbams wasobtained for the fission cross-section.
4. Fission studies of ™£*u are of significant interest dus to i t srezi? impartent sole In molear power production. Although f Isa ion yieldsin tile thermal neutiwi fission of ^Fu wars deterrainad earlier thedata available i s not as extensive as in the sase of 'nOT and feezeferathe present investigation was undertaken. Ihe newly available Ga(Li)d©te>ctor was «eed with tt» purpose of investigating tSie nalatlva use-fulmse of the detector for determining tile fission yields using gaaaa-ray »psot.za by direct counting without ohemioal separations aa thiawould aava t-hio. Fission yields of sixteen nuclldas wera datazainad In
the fission of uelng Mo as an internal standard and raaking usa
..A, ... «^'iWJI SsHSt te?^ B-*.'i.4*aS-iM«*'l<:f'--^:'
of the 'comparison matiioå'. Eleotrodepooitofl tasgsts of enrichedumnium ana plutonium on gold-coated aluminium foils wore covered wifepunched circles of 1 mil tttlcik 'sapespaie1 aiuirdniura catcher foils andirradiated together. 'Hie catcher foils ware counted on the Ge(ii)detector avå the garcra&-3ay ap&etra recorded using a £öQ-channel analyser.*Bie activity ratioa w©re tak an from fte decay curves plotted f*»r theidonfcified photopeaks. From «to sixteen fission fields determined i twas not possible to détermina file normalisation factor for toin the fissioa of ^7Pü and * 70. •Rserefoie litai»tuj-e values for
d in Pu ana U fission had to be useâ. Sia yield of 9SM230
in 259Pu ana S55U fission had to be useâ. Sia yield of 9SMo infission rewüxtod in literature varied over a wide ran«?e from
5.6I to 6.1?9« %e large validation end the d i f f i cu l t in seîectiKg aparticular value of Mo for calculating the fission yields snade i tmcessary to investigate tM® yield value in detail* r3ie yield of °%owas determined by the 'compairtsora raetiiod' and also by the 'absoluteaethod*. A value of 6.79 ± 0*15 was obtaimd by ttie •cofapariso» method'•tn a l l expffrinor.ts isotopically analyzed and accurately known aî ountu
99of uranium and plutonium were irradiatefi. Yield of Ho traa ealoolstedby 4he 'absolute method1 using matron flux, time of irradiation,efficiency of the counter arid a value of 6.66 ± 0,07 «as obtained* In
239order to investigate «onra of the yields in Pu fission* furthermdiocheaical wosfe *ao carried out- Fission yielâa of *Bu &nâ '
axe a'aoit 25-35? hi^hiîr vexe investigated in detail . ID all»fiasion yields of 29 nuclixffiS ware determined in the present work aad&re compared with the îitcœi^iure date*
(*) The Mo yield of lins present work which is 6.?9 is the hi^isst ofa l l . the nest lommv value being 6.59 detorcdnsd using Ge(ti) detectorby Idaho Croup anâ 6*44 the interpolated value of the nas» spsctro-aetric data of F.TCKEL aaä TO ÎLIKSON"'. %e lowest is -aie radiochemicalvalue of aAHSBEÎI and YAFiT64 whioh io 5.61.
(b) 3hs nasa-yield OUST» O£ the present wark covers an aree of about
• f', iii tea 4t USB»»-'
206^ while that of MRS8EN axA YAïW* has bee» reported to cover 1$0f°and thus t»king a difference of about 16 in a total of 200.
(o) She differences between the pieaant values and xadiocaemieal valuesof &ÈS8WS and YJFFS seero to be In both ©ie peek xagions while the mindifference between äie present values and tne mes epectrometric valuesaeeraa to be only in the light peak region.
(d) Fission yields of *fiu and * I fseta iho present investigation ere25-35/- Ui$ier thar> the aass speetrometrie values.
(e) 3he pzosent values aeem to be al&se to the case 8|^etxoraet?ioveluoe of FICKEL and 20I&ÏHS0N5 end Idaho Group2 nhicto as» in gsneralagzeenent between themselves. Tha exception lis in the ease of a fewmolidea like 85^Cr. 8%r, 1° 3S I ,
1 * I and 142J*.
(f) Of the oethoda which axe being coapared, raüioohe&ioal methodiiwolving four-pi counting used by ?M.BSm$i ana YAFFÏT end the » s s«peotrometric method by FIGKML ana TOMLISSOS and tine Idaho tiroup axebetter than the 'comparison aethod' used in the present Investigationas the • comparison netb^d' involves the use of fission yields of 9and Uie assusiption that the charge distribution am g»ne tic
ships in Uie and 239JPu fission axe the se&e.
(g) Inspite of the differences in the methods mentioned «cove, thebetween the pxeseat data and the mtta apoctronetric dat»
to be closer compared to Hut agzsemni between ness specizonetriedata and four-pi counting data. For this xisason the yield data of theprésent work axe considered a significant contribution*
5 o A nuaibe of inven tiga tior» was» carried out on the eitaactioaof netals by trilourylaminB salts. Several nuchaoisms ware proposedfor the extraction and the etoiehiometsy of th» «xtxaoted conplexee.
v i l
sa,n
Th® difficulty in obtaining these Informations from the variation ofthe distribution coefficient with the sraine salt coocentratlon in feeorganic phase arises from the fact that the ami» salt i s aggregated,the degree of aggregation depending on Its concentration and aie natureof the dilueat. In ordar to obtain seae more inf oroa tion about thevalidity of «ils distribution rasthod from the point of vier of de tor-mining tile nature of toe extracted species* the distribution of 4 Anwas studied between aqueous solution containing LiCi, CaCl- and dilateHCl ana solutions of triiaurylamiw» hydrochloride (TLA.Wl) in differentdiluents at tracer tretal concentrations and under seta}, loading condi-tions* The concentration swinge of the amine aalt «as kept as large aapossible in order to vary the degree of aggregation in the organic
241phase. A log-log plot of the distribution coefficient of to Tarsusconcentration of the araine eal* ®ave a eoasient slope of two inenSise oonaentxaticm range of TLA -HB1 in syolohexent (1O~ te 5 z 10aoles/litjfe), altiiou^i TLA.äCl «at found to bit aggregatsâ in theorganic phase* Studies under metal loading conditions showed that ttterewas & loading effaet «hen aïe concentration of in in aqueous phase
butrequired «as too large for
"
the concentration of amine salt but i t was not possible to241get a 1 i 1 ecaplex as the amount of
tile «xpaTiarantel oondltioas*
1 . R.C. JEBSEB anS A.W. FAIHIAIL, Shja. Ker., U 8 , 771 ( i960) .
2 . R.S. FOSÏlîB Jr . , Bâta presented &t the 1 5 6 * An. Chenu Soc.
Meeting and Pexseml Oowaunication by Br. FCJSflER {1$6&) «
appeared i n ïluel. Sc. and Eagg., 4J., 191-214 (1970).
3 . B.R. FieSËL ani B.H. TOJLIH50H, Can. J. fhars., 2^, 916 (1959)
4 . S.A. MARSDiui-; and !>« tam, Can. J. Chcm.» 4Ï , 249 (1965).
V-»; (SÎBDEMT)
«^gsa
S 0 ULJLJ 'i
De.
SSCÏÏOK 1
1.1
1,2
1.3
î . 4
1*4*1
1*4*2
1*4.3
1*4*2
1.4 «3
1.5
g
2.1
g.S
S.2.1
(a)
Ct»)
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(4)
e a o o o o
a « «t o <- o
fåliMm IMKOSBC'JMS
Historical % * s m d
Fission Pïoesao
i.îaao Biotsfbation
Flaaion YieMs aaä ïïeoî©âaof îfeeaasemeiat
Befiniticms
tfethoâs of ïaeasasîejasnt
ïteiôioeîîeaieal motS'âod
fess speetsometsie m©thoâ
Ssma-iay speefesoîaotagr usinga Se(l.i) dstocfeor
Iteaent ïnvestigEtioa
XI®W1D FÏSSIOS Cgi1 ÂCÎÎHHJM-227
Intsoâaotlon
arpertor/ital
•Ëircet 'Aiepax&tion
i i
i l l
1
1
2
é
12
12
13
13
15
16
17
17
20
SO
21
21
LJ
2.2.22.2.3
2.2.4
2.2.5
2.5
£.4
a ,5
3.1
3.2
3.3
SECTJOä 4
4.1
4.2
4.2.1
Irradiations
Cheiaical separations
Mounting
Counting
Calculations
Ereos»
Results and Discussion
FISSIÖH OF M»ia»-225 BYBEâCTOH HE011O1©
Introduction
Experimental
Easulta
Mmt lMTIGS CF K&ÜT0HIÖM-239FÎSSIOS YIELDS
IntroduotioR
Experinienial
target preparation
4*2.1 (a) Determination of apeoifie aotivity
4»2*1 (b) Detessidaation of the isotopleoeapoaition
4.2.1 Ce) Calculation»
4.2.1 (d) Kaamt»
4*2.2 ïxsadietiot»
Paga Us.
23
23
24
24
25
25
26
34
34
35
36
39
39
42
42
43
44
45
45
51
Fag» Ho.
4*2*3 Dissolution and xndiooaemicalseparations 51
4.2.4 Counting 52
4*3.4 (a) Ce(Li) system 52
4*2.4 (b) Disintegration rate of MolyMewua-99 66
4*2.4 (o) Disintegration xate of Iodine-131 70
4*2.4 (d) Die integration zate of Cobalt~60 76
4.2.4 (e) Beta counting 76
4*3 Caloulationa 76
A «4 Hrrera 61
4*5 Results and Discussion 84
SECTION 5 EXTMCTIOä OF ÂMSBICIU&241 PEOMCÖBCERTEATED AÇygOOS CSLûKE)E SC&ÖTIQUSBY TRILÅURYLÅMESE OTBEOCULOSISS 116
5o1 Introduction 116
5*1.1 Aminé extraction system 117
5*1.1 (a) Acid base reaction 117
5.1*1 (b) Organic diluent 117
5.1,1 (o) Degree of association of
ammonium salt 118
5«1.1 (d) Third-phase formation 119
5.1.1 (e) Excess sold axtsaction 120
5.1.1 ( f ) Extraction of netale 120
5.1.2 attraction of txivalent actinldes 121
5*1*3 Present investigation 123
T*
Fags Ho.
5.2
5.2.1
5*2*2
5.2.3
5.2.4
5.2.5
5*2.6
5.3
Bxperioeatal
TrilauEjrlOiaîne hydioohîoride
Biluenta
Aqueous Tplns.ee
Organic phase
Equilibration
Counting
Saaulto aod Mecussion
SîlâTEîJSHr (JIŒER O.413
123
123
124
124
124
126
126
127
139
;
1 •
1 »1 Historical Backegoawt
The discovery of neutron by CHADlïICK in 19J2 and the seriesof experiments carried out during 1934 to 1938, thou$i most confusing
2ae described in a review art ic le on tmnsuranie chemistry by QOIL1 »
led towards the discovery of f i ss ion. The credit goes to the Gexnan
radiochemists HAIÏH and S7BÂSSMM^' t «ho proved that the confusing
protects of irradiation of uranium with neutrons were not the heavy
element isotopes» but isotopes of Bjediun-nroijtM elements produced by
an entirely unexpected nuclear phenomenon. MBlTOfiSB and FRISCH* proposed
tile term "Uuclear Fission" for tliia new phenomenon. The experiments
performed by HfiJIîJ and smftSSEMM as well aa by CUKIE and SåVITen6*7,
who were woibing simultaneously in Franca, nere to study the properties
of radium and actinium Isotopes in neutron Irradiated uranium sanples.994
Inactive barium and lanthamn were added as carriers» Th X ( ^Ra) or
0s îh^ ( Sa) and vJe lhg ( Ac) nera used ae indicators for radium
and actinium* During partial separation of barium and radium by f mo-
tional crystallisation» strange beta act iv i t ies were found to concen-
trate with the barium fraction. Ineae unidentified act iv i t ies carried
on barium were isotopes ef barium and not radiuxa isotopes. Similar
results were obtained in case of a partial separation of lantbarns and
actinium. These expérimenta that nay look vary siaple now, are described
as most exciting» careful and unaabigttoua ever carried oat in radio-
chemistry.
1 . J. ÜÏUDWIÜK, Frde. fioy. Soc.» A136. 692 (1952).2 . L.L. QUILI», Cham* Bevlewa, 2J, 87 (1938).
3. 0, HUM sad F. STRAÜS.MANN, Ifeturwis»., 2J.» 11 (1939)*
4 . 0 . mm «3» F. STRAS3MAHH, «atuxwiBB.» Sb 09 (1939) .
5 . L. WZVam and O.P.. ARISCH» Mature» 24i» 239» 471 (1939)*
6 . I . CURIE and P. SAVITCH, J . d* Fbys.» (7) £ , 385 (1937)*
MEIÏHER ana PBISCH5 also rocognioed that on exceptionally
large amount of emxgy should be liberated in this reaction. FBISCIT
firat verified i t , Eafcing use of the ionising property of fiosion
fragaenta. Froza a study of the ion chamber pulses, JE8T8CUKS and
PEÄSKL concluded that there were two groups of f iss ion fragments -
one centred at an energy of about 60 r.!e¥ and «ie othor centred at
about 100 IfeV. Thio «as the f i r s t evidence for asymmetry in f iss ion.
Ihe emission of neutrons produced in the fission process was observed
by VOS HAtBAH, JGLIOT and KOWARSKI10 in Parla and by ANDERSOlî,
and HAJ3STEIN11 in ifew York.
1.2 Fission Procasa
Since the dlseovszy of the neutron-induced f iss ion of uraniaa,
i t ses established tisat a l l m c l e i in the actinide region can be sade
to undergo f ission by supplying sufficient energy to overcome tiie
f iss ion energy barrier. Soas of the heavy elements (Z >90) undergo12fiss ion spontaneously. M.ERGV and PSïKZAK «ere tiie f i r s t to report
spontaneouo fiasion in araniœn. Spontanooue f i ss ion hal f - l i fe ranges
from > 10 years for * 9h to about 6 seconds for ^ H B . A quanti-
tative study of the spontaneous fiseion half- l i fe nay giv» valuable
infoxaation about ttue ehape of Hie fiasion barrier. Becent'iy Aaesian
workers '** reported iaotuerlo states of heavy nuclei which were observed
to decay in past by spontaneous f iss ion. A large nuaber of spontane-
ously fissioning ieoners in uranium, neptunium, plutonium aad aserioium
?. X. CUKIE and P. SAVIïCH, j . de Fhys., (7) 2t 355 0 9 5 6 ) .
6. O.E. FSISCO, Ikture, \*3, 21$ (1959).
9 . W. JEI TSCHKE and F. PMr«L, Naturwls»., ^1- 134 (19?9).
10. H. VO:' HALBAK, Jr . , F. JOLZOT and L. KGWAKSKX, Sature, l u , 470 (1939).
1-9. Q.L. AIIDEHSOH, £ . WWOL and B.B. HAUSTEIH, Phys. Her., j S., $10 (1939)*
12. Q.IU FIEWV and K .A. PETKZHAX, Phys. F«v., 58, 69 (1940) or Compt.
Hend. Aoad. Sol. Ü.S.S.B., 2§, §00 (1940).
ML- , >*»**.*%
17hav© been reported . Fission can bo induced î>y protons» neutrons,
positively charged ions, taeaoie, etc* Of tfrese, nautxon-lnduœd fission
ie most widely studied due to the fact i t can give r ise to a nuclear
chain reaction and thus finds use in nuclear reactors.
mechanise of fission can bo sepresentad in steps ana In
respect of tia» as shown in Figure 1 taken from HI/IZEîîGA and GMDLER .
ïhe target nucleus with naaa A and charge Z in neutron-induced fission
captures a neutjxm to form an excited cosipoand nucleus, îhîo excited
nucleus can deexcite in two possible ways. She f i r s t i s by gamm-ray
emission and undergoing a beta decay « leading to the formation of an
element with moe and charge one unit higher than the original nucleus,
second is i t s division into a t least two fragments (2L, 4 . ) and
, Ag) of intermediate rases and hairing various amounts of excitation
euexgjr. In most of the fission events (Sj + Z„) - Z ana (A. + A,) * (A * i)<
Sose experiments have shown *&« «aiBsion of alpha particles and in » r e
events the emission of a third large fragment, i . e . ternary fission.
I t is not ex&otly kvicwn whether tfeeee alpha particles are eaittcd a t
the time of scission or i'-œaeâiattily after that» but these are definitely
emitted before neutron evaporation*
14.
16.
17.
S.?.3. POLIKAaOV, V.A. »MJTO, V.A. KAffiiAUKUOV, V.L.
A.A. H.BV£S W.K. SfCOB EV, V.G. SUBBOTIM, G.M. TEB-AKÜF«ÏAH and
V.A. FCSICHE?» Soviet Phya. JETP., J^, 1016 (1962).
V.P. PERELYGÎÎÏ, S.P. ALfASOVA, B.A. GVTQZSEV and Yu. ¥.
C
^mm
ïhe primary fission fragments acquire tîioîr maximum kineticenergy in a tin» interval of about HO secondB and fly «part inopposite directions due to the znolear ooulombic sepulsion. Studies,at this stag»« of angular correlations and mass and charge distributionsof fission fragments, alpha particles anâ pronpt gaussa, rays help inunderstanding the transition state of fissioning nucleus which repre-sents nuclear matter in a hlgily deformed state «
Bie next stage is the evaporation of prompt neutrons from theprlaary fission fragments in a tine interval of 10 to 10 7 seconds.These neutrons comprise HOS t of the neutron yield in fission* PhysicaloeasurcBients lika time-of-flight study in combination with neutrondetectors give useful data on Hie •variation of number of neutrons«•sitted with the mass and kinetic energy of fragaenta. An accurateknowledge of the average number of neutrons emitted In the fission ofnuclei like " ü t Ö and ™?u is vary iraportant for reactor designe Se. HÛW oassee of the prinasy fission fragments now reduce to (^ - V )and (Ag - >^)f while the charges remain the saiae* l*e* 2^ and 2gxespectively*
The «tcitation «nergy remaining after the neutron endesion is—11last by gBsare-zay emission in about 10 seconds* The products are now
termed secondary fission fragment» or fission products. The fissionproducts are radioactive since they are far removed from tfce zuclearbeta stability. ïïhey decay to stable end products foxming radioactivedecay chains* Iladiochemieal studies ara carried out on these radioactivefission products* Hess soas of the beta decay leads to a level which isneutron unstable and the delayed neutrons a:?e emitted= These neutronsfora about 1?S of the total neutron yield in fission*
18. J.K. HUIZEHCA and J. GÎKDLBH, Chapter on Fission in "IbelearChemistty11, edited by L. YAFFE, Vol. tlt Axadsmic Press (1968).
Primary fission fragmenta (2^, A,) end (Z^, &^) have a videdistribution of macs, cbarg», angular moraentura and kinetic energy» Ifi t mis possible to study al l these parameters for different fission-ing nuclei «cited under a variety of conditions i t would have givena clear picture of flealon phenomenon, but unfortunately i t i s notpossible due to the short emission tines of the order of 10"20 to 10"11
seconds* ïhe different aspects in the fission process hare been dis-cussed in detail by KÏDË19, in the proceedings of the Firet IAEA
20Symposium on Physios awl Chemiatsy of F i s s ion , ïlEîtMAHS*", FRASBK
and MILÏOM22, GÎHDLBR ant! HBI^NGA18 and i n the proceeding*? of the2^Second IAEA Syaposiura on Physics and Cheaiatry of Fission2^. It
be restricted to the mass distribution description since i t will havea bearing on the experimental «ork carried out and described in thisthesis.
1.3 Mas» Distribution
About 400 to 5 0 0 nuolldes hove been Identified to be formed in
the fission process and pediape many more axe formed which are yet to
be discovered . Mass distribution c&n be described as the relative
probability of formation or the 'fission yield'* of all the fission
J
19* E.K. HYDE, The Huclear Properties of the Heavy Elements,
Vol. I l l , Fission PhenoBonon, Prentlae Hall, K.Y. (1964)*
20c 'Kiyslos and Gwnistry of Fission1» Vol» I and Vol. I I , IAEA,
Vienna (19*5).
21 . a. HERSaAHN» 25 years of Nuclear Fission, AEHE - Translstione,
1036 and 1097 (1965).
22. J . 3 . FfiASFB and J.G.E. MXLTON, »Kuolear Fission', Ann. Bev.
Duel. So l . , Vol. 16, (1966).
23. 'Physics and Chemistry of Fiwion' , IAEA, Vienna (1969).
24. A.C. KAffl., ȕhyeios and Qteaistzy of Fiesiori', IAEA,
Vleima, 1 , 517 (1965).
i
fragments or fission products of the sam© nsass, i . e . nuclei frxned befor©and after neutron evaporation respectively in the fission process.Cuaulative yield of a radioactive nuolide mar the end of e radioactivebeta decay chain is to a very good approxlsaatien equal to the totalchain yield* Tïiia ie determined using the radiocheraiaal method, massapeetronetric oethod and recently garara-ray spectronetry using Ge(Li)detector. Most of the raeas distribution curves have been constructedand different features studied using cupaiiative yields. Physical methodslike tlae«of-l£13ght measurement and kinetic energy measurement in ion-ieation chambers or by solid state detectors, axe employed to «eaaos-eprompt yields of fission fxagserôs. 5he raass distributions in the tiieitoalneutxon-inâuced fission of " u , ™V and ™Pu have been studied by•asp imeatig&tors due GO their importance as nuclear fuels sinee theyaxe highly fissionable with thermal neutrons. Similar nass distributions
oïfl PAO I7â9
have been observed in the spontaneous f i ss ion of ^ Uf ^ PU, '^ Ca and852Gft in the «heraal neutron-induced fission of 227ffi»f
229Sfc, 2 4 1ÏU,^ A ^Am, ^'Cai and **Cf and reactor neutron-itiduceâ fission of, 235O, 2 3 8 ö , 257N|>, 239Pu end ^Ära. A recent review by VGB
compares the different features of the ntass distribution in spontaneousend neutron-induced fission of heavy elements. SOD» inportant features@f these nass distribution curves are outlined here.
In low energy fission the fission yields for unequal trasses axemuch cioze than fos? equsl causes. This resulta in two peaks, i . e . Hbelight näsa peak and the heavy a»ss peak in Ute Bass distribution curven.Different explanations haw been offered to understand the experimentalresults in the mass dlstrltaatlon in the fission process. To date thexeIs no single fhcexy whiek without assuming son» or the ofter paraastercould explain a l l the nas» distributions, ftie first statistical model
25. Aotinid»s I , 275 0969)•
8
of POMCr which waa modified latez by bJm2^ could explain aayametrlo
mass distribution in the case of thermal neutron-induced fission of
T»at i t failed in the oase of 2^Pu and etfce» mol iâes . ïhe random&26model of BÄHÄHM&26 and cluster model of FAISSÖEK anâ I
f i t &e experimental values, bat in each of the calculations at least
one of the parameters bad been adjusted to give the desired agreement.
The liquid drop nodal f i r s t proposes by BŒK and ÜHËELEK30 and recent
calculations md« by CQIffii and SWIATECKI31, ÎI2X32 and KELSOE33 ceeld
explain only symmetrie f ission in nuclei with Z < 88C Ihe asymmtry of
the ottsa distribution may be predicted approximately by the semi-empirical
equation given by SWIATECfCI equation (1)
0.090 f (40.2 ± 0.7) - J (1)
where«fitted per f iss ion event»
anâ T i s the average number of
J
position of the heavy mass peak particularly on i t s low oass
aide i s fixed due to closed shell structures of 5° protons and 62 noutroec.
She heavy oass peak fal la at an average mass number 133*5 ± 2*5 in th»
neutron-inducad f iss ion of 'Ac to ^ 7Cf. The position of the l ight oass
peak varies with the nmss of the fissioning molens and i s a linear
variation with a slope of 1 in the nsutron-iadaeed f ission of ^Ac to
26. P. FC3G, Riys. Bev.f 10^, 434 (1956),
27* P* F0H6, fhys. fttv., 1 ^ , B1380 (i?64>*28. P.. EALtABHA, Phys. Letters, 10, 521 (1964).
29. il. FAïaSÎEF and K. WILUfcTCMH, Nucl. mye.9 ^3 , 177 <1964).
30. 9. SGHReBd J.A. 'MSf-lER, Shys. Rev.» 2$, 426 (1939)•
31 . S. COHEN and W.J. SWIAÏECKI, Aim. Phys., (»*T)y 2£, 4O6 (1965).
32. J.R. MIX, WCHL-10695 (1963) and 11338 (1964).
33. Ï . KELS013, Phys. Hev.t !3j&, B1667 (1964).34. W.J. SWIATECKI, Fhys. Rev., 100, 936 (1955).
1.-y
ïho fiesîon yields in tins light and heavy casa peak regionsOÎÎOW fine stsuetm©. Sîïis is atta&fouted to the variation of the somberof neu trois emitted aa a function of fission fsagnent ESSS^*^ . Further
psefersnee in the fiesios act i tself leads to the foxsaation ofproducts and ase sala tea to ciooeâ ahell eteieteiïDS *
A ÏOÖ^Ï estinate of Uie average raîdbor of nautrons ^ emittedper fission event can be obtained from 1fee averag© sssseB of fee l i # tand heavy peaks» A. ©no 1» xeepectively. If (A + 1} Is 'SJe ssass of the
melsus
m (A + 1} » (2)
Ån approximate estimate of V can also be obt@imâ frcre tho averagetsass of tiie meliâes fositwdeveisge siass for syinmetric mas »splitting
the symmetric xegion* If  i s the
Y (3)
ïhe ntmboc of neatsone asittad by each fra^naaat can be derived frcathe proapt isaas distribution deterraJued by velocity ;ne«eur«mentB*'5**'ana the mss diatcibution carve on the basis of curwlative yield» •
wMth of the trou#i o? valley in the mm distributioncaxves doozease» triât the increasing EBBS of the fissioning ai cloua.
35,
36*
37.
J. TSEULt, fhysu He?., igZ, 880 (196a).a. FAPMR and H.H. TCIILIIffiOil, Can. J . FhyeM | 0 , 943 (1962).
J* EBBELL, •Phyaiea and Ghenistzy of Fission'» IAEA,
7i»am, I I , 3 (1965).
1 O
îhe depth of tbe mlley ia dependent on the excitation eKes?§y of the
fissioning nucleus» ïne peafc-to-trougfc ratio decreases as one passes
from apontaueous fiseion througli thornal nsutroa-inäueed fission -
reactor neutron-induced fiseion to high energy fission, ïhis iras
demonstrated by LEâCHMâSr in the case of " u fission by neutrons
of different energies. A cimilar dependence TOB observed by COLBÏin 238
l " in the K fission with helium ions of different energieswhile in the case of " u fisBion with hélium iona these authors
ebaesved a third peak in the symét r i e r»sl«» and tills peak broadened
apart froa the decrease in the peak-to-trougft r a t io with the Increase
of the energy of the bombarding ions.
Studies wii& resonance energy neutrons (neutrons having energy
in -aie electron vol t region Just above theasaal neutron energy) of the
mass d is t r ibut ion i n the f iss ion of
oat by n»ny investigators^"*4 '
2330, 239ana ' Pa «ere carried
fo» neutron»infiucad f i ss ion of
. She f iss ion yields in the valley region
U and U showed only a small v a r i -
a t i o n . However, for ""^Pii the psak-to-trough r a t i o «as found to be
markedly different due to sharp resooanee a t 0.297 eV.
56. N.B. tEAGWSâS* U.ll. I n t . Conf. FÖAE., j ^ t 229 (1958).
39. L . J . COLBY J r . , J»W. COB33LE and M.I.. 31I0AP, Fhya. Eev.,
1410 (1961).
40 . il. îiâSMOiiW, 3* lïABüï, O.H. Rlï«JÜ, L.H. CLE33D3BB1 and S.P.
STEÏBBERG, Hjya. B»v.t 10S, 1522 (1957).
4 1 . L.W. KOELAHD, L.M» BOLIISSEK and C E . THC^S, U.ïJ. I n t . Conf.
POAB, n . 440 (1958).42 . S.B. SSCXE&, W.H. BVHOOiS ané R.L. TROîîP, fhya. Pev., U I , 1589 (1959).4 3 . BcB. HEGIEîî, W.H. BUBCUS, R.L. TRCEB? att4 B.H. SOREÏföSïJ,
Phy«» Eev.9 2J2. 2017 (19«O)*
44. Û.A. QOmJif A. TOïKSVICaî, C I . BR03HE nnà Ï.AÎX, %dioohenistry
Group, Phya. Bcv., 122» 1296 ( i?66) .
1 1
Maas dis tr ibut ion in the f i s s i o n of l imi ter elements l i k e lead
and bisnuth wao observed to be predominantly symmetric a t a l l energies*8 OFiss ion of 8 O 9Bi with 42 SfeV helium ioas gave a ait>gle peaked mass
226l;a was
T
distribution curve* !%SB distribution in the fiasion ofinvestigated with different projectiles aiid with vazyingtriple-peaked ORBS distribution we observed and the height of the thirdpeak in the symmetric region increased with the increasing projectileenergy until symmetric fission predominated. MI HALL et.al^ '•* triedto explain these observed trends in .mat* distribution on the basis oftsrOMQOde fission hypotheBls and the triple-peaked rn.se dia tribut Ionwas explained on the hypothesis that there is a sharp transition fromayoaetric mode of fission to asymmetric mode as one parses from fission-ing nucleus actinium to thorium. Maes distribution in the fission of233U with helium ions'9 and in ihe fission of 2'2!£h with reactor neutrons5'leads credence to the two-mode fieeioa hypothesis, Sje two-mode hypothesis
RJ
i s attractive for i t s relative simplicity* According to P&PPÅÖ et.al"^the two-mode fission hypothesis compotes In some sense with the fragmentshell theory of fission which has a more physical basis. The conceptualdiscrepancy, however, between these two is not large» tii© differencelying in going from a liquid drop (synmetric fission mode) to & shellconfiguration (asymétrie fission mode). Here 1toe two-node hypothesisassBses the presence of these two-sodes in a transition region whilethe fragment shell theory assuiws a gradual transition fro» one rode tothe other*
45.
46*
47.
46.49.
J.G. CUNÎHCaïAîJE. G .P . K HT and E.R. EAB, ï*iol . Phys . . 21 , »54 (19&).
6^k. COWAfJ, B.P. MYHÜES2 and B*J. ïïii&BQW, Ways, Rev.,
130> 2380 (1963) . ,
J.G. GVMSWÈM, K. PHITZS, J.S^ hYEILi aad C.B. WEBàïEB,
Sucl . Phys.t M . 49 (1966) .
E.G. JKNSBH and A.W. PAimiAII,. Fttjs* Hev. t 102,, 942 (1958) .
R.B. HJFFIELD, B.A. SCrBOTTT and H.A. SHARP, O.K. I n t . Conf.
PUAS, 1 £ , 202 (1958) .
"ff
i
\ 1
1*4 Fission Yields and Methods of ffip^
1*4*1 Definitions
Fission yields can be considered uncle? three nain headings
(a) Independent yield
(b) Gunuletive yield
(c) Total yield
She term independent yield i s the probability for the formation ofan isotope dlxectly in the f ission process.
Cumulative yield i s the sua of the probabilities of formation
of a given isotope directly and from tile decay of precursors in the
radioactive beta decay chain* To a vexy good approximation this 1B
equal to the total yield i f determined for an isotope near tfee end of
the beta decay chain*
yielâ is the yield of the final product of the beta
decoy chain for WBSB number 'A' * 'Bie sum of the total yields is 200$.
50.
51*
52.
5J.
54.
A.W. FAIEHAIJ,, S.C* JEK3QH and K.F. EEUZIL, Ü.N. Int. Conf.
PtJAE, J i . 452 (1958).B.C* JKÏ3EH and A.W. FAlKHåLL, Fnys. Bsv.v 21å* 771 (i960),H.C. BBT2V, U.K. WSÜriEF. aal J*C QVSSKI, Ifeya. R*v.t 122,, 2239 (196}).
R.U. IYEIf, C.K. miSg«Sf K. RAVJNDFAII. X. BEWAS, D.V. SIHGH,
H.¥. RAMAKIAH anft B.D. SHAI .U, J. Inorg. BBCI. Chem., 25., 465 (1963).
A.C« PAP?A3, J. ALSÎA» and S. ÜACEBO, •Physios mvå Chenistry of
Fission*. IAEA, ViBiim, 669 (19©) .
11 3
1.4.2 fJfethoda of noaaurement
She öifferent raetnods for the de termina tiou of fission yields are
(a) Radiochemieal method
(b) filas» apectrometrie nethod(c) Physical measurements(â) Ganna-ray spectroraetry uâing a Ge(Li) detector
She first three have been described by HEEBMåHIT1 giving references tothe earlier vork and their resulta. Here an outline of the methods willbo given enä the advantages and limitations of each are pointed out.
1.4.2 (a) Hadioe&eraical method
The first concept of fission yields «as given by AHDERSOU,FESMI and GROSSE"* usixtg radiocheroloal oethod. She activity formed inneutron irmdiatlon end fission i s given by equation (4)
(1 - (4)
1
If on» can determine the disintegration rate A^ of the fission productana calculât* the number of fisalons(H^+) tten one ean detexnlae theabsolute fission yisld Y . ^termination of absolute fission yields isa laborious job and precautions have to be taken at each step* Ihese
99ar» usually detsnained for some of the mel ides only» e.g. for Hoor 1^°Ba eto «hlch axe later used as standard to determine other yields•Other yields can bo determined relative to ttiis if the disintegrationrat» or the number of atone of other fission product» forsed is deter-mined» The determination of diaintegration rate i s also oircuavented
55. AH1EHSOH, FEBU and GEOSSE, fnys. E»v.t *j&« $2 (1941 )•
1 4
by deteroîBine fission yields by Hi© 'comparison method'. 2n this cas©omnium is always irradiated simultaneously with the target naclldeunder study, and the fission products under eonaidesatioa are isolatedfron both» One reference nuelide is isolated In al l irradiatione andused as internal standard* Mounting and counting of the correspondingsamples is done in the same way, so that geometry, absorption andscattering corrections are cancelled. Defining ' 9 ' as the zatio of thsactivity, A of any fission product X formed to that of the activityA of the reference tuolide S formed in the sane fioaion under the sans
S
conditions, and 'E' as the ratio of BL, the B-value in a particularfission («here » » tfoe target nuelide undo? study) and D„ • the D-valuein uranium fission
1
The activity A is related to the fission yield as given by equation (4A)
A - Y (4A)
«here Y is tile fission yield of the particular luclids, A i ts decayconstant, F the total number of fission events taking place in th«target and E the counting efficiency fox the fission product, substi-tuting for BJJ one gets
OL K(rB\ \ \ \
. . . (4B)
(5)
1 5
The ratio of the internal standard yield (*aAg) is arbitrarily setequal to 1 and the normalisation footer is applied to total all theyields to 200;». ïbe internal standard can alao be eliminated byirradiating an exactly known amount of the fissionable aaterial andusing the fission cross-section values. In that case the fission yieldÏ is given by equation (6)
(6)
She radiocheroioal method has the distinct advantage that i t ia veryspécifie as regards charge and raaso. Lon fissîor yields in the symmetricregion of short-lived nuclides can be reliably determined. Activitiesof very short half-life of the carder of a few minutes can be studiedusing fast radlochsniaal techniques»
1.4»3 (b) flåsa speotroaetric method
The ose of maa speetionetrio method in the study of fissionyields bed been a great improvement because the isotopic abundanceratios could be determined with an accuracy of better than 1f£* Therelative aaounts of the various fission prodaote «re neasured in theaass-spectroneter. ?he absolute amount of one of these Isotopes isdetermined and the other ratios converted to absolute amounts. For this,tile isobarlo technique or the isotope dilution method is used* Sheabsolute yields determined by this method have an accuracy better than3';J in most oases and this is the nain advantage of this method overother methods* For stable nuolides or rezy long lived ones this methodis recommended. Mass epectporaetric method has the limitations fromcontamination point of view and at least 10 y ga of fission productsL& required for accurate determination.
i
1 «4*2 (o) Physical ceaauremonta
In thiB method the kinetic energy of tfee fission fragmentis deternined from the pulae height neasureirent in ionisation chambsror by solid state detector and the velocity is derived from taie tine->of-flight BBaBuxamsnt. If M an* HU represent the light and heavy pronptnasses obtained from the kinetic energy E, and velocity V asasurenents,en the basis of conservation of noœantum
- K (7)
an* (7A)
where (A + 1) la the tmaa of the fissioning compound oioleus* Fromequations (7) and (?A) one gets equation (72)
1(A + 1)
K(7B)
Usually the correct prompt aasses &xe derived fron velocity measuraaonta.Masses after asatron eaission can be obtaioed from kinetic energy andvelocity measuraaent simultaneously. The nnnber of neutrons emitted bythe fineion fsagœnte i s deterndned by direct coanting ant! following thaoeasurement of pulae height nv& time-of-flight. ï.Ha main advantage ofthis raethoâ ÎG -Bhat i t is poeoibie to get prompt mass distribution inthe fission procftSSo The tnasa distribution obtained by this method isin general agreement with that obtained by the radiochemical method,but due to poor QBSS resolution (?-4 WLBB units) i t doss not agree inal l details» It I* not possible to determine yields in theregion by this method.
1 7
1.4.2 (d) Garosa-ray spectromatiy usiag a Ge(Li) detector
She high resolution obtainable with a Gs(Li) detector provedi ts usefulness in the field of fission studies. 2t waa shown recently56'57
that garasa-EBy apeetroaetry using Ge(Li) detector ©an be used to deter-mine flaaion yields. In the gross gamce-my spect.ta of fission products,aooe of the well resolved photopoaks axe due to specific gamma-rayenergies, and these peaks are used to deteriaine the activities of fissionproducts. From these activities the fission yields can be dotersinedusing the • comparison nettood». This method has the main advantage thata nutnbei? of fission yields oan be determined in a single experiment.The yields of gaseous fission products and rare earths can be determinedeasily, which are otherwise difficult to determine. The limitation ofthis method i ts lov efficiency and high Ootapton contribution particalaryif the detector is saall like the one used in the present investigation.
1.5 Present Investigation
The fission studies were carried out wife the objective ofgetting as i n s i s t into tte trends in nsss distribution in the heavy
227element region* Fission of Ac «as considered inposrfcent in view ofthe result» obtained by JRKSEN and FAKHALL51 in. the deuteron and hellim
226ion-inftuoed fission of Ba and A proposal made by them to explain tin»triple-peaked raasa distribution on the assumption that there i s a «harptransition from symoetrio mode of fission to asyranetric sods as ons passesf£oo the fissioning mol«us actinium to thorium. I» was considered werih-
227* i l e to investigate the neutron-induced fission ttf 'Ac sines thisshould girs a pxsdonimntly triple-peaked aass distribution If the»
such a strong dspendencs of 13M shaps of mass distribution ouxvt
36, G.E. GORDQH, J.W. ESRVEY and H* 3AKAHARA, Kioleonics,62 (1966).
57. D.J. GORAH and H.ft« TO?fl,I«SOJi, referred to in Can. J. Chsa*»2911 (1968).
• %
on the charge of the fissioning nucleus. Fission yields vexe detornâncdin -toe reactor neutron-induced fission of ™Ao using the 'conrparSaonmethod' and employing »adioeaemlcal techniques. As the amount of '&oavailable was small, the reeoil catcher tochnique «as used to consezvethe target material» Since the fission cross-section is also snail»fission yields foe only twelve nuolldes could fee determined. However*sufficient maas-yield data w«re obtained in the trough region.
In view of the results that «ere obtained in the fission of227
'Act we were prompted to study the neutron-induced fission of s t i l llighter elements. ftaäiui»*223 was one such isotope for which an upper
CO
limit of fission cross-section of about 100 barns was reported** .227
Hadiom-223 was milked from 'åc and checked for purity by alpha223
speetrosetry. Carrier-free Ra was evaporated in the matrix material(isaterJal ueed. for retaining fission products)• A blank was alwaysprepared under identical conditions anä irradiated. Badiocheraicaltechnique was used to separate and purify high yield fission productsl i te ° Sr. Preliminary experirsents showed that only a few counts abovebackground could be obtained* Though the studies were initiated withthe idea of ds te mining the mass-yield carve» i t was found that thefission cross-section is too low to enable any detailed study and anupper limit of 700 Eillibam» was obtained for the fission cross-section.239Fission studies of *"Pu ax» of significant interest du* to itsvery important role in nuclear power production. Although fission yieldsin the thanml neutron Mission of I'll were determined earlier the dataavailable is not as extensive as in the case of 'K and therefor* 'atepresent investigation was undertaken. Tte newly available G»(Ll) dete-ctor was used with the purpose of investigating the relative usefulness
58. S. FljïJiJiSOJî and A. GÏIIOKSO, The Traneur&nlum Elements, Vol*Paper 19*4, M.H.E.S, McGraw Hill. Now York (1949)*
À
^"'i*J.8«J.a-
. 'å
1 9
of tho detector for determining the fission yields usingspectra by diiect counting without chemical separations es this wouldsave tisa. Fission yields of sixteen nacliôen were determined in thefission of ^PQ using ™Mo as an internal standard and inaking usa ofthe 'coinparison method'. Electrddaposited targets of enriched uraniumand plutonium on gold coated aluminium folle wore covered with pupshodcircles of 1 mil thick 'superpure* alwainluia catcher foils and irrad-iated together* The catcher foils were counted on the Ge(li) detectorand the gamma—ray spectra recorded using a 400-cïiannel analyzer. Theactivity ratios were taken from tho decay curves plotted for th« identi-fied photopeaka. From the sixteen fission yields determined i t was not
QQ,
possible to ietermine the normalisation factor for Mo yield in thefission of 393?ü and *5U. Therefor» literature values for Mo yield
2^9 S ^ " 2 3 9la 2^9Ptt and S ^u fission had to he used. îfee yield of "MO Infission reported in literature varied over a wide range from 5.61 to6*59. She large variation and the difficulty in selecting a particular
99value of fuO for calculating the fission yields cads i t necessary to
investigate this yield value in detail. 'Ute yield of ^Mo was deter-mined by the 'comparison aethod' and also by the 'absolute method'.A value of 6.79 ± °«15 «as obtained by the 'comparison method'. In allisotopically analysed ana accarataly known amounts of
uranium and plutonium «ere irradiated. Yield of i«o was calculatedby the 'absolute meüiod' by determining neutron flux, tine of irradi-ation, efficiency of the counter and a value 6.66 ± 0.07 was obtained.
239In oxder to Investigate some of the yields in Pu fission» furtherradiochenlcal work was carried out. Pission yields of ^Ru euû ' Iwhich are about 3'j-3!?fe higher «ere investigated in detail* In all)fission yields of 29 mclides were determined in the present work andare compared with literature data*
2 . MASS miamwwicm ia gas
20
g) FISSIOS qsr ACgnmi-227
2.1 Introduction
Î2ass distribution In the fission of nuclei In the segion of59 60 61
gold t bisnuth and lead is symétrie while in low-energy fissionof uranium, plutonium and heavies? elements i t i s M#ily aoysmaetric .Once again syiffiaetrlc fission predominates even in the higjisr mesregion as observed recently in the caae of f0zmiura-257 • 2n ttie losesrinss region betneen lead anS uranium^ a tsansition from «symisetrie topredominantly asymmetric fission 3aemå to exist . Fission of Bainduced by charged particles * and photons was found to resulti s a triple-peaked maas distribution. Helium ion-inäneed fission ofeven a heavies nucleus like " u was found to give a triple-humpedmes distribution while U and U gave only double-peaked curves * ".gp
results obteined in -itie fission of Th by reactor neutrons shewed70
presence of a SEEÎI ih±sâ peak in the symsetric region'. JESSEH and6ÅPJIâLL^ «hile discosaiag üie resulta of triple-peaked r-ass dis t r i -
bu tion ia tfaa fission of Ba with deutaxons and helium ions hypo-
thesised that a tsmisitioiii from gysnretrlo node of fission to asymmetric
mode takes place at the fissioaing nucleus actinium. I t «as considered
that a study of til» nsutroit-induced fission of actiniun would be v»sy
59. E.F. Ï3EÜ3IL and A.W. FAIRK&LL, Htys. Rev., i2i» 2?O5 (1963>.60. A.'.V. ÏAXTuiÂLJL, Biya. ï'eTf., 102, 1335 (1956).61. A.W. PAlKlåLL, B.C. JSîEiîa aoâ B.F. WH2SL, Ü.S. Int . Conf.
FÖAB., I J , 452 (I958).68. E .K. ÏÏÏDa, îho ïïuclear Properties of the Heavy Elements, Vol, I I I ,
Fission Fhenonenon, Prentice Hall, Inc. H.Y. (1964)*t'ÖA. 9 . JOHH, S.K. HÜLEÏ, B.W. LWGHSED and J*J. IÏES0L0W5KÏ,
Fàys. R«v, l e t t e r s , g£, 43 (1971)*63. R.C. JEHSEB ani A.W. FAZRHAUi, £hys. Bev., JO^, 942 <195S).£4. B.C. JEÏföEïï and A.W. FABlBAIiL, «ays. Bev., t i g , 771 (i960).
<yaU.iA~M^U
21
holpfal in eonfismiag or dispsoviüig this hypotisesiB. f i t t e r , therr «aeno reported data on the fioaioa of any ectiaiara isotopes» For taassseasons the ross distribution ia the fission of 22^Ae with reactorneutroae «as studied.
2 »2 .Expérimental
2.2.1 Skeget preparation
Aeiinios-227 obtained from the Badiochomical Centre, toershara(England) was used in this study, 'iïie Ba content of the sample «asestimated and found to be leas than O.1?£, am the fission contributionfrom this would 1)0 rauch less than 0.1^* actinium viaa olectrodepositedon platimun tacking in lOOyug aoou&ts following the procedure of XÏSB
71 22?et .a l end used aa targets* Amount of Ac on the targets «as knownfrotn the originel assay «hen a l l the daughters were in equilibrium andfinally following the decay of the superstate after eleotxoâeposition*'The target «as covered with two thin aluminium foils of about 200/ag/cmeach (to pie ven t direct contact between the recoil catcher ana actiniumand i t s daughter products) and then «ith 'superp&re' aluminium foil»1 rail thick (about 7 rag/era ) as catcher for recoil ing fission fragmenta.A few blank foils of 'supsrpurs' alundniuia «ere also kept behind the
e target assembly is shown in Figure 2. 3his «as «zapped ina '©raperpuïe1 eilualniBm foil to avoid any contamination froa outside andfinally with a cadmium foil (about 500 rag/on ) to reduce the fission of
'i/h (daughter of 'Ac) end (n t Y) reactions in actiniuat ana any
65* H.C. BKITS, H.S. WEeiiE and J.C. OBBSSY, ïfeya, Eev., 1@l, 2239 (1963).
66. J.P» WOK and J.B. HOXZSÜGA, Phye. Rev.» 124» ^ ° (19^4)»67. H.B. BOFPISU», E.A. SCBMITT and H.A. SHARP, Ü.N, Int. Goaf.
PÏÏAE., îâ» aO2 (1958).68. R. G0K»K and J.W. COBBLE, Phys, Rsv«, Hä , 1247 (1959)»69* L.J. CüLBÏ, M.L. SflOAF and J*W. COBBLE, Fhys. Rev.» 121., 1415 (1961 )•
k
I
22
TA i..'G 'f ; Y
"ir ; if ; ; • _ o
1
i 23
impurities in the secoil catcher. îhe entire assembly was enclosed in
an aluminium container and irradiated. The recoil technique allowed an
actinium target to be re-uaed for irradiation and alao sinplified ttue
cheiaical séparations by avoiding tfte presence of actinium and i t s
daughter products in aie solution to be analysed. Natural uianium in
amounts sequixed to give f ission products of tbe sam» order of magni-
tude as the actinium target vexe evaporated on 'sup>sspure' aluminiun
fo i l 1 mil thick, folded and wrapped in another aluminium fo i l and
enclosed in the satm container as the aotlniuci target and irradiated*
3.2.2 Irradiations
Irradiations were carried out in a fixed position in the swinœing
pool reactor 'Apsara', so that the same neutron spectrum would cause
fissions with no major variations from one experiment to another. Ihe
duration of an Irradiation varied fron 9 to 48 hours depending on the12 —2 ~1nuelides to be studied. ïhe neutron flux «as about 10 n e o sec .
2.2.3 Chemical separation*
After irradiation end proper cooling the catcher foi l end tilt
blank fo i l s «ere sépara tod from the actinlua target, ihese «are dissolved
in alkali or appropriate sold in the presence of inactive carrier where
necessary and analysed radlochemleally. Strontiua-91 «as isolated as a
reference nuclidc in a l l experiments. In some cases only one nuclide
(and the reference) could be isolated r«r irradiation since the activity
«as low. Blank fo i l s irere also processet tor the nuelides in question
(foxiaed by neutron activation) and no detectable act iv i t ies were found*
70. S.H. IÏEE, C.K. LLVÎïtëWS, H. MVIIISMN, K. REHGAIJ, D.V. SHimt M.V.
MriAIKAH and H.2). SIîA>tfîâ, J. Inorg. Kucl. Chan., 2 ,» 465 (1963).
71. H.!I. Itm, U.C. JAIM, I5.V. M-h'AÏSUn and C.I. ÎÎAO, Hadloehinioa
Acta, 2., 225 (19É4).
targets were also tzeataä similarly. Standard radiodiemiealprocedures takes from literature72"*74 were used oitli appropriatemodifications where necessary . usually more purification cycles werecarried out than prescribed in the standard procédâmes* Bue to conta-mination by raôioiB anâ i t s doubters, barium vas purifiai and kept for
4 x»a gsowtfc. Fiœlly the 4 La was silked aaâ the activity of ^Bacomputed» ïhia «as CoHoç/ad for Tioth aetirdusa and umaium saraples.
2.2.4
'Xhe precipitates were filtered through Uhatoan K0.42 f i l ta rpaper using a perspex f i l t e r assembly, waahed, dried and weighed alongwith the f i l t e r paper» centred on aluminium circular aises with double-coated cellulose tape and covered with cellophane paper of thicknasaabout 3 «g/W
2.2.^ Counting
Activities of separated fission products were very Ion (saoe-tis!@s as low as 5 counto/ain. above badcground) since the amount of22?
Ac used «es snail and the fission croca-section low. For this reason76
a low-^aclcgxounå counter consisting of meiSiane gas flow beta propor-tional counter and a plastic Bcirctillator oosaic-ray guard «aa used.The plastic acintiliator »as sensitive to gasm raya. When a beta source,which hstl i t s 01m oolneifent giiiaaa rays* «aa counted in the assemblysome of the beta count» would be lost as coincidences. ?he percentage72. CD. COSYELL and H. SUGAKÎAH, Racuocheaical Studies 1 The Fission
Products, N.îJ.E.S., »iv. IV, Tol. 19, McGraw Hill Book Co.,
Inc., Hew York <1951>-73. J . KLEpSHG, Collected Radiorfienical Procedures, M-1721,
2nd edition (1958)*74. M. LHHim, Radioeheiaioal Procedures, nCHt-4377 (1954).
25
loss of beta counts vas-ied with tîi© energy of the gamma says from thesource. This uncertainty was removed by keeping the discriminator biasfor the aclntillator input at 40 volts so that pulses das to garasse rayaof energies upto 2.7 £3QV would not enter the anticoincidence circuit.This me-öiod eliminated interference from gamm rays of fission productnuolides nomolly counted. A background of about 2 eounta/isin. wasobtained. ïîie decay ourvee were plotted and the activity was read froathese for calculation.
2.3 Calculation»
Relative fission yield values in the fieaion of 'Ac werei ii
determined using the 'comparison method' described earlier^.4*2 (a).The ratio of the internal standard fission yield valua for ^ Sr
/ ^ ^1Sr^ïï w a 8 8 J * 1 * r a r i l y 8 e* equal to 1. Sie arelative valueSrAc Srïïof fee fission yield of a nuclide x in the fission of *Ae would begiven by tfee equation
«VJ. . . . . (3)
Sr
2.4
Ske various factors that contribute to the errors in thereported values ara the following!
235i . The errossJ in the U yields used for calculating the
relativa yields will be reflected In the values reported hero.
75. F&diloohemical Procedures used a t Kadioohemlstoy Division, B.A.R.C.,Tronbay. Bombay, HÏÏÏIÂ (1965)»
76. M.V. RaÏtóEMH, CL. MO and J.K. SAMIM.» I-Jual.
oethod*, 2S.» ?39 (1965).
26
i i . The experimental errors associated with sasjple raounting,counting êtes and particularly due to low counting ratemy be important.
l i i . The error involved in the assumption that the geneticrelationships and ths charge distribution in the xeaotor
227neutron-induced fission of Ac axe seme as thoae in thethernal matron-induced fiesion of ^Ut is probably minorin the case of many nuclidea.
It is gather difficult to estimate the individual errors andthe oveall vel lability of the values nay be considered to be good toabout 1Q$, although internal consistency of the data is ranch better*
2.5 Basalts Discussion
Relative fiseion yields of 12 zuclides In the reactor neutron»227induced fission of 'Ac axe given in Table Ï . Most of the yields «ere
determined in more than one experiment ant in such eases the reportedvalue is the average of the determinations. The data are plotted inFigttze 3» A smooth curv® «as drawn through the experimental points andthe slrror points as the data «as United. The mirror points wereobtained by using equation (9)
(9)
whore A-, „ is the mes number of the fissioning nnoleus» À is the massnoimber of the fragment for which relative yi«ld is knosn, A' is themirror paint of A» Vand "^ ar» the nunbar of neutrons emitted by the
fragn»nts obtained from77universal ouzrs * This method of
77. J. TESEELi, Phyo. Kenr., 122, 680 (1962).
2 1
TABLES I
ïïucîiâe
«•r
«0»
9 1Sr
* a r
9 9 M O
1°5fc
11V
121 a,
132 îe
1«Ca
Ralativa fission vlelds of 22^Ac
Pission Yield
7.01
8.02
5.81
0.32
0.11
0.0S4
0.24
0.1 e
0.17
0.12
5.13
3.48
6.10
number ofde te ml nations
,/
4
Standard
2
1
2
3
6
5
1
1
3
2
Calculatedmirror pointï.fass number
143
137
135
129
127
119
115
115
112
105
94
86
83
•*' ''_ v - M ir ,ii i tffa. 'y i i" *ê>*Bit.r.«-t.i.-.-r-
28
1 0 0
1 0
Q
UJ
2O
!£?IL
LU><t_ JLUCK
Of
OOI I I
o DATA POINTS
• MIRROR POINTSI I
70 82 94 106 118MASS NUMBER
FIGURE - 3
130 142 154
*6*etei-^Ä-;
ii
; 'M 23
obtaining mirror points i s considered somewhat better than using anaverage number of neutrons emitted per fission event. Corrections ofupto 7$ wese applied to tbs relative fission yields to account forthe différences in the fraction of the fission fragments stopped inthe spacer foils (about 4OQyug/sa2 aluminium). The relative yieldscould not be converted into absolute yields as i t sas not possible toget yield data in the entire ratas region*
From the data, a rough estimate of the fission cross-section227for Ac fission with reactor neutrons was mride and i t is about 50
mlllibarns oorapaied to a value of 2 barns rported by PE.TKRSOH andGHIOHSO' ,the only literature data available*
'Bis yield data conform to the established trend that ite heavypeak in the masa-yield curve remains rather fixed while the light peakmoves to lower mass numbers with decreasing mass of the fissioningnucleus. The separation between the light and heavy peaks is about 50raaas numbers and i s in good agreement with 47«8 mass numbers* calculatedusing the equation of SWIATISOKI'*. The ratio of asymmetric peak toayœtastrie peak is about 42 ana a small third peak in the tiough rvgloasimilar to the on» obtained in case of v ïh fission with reactorneutrons was also present, 'ühe third peak covers an area of about 1$of the tota l .
and WAim&LL J ware the f i r s t to obtain a triple-peakednass-yield curve in the fission of lia by 11 MeV protons, f his wasfollowed by their observation of a triple-bumped mass distribution inthe 14*$ and 21*5 MeV deuteson fission of radlum-226^. Fission of
Re, by 20 and 30 MeV helium ions, however, was found to give the mer*
73. S. FETEBSQH and A. CHXQKSO, lbs ftcanouranium Elements, Vol* 14S,Paper 19*4, H.H.E.S., McGsav Hill, New York (1949)*
79. W.J. SW1ATECKI, Phye. Rev., Ifiâ, 936 (1955)»
30
uaoal double-humped curve. JE3SJSBH and FAlKSåLL^ explained their resul tB
on the basis of a Mt&odel f ission, f i r s t suggested by ïOnKE?ICîi and
HÎBAÏ^ the triple-peaked curve resulting from the sapei^-position of
a doubla-peaked one due to asvtnreti'ie fiasion, and a narrow single-
peaked one, similar in shape and width to that obtained in the 22 MeV
deuteron fission of blSBUth-209 . The non-existonce of a third peak
in $he helium ion-induced f iss ion of Ea was then explained as doe
to a strong dependence of Hie shape of the smoa-yield surve on the
charge of the fissioning nucleus, a sharp transition from symmetric
mode of f ission to asymmetric mode oooar^ng as the compound nucleus
changes frös actinium to thorium* From $ha present data on the raass-227yield curve in Ac fission with reaotor neutrons, the eysanetric
nsode of f ission i s only 1?' of the total as contpaxed to the asymétrie
mode of f i ss ion. In case there «as a strong dependence of the shape
of izass-yleld curve on the charge of the fissioning nucleus , one
would hare observed the symétrie node of f ission coropaiatile to Ute
asymmetric mode. Thie shows ttoat .there is no strong dependence of the
shape of the nass-yield curve on the charge of fissioning nucleus.
Mass distribution in general in the fiesioa of bismuth andheavier elements mey be examined in terms of tiae two-mode fission
anhypothesis f i r s t suggested by TUKKEVIGH and Ü1MT and farthersupported by the resnlts of SCHMITT and SUGAKiAH81, tEVTf e t . » l 6 2 and
BRIOT e t . a l " * ' . According to this hypothesis any nsasured mass
distribution In fission i s due to the superposition of two coaponents,
one characteristic of asyisnetrio fission and the other of symmetric
fission* lbs asysraetrlo isods of f ission produces a double-peaked curve,
80. A. TBMEVICH and J.B. 2SIDAY, Phys. Hev., J&, 52 (1951 ) •Bl. B.A. SClfcîIïT and 1U SUGAHMAN, Phys. Bev., 25.» 1260 (1954)•62. H.JJ, LEVY, B.C. HICKS, W. HEB VIK, P.C. 3 TEVENS ON, J.B. KIMT
and J.C, AmffiTEONG, Phys. Rev*, J2J,, 544 (1961).85* H.C. BKÏÏT end S.L. Jr. WHE15ÏÖHB, Phys. Hav., J2i , B60J (1964).
_^--.^u«Ii53äs *ä««sÉhrw~'-.
JU; s- - - ^ .^jZegä Âfeî^s^r-^^gjEgaijaâA'-- ;y»%u -|
31
the heavy peak of which semaine ssäatively fixed (and ia insensitiveto the maas A and the excitation enos®r, E*f of the fissioning nucleusF »H.) dus to the préférertîal formation in fission of 50 proton8*aad/cr 82 neutron 5 .fxagmentis, while the light peak adjust» itselfaccordingly, resulting in a shift of the game towards higher raasszrasbera with increasing A of tha F.SJ. (spontaneous fiagion of heavyelemante provides an example for a nearly true asymmetric fission).Symmetric mode of fission yields a single-peaked curve, the peakposition beicg at a B»BB about (A ~ Y )/2. 33ie probability of aymaetsicfiaeion is dependent, at least to a large estent, on E of the P.B.aod increas80 witt» the incxeiaslng E . The width of the slagle-peakedcurve also increases with inoreasing B due to the compétition ofparticle etaission with f lnion and the resulting contribution tofission of more than one nucleus. As one passes from spontaneousfission through thermal fission to fission by particles of tens ofMeV energy, the peak-to-trough, ratio of tha mass-yield curve decreasesgradually until finally at high energies only a single-peaked distri-bution is observable when the uyiametric fission becomes prédominant.In the lew-energy region and upto 50 to 40 MeV in aoae cases tripple-peaked distributions are observed 3»tv*t »' . îhese oay be explainedaa caused by tac superposition of the two types of distributions» Therelative prominence and observability ef the sycasetrio peak and theasymnetric peaks then depend on the relative contributions of asymmetrieand symmetric (which is dependent on E ) nodes and the relative positionsof the asymmetric peaks (dependent on Â) . A dsoraase in the separationbetween the light peak ana the heavy peak (resulting from increase inA) can lead to the zsasking of ths centml peak by the asyœnetric peaksparticularly if the central peak happons to be rather broad and snailin magnitude*
84. A.lirW. ATEfl, Jr., Physica» 2£l» 262 (1962).85. E. VA1ÏDEHSOSCSI, Nuol. Fhys., gg, 129 (1963)•
3 2
In addition to the above two factors», the variation in neutronemission with fragment BBSS may contribute to the appearance of a snail
in the trough region of the fiaaî nsasa-yieid carve. If
universal neutron yield curve' with i ts sawtooth shape suggested byTSRESLIi1 is assumed to hold i» a l l eases, i t appears that startii a
from en assuraed constant prompt fission yield in the mes seglen ofabout 110-120 one eoiald obtain a eraall third peak in this region of
the final »ass-yield carve, similar in magnitude to that observed in70the neutron fission of thoriura-232' . Sfe»» again, the observability of
this email central peak will be strongly dependent on the position ofthe light peak. As the third peak in th? trough region aslsing from thediscontinuity in the neutron yield curve is expected to Ken«.in relativelyfixed in the ciaaa ragion of 112-113, a shift of the light peak towardshigher masses might mask the third peak to a large extent* The aboveconsideration eearo to make i t unnecessary to assume any sharp transi-tion in the shape of aasa distribution e,nå i t s strong dependence on Zof the fissioning nnoleus as has been suggested by FAIP.il&LL ani colla-borators. In law light of the above qualitative considerations regard-ing mass distribution, the email third peal: observed in the fisrdon of227
Ac cay be eonsidered to be due to the super-position of the twotypes of Sistcibatioas and/or neutron csüssion. I t is difficult to«aêiaate to «eat extent these two effects contribute. Fimily i t saybe stated "that the two-mode fission hypothesis eaeaa to explain quali-tatively different kinds of »ass âistribntion i» the fiesioa of elements,bisnata and above inclttding «lose obtained in 22^Ac and 2 3 2 ïh . EAVIMSSAH
8^ anå WLYiM and VOIä GOïïSSiS ^ did aot obaenre third peak in th*
86. H. RAVIWBHAïJ, K.F. FLYÏÏli and L.JS. GÏABKBIN, J. ïnorg. Sucl.Cbanu, £8, 921! (19^6).
07. K.F. FLÏHH and H»K* VON GÜKTEN, 'Physics enû Chemistry ofFission*, UFA, Viaiim, 731
-t-é-i-
33
distr ibution curves of 2 2 9 ï h atiâ 227 |fh f u s i o n with thesraal88
neutrons. îtecently BOIîISOTA e t »al carried out a detailed study of
tha f îsaioa yields in the symmetrie region in the tfcerasal neatxon-opa
induced f ission of "*fh ana th©y saported a sraell täiird peaîc oorres-
ponélng t© ssraaetric fission* å dfeect oomssiiacaa of the IDBGS d i a t r i -
bution in ths Tsaotosr mttteojv-in*»oed fission ©f 'Ac afiä ^ Si with
t!jat <3t f&evml nmtvo^tvåaoeå f ission of S2^Th and 2 ^ f h i s not
pessibl© ainoe t tese åietriitatioiss ttr@ studied with neutrons of
diffexent ensjpgiy. Again ttisis ia contxovarsy about the yields in the229flynssatrle issgion in the tîneimaî aaatron-induced fission of "Sh and
f ina l ly those mey I39 dlffer^ncos due to 1© ccHBptwltion of the fiaaioïs-
ingr conpouM miel eus forimsd f TOSS ( îh end 7i£h) sven-avaa» (
svan-odd and ( ' â o ) ^ oad-oâd viaellel.
88.
89
ÎÎ .Ï . BOBTSWA, S.A.
V.I . îîOVGOîîOîJBVAv V.Ä. FOBELIH, L.V. CHÏSTYAKOV and 7.M.
SaBBKO, Soviet Jonraal of luol. Phyo., 8, 404
H.R. 1GSH mwam, ÄetiBidea Rev., 1 , 275
^t-_A.
FISSION QF ZSa BY SEACTOK
3»1 Introdaefion
Mass distribution in the fission of 226Ba by charged particles90»91
no
and by n e u t r a » of diffazant energies 7 led to a suggestion that a tran-
a i t i o a from predominantly asymmetric modo of f i s s i o n ta synraatric mode
e x i s t s ae the f iac ioning nucleus change» from thorium t o x&dlua.
Th i s suggested tzwod anfl a atudy of t l » nass d i s tr ibut ion in the
f i s s i o n of Wrium-252 9 * and actinims~2279'* described e a r l i e r in
Sect ion 2 prompted us to study the f i s s i o n behaviour of a l i g h t e r
isotope of radia» wita xeaoto? neutrons. Saäiua-225 «afi chosen due to227
i t s a v a i l a b i l i t y aa a daa^itei* product of 'Ac. Ihe work «as under-
taken with a view to e s tab l i sh ing , i f pos s ib l e , f i s s i o n o f 2 2 3Ba with
xeactor neutrons «aa study the raaeo d i s tr ibut ion it s u f f i c i e n t a o t i v i t i e s
wese obtaiKod. Ihe only atterapt reported i n 1 i térataj» to obsemre f i s s i o n
of ^ R a with neutrons was tliat of PEÎSiSOîI and GÎÎIORSO95 end an e a t i -
aat ioa of the upper l i m i t of 100 barns was reported by than a s the f i s s i o n
oroise-'aection. lk> de f in i te evidence of f i s s i o n waa obtained* A ee l ou nation
based on the enpir ica l formula of VAÎŒI35BOSCH and SEÄBOEG96 indicatedthat the f i s s i o n croBB-section for
of tfea order of 1 bare*
223Ha with reactor neutrons could be
9 0 .
9 t .
9 2 .
9 4 .
95.
96.
BtC. JEiSISi' and A.M. FâlM&U., J%ys« Hev., 102, 942 (1953)*
B.C. JSI-SSIÏ and A*W. FAIHHAI.L, Phys. S i v . , 118, ??1 (1?60) .
E.» KQ3LES and B.B. LEACHiMN, üuol . Pbys . , i , 211 (1958)*
R.H. nm, u.K. umm, ü- MvumMs, K. sm&aa, v.v. sum,HAMAHIiR and H.D. SHABKA. J . Inorg. Huol. Chen., 2 5 , 465 <1965)«
S.S. HEB, n.C. JAliJ, M.ÎÎ. HAMBOOSXaZ, M. EAJAOQPALifl, BAJKISHOfiE,
M,V, RAMÄKIAH, C i . ÔAO, S . RAVIiJDEAH and B«S. afiABMA, 'JPhyeios
and Chenistaty of Fiss ion'» IAEA, Vienm, 1 , 439 (19*5)
S . FE ECSOa and A* CIIIOESO, £he Sransuzaniun mènent». Vol. 14B*
paper 19-4 , ^.N.K.S. , MoOzaw H i l l , %w ïoric (1949)»
B. VAHÎEHBOSCH and 6.T. SEABOHC, Phys. Bev. , Jüfi, 507 ( i 9 5 0 ) .
35
3«2 Experimental
About O.OJ/ig of 223Sa «as milked from 60/ig of ^ A c by»swing 2 7Ao and 227Th on Fe(QH)_. Freeh 22?Ka was milked frca thesans source of
227end
227 J P27'Ac after sufficient growth. Complete removal of " 'Ac
was ensured by performing about six Fe(OH)_ scavengings. The221 '
parity of '''fia was checked by i ts alpha speotrum and half-life« Theresidue left after evaporating the solution was ammonium nitrate andthis was reraoved by heating* Cavrlar-frea *8a thus obtained waadissolved in « small volune of dilate HNOL, assayed by alpha countingand dried in the matrix material (material used for retaining fissionproducts)* A blade was always prepared under identical conditions andirradiated* Strontium-91 was chosen as a typical fission product sincei t is formed only through fission and not by the neutron activation of
8? 97Inpurftles. Other nudities liks 'Br» 7 l2r ware also separated Is eon»experiments bat because of the possibility of their fornastion throughactivation of impurities, theso nuclideb were not considered useful «ndtherefore not isolated in subsequent experiments. Preliminary experi-ments showed that only a very araall amount of activity would be formedby the fission of
Difficulties were encountered in getting mt#r$al sufficientlypure for use aa a mtrix* Even 'superpure' aluoinium foil of 99*99^
91purity gav» significant amounts of ' Sr activity presumably due tofission of uranium contamination* Other matrix materials such as ferricoxide and cellulose nitrate «ere tried, and cellulose nitrate was foundto give no ^1Sr activity* Small and latin cape of cellulose nitrate wereprepared, weighing about 70-SO ag by drying thin layers of oellulosenitmte in acetone in a shallow cup (the botton cone of a centrifugeglass tube). Carrier-free 'Ba «elation was dried in the cup and tillsvita wmppeä in two more cups and sealed in a quarts tube. Quart* tabeswere wrapped in polyfehem, sealed in an aluminium container and irradiated
36
in tha swiasraing pool reactor 'Âpsaia* for 10 hours with e neutron fluxof about 1012n cm"2 sec"1 .cover in some experiments.of about 10 n cm"* sec" . 'Site samples were alao lxxadlatsd witâ» cadmium
After irradiation, quartz tubes were cleaned with acid» czushed
end cellalose nitrate was destroyed by heating with concentrated HML
in presence of strontium carrier* Badiura «as removed completely by six
bariuH chxoiaate scavengings and strontium «as purified by a standard97radiocheraieal procedure . (The efficacy of the procédure was checked
by carrying out the separation and purification of strontium carrier
added to a similar quantity of unirxadiated **Ra, and the strontium
obtained was coinpletely free from contamination)» All final saoplea
«ere free f we radium contamina tion as found from the decay curves.
in most of the experiments, only 5 to 10 counts/rain above background91
of 7 Sr activity «er« obtained. The decay of strontium nao followed in98
a g&a flowf low-background beta proportional counter with a back-ground of 1.2 counts/snin.3.3 Results
The fission eross-seotion for223
225Ka was estimated by coaparinf
the Sr activity foxsed in fission, with that froa a known «mount223 91
of uranium irradiated along with tha la target and assuming Sr
yield to be the asse in botat eases. Although tails assumption i s not
correct, sines the peak of the l ight wing in the mass-yield curve of
n& would have du i f ted to a lower oase number t In the absence of
any other alternative method, this nsthod had to be used to obtain an
97. J. KLSIHBSRG, Collectsd Saaiochemical Procedures, M-1721,
2nd edition (1958).98. M.V. aâMAîîIAH, C.!>. RAO and J.K. SAMUEL, Inåt*. Methods,
2S,, 339 (1965).99. A.C. WAHL, Faysîcs and Chenlstry ot Fissions, IAEA» Vient»,
I , 317 (1965).
37
approximate estimate of the fission ogoss-seetion. On tfie basis of theabove assumption the average value of the fission oroas-sectiou withreactor neutrons as «ell as epicafeiun matrons works oat to be about700 millibama. A typical irradiation data for calculation of fissioncroae-section for 28'sa is given in Table
223,If the yield of 7 Sr from thercal or epiläieraal fission of
'fte should be appreciably lower thaa 0>, the fission oross-aectionfor this otolide would of course* be lasger than 700 aillibarna. Onewould expeot töat the Aifferenoe mi^it amount to a factor of 4 or 5at the moat» ïn any case i t would be worth trying to as termine themass-yield curve for the neutron-induced fission of * "Ra with a largeroraount of target material» higher neutron flux ana a better low-back-ground eountiag facility.
TABLE I-A
Sroical irradiation data for calculation offission croag-sectlon f oar rofliuia»223
38
1 .
2.
5.
4 .
22?auraber of ' Ea atoms irradiated
Number of 255Ü etoaa irradiated
latrix material
6.0 x 101*
8.5 x 1013
Cellulose nitrate
Sample irradiated in A, position in'Apsasa' reactor with pile neutrons for 10 hoars
91Sr (2238&) activity at 16,00 hearson I3/4 for 25.8 ng of SrCO.,91Sr (blank) activity at 16,00 hourson I3/4 for 25*@ rag of
7 "9 counta/nin
2*3 eounts/ain
16»5 coanta/aia
et t r ( ) e o g at 16,00hours oa 13/4 corseoted for chemical .ylsld . . 1.98 x 10H counts/Bin
7. îîett 9 tSr (22?Ea) activity correctedfor chemical yield and the blank
8. Hett
9.s % 223,
10.8.5 x IP15 » 577 m
60.6S1 ban»
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33
Z>B££IiivI2MA?I0a OF FISSIOH
4*1 Introduction
The improvements in lithium-drifted germanium detector tech-100
oology made by ÏAVEHBâLE and MAN1 , after i t s f i rs t application togama-xay speotro3copy by FBBCü and TOK8FÏELD , revolutionised this
f i e ld . Various laboratories started producing detectors and the tech-
nology vsa developed to such an extent that detectors of various s ises
and shapes are available at present commercially. Sinsiltaneoua develop-
rcents in los-noiae electronics helped very ranch in improving the reso-
lution obtainable with ö©(Li) detectors. Cooled PST pxearipliflers with
0.7 KeV resolution ware also developed . Recent experiments with
optical feed back methods In the preanflifier Indicate that the eleefc-
ronic noise contribution to the peak width could be reduced by a factor
of two . The improvement in resolution of Ge(ïd) over Hal(Tl) i s so. _»> 137
muck, e .g . from about ff> to about O.5S for Cs gamm rays, töat aany
EOre Bsw applications of gamma-ray spectroscopy bacame possible* %•
high resola^ion obtainable with Ge(Li) detector pr«Jved i t s usefulness104in the f ie ld of non-destructive activation analysis ^ as »e l l as in
molear studies . Pris%rily because of the advantage of non-destruct-
ive analysis, the Gö(Li) detector was used for the détermination of
f ission yields1 0 6»1 0^ and i»coil xangas106 withoat radiochoraical sep-
arations* To investigate how good this technique would be tc reproduce
100. A.J. TAVW5ÂLB and G.T. SWAN, Hncl. Inatr. Methode, 2%t 185 (196J)
101. D.y. PiffiXK and J. WAKEFISL», Mature, 121, 669 (1962).
102. E. ERA!), Hucl. Instr. Methods, 2J, 327 (19Ö9).
103. F.S. GOlJIiBIKG, J. WjttïOa and D.P. MALOME, Kucl. Inatr.
îlathoda, 2 i t 273 (1969).104. S.G. PHÏJ33T?;, J.A. HA1ÎHÎ3 and J*M. HOLLANDER, Ami. Cher-,»
51, 1127 (19^5).105. J.M. aOLLAHDBB, Mucl. Inatr. Methods, ^2., 6[
or approach the resulta obtained by sadiocheaical and other methods,
f iss ion yields sere determined in the thermal neutron f iss ion of ™Pu.
The results are compared with radioeheraieal and mes spectrozaetric data
available in Hie literature.
An aocurate knowledge of ifo f iss ion yield in different f ission-
ing nuclei i s easentiiil since quite often i t i s used as a standard due
to i te convenient half »l i fe t simple decay scbea» and hi Jï f ission yield*
Several investigators measured iS&e f ission yield of "Mo in the thermal
aiautron fission of plutoniura-239 . However, the values they obtained
varied over a wide range as 5.61, 6.03, 6.10, 6.44 and 6*59* This large99variation and the difficulty in seleeting a partiealar value for Mo
yield while determining the f iss ion yields of other nielides in the
™Pu fission using gamm-xay spsctroaetry vrith Ge(li) âetsctos led us
to investigate i t in detail . ïhe absolute disintegration rate of ^Uo
«as deterisined taking into account the recently published work •
The number of fissions was calculated by irradiating accurately known
and isetopically analysed anounts of °Ftx and 55U and monitoring the
neutron flux using ^°Co(n«V ) Co reaction. The epicadmium neutron flux
contribution towards f ission or cobalt activation «as lese than 0,f/c
106. E.G. Go D0H9 J.W. HA8VEÏ ani H. ïtóKAHaM, Nucleonicsf
2 i ( i 2 ) , 62 (1966).
107* D.J. G0MÄH and B.H. TCXILIiKSOH, referzed to in Can* J.
4É, 2911 (1968).103. Bdl* îlaRSIffiîî and L. YâfS'E, Can. J. Ohea.» 4 i , 249 (1965).
109. Ö.P* ItSS e t . a l , IA-1997 (1956).110. E.P. SÎEIKDïiKG and M.S. FBEEKÎA.U, paper 219» Badioch«isio«l
Stadias f Flöaion Product», H.îî.E.S., Divn. IV, WcGrow Hall,
ITew ïoik (1991)*
• . v .
Molybdenua-99 fiaeion yield in 235ÏÏ fission was âecerrninsâ simultaneously
to find out any major discrepancy ia the expérimente! procédais used in
determining 99Mo yield in 239Pu fission. Molybdeaua-99 yield in 235U
fission aas reported by more than ten workers and is cell eatablishad
as 6.16117
Fission yields determined in the therrael notitron fission ofAin
^ P Q using Ge(li) detector pointed out oejor differences in tbe yields
of &3mKx, 9 %o f 9 1 Sr, 103B« f
1 3 1 I f 1 4 iCe and Hha «hen compared to
the literature mass speetronstric data* It rsaa oonaldered woriawihîle
to invaatigate ttiese yields by radioehemlaal method ana determine yields
in the ayras&tric xogion a lso, where the Ge(l>i) detector coula not be
used due to ttks lo» yields and low efficiency of the detector» Fission
yieldsof 1 3 1 I in 235IU and 2 3 % fission were determined by the »Absolute
settled* sinoe from Ge(Li) work and also xadtloohemical investigation the
fiss ion yield of 3 I in P« fission gave valtseo very different f ran
iitaiature data. la al l» f ission yields for twenty nine awl ides «ere
determined in the present investigation*
111,
112*
115.
114
116.117.
£I.B. FÏCKEL anä R.H. TO;a,Iîfâua, Can. J. Fhys., Ü , 916 (1959)*
E.E'. FOSTÊS Jr. , Data praaented at &e 158th American Chemical
Society Meeting ana Personal Comninication by Br»Foster (1969) -
Racently appeared in Kuei. Se. anä fåisg., ég.» 19t (197O)«
1\ GEOT2ÏÏ and HF-üTïI, Uu c l . Fhya.t 66, 391 (1?6^).
?• CEOWTüERand J .S. ELMIDGS, îiucl. JPhya., 66,, 472 (1. " ) .
e.Ca LOCM-i-KiAI,, J. EQBSO27 and 1.0* SKSHPAHDS, AâSC/-W 574 (1967).
I.W* GOOSXBB aid A. WILLIAMS, lia tun», ggg, 5036, 614 (19^6).
H.H. YOU &SWm and H. HERfaiNN, Eadiochlmioa Acta. 8, 112 (1967)*
4.2
4*2.1 target préparation
For f iss ion yield determination using a Ge(Li) detector*
plutonium supplied by the Fuel Reprocessing Division of B.A.H.C. «lth
high 59Pu content and enriched uranium containing about 9«$ S55U
supplied by Raâiochemical Centre. Amersbam (England) «ere used after
chemical purification* Thin, eleotrodeposited targets of these eleaent»
«ere prepared by the following procedure* 'Superpure1 aluminium fo i l s
(10 mil thickness, supplied by B.D.li) vexe cleared by dipping them in
a phosphoric acid-sulphuric acid-nitric aold misture for one minute
and then «ashed with water. A layer of aine (about 0*4 og/ca ) «as
deposited on the aluminium fo i l by iomeraion in a sine bath (contain-
ing SaOH, ZnO, Rochelle salt ana FeCl,). Gold (about 50/jg/ca2) «as
electrodeposited from a gold bath. Uranium and plutonium «ere electro-
deposited on gold-plated aluminium fo i l from isopropyl alcohol nsdlus.113Detailed electxodeposltlon procedure i s given elsewhere •
In the case of Mo fission yield determination,, solution of
purified plutoniura was analysed for i t s specific activity and isotoplc
composition, '1MB analysis «as carried out on a number of different
saoples^ a reproducible and reliable value «as obtained* Subsequently
tbs mass spectrozsetxlo analysis «as also carried out on one of thes»
plutonium
118. SATYA PRâKA3H, 3.E. MABQBAl. B*J. SXHGB and M*V« EÄMAH1AH,
Int. J. Åpp. Bad* and lËtotopes*t 22» I 2 6 0971)*
ESSHÄS
(a) Stotarc&aafcioia of
( i ) pxepasatieia
ptatessisan oatsploo œeâ ia thlo üosfe TOSS öbtaissu aft-ss-
rtotal pîtitoninQ eoatesrt wao detsraiasa p©t3Safcâ@H3tei<eûlsrQsisplss ©BOQlly föad soBGeafesatioïi of a^omt 10 E^ ©f ttatetóraïu pss gaas©f s©Iis$i©Ei» A åiliatioa faator of 1CT aas aeooosaïy to take suitable
SUS mklïtg saaplsa fes? eeaatiiag. Silo was adtievsâ fej? tooTBis f i rs t dilution oas easreieâ eat iia a glcwo feos ©a a
anä tte seeotó cao ioœ> ia a ffeEahosä usissg a' Mettles'iaises* All âilatiosa esâ pœpassi'im ©£ OQE^IQS &JB oount-
Ing wes© ess^ioâ oat % weâght tsaitsfär toeteiâ^p©. ÏMG moiåa pipet-ossogo aai ealibsaüsioa esseso of volœietrie fleste aså raicsîs-
c â 10 tal eapsoi^t? fôlytîfâno âsopplBg' bottle with a fine long©aplllax-y t îp e ceigMisg 3 to 4 ©saïas, was useû a.s a ueî#it-lburette.Åil âilatiosîo e.Eâ sortiples foe eoantirag tros© safe in triplicate or
Bepsoâwciisility of tefetex than O.'l/J nas obtained for©f aföemtë 1Q0 rsg.
(ii)
sa®plos woxa eountsâ in anoo XIQII ao iia an alplm iiqaiâ aeintil latiea counter. Accocateljr
(abaat 100 mg) vrase ts&asfeiajoå on to sleetropoli3hedotaiïû.«3OB oteel pisnetfâts. ïhs solution «as eorjfiosd to the cents» by
Q 1S»in lagfâ^ ©f cellulose nitsata lacqssor «n the rim of plancheto.solution rass slowly evapiaateå amies an Infsassd lasp. Finally fte
igiaiteâ on s îmufôff enä vrassî eoantaå* Sanplos for alpha liquid
(1970).
sc int i l lat ion eountiag was» praparad by tmrnisnesivg accurately weighedaliquots (about 100 ag) to glass vials containing 5 ral of liquid aointil-lator . ïhe composition of the liquid scintl l lator was, aa uaed byIHLS ©t*al12O
f 0 . 0 ^ 1, 4-Î5l8-2-(5-ph©nylexasolyl)-î)ena9ne (POPQP),0.7$ 2 , 5-dipbenyl-oxaiole (PPO) end 10/f- naphthalene in purified dioxane,a l l being Bsaaored W/V. Max/it» was purified by the procedure g i w n byB8BZ1B121.
( i l l ) Counter efficiency determination
ïhe ©fficiencdoa of the countess itère determined using
twc independent calibrated standards, v i s . an Am disc; source from
Harwell and a» 24tAm eolation supplied by IAEA. The efficiency ot the
alpte proportional coaster was found to be 49 «47^ with an uncertainty
of O.J>i using eleotropolished atainlee* steel planehets and that of
alpha liquid sc int i l lat ion counter to be 100 ± 0«4^.
4*2.1 (b) Uetextaimtlon of tsis Isotoplc coaiposition
( i ) preparation
Tbln unifexüs and weigfetlese sources were prepared for alpha
opeetroraotry by eleotxodepoaitii^ pîutoaiuo on electrupolisfcad stainleas
steel or platinua discs* Tbo ©leotrodepoaition was carried oat either
from ni tr ic sold sediua or from isopropyl alcohol aedioa •
120. iï.fi* IBLEt If» KABiXAfflS and A.P. MORREH HCFF, HStfti)d»sdisatioa
of Radionttolidee", IASA, Tienna» 465 (1?65)*
121. fHÎLIPPB IffiBiSB» "MESS aHHEXE t Facuit» dea Science», University
de Liege, Belgium (*966).
122. V.G. KHtOPIK, Badiutn Institute of tije Academy of Sole noes of
'J.3.S.R.. AEC-tr (Cbeœiatry) 449T*
mm»r*aà'.
M
( i i ) Alpba opactrum
The alpha spectrum was cbtai;ieâ using a 30 mm surface
barrier ailioon detector in conjunction with a 400-chanml analyse?»
Tha resolution of the detector was 20 KeV mm at about 5 WeV. 'fhe
alpha spectra were recorded for the two tjrpe3 of electroplated sources»
which ware prepared from the original plutonium aaraples and from
plutonium purified through two anion-exehange raicrocolornns<
4*2.1 (c) Calculations
The alpha apectxa of the original plutonium sample (Figure 43}and the pluteniua purified from araericium (Figure 4C) show two nain
peaks. Tia. 5»15 Me? and 5«5O SteV.240,
5.15 S©V peak i s due to 259Pu •
fti in both cases. In ths case of fee original plntoniuiE nanple the
5.50 MeV peak i s due to alpha particles from yvti and Am whereas
in the case of the purified sample i t i s åoe to J?U alone. From these241date the percentages of """ Pu and Am in the sample were calculated.
From the specific activity due to 5 Pu + ^ Pu only* the percentage
of 4 Pu was calcuieted using the data in Figure 5.
4.2.I (d) Eesults
Table 1% gives the specific activity values of plutoniurasamples. Pure plutonium sulphate refers to the "standard plutonium
122 Asulphate1* prepared by following the procedure given by WJR e t .a l'She specific act ivity values from the two independent counting syateas
(alpha proportional counting and alpha liquid scint i l lat ion counting)
compare well within 'l%* The standard deviation obtained was less than
122A. G.H, JtftlB, H.P. SÎÏÏOH, KESHi? CHAÎ315K8, J.K, JOSIII, A.C.
GODBCJtS, P.H. SHAK end M.V. EAMÎÎIAH, B.A.R.0-560 (1971 ) .
tlV.M*!'.i# iif.-
46
ya.
TJ*— —
F3
Y
v>
i I
I I
1ABLE I I
Sample
*Specif ïc activity x «f Igotopîo composition
Alphatloml
counting
Alpha liquidscintilla tl on
counting2 4 1 Pu
2B
SC
28
2E
Pltse(
1.5904 / 4+ .0067 (15)
1.5834• .0141 (11)
1.58274 .0090 ( 8)
1.5798• .0177 ( 8)
1.61594 .0067
5• .0110 (18)
1.62144 .0158 (26)
Mass Bpectrossetric
• .0069 (12)
1.6057± .0110 ( 6)
I.6105+ .0047 (12)
1.6080• .ooao (is)
1.6067• .0071 (23)
0.006 0.015 „ 5»1 0.4 94.46£0*85 J £}•*
0.4 94.58
O.OO4 O.OI4 _ 5.0 0.4 94-58
p.006 0.014
0.006 0.014 _ 5*0 0.4 94.58
£Q.SÓJ f3.31 J
0.007 0.014 5.0 0.4 94.58
5.417 0.576 94.21
* Am ecmtritution hao tenn subtracted. Ths number in the paxeintheels ( } Indicates the wsfcesof independent determinations, i . e . tha auraber of counting aampîaa preparaô from variions dilationa.îh» value in the parenthesis ƒ" _ / Indicates the ii3otopic eotaposition in t«rns of the 5* alphaactivity.
co
49
An accurate determination of spécifie activity depeuäs on several factors
such ae eounWng efficiency, calibration of mieeopipettes and volueatrie
flaska and determination of the total plutoniua content* ihe counting
eff ic iencies were determined using two Independent standards am these
»ere found to agrae well within 1$ of the valtsoe quoted for the stand-
ard. Kleetropolished or aechanicolly polished stainless ateel planche te
used in this work gave counting rate which agroed well with that of
tha alpha liquid scint i l lat ion counting. The efficiency was »»producible
using thase polished planet»ta. In ths case of dull surface stainless
ateel th» counting sate was alviaya lesia by about 2?S and in the eaas of
platinum i t was hi$i»r by about t% as compared to tsue oounting rate.
Tais has a lso been emphasised by SGMRIDEH e t .a l . 'She lnacouzacies
in tha voluao ssaoireiseatB were avoided by weight tx&sufer techniqita
using a poly thesis wei^it-busette.
The ïïRSie apeetronetric sethod in rcoœ preoiee for the ieotopic
a m l y s i s , but in the case of Pu as tiio naoutt present i s snällt ti»
radios» t r i e nothod i s preferable for the accurate de termina tion since
in Èhe maie spectroaetrie method i t i s d i f f icul t to correct for the
^% interference and linltationa on 12» amount vhioh can be used for
analysis on account of i t s very hi#* specifics aotivity (about J00 tiaes
than that of 2^JFu). In oxder to check file complete ruaoval of * An
wftich wi l l otheEwiee contribute to 2 3 T u at 5 »50 M** Peak, aeparatioa
was carried out on aynthatic misturea of ^ A« and plutoniiui e t traoer
soalG in the ratios 1 i 10 and 1 * 100. The alpha speetrua of the ama^le
after anion exehangs purification «h?weå that the peak a t 5 »50 M»¥ le
due to ^ ^ t t only* I t i s advantageouii to détermine ^ Pu irnss apeetro-
123. H»A. SCHBBISEB and K.M. HàEMOH, Alpha counting methods,
124. PETiïîi «OIF and JÖ&JflH fiElHHARDT, Gasellschaft, mbH,
KABLSBUHE, KFK-339
WtVSV.W!'
50
nœtri.cally since i t ia usually present in eigaificarat quantities. The239
Pu content estimated sadiometrically compares wall with «he aaaaepeotrosBteic data reeently available on a plutoniuia sulphate saspleas given in 'fob?.© II last rot?*
uranium solution analysed for 2*"*U content by saesepectrcrastry and estima ted graviraetrically was used, "fergets from thissolution were prspaxed by evaporating accurately weighed aœounts ofsolutions on 'auperpuxe' aluminium foil of OH® rail thickness. Thesewere wrapped ia anotiier alamslnium foil. About tO>ug of 2* l1i or %sexe used to avoid any self>shieldiag. Similar targets ware used forthe Eeasuremant of absolute fission yield of " l in ^ P u awâfission*
Plutonium and uranium targets for radieeheaical Investigationwere also prepared from the above isotopicaîly analyead and accuratelyknown ?ü and JU solutions evaporated on •superpure' aluœiniam foi l .
Tho targets fos neutron flux monitoring should be vary thin toavoid any self-shielding. ïàsy axe beat isaâe froa Co-Al alloys contain»ing 0.1 to 1$ cobalt known accurately and måe from nuclear pure aaterials.There ware a few such foils available from a stock supplied by the IAEA,but i t was not possible to afford one for each irradiation. Cobaltsolution was sude from spsepoxre cobalt ne tal wire. Sargste froa thissolution were prepared by evaporating accurately weigîiaâ amount» ofsolution on 'auperpure' aluainluo foil of 1 oil thickness. These werewrapped in enothe* aluminium foi l . About 1 mg at 59Co was uasd to avoidaj^ Balf-ahielding. Beution flux aoaitori supplied by låBå (Uo-il alloycontainis« 1'/» cobalt) were also irradiated in BOSB of the experiwnftato check the self-ehielding effect, tepurlties etc in the cobalt solutionused for flux
ä9»*J>!V<WS» Wf,*V":.
5 1
4»2»2 Irradiations
In the ease of fiction yieid deteraimtion using a 0e(Li)detector, uraoiam and plutonium eleetrodeposited targefcs were oovaredwith 1 mil lBup«i'purel aluminiu» foils (1.5 cm dla), »zapped in anctiiaraluminioa foil aafl eealed in polythene. Both, the targets were irradiatedsimultaneously aither in the swiming pool reactor 'Apaaas* with atherasi amitxoa flax of about 1018
n ca"2 sec"*1, or in CÎRUS with athermal neutron flux of about 10 'n cm"2 see"1. The irradiation tinevaried from 5 ainutes to 24 hours depending on the Euclides of inter«8t.
99For ?Ko fâseion yieîâ detsrriimition, plutonium, uxaiaius and
cobalt targets wea-e iarradlated Qiiailtanecaslj for 6 to 10 houra in onsof the outer positions in CÏRÜS v/ith a theanal neutron flux of about10 n cm*" eeo . The cedmiui» ratio in this position wai; foend to bsgreater than 200. One irr&dic tior- was nasriad cut with about 1Cr n ea
c"*sec ie a Uieisral neutron position* targets fornsasureiaent of absolute fission yieiâ of I or racUoohemict;! investi*gaticn irxadieted in the aaoe position in Cl&JS for which tkt
cadraium m tio was âetertnined expeiimscteiiy. ?he period of irradiation12varied fsoa 10 hours to 24 hours »ith a neutron flu» of about 10 a
»2 -1CEI 3 3 0 *
4*2.5 Dissolution and radiochemical separations
After irmdiation, the targets srere separately dissolved inacid or alkali with or without carrier depending on the element* tobe isolated» A known amount of inaetiv® carrier waa added to a» aliquotof Utfå solution and allowed to interchaisge with the fiBeion producteloBBnt of laterest . After the intarobange via» cooiplete, th» elementwas senstated a»« purified from ti» tsrget raaterial and other fiesio»products and finally obtained &s a precipitate convenient for mounting.
•"fifj*i«^t«
52
Most of the xadiocheiEleal separations were carried out using standardprocedures described in litemtare125"127. A collection of these inclad-iag any aadification ie given elsewhere128.
Mounting
5fca precipitates were filteied through So. 42 f i l ter paper(2.5 cm disaster) uaing a perspex filter cUisiaey. They were »ashed,dried and weighed along *ith filter papor, isountró on aloniniusn plateswitt: double-coated cellulose tape and covered with cellophane paperof thickness about 3 ng/cm •
4 »2 «4 Coaling
4.2.4 (a) Ge(2-i) system
A 2 00 (4 en area x 5 mm depletion depth) Ge(l«i}
supplied by îî/a ftrfLnoetcn Gamma 'ifech. wae osed in HdB Btaây<>
detector» mounted In a vacuum o^^ostat chamber wee kept at liquid
nitrcgen teœperstoire aa shewn in Flgare 6« Tba vaeaus vas snîntairad
hy a cryogenic porep, together with a VaoXon pump. 3ï« detector WRB
connected to an ORTEC model 118A reois température f ET preanpliflsr.
îhe otîtput of the praaraplifier «sa fed to s Packard model IEP-C
fbe scp l i f i er output was analysed with n Bacfcsrd model 116. 400-channel
analyser. 4 hlodc åiagsm of the electronic circuit i s given in Figur» 7.
125* C.B. CORIEEL and S. SBGAHKâH, Kadiocheaicstl Stadias s The
Products» S.H.I.S., » iv . IV, Vol. 19* MoGrow-Hill Book Co.,
Inc. , nom T o * <195t).126. J . KL£ISBE3te» Colleottd Kadioe&aaio»! Proeedu»», ÎA»1721,
Soi edition (195®)>127. M. LIHDER, B&dioehe«i«Bl ïroc8duraBt. UCEL-4377 <1954)«
128. BadioeneiRioal Prowdu»» ua«d at Jfediochendotry Division,
B.A.R.C., ïroatay. Boaï»yt XM»IA
cyr,» •
I. I
f)l-, 1 i r f
53
54
' I ' • ! 'r. f ir.
i i-!e 00' :M0
BLOCK DIAGRAM OF AN IDLAL IA EG TRONIC SYSTEM
E3ÎA5
i ut rOR TT f.
,' I O Af - A C !•,•/".; .
ACK'A;-:O 1
VALöUU V'COOl.fs K">
rK;,wRt;.-_. 7. BLOCK OF THE ELFCTROn'C SYSTEM fj£E5)
ïh© system gave a full width at half fiaxinmn of 3.6 keV for 122 keV5T
ganraa rays of Co and shoireô a raaxinara drift equivalent to 2.2 Is»?at 660 keV during a period of 24 hours.
After irradiation and appropriate cooling tla© catcher foilswere separated and mounted on aluminium plates. ?he gaimaa-ray spectreof the fïasion products in the catcher foils from both uranlura andPlutonium targets were followed using the Ge(Li) detector under iden-tical geometry. Depending on the activity levels» the samples we»counted in ora of the three fixed geoinetry positions availabla. Foreach set of nuclîdes the spectrum «as followed as a function of tiae»in a fixed geomotsy which was selected so as to have a convenient totalcounting rate not exceeding that which would give more than 5($ deadtine on the analyser (beyond this dead time the resolution wae affected).fhe counting was done for a tiras sufficiently long to give good countingstatistics, but at the same tine taking into account the half-life ofthe nueiide under consideration. In general the energy region 0 to about660 keV was recorded sine® most of the fission products have gam» raysin this region and also because of the fact that the efficiency of the&? tec tor i s low at higher energies.
Hhe photopeaks obtained froa a conplex mixture of nany nuclädeslike the mixed fission products nsy be divided into the following cate-gories»
(i) A pbotopeak due to only one nuclid** having no contributionfrom otter gara» rays» this being possible only wiüii the highest possibleenergy garara ray in the mixtu»»
( i i ) A phétopeak having Corapton contribution fro» higher energygamna says anä no interference due to any ottoer close lying fianraa rays.Here, the peak azea, after proper «ubtaaotion of «ho Cotton contributionwill deczeaee with the correct half-liffe of the nuclid».
tttMMhUi ä J 3
55
( t i l ) A photopeak with interference from a close lying gaocasay f eon a nual ide of a shorter half-life end the contribution sergingwith the photopeak ondes consideration? i t ie necessary to allow theshorter-lived component to decay before using t*» counting data.
(IT) A photopeak with interfering contribution from a molldeof longer half-life raerging with the peak* the activity due to thenuelide of interest can bo resolved from the loi^cr-lived ' tai l 1 .
(v) A photopeak due to unresolved gams» xaya from two or morenuclidea wiUi too dose half-lives) i t is impossible to obtain anyuseful data from each peaks*
In the présent woik, since the spectrum WAS recorded only uptoabout 860 keV, no photopeak belonging to the first category was present.The lower peak efficiency of the Ge(ti) detector for high energr ganaarays together with the low abundance of such gams» xaya in the decay offisrion products of interest made i t essentially useless to scan thehigh energy part of the spectrum. Most of the nuclides investigated hadpeaks belonging to categories ( i i ) , ( i i i ) . In sons cases peaks of type (iv)were also used*
She amlyaer data wem typed out and also plotted with the helpof an X-Y plotter* From the plot of the different gasraa-ray peaks» thenuclidesof interest were examined and the peak with least Interferencewas selected for calculation. Sible III gives s l i s t of fission productmclides of interest together with ttieir half-lives, gaana-ray energiesand abundances* 2he counts under the photopeak wese eumd up aai theCoapton contribution from hisses ener«r gamaa. »ys mm subtracted usingthe method of CO7EÎ.1.129. In gênerai, for each nuclldt the dec*y wss
129* U.F. COTSLL, Anal. Chem., 2.» 1765 (1959).
57
TABLE III
Fission product anwm says and
Huolide
(1)
8 7Kr
8 8 Hb
Half-life
(a)
©norgy, keV (intensity,photono p r 100 dis
y gy, (niobsr of photono per 100 dis-integrations)
(3)
4-4 h 151.2 (74Î, 305 (13)
76 min 402.4 (84), 850 (16), 2570 (35)
2.80 h 166 (7). 196.1 (35), 360 (5) , 85O (23),
1550 (14)* 2190 (19). 34OO (35)
17.8 min 898.0 (13). 1863 (21), 2680 (2.3)
9.67 h 652.9 (I5)t 749-8 (27), 930 (3).
IO24.3 (30), 1413.6 (5)
5O.3 tain 555.6 (95)
2.71 h 230 (3) . 43O.5 (4) , 1384 (90)
3.53 h 447.9 (2-5), 490.5. 560.8 (2.6)
934.4 (14). 1405.5 (4 - î ) , 1830 (0.4)
10.3 h 266.7 (6). 670 (0.7), 947.1 (2-3)»
1420 (0.7). I9OO (0.8):. 2180 (0.3)
65.5 d 235.7 (fro» Bb-95«») 724."? (49)
756.7 (49)
35.O d 765.8 (100)
17.O b 254.1 (1.5)» 355.6 (2.8), 507.8600 (1.6), 690 (1.2). 743.2 (92t with6 ( ,97aöb). 1147.9 (3) . USD (2.6)
Contdi
58
III (Contd.J
(1) (2) (3)
97,Nb
99,
72 min
51 min
66.7 h
6.049 h
4.44 h
Sh 35.88 h
106Bu 367 d(in eqme «rith 1 8 1 0 6 » 0
*5 aln
125,fen 9.4
125,
127« 2.05 h
657.9 (98)
330 (9), 720 (75), 767 (100), 1160 (30),I44O ( i0) t 1520 (4) , 1660 (10), 1980 (4)
1930 (e)
41 (2), 180.9 (7), 566.2 (1), 739.5 (12)777.8 (4)
140,7 (90)
496.9 (88), 6IO.3 (6)
263 (6), 317 (11), 400 (6), 475 (20),670 (16), 726 (46)
506 (5), 319 (19)
511.9 (21), 616,5 Plas 6??,1 ( i l )
873.5 (0 .4) , 1050.4 (1 .5 ) . 1130 (0 .5) ,
1550 (0.2)
150 (84)
342 (0.3) , 468 (0 .4) , 811 ( I . 5 ) , 904 (1.4) ,
1068 (4 ) , I I70 (0.14), 1410 (0.14),
I97O (6 ) , 223O (0.05)
£b 2.71 y r 175.4 (6 ) , 428.1 (31), 463 (10), 599 (24),
643 (11), 660 (3)
44O, 49O, 820, 1100$ 2000, 2320, 2580,
2680,
127,6b 93 60, 250, 310, 460, 770
59
Sabla III (CoîrtdU)
(1)
128,Sn
128,'Sb
129n
131Te
132'Se
132,
133,
(a)
59
10*8 aln
4.3 h
34.1 d
68*7 min
30 h
24*8 min
8.05 d
2.26 h
50 min
20.3 h
(3)
44 (7). 72 (19), 500 (61), 570 (22)
320 (83), 743 (100), 750 <100), 1070 (4)
73, 34O, 46O, 54O, 810, 910, 1040, 1240
690 (6)
27 (19), 275 (1.7), 455 (15), 810 (0.5),1080 (1,5)
61 (2), 108 (5) , 181.7, 200 (8) , 241 (8) ,
336 (9)* 780 (60), 850 (31), 1127 0 3 ) ,
1206 (11), 1629 (3)» 1860 (1) , 1965 (2)
149.8 (68), 453 (16), 493 (5>. 60* (4)»950 (3) , 1000 (4), 1147 (6)
80 (2.6), 284.4 (5.4), 364.5 (82),637.1 (6.8), 722.9 (1.6)
53 (17), 112.1, 116.7, 228.5 (90)
147.2, 262.8, 505.8, 508, 522.7, 546.5,620.9, 63O.2, 65O.6, 652.I, 667.7, 67O.O,
677.2, 727.6, 729, 772.7 (89). 809.0,812.3, 875.6, 910.4, 954.6 (22), 1136.4,1142.0, 1398.6
310 (21), 334.3 (13), 390 (6), 432 (50),470 (22), 557 (35). 630 (18), 700 (24),754 (85). 912.6 Plu» 915.O (57). 970 (10)
350, 510.5. 589.8 (90) , 710, 870 ( 8 ) ,
1050, 1240, 1300
<-#3SI
60
III
i
(1)
1M
'Ce
155,
137f
139'Sa
141Ce
(2)
5.270
52*0
2.046 yp
C.68 h
3O.O yr
82.9 min
1S.80 d
4O.22h
32.5 «
92*5 œin
(3)
61 (37)
135 (3)i 405.4 (8), 550 (8), 610 (13),850 (95), 890 (65), 1070 (1.4), 1135.7 (1O),1460 (4), 1620 C5). 179O (5)
604.6 (9a), 795.6 (99), 1038 (1), 1167.9 (1.9)1365 (3«4)
220.5, 208.3» 417.6 {6.9)t 526.5, 595.3»836.8, IO38.7 (9)t 1101.7 (37)» 1123.8 plus1131.5 (34), 1457.6 (12), 1678.4, 17O6.7,1791.3 (11)
661.6 (85)
165.8 (23)» 1430 (0.4)
162.8 (6), 304-8 (6), 423.7, 457.5 (5).
537.2 (34)
IO9.4, 131.4, 173.5, 24I.9, 266.6, 328.8 (20)432.6, 487.0 (40), 574.4, 751.8, 8I5.8 (19),867.8, 919.6 plus 925.2 (10), 95O.O,1520.8, 1596.4 (96), 2348.3, 253O (3)
145.4 (48)
641.1 (46)t 860 (2.5), 894.7 (9),1010 (5). 1060 (4), 1160 (3),I25O (2.8), I375.9 (2-5), I54O (2.7),I74O (5), 1910 (9) end othaw
6 1
. i
Table III (Conta.)
(O
143Ce
144'Ce
147,:
H9;ïîd
(2)
53 h
264 d
17,2 oln
11.06 d
1.64 h
(3)
57 (11), 231.7 (2.5)» 292.9 (46),349.7 (3.8), 490.5 (2.4), 664.5 (7),722 (7)t 8B1 (1.4), 1103 (0.6)
60 (2), 133.6 (11)
696.5 (1.5)
91.1 (26), 275-4 ( M ) . 519.4 (3),430 (4), 530.0 <15)
114.2 (18), 156 (4), 211.3 (27)9
240.2, 270, 527 (5)t 424 (9),
541 (10), 654 (9)
Data ass derived from
(a) C.H. LEBERER, J.EI. HOLLANDER and I.Oteble of leotopae. Sixth edition (John Wiley, 1967)<
S«l. HBAÎH et.«l, 18-1218
wra
62
followed to the point where the photopeak became indistinguishable fromCotton contribution or «hex» the Conpton correetion was ao large tfiaterror in the peak area would be very hi#*. Details of the selectedphotopeaka of nididea determined together with interference, irradi-ation ana cooling tinea necessary etc are surnmriaed in Table IV.
In the relatively long-lived spectie, subtraction of the contri-bution of some najor components l ite i4°Bae
14°La, 132Te etc was triedraking use of a computer programs» as i t was thought i t way help Inthe accurate calculation of peak areas of other nuclidea. ïhe raethodwas based on the assutsptlons that the Coapton contribution due to anyparticular photopeak between a small number of channels is virtuallylinear* Further under a particular setting which was always followed,spectrum of a pare nuclide wao taken such that the count rate wassufficient to give good statie tics. The counts in each channel of aspectrum when divided by the area under the photopeak « weald giverespective coefficients for each channel* When the area under the sanepeak in another spectrum was multiplied witii coefficients obtained foreach channel earlier, the spsctruro was reproduced» 'this would be tra*under ideal conditions only when no other peaks contribute to the peakused as standard for subtraction while errors can be due to change inthe shape of the photopeaks and son» drifting caused by the instabilityof the analyser ana the amplifier. îhe following procedure was adopted*The gBBfflB-ray spoctxa of a number of pure aiclldss ware obtained undsrthe sacs conditions of counting as the catcher foils were counted foreoœplex apectra. The standard spectra of pure nuclides w«e read bycomputer. Using the epacified photopeak the coefficients for each ofthe 400 channels were calculated for al l the pure spectra to be sub-tracted and tills information stored in the msiiory* Next th« computerread the ooœpoeits fiaeion proftiot speotruo and starting fro» the
«mxgy side (815.8 ksV 14°la in the présent cas»), «is photo-peak area was dst|nniwd and this wao oultlplicd by the coefficientsfor each ohanosl storsd in naiaory fc-a?14 la puss spectj». Ths rssulrssultlng
f'i'j ' ww^yvic.""
ÏAHLK IV
Data on TBielifles determined
lîuolide(1) <2)
Irradiation(3)
Energy ofphotopeakused (keV)
(4)
Interferencemel ide t
photopeak (keV)(5)
Eooarks(6)
952,.
103.'Bu
4-4
9.7 h
65 å
5 rain
24 h
24 h
151,2
555.6
724.1
_99mTo 66.7 h From a l l iraalatiosas 140.7
59.5 à
8.05 d
24 h
24 h
496.9
364.5
ü&knovn short-lived
(560.8)
144Ce(i55.3)and
141ee(i45.4)
14°lQ(487.O)
"îto(366.2)and
Decay after s ix boumcave correct half-life( 17).
? 2¥ allowed to decay(Flgira 22)
Counting «as dono aftercool lag tiie sample for30 days
contrilsitioninit ial ly i s o£ theorder of 0*1^ only.
* Ce contribationBubtracted graphically(Figar* 21)
Foil »rod after 30 days.
"After 10 day» coolingtho photopeak wasfollowed.
ar>
iffr
S J*«*ï«Sfe.» >*"_*!«*!
Table IV
(1) (2) (3) (4) (5) (ê)
- 1 3 2 I 77-7 h
133,
1 3 3X«
139,
20.3 h
9.2 b
82.9 aln
24 h
24
24 h
24 h
5 min
220.3
667.7
.a
81.0
249*6
I65.8
143Ca(664.5)
1 ? â l (522.7),135Ï(526.5)
and14OBa(537.2)
Followsô aftoï faw dayo.Contribution fxoa i43i e V/S.
Followed after 5gives correct half-l ife.
Allowed 3 5 I to dficay(30 hears). Gsaphiceîlyresulveâ froro132I(1te) and i4°Ba contri-bution (Figoœe 20)
To seduce Coapton 'back-after
clearRiotopeskonly aftes? tw©(Figure 22)
Followed after 1(Figuee 17).
i
H
IV (Contd..)
V.-KÏ % '•
6G
satos ffor a l l -&© 400 okaaaelo uoso oabtaseSoa C&USSDI fcgr
f sons ûto ÖQ330GÜ-3 spoefcsa» SIG S a cnfotejeftîâ opo©teaa caa
ea t « ïtiie psseoao çaa sog©atoä BO lag £ÏK> nisst Mgîœafc cssias®
fhla posa l t to t Gal©siati©a of gook axsoo fesa t&> Mglaoot Gsosgy oiåo
îsy ©m OÏÎOEO ^13 eoE;p ©a tocï^ïoasEa fœ? tào oasliGi' @E3 trea
l® Ito oSSmst liv/3, not lîaoîi vosy cjaeceasSsï â » to fcto
•Elna* peak pooitÎOHO trcso not alvnyo o-fcricfily a t tho BESTIO loealäoa so
in FK.r-0
.4 (li) of ?3o
'fes SE»
•Sia a
onte ta «eaiataa? a»] applj? sasreocftâono fos tho effîc-
991
i givoo -tio öeeay ooteno @£ "^EEsate of tfaio oettei"^
activity casaple oves ? tiaso withlia 'Ste
ioaoiao o£ tio ta© te ta onssjss/1 gEompo ©£ "Ho SES tfc
bota psspastioiiril essaufes rri% rosgaet to îoaâ ^olytfetQ psrocipitai©i t io aicaya son^snisnt to
'5?e o©tavi% ©affEiei OB an inactive
in Q aopEQiSaoaüSo RQSÏSDS DÏJÜO to ssaEt iså itetis^pi l©ts counter onW13S files ÖÏO acasaat ©f saoiômo s^^ Kssgr »ni 4t la âifficult to
•feko aol ^ofeosjypfeioE Q4S åu cacti easplsr High spocifio activitySü^fFTl A. 4 S K A f f A # * ^ rf?O«\* fink
3 „, ' ' ' ^ g GoîmtâOîî was pioj-srca fey ije^aaâatiag Qiœichoâ Mo. fjSie©ao eboekod feora fcîfâ eassa-say spsctmsa using C©(Li) åoteotor
Uoïïi^ '"&) tolii»îâ£c. Sa^pleQ fiées thio soluticn having rssidassÎG3G t laa 10/as »OKS pEogsroa oa VYSS filas ccateâ wità gold. Shese
eeaatoâ in -Èîis foœs-pi te ta anâ foai?-pi î>ota-@Gï3!3i coincîdanee9%,
GO
sansglos nitlj Mo
99» ïîia o£££«3iow fos? t to too beta ensxgar greaps of îlo,
1.23 Eb'if (alDcaS @|^) a®å O.45 Mof (nfeesut 1T?Î) on these WIS fîlES «ae
G' «ÎO Eettioa of OSQïTŒR anâ SLMîïes ^ . îhe Bin^Le chara»!
oK of l&o four-pi î»ota-goE23Q coiîieiûe«co an i t was gated to acoept
ftotneen 0.74 aaä 0 ' 7 9 v » wîaioto âa in coincidence with
67
\ I
W \
\\
Q • 7,7n i R I
Y ' . • y
i l l • ) .
t t i ,' I-
only the O.45 MeV betas. Wson this the ratio of gamm to coincidencecounting rate gave the te ta counting efficiency for the O.45 Me? betagroup, ibis was found to be (87.5 £ 2»5) #. ^te eff icient of the1.25 fifeV beta gscap wae estimated to be (98 + I) #.
contribution was âetamdned by throe different methods,(a) following the growth of "ffiTc in a purified 99Mo sample in thefous-pi beta counter, (b) counting ^ ï ï c on Ge(Li) detector with kn«m
57efficiency for Co peak and counting a saaple prepared frön thissola t ies in four-pi beta counter and (c) by determining "mTc in thefour-pi beta-gnsçna coincidence counter according to the procedttïe ofGOOBIER and WILlïatiS end calculating the bâta contribution. Biffèrentagtb&åB wess tried to sepaisto pure nTc from Mo activity. Thesimplest :Dothod DBS the extraction of teclmetian with purified ethylmethyl ketoao from 4-5-S2 HaOä solution of tiie yMo a c t i r i ^ . Tbe puritywae checked by taking a gacm-ray spectrum using Ge(ï>i) detector andfollowing the half-life. For purifyi«e r"° f <>° °mTc,tion t?itb tetraphenyl assonium chloride in chîorcfora WHO usedprocedaaas followed in (c) above for estimating the "^c contributionTOO found to give a better eecuraey. She decay scheme of " " î c io shownin Figure 9» The internal conversion coefficient of the transitionsVt and "Y- &TB veiy large end that for Y g is about 0 .1 . If coincidence
wexe observed between tiie tmnaitionsYj detocteâ in the beta counterató Ya i n ^ ^ go"81* coa«*»^? ÎS» ralatienehip betoean 'fl£ the absolutedisintegsatlon sat», anâ the o&ssi-ved beta count rate H/3> «ad gscnm countrate H y ead the coincidence ccant rate UQ iia a simplified form le givenby equation (1O)
extrac-
1-5•ƒ3 ij/... (10)
130. S. miBAUT and J . BEÏDOH, J . Anal. Chin». Act», 8, 22 (1953).
r
99-
69
T / '- a
FIGURE ~ O E C A v *î C i ;
-* "
70
Bare E^ is the efficiency of the beta counter to the 2 keVtransition Y1» ** E ^ is varied without altering Eft , extrapolationof E ^ - 1, gives the absolute disintegration rate »l£. Using thismethod sources of 9""Tc having practically no resiâae were counted inthe four-pi heta-garana coincidence counter. The efficiency of the betacounter to conversion electrons froœ «te y 1 transition was varied byaltering the beta counter voltage* AIA raeasureaents were carried outwithin the xange of the normal beta platoia». BO that E p, was notaltered. A plot of the observed quantity 8fi H r versus "* " E/&1
is givon in Figure 10. This gave a beta contribution of 6.8 electronsper 100 disintegrations of **^2c counted on VÏI&ï f 31ras under the aaoe
conditions of counting aa the high specific activity "Ho -solution* 'Chreo such experiments gava en average valu® of 9«0 * ®*5electrons por 100 disintegrations of ""'lo, 'fee ^m<So activity wastalcen to be O.964 tistos the Mo activity at equilibrium 4 . From theaedeterminations it was possible to calculate tha true disintegration
99 99 99m_rate of lio alona in tte solution containing Ho - "^Pc equilibria»activity* Using this solution the efficiency of an end-window methanegas flow beta proportional counter was detarained with raspa et to leaämolybdate precipitate «eight mounted and counted under standard condi-
9999 activity alon»tiens» Figurs 11 gives the efficiency curve for
(aftar subtracting "'"'Te contribution) versus lead aolybdate precipitate99-wolçht. From this curve the disintegration rate of Mo was determined
in samples of about 20 ag precipitate weight.
4.2.4 (c) Disintegration rate of ïodine-151
Bie activity present in an iodine eacple from fission productsolution (without cooling) is due to different iodine isotopes and theirdaughter products. The seoples prepared In this investigation for Idetermination were always purified from irradiated target» oooled forraoro than 15 days to allow al l other iodine isotopes to decay. It i*
7 1
UJo<Y-_ )O
CO
oo
Oinv~o>oo
o —O COo <y>
ooO
S
«ruUJ :
ro CT»
o
o
oo
•s.
"o.
S
oo 1o
in
UJUJ
o:Z)
u.
c-1
\ :?.
O
PERCENTAGE EFFICIENCY
O-(J!
cr.
o
T,
O
X
—
T i
ni
UI
Ö
-o
à
j
73
possible to count 1 in practically carrier-free foztn on VYK3 gold
coated f i l i e in a four-pi beta counter but i t i s diff icult to reproduce
the sans amount of residue in saeh saœple and correct for the self-
ab8orption laaeee. To count the activity on these f i las in a four-pi
beta-gamma coincidence counter» limitations aie on the amour* t of carrier
which can ba used while processing and finally correcting for the
chemical yield» Moreover the specific act ivity i s also not sufficient.
Therefore i t was preferred to count the activity in eamplen of about
20 mg FdZg precipitate mounted in a standard way using an end-window
methane gas flow beta proportional counter* The efficiency of this
counter with respeot to Pdlg weight was determined in the following way.
Figure 12 gives the decay scheme of ^"1. I t i s possible to
count the activity by beta-gamca coincidence technique in a four-pi
bota-gamsa coincidence counter to détermine the diaintegration zate*
A high specific activity carrier-free ' I solution was further purified
by two cycles of solvent extzaction using CCI,. The purity was checked
by taking a gataaa-say spectmm on Ge(Li) detector. The purified solution
was neutralised with LiCO_ (about 10 mg) and diluted "£<? 100 ml. The use5 131
of a acsl l amount of lithium ions i s recomraeaded by KJELBERC et.fcl
to avoid any escape of iodine while preparing sources by evaporation
under an infrared lamp. Samples from this solution were prepared on
gold coated VYNS fi las using the weight txansfer technique and were
counted in the four-pi beta-gams» coincidence counter to dotermine
the disintegration a t e . å known weight of the calibrated solution
was mix«d with standard iodine carrier a Samples of différent weights
of Pdlp «ax* prepared, mounted under standard conditions and Hie
efficiency of the end-window nethan* gas flow beta proportions! counter
was determined» Figur» 13 g i w s a plot of the porcentage oounting
efficiency versuo Fd^ wwtght in ag. Being this the disintsgmtion
rate of * I sainplos watti d«terndn«d«
131. A. KJELBKHG. H« WMIQUCHI and L« YAFPE, Can* J. Chen., 22, 635 (1961).
\ \
74
i
: • ! • . * !
!
-f f! I • ••'•>. (\ x
O '.'-Oris1/2
\
f "T• i l - -cr -
o-
0-1772OR
O "7>?58
0-IG40
0-080!
To
.J f
"C /V T."r nr
75
i O
in
cc
5
if
o
o
o
j
oto
inc i
o_ l
o1—
o
76
4.2.4 (d) Biaintegration rate of Cohalt-âO
ïhe dooay scheme of Co ia given in Figure 14. In principle
i t should be possible to assay the activity by bets or scum» counting.!Po determine the disintegration rate of 60Co by beta or gaits» counting
i t i s necessary to know the counting efficiency accurately and reproduce
the aainpl© in the flame counting conditions as the standard. Ttm psesence
of solids Interferes IK the case of beta counting* For those season*
four-pi beta-gatüüB coincidence counting was found to be isost reliable
and gave reproducible results . A standard Co solution supplied by
WPA was counted la this counter a&à the disintegration rate deter-
mined- was found to be in agreement within 0.3;' of the value cjnoted.
4.2.4 (e) Beta counting
Most of tile camples from uranium and plutonium for the
radieohecdcal investigation were counted under identical conditions
in an end-window methans gas flow beta proportional counter* All saraplas
nere counted each time, long eifflugh to keap otatist ical errora below
V/o. Wherever possible» s a b l e s were counted t i l l background levai »as
reached. For determination of act ivit ies of individual nuclides in
the case of r i 2Ag « ^ A g , 1 « J h - 1 0
the samples »axe counted on &e(ï»i) detector.
and 1 4 1 C e -
4.5 CnlCtlliatiOBS
In tbe case of garana-ray speotxoœtry using Go(li) datector,
'coropsxdson method* was used for the determination of f ission yittlis,
As already pointed out, both plutonium and uranium targets w«s»
inadifttea slsulfsntously. The catcher fo i l s fro» both the tazgsts
were oount»d aM counted under identical conditions, Molybd«nuB-99
*aa celeotoà M an iatexml standard oinoe Its yi«ld and hal f - l i f t
are O9nveni«nt and i t» aofclvity could be aieasuïwd in a fairly wide
$abjèï.!&".^
so.27Co 5-2 8y
:O-O8%. 1-492 fVioV
: 018%. 0 670:99-74%,Q-3f5 M«V
0 +
77
333
.-99-72%, 1-17323 MeV
Yj>:99-93%, 1-33248 MeV
: 0-18 % . 0-8225
y :<|-5X !0"5% , 2-155 IWeV
c ; 4X iO"% „ 2-506 MeV5
l20
Ni(stobie)
60FIGURE - 14 . DECAY SCHEME OF Ca
J
•-T-j—.m -
78
Uvae* Moo tho jïolü ©f ^\<Ù to2 3
toy tekisg fäts asfcivity mises Sms tko selcroaat
eusvcsa* ïho yiolâ valus© £or tlîs ttesraal Kctttssa-isÄcoa ifisaton ©fS 5 ïCE! l i%sa ta»o 1 3 S . If ( \ J ^ I C^fe)g ^ aostEBÔ s©
yielâ for I i a fltatoMisss £äeei©E te ©btalsoâ. By
t te sslat iva jrloîâ vnltaes ao a f ï as t iea ©f is>so maaibos asâ
^ t!ïo to ta l yieia to 208$ «te TOIWO of C ^ ) ^ / C\ ! oî ï ï «a»
bo obtainoä» S-jaee suffieiosit saisbes of ssîativo yâoîâ walecs wess not
available from th i s wosfe aleœs to piot l ia «Oiaploto i
tbs vBittea ©£ ( ^ g ) ^ avâ (ï£ î o) | j TOI® fekeE ffsom l i t e r a t e s 1
ths f iea isa yiolâs ÏSSO ©aîcalateâ ssîng eipattoa
s 1 0 8 " t S * 1 1 '
'&e ©îjsoîetto yields of W
ealsulatsâ asiiig eqaatiOB (4)» Shese two yiaMo aad s î l e^her yieiâo
w>ô tresB ®£ .®îîlatei osing a aoûifieâ f «oss ofa usias Qqpatioïa (Sju 'ite A S E S Î E3atî?en fies ion
239 235
essss-saotlum val«9S o£ ?41 lasoa enâ 5?? te» for Bi and 'u
s"00paetiv©ly oos© takeza fa?oia t te tsMe ©f isotopes • 5ÎÏS half"»lifiS
o£ M© isas €9Epa?Sisentally ®'fea0S?o;Bâ t© î»e 66.18 ^ 0.1S hours l&sed o»
ths âe©^ ef nese tbe® 60 soa^ies anâ a least sqaass calcalation usinga
)neutieon flus using 5yCo(»»Y ) Go
i s a wall teoteö ss'BïOa end sas useâ as a Btaaâ&râ procédure
t t a a a dessen la^omtösies **. The neuftcoB Hase in leaotojs can
ö© eonsiâaïQa unSes three categories
1J2C II«B. ISEBÎ anâ B.B1. B1M1, SîTffiïâlï OF SISSIÛB YISL1B»
O.S. IEDSBBR, J«ES* laOlÊiSKBBÏî and X. ESBK!Ôlit ffiabî© of Isotopes,
John ïïiley and Sona Ino.» (1967)»
79
(a) ïhenaal neutron flux with Maxweilian energy distribution(b) EpitJiersal matron flux wlfto an energy distribution
proportional to the reciprocal of the neutron energy"S" ana
(e) Foat component in the MBV range.
AB mentioned earlier the irradiations weae carried oat in the reactorin a position nhere the cadmium ratio was greater than 200» For thisseason i t i s not accessary to discuss here the calculations of the0pif.herml or fast component of the neutron spectrum. The kernel neutronflux does not show a perfect HaxwelHaa distribution. Basse factorahave been discussed by different authors. 111» WESSCÛïS *% who quotedeffective oxoss-seotions for well-moderated reactors. another importantrequirement is that there should be no self-shielding in the targetmaterial as othsxwiae i t caa lead to large errors . The reactions in59Co irradiated with thermal neutrons sse shown schematically inFigure I5(a). Bus ts the Bhort half »life of "*""Co and nearly ooaplet©
60decay to ground state through Co» the reaction seheae can be simplifiedas shown in Figure 15(b) with negligible loss of accuracy.
59, 60,The burn-out eg 77Co anâ Co during the irradiation period ofa day and at flux of about 1012n oa"2 eeo" i s negligible. The half-lifeof Co is nuch longer than the irradiation period. 3he actiTify foxMdis given by equation (11 )
A<T) - (11)
whers 4- to tk» average thermal neutron flux during tis» t of irradiation.
134
135
I36
W. KOKLSB, working paper IaBÂ/bt/6 f<The Dsterraination of
îhennal Hetttron Pluenco by Cobalt Aetivotion ftonitora' (19®)*
C.H. waSîCOOS, 'Kffeotiw Crooa-Mction » l u e s , for w»Xl-
BOd«aate« thermal «eaotor spsctra, A8CL-1101 (i960).
T.Ä. EASIWCXa) «nd E.B. WBEHSH, Huol. Sol. and Bngg.» U , 585
53"
0 i
' ( ; < • • ( " • )
6 0
i / i ' =• O .'O y
I'll
FIGURE- 15 ( b l
8 0
I
A(ï) is the activity of Co naaeused after tin» Ï from the oni ofirradiation, "À the decay constant, <é> the neutron absorption cross-section and Hc is the meber of ™Co a toss. The following nuclear dataassessed and zecoasaenäed by KOMLSI?1^ «eze used fox calculation of ' ^ 'using equation (11)
(n, T ) CïcaB-aectioB cf60Decay constant of Go
59Number of Co atoms
< a 37,3 ferns.X « 4.16 x 10"9 sec*1
^ o - 1.0219 x 1019 og"1
4*4
ïhe various factors tiiat contribute to the errors in the reportedfission yield values on ™Btt from the piosent work using a Ge(Li)detector and mâiocheraical aetheâ axe tnentionsd here briefly*
( i ) She errors in the R yields useâ for oslcalating thebe reflectedrelative yields by 'coaparison method'
in fchs naluos of y7Ri yields.
erro? involved in the assumption that the geneticrelationships and the charg» distribution in the
239
(ll)
239fission of Pu are tile «ana as those inthermal neutron-inäuceä fission of ^5U is probably
raj nos in the case of mry nuclideo
( i i i ) Goons-ray spectroaetsy using a Ge(Li) detector
(a) The sain source of errors in the g&raaa-xay spectre»œtrie data using a Ge(Li) detector is due to errorsin calculating the Compton contribution uzkfer a photo-peak* Tim possible errors arising « i l l vary from peakto peak, depending on the degree of interference from
82
nearby peaka and also, the inaccuracy inherent In•&e method of peak ai*ea calculation, flhen a stand-ardised procedure Is strictly followed the error mybe about t*o to three percent* Effort «aa made tokeep «ils error to the minimum possible by caking adetailed study c€ the different peaks used In thisstudy. The details axe given in Table XV (p.63). Theactivities were read from ttie decay curves plottedfor individual niclides. Further the *B* values «ereobtained from the ratio of the count Kate. Sane ofthe systematic errors may be cancelled»
(b) Relatively less isrpoirtant but e possible source oferror is the geometry used for mounting the catcherfoils us precipitates relative to the sensitive volueeof detector» Sts same possibility arises «hen thecatcher is itself (severing the target In eccentric way.Shis ervor was estimated to be below one percent*
(c) 11» error in the internal standard yield ratio
( W h / ( W s *m * oaIried t0 e11 tbe otheryields determined using a Gf»(Li) detector* In thepresent case this nay lead to uncertainty of
on 239
to five percent due to the ??Mo yield in
fission*(IT) Kadioeha»ical method
In addition to the errors mentioned above the fissionyields deternlned mite the modified 'coaparison aetaod'(equation (6)) will have the error do» to the followingfactor»
IJC-!^
"-" ~
83
(a) She reliabil ity on the number of atoms of '*ftt ana235
can fee placed ae about one pa reent.
(b) The fission cross-section values for 2^Pa anaare considered to be accurate to better than 0.5percent.
(e) The error arising In the activity determination dueto volume measurements, weighing, mounting» oountingand reading the activity from the decay curves couldbe of the order of two to five percent»
(v) la the measurement s* absolute f ission yields the errorsbe due to uncertainties in
(a) the «ttsber of atoaa of 239Pu or
the fission oroaa-ssction value
(0) the error in the detesiination of dlslntegzationrate could be of the order of three percent
(d) the neasasmont of neutron flux can be consideredto be accurate to about two percent.
îhe reaaltant effect of these ex-rors oa the fission yield valuea of«aa estimated to be about 10^ oa the values from Ge(Ll) detector workare. about ^ to 1<$ on the yleiae deteralned by radlocheaical netbod.
259
84
4.5 Basal ta and Mgcuooion
Figure 16 gives typical gonaaa-aay spectxa of fission products
obtained at different tines after a 5 mim to irradiation. Bata ma
obtained for three short-lived «iclidgs, via. 82.9 n4n ®a» 92.5 ain142k» and 4.4 1» 85fflKr. %e spectra mxe followed starting fron 60 ainutes
after the irradiation. A3 pointed out in Ikble IVAthese was no inter-
ference and the decay of tke respective peaka gavo eorrect half-life
values. 'Hie demy curves are shown in Figure 17• ïhe 151*2 iceV peak
showed a shortor-liveeL conjponant of about 40 sdn half-life. Tne shorter-
lived portion could not be assigned to any fission product. Figures 18
aaà 19 show gasm-ray apectj» obtained at different times after a 24
hour irradiation. Many peaks axe well resolved. la general, the data
for ahort-livad aaolides were obtained in the first few days. Data for
lo^r -Hved rmcûidee Ilk* 95Zr, 1°31». 1 J I I , 1 4 ° ^ •*» « » obtained
from spectra taken after several The reason for this 1« «vident
fxoo a glance at Fi&aoa IS sad 19. a.ê. 496.9 **V peak of Eu which
M co^ietely msted in the first few days naa »ell resolved in the
spectra tekea 13 and 31 daya after irradiation. The details of peaks
selected for sach nuolide together with information about interfereoce
etc ase given in !feble IV. B» decay carves obtained for different
mclldee a » dwm in » 0 » * SO to 85. « can be •*•> from these curves
that in the optima time selected for the different »elIdee the decay
was propor, theïeby indicating that interference from other mclidee wae
negligible if any.
The fission yisld values are givan in ïable F. Aa aenUoned under
fioaion yield caleuUtloa in Section 4-3. literature values for Mo
yield in 259PU and ^ ^ ha^ to be used for e o l a t i o n of fieoion yields.
AS „sny a. five » 1 » - ~ reported in l i t e r a l Mr the Mo yield
in « » Ä . Sine» tne variation was too large, fission yield» we», calcu-
lated based o» all m < l » ^ ^ » « * ~ l u 9 8 i O ^ « ^ - ^
available in literature and are presented in Table V. Each of the yield
f;<t"!i!>Wl^*M" * l f W
(S çr)1""
J
! î
85
'i L .
X î 13N
1
*tI
ü o •
98
Ci Ar, AKtA' j (KH ATIVL >- - - ( I T i l l
8 7
ix\
89
en•ri
i
i : i V > I 1
o .if
JT
sr
i i l l i ; i t
i L
i „•?
I . I I I I I I I '
/ I
90
91
T
i i
92
*;JMOI^< « v t a u M *
AREAS (RELATIVE)T - r - , i " ' T " >• i " ' ' ' ' ,
-r-r -rrn ] ,
4P ! '! ! o
/ iriy
94
... I
VV 1,1
TABI.K V
Fission .yields of "* lix us lag <>e(Li) detector
Euolièe
Fission yield f> based on différât ^"t$o yield -values
5.61 6 »OS*-» 6.10*«-» 6.44 6.59
91
95,'ÀX
99,fee
133!
133&
135».
0.6Q 0.64 O.65 0.69 (0.54) 0.71 (0.57) 0,56
1.89
4.40
5 .61
6.19
3.67
3.66
4*62
6.23
6.44
6*00
(2.41)
(5.06)
(5.61)
(5.79)
(4.04)
(3.Ö0)
(5*51)
(5.53)
4.74
6.02 (6.02)
6,65
3*94
3.96
4.97
6.69
6.92
6.53
2.06
4.78
6.10
6.73
3.99
4.00
5.02
6.77
7.00
6.61
(2.30)
(5.60)
(6.10)
(5.5O)
(4-70)
(3.60)
(4.90)
(5.00)
2.17
5.05
6.44
7.11
4.21
4.23
5.30
7.15
7.39
6.98
(2.59)
U-99)
(6.44)
(5*63)
(4.53)
(3.77)
(5.26)
(6.90)
(6.90)
(7.25)
2.22
5.I7
6.59
7.27
4.31
4.32
5-43
7.32
7.56
7.14
(2.52)
(4.86)
(6.59)
(4.55)
(3.60)
(5.09)
(7.18)
(7.18)
2.56
4.93
6.52
5.63
4.54
3.69
5.17
7.04
7.04
7.25en
v (Conta.)
Table V (Conta.)
9%,Nnollde Fission yield > baaed on different Mo yield values
5.61 é.02*•» 6.10*«» 6.44 6.59
159»
145,Ce
144C
147.
§»09
4^9 (5.4T)
4.90 (6.11)
4*82
3.71 (4.28)
3.36 (4.O9)
1.78 (I.46)
5.47
5.83
5.27
5.19
5.99
3.61
5.53 (5.4O)
5-32 (5.36)
5.23 (4.90)
5.23
4.03 (5.1)
3.65 (3.70)
I.94
5-e4 (5.99)
3.61 (5-58)
5.62 (5.23)
5.53 (4.97)
4«26 (4.56)
3.86 (3.94)
2.04 (1.99)
5-98
5.74 (5.6I)
5-76
5.66 (5.O4)
<i.36 (4.4S)
3.95 (3.78)
2.09 (2.15)
5.99
5.60
5.23
3.01
4.52
3.81
2.07
(108), ** s ïief (109), *** Î Hef (HG), • t Kef ( m ) , **+ $ B®f (112>
aeoa of the literatust masa apcotioraetric values
imlue In ttie parontheeia ( ) &TP. tiie csrïespotóiag sefesenjse îîtes^tux© value.
IDCD
97
values thua obtained x& eosjpared witSi ttie correspondis^ value reportedby the particular group concerned, ana täese ase indicated ia paren-thesis. In the las t column of Sable V9 sean of the moss spectsoaotricvalues of PICKEL an* VQE1I.I1BQB111
anâ those of the Idaho Group112 asegiven* Fission yield values calculated on the baaia of 5.61, 6.03 and6.10 for 99Mo yield in 239Pu fission axe in general loses than the1 iterators «lata» while the values baaed on 6.44 and 6.59 aipree «©11.A high value for *fti haa aleo been reported fey ÏÏOÎBA and I«R157 intheir work on fission yield determination using <k>(hi) detector. Svanpresent xadiochemical investigation gav© the sane velues as obtainedusing Ce(Li) detector for 105Ru and 1 ? 1 I . ftxr expérience has shownthat the Ge(ki) detector Eethod cannot be used for the dotezsimtiOBof f iaaion yields in the syiaiaetric region with tëie limitations of thepresent cietootor set-up. Fission yields in thia region were determinedxadioehaoically. ih(ld) detector was used to obtain garnaa-rey spectreof purified silver samples to deteraine Ag and åg in a mix turaof Ag, Åg anâ àg» Figure 2é shews typical s pec tie. of the puri-fied silver saraples» îfaô jjeakg ooTxaapanålng to energies 616.8 k©V aad298.6 keV for Ag anâ Ag seapectiveiy showad correct half-lifevalues. Qe(hi) detector was else uasd to determine tis® activity ofindividual isotopes in the case of csrium and ratheniura aatnples puri-fied radiooheraically*
anA SKUffljaiy of the fisaion yields of ^ Mo detersràned in the thermal
neutron fisBioie of 3^Pu aad *0 i s gi^en in Table VÏ. An averags value99
of 6*7? ± O.15 «as obtained from ten irradiations for the 'Mo yield i s
^ fissiosi by ft© 'comparison method' ueiag equatiOB (6) and 3Mo;dolâ in 25^ff fission aa 6.16. Ti» BBaaurement of absolute yield gave avaiua of 6.66 • 0.07 and 6.06 + 0.16 In caee of 233Pu and &5V fissionaraepsctively. îheo© are about Zf« lswwr «h«n cosgfered to 6.79 «nd 6,16 in
137. Å. 90TKA and 0.
947
, 'PhyBico and Chosaiotry of Fisaion1, IAEA,
i
93
'S&2S& VI
Fiaalcn .vlald of ° Mo
Piasion vislô2 3 9Pu fission
1 comparison raethoâ'fiaaion
'absolut©
* Excluâsd from tbs»
99
255U fission•absolute raeliiod'
1
2
3
4
5
6
7
8
9
W
Averag© value
Accepted
value
Valus seoostmenâetlfrom the presentwork
6.83
6.80
6.80
6.62
6.75
6.64
6.83
6.35
6.80
6.96
6.79 + 0.15
?
6.79
6.63
6.63
6.76
-
6.6s
6,66 ± 0.07
5.52*
5.89
6.28
-
6.00
6.06 1 0.16
6.16
"6.16"
,
Ka
p?
SrSÄlita
00
tfca tras eases» %© amsrts.inU@ss ©TOSJ a f ter easeful âetssœination of a l l
'As iiffesöK'ó feetoss i a ®qu&tioa (4) as?a tmaös n-ssa than te
thise leads S© a slig&ïtay looes valus, Theiefoss tho
i s «Sois i W 5 « Sto CTOEQII asôlnatea QTSÙS as éiseaosoâ IÎS
bs a cssisam of gS. «Sa vaïp.e 6.06 + 001S öbtaiHsu f@s Jiîb l a
'afeoeliate cstînoâ* i a ths asti© s©sias ©f
sess©Ezaî)Ï2r trall xjith S.16 tóïieh ia -She literates*© seisopt9å
2able VH gives tte fisnion yield values fox- 1 ^
a Go(ïii) èsfeetsa'o Ea«îioeà©mîeaî nothod rasiag @qtaati©n
by tcaaOBreasat ©f sboolato åiaintegmtion sate asä maniTstsE of
e te eqeatiOE (4)» â î ï ^te feteoo œsthcâs lead to tho sans® fission y is lä1 339Ï ia P«2 within tha lirai te of «sKporimasfel Qffrors. ïlie
'sales fes ^ ï fission j î eM fsora feSis pres©at wcafe i s
4064 â O»1O« ÏÎΩ ©ïütaEstoö wesa î i e«?9r &ora &e «ti£f@s@nt factors
diocaseaå lia Saet£©s 4=4 sffeeôisjg Siis valus is afeoat 9^.
?2II giwes th.® f ission yields of tsrasty nim Eacïides
å i a 'öfeiia HtwostSgatioH äu t te thss ïa l steEtteon^iEauesa f ission
uoins s2âi©eîiaEiiieal aotâioa ('eos^axison netfoeå8 using equation
(6) aîâ ErjooiiEefflQ&te of afesolats yiei to) aM Épnas-iay spôCt3?oastïy uoing
fe(M) feteotos?» l7iej3loa yäslds ffsoa Ge(Li) woa& eœs s n o r t e d hexe on
«Èo lîasis ©£ îa© fiasloQ yield 1B J îta as âo?9 täte ^slue
fs?©Ei tte© psssosat tîsà'o In tho ease of J Sr, 1
osa ^COB tho f i s s iez yioîâs ÜBJE® fietsssiiEQd uaiisg 6e(ï«i) detector
I lates ' ©a jKiâiodioiaicaî lnwostigation WBQ aîao cas2?ieâ out. Fisoiossâ by the tw© methodo
nithli i tbo osspesinsmtal oss»rs, whilo fes» ' Sr aad Ea tixo âifffas>*cases ea» Eocosafrondeâ on theûtaeoa aso Îase3 . FAosiera yiolåo in
tooio e£ aeadiesteEsicsï âetonalEatiens GS the tsKiegirteisstiea involved ia
•feîaâo Gottoâ aso loos at? eoapaarad to tho fe(Lâ) «tetestor fletanainationa.
10
Method ofdetextairation
ïïaing Ge(ti) detector
Hadiochsaieal'comparison method*
ladiochemia&l'absolute method'
Accepted litoreturovalue
Value rscoœaendedfxcn pxesaat woste
TABL2 Tt,l
Fission yiald of ^ 1
Fiaoiöii vielü o259fti fission
4.47 + 0.14 (5)
4.64 ± 0.10 (6)
4.6B±O.O5 (5)
3.69
4.64 ± 0.10
255Ï
2.89
2.90
2.89
1 fission
± 0.04 (3)
> 0*04
•
Biiit
The namber in the paseathesis ( ) indicates
number of detesaslsatiOBs.
OJ
TABLE V I I I
Plaalon vialda of
i?\
Huolid»
7Br
89c
Sr
95SSr
97Zr
99«
Present «ork
0.290£ .015 (3)
O.72• .03 (4)
1*95• .16 (6) (E)
2.29• .07 (2) Go(ï»i)2.64X .10 (6) (B)
5-35i .18 (4) Ge(l»i)
5.58à «13 (5) (S)
IG1969
F&T1959 1965
S&O1955and *
0.301(Kr)
0.574Eb-Ar
6.79+ .15 (10) (K)6.66+ .07 (4) 'Absolute ootîrod'
7.50• .51 (5)7.61+ .08 (2) (K)
2*52(Zr)
4.86»
5.64*
6.59*
O.29(Kr)
O.535Hb(K
I.71
4.99()
5.63
1.74
2.41
5*06
3.61(Ho)
6^44+ 5 »61
5.79
2.30, 2.45*
5.60
5.30
6.10, 6.Q21
5.50
yi«ia»
0.06,
1.60,
0.292,(Kr)
O.552
(Kr)
1.714
O.29'(Br)
0
1
4
.51
.30
.76
5.81
6.20
5.9O
6.16
3.00
^ - • * uj s
'JPAHLK V I I I ( C o n t a . )
'JAHLB VIII (Conta.)
NaclidaPlaoicn
IG1969
F&ï1959 19É5
S à 6 1955
anâ * yield»
1
111
127,Sb
4*44& .10(2)
0.34• .00 (4) (H)
0.105• .005 (4)
0.08± .004 (4)
0.0025i .0005 (a) (R)
0.037
± »004 (3)
0.0400.034
i .004 (4) (B)
0.084± .015 (4) (a)
0.46• .08 (3) (B)
4.55* 4.53
0.116**
4.04
0.55
4.70
0.28 0.27, 0.20% 0.212e
O.O93 0„10t 0.121, 0.116
0.065'
0.003 0.003
0.033 0.045, O*O341
0.048
0.041
0.068
0.37
O.4O
0.019
O.OfO
0.011
0.0007
O.CO97
0.011
0,021
0.137
CD
CO
TA3I.R viia (conta..!
TA3I.E VIIÏ (Conta.)
•JudideFission yield £
10 F&TPresent work 1965
S & 0 1955
and (1-10)yields
131,4 ' 4 T , >
± .14 (5)4*64
4 .10 (6) (H)4.68 «Absolute cwtfcod*
± «05 (3)
• !i2 (10) Ge(Li)
7.55 t x
• .18 (4)
7*81• .14 (3)
7.37± .19 (9) ««(M)
6.17+ .10 (4)
5.91± .15 (14)
• .10 (7) (B)
3.60Xe
5.09Xe
7.18Cs
7.18Cs
5.61
3.77
5.26Xe
6.90
Ce
6.90es7.25
5 «99
5-58
3.80
5*51
3*55
3.60,
4.90, 5.29
5.00, 6.95*. 5.265
6.80°
6.955
5.40, 6.074
5.47 5.36, 5.S23, 5.
2*90
4.26
6.69
6.69
6.17
6.46
CD
VIÏX (Contct.)
ÏAEI.E VIII (Cowta.)
WllClirtG
Fassent work
FjBBioa yield j
ÏG
1969 1959 1965
s & e 1955ana others(( i - 1 0 ) Yields
( s )
5.5O* .09 (5)
5.19i .15 (3) (R)
5.85• .21 (4)
4.39 , x+ .54 <9)4*60
5.25* 6.11 4.90, 6.O83, 5.?14
5.O4 4.97 - S.663, 4.938
4.48 4.56 4.28 5.10, é^Q5, 4.553
4.5T9 . t O
nanber in the pareiitheaie ( ) indicates the lumber of
t Fission yields detezmined «sing sadiochettical mothod and equation (6)
-52L. ( y )741 y' V n
ïtl
5.66
5.04
5.91
3
.08
.85• \o
.17
(5)
O)
Ge(l.i)
3
2
.76
.15
3^4
1.99
4.09 5.70,
4.099
5.503, 3.T98
. 3.4910
2,58?, 2.5a5
5
2
.40
.19
en
vu (conta.)
§
S
CA
Cv)
m15
S• Ut
oOl
1 06
T- CM (fN^f tf\VO fr-©
s
1 07
l i t e r a tu r e valuaa for the fiasien yields of the melidas in 2^Va f ission
and those for 55U flasion used in calculation ara also ineluded. As
een be aesn fioa tfes data in Skble VIII, yields of the present inves t i -n g
nation «tie close» te the raass spectroraetrie vaiugs of Idaho Group ' andPïCKEt and TŒ3LIHSON111 which agree well between thensoives. In Table IX,the differences between the values of the prosent work and the literature
' 1values axe given in d e t a i l . Fission yields of 10^Ka and ' 1 I from the
present investigation are 25-35$ higher than the mass Bpeotrometrie
values» These yields vexe determined using <Se(Li} detector nethoil es
well a t sadiochemical method equation (6)» ana in the oase of I
absolute measurement was also dom. Values of 4.60 +; 0.05 and 2.89 + 0.04131 239 23H_
»ar© obtained for the Î yield in Pa asd ^'U fifssion rospectively
(ïable VII) . The value 2.89 ± 0.04 obtained for 1 5 1 I in 2^5U fission
by the 'absolute method' in Ifee aarae aeries of expérimenta compares ««11
with the accepted l i t e ra tu re value of 2*90 end this indi «a tea the
accuracy of tbe procedure follcwsd in this determination. Though the
yield of *M sad I are higher than l i t e ra tu re values fee feet that*£ ie provable comclomnt to masa nuirJtas 134 and the yields in th is
*region are about 7.50 gives support to the value of * Su from the
present WOÄ. Sioi lar ly ? 1 ejoä i to probable compleEient Eu have vexy
nearly the same yields and this enables one to bave confidence in these
values. %ere ccmpirisen iû possible with the mass spectroiaetric values
i t i s seen that IS of the pxesent values agree within W- and four within
$ . feaaons for the differences in the yield values of " ^ r t S? and
aie net c lear . £he data in the symmetric ragion from &g to
are d i f f icul t to coœpaï» since» of the two s e t s of values avai l -
able* e i ther a l l axe not available in both the se t s ox the differences
be i-ween these are appreciable*
fisaion yields obtained in the present «rosa: along with
l i t e r a tu re values are plotted &e a function of the mass number to giva
the szfiss-yield curve shown in Figure 2?. The raass-yleld curve is synaet-
r i c a l around mass number 118, The width of the petites a t half height i s
OStoSM
È31
cji
»!«o
<S O81
IQ
•3
T t
1 08
l f 1 I \
©
al
* ?
i Î *«- *- O SÎ
tr\ C- TT
T ir» • -
I T ç
If I I I I
i l
I i ! ! i I
1 ff *********
Table IX (Contd.)
Httolide
135j
139'Ba
142J
143£
144,Ce
147.
IG (1969)
- 2 3
•29
+10
• 5
+S
•5-3
+1
F & T
•23
+7
•»9
+13
+3
+3
-2
-1
+18
+1
0
B * Y (1965)S & G
and ethers
Mean of maasspectronietris
values
-16
•22
•2
+37
—
0
-15
«.
+7
-6
•50
•24
•24
+29, +22
+14» +6
+50, +9, +44» +11
—
—
+14, -2
+2» -1, -4
+5, -14, -10
-«, +19
-10* -«4» +2, +1
+4» -JO, +g
-16
«*—mmtXs
+26
+8
+7
•11
1
+3
-2
-1
+17
+2
+1
+5
The naihbers given in colnssn 2 to 6 are ttoe ôiffereneea b© twee a the present work values and theliteratur» âafca expzeased in percentage using Ike literature value as iBfea»no«.
The + »ign indice tee ttiat the value from the preewnt work i s higher than too corxespondiap valueof the particular ï«feï«^ce.
Oinilarly •»sign lr»icat(98 tlu?.t i t i s lower*"0" Indicates that tho value from the present woik ie same ac litesa&ue value.
U3
Î O ' O
t -o i -
0-
© PRESENT WORKO MASS SPECTROMETRIC DATA
X MARSDEN AND YAF^c ( i 9 6 5 )D S a G ( S956) AND OTHERS
1 1 0
OOI 1 JL
90 102 114 126MASS NUMBER
FIGURE - 2 7 -
138 150
f
111
•agscocoisö uätta
t3îo scat^-Qo^ssîE^à sati© 3D 225 O Steno iafe aso
lâtogatsaso flats ©a tliossaî EciateaE=»âEûsaeoa
^ ?01 emas^ 5 " âa G soviow asua«âo ©a ESSO
taöioa ûa QpaiatasoQuSQ aaâ Eoirts»»iiAGcâ fâosieao Sfâ oma ©£ tîio
yloîâa ta 2Q@fi» Tuia euEsaftiOBs csiO ÛOEO laeis^g tîjo yioiâ melass fzea
'SÎQ psosQnt wo lï QHö »sot ©f t!î9 vältass •Êolïca oo seas @f tâo eass
sgoetsoEötsle KÛKea ©f W1QKM assâ SOiSIïïSCSI QES tl&®3o ©f t î»113
• °Sho mass0QÎVC3 Gscopt tùo yie&ä valuoe? f os ÏTBOO EUH^OS? 10t9 1©g9 1©4 asö 150wSïi i ûf££Q% îçr aîjeat Î 0 * ï t naa »ot gosoâîîlo to usoo ftto iatsa^oîafsâvaluoQ ^SOÏÏ! tr&o caaoëa etssvo âsawai Ira tho eisfeiso nsoo sagloîa Saa to tîie
usa voggr âiffeseat yiolû VOISGO a t tös two foalsÈiiglî yieiâo la tîie poalv a@gi@n as?o p3.©tto€ osa a lltsao» oerilcmsfesr mû sfoown in Figase 28. Its casa 60 ©eosi feso 1to fi@iso that
fine stsaofeiïG appessa t© te pseaoat to Q eesffaisä osteat» He svos?» teview ©f tîiG feet fâiat we teve not ©fttaisså te'feo ia tliio ssogloa ezfeaast-
ao troll as oast t e geaîs jsegioas
finein Figaze 28
, €ôtauo ©f fina atsaetesa con not boîâ&e t o . In Figtsx'Q Siâ9 ta© Emss yfelås
aso plot tei aftos? eoraootlïîg fea? tbs sssatseassoutsOB eaisoioa SUETO» åo ssea fjKsm tfeis gin s»4 psoseate ï f fftao otsaofe^ IS positively
tîio yial<lo ceas net coxxeotod fo« nattt»3SE oratssion, feen theef tfco oece oa apflyi^g tbo cosassetica smy fee espîeined
o» tho MeiQ t&at tb© fiao atssasfeise is pcobsbly to a IQE^S extent dueto tho goot fiooiea sauÊson ovapojgatioa. Bttt to come to this 1g?pe of
if tK> i'eol tlist täe âota Is not suffioient» I t csan be seen£xm Figuso 28a that the psseaeat tote gives mere or less the sane l ight
112oaS feeaw nass psska w&Slo the âeta cf laaîio Oi?œiF as well as that
111of Fï€KM> aoâ SSMöäöir give s aoBOTdiat loner l ight peak conparBd to
ümiS3 s Yu. M. LES. , VA. IBBEIBF and
PRESENT WORK
MASS SPECTROMETRIC DATA1 1 2
r
4 -
80 !00 HO I20 (30
MASS NUMBER
FIGURE-28
I40 150 oi;
8 -
PRESENT DATA
MASS SPECTROMETRIC DATA
|~I2O- 155
| 120- 85
120- 155
120- 85
1 1 3
2O
I20
I20
I25
I I5
FiCKEL S TOMLINSONIII
\ *
I30
MO
135 140105 100
MASS NUMBER
FIGURE-28A
I45
95
I50
90
I5585
1 1 4
îhe advantage of ganraa-ray apoctroastry using Ge(Li) detectorwas that data for niclides which coula not be obtained conveniently byradiocheaical method were alao obtained along tóth other naclides, e.g.for nuclides like B5nfcr, 133Xe, 1'^Xe and 147Wd. "Hie present Investi-gation indicates that G«(Li) detector is useful fox- the determinationof fission yields and förras a complementary method to the radiocbenicalmethod. The precision on these yields ia about ?£ while accuracy i sabout WA. Improvements on the detector ayatera to give better xesolutionand hit ler efficiency and with no complications of internal standardyields nay lead to better accua&cy. The Ge(li) detector could not beused for the determination of fission yields in the ejrarotric regiondoe to low yields and low efficiency of the detector. Ge(Li) detectori s quits useful in the determination of activit ies of individual au elidesin purified samples of 97Zr - 95Zr - 95Hb, 1°5B« - 106Fu, 1 1 1 i g - 112Ag -
and Wfl , - '*he - 1^Ce etc .
To siumaarisef the following general commenta may be made while
comparing tho fission yields of the present vork with the literature
values i
2he yield of the present work which i s 6*79 i s thehighest of a l l t the next lower values are 6*59 detenained
^ ^ 112
usiner Ga(ï>i) detector by Idaho Group and 6*44 the inter-polated value of the nass opeotrometric data of FKKEL andTOiaiilSOH111. She lowest is 5.61 the radiochenioal valueOf HABSBBH aaå YÄFPS108.
Fission yields of ™Ku and * ' l from the preasnt investi-gation are 25-35?' higher than fee mas spectronstrie values*Detailed investigation carried out on thess nudldss inthe present work as disoussed earlier and a high fissionyield valus for 10^Ku reported by HOEEA and MB *' leads
1 1 5
one to have confidence thet these values are higher thanliterature values.
5» ïhe BBSs-yield carve of the present work covers en area ofabout 206$ while that of UABSWË and ÏAFFE108 has beenreported to cover 19°?' and thus asking a difference of about
in a total of 200.
4* ïhe difference between the present values and raâiocaemical103values of MABSBEK an* YAFFE Beems to be in both the peak
regions while the main difference between the present valuesand the naoe spectxoraetric values seess to be only in thelight peak region.
5» The present values seeai to be dose to the raasa epectro-taetric values of Idaho Group112 and FICÎCEL and TO?!LIMSOH111
which are in general agreement between themselves*
6» Out of the raethoda which axe being compared, the aassapectroaetrie mattiod and the radioohemieal method invol-ving the use of four-pi counting and deternination offission yields by 'absolute method' ere better than -Si*'comparison method' used in ths present investigation asthe 'comparison method' Involve the usa of fission yieldsof **0 and the assumption that the charge distributionand genetic relationships in theare the aan».
and 239Fu fission
7. Inapite of the differences in the raethods mentioned above,tiie agreement between the present data end the oass apectro»metric data seen» to be olossr compared to the agreementbetween mas apectronetric data and four-pi counting data.
1 1 6
OP AMERTCI0î,f-241 FKOE3 CQHCEHgBAgEfl AQHEOgSCfgiOBIDS SQLlETIQig BY THILAÏÏfiYLAMINB tfEDHGCHLOHlBE
5.1
The f i r s t use of hlgt-BOlecular-weight amines to extractac ids f ras aqueous so lu t ion Into an organic r>hase «as reported bySÎSITH and PAGE * . Long-chain high-fliolecular-weight amines found a»Ida app l i ca t ion in nuclear process chemistry for the s e l e c t i v eextraction of metal ions* purification of ferti le and f i s s i l e materialsfrom irradiated fuels and isolation of transplutonium elements. Theadvantage of the aciine sal ts over the organophosphorous extraetants i s ,their greater stability towards xadlolysls and hydrolysis. All these leato a systematic study of the funSsaental properties of the amins extrac-tion system. Curing the past two decades a number of publicationsappeared on the araine extraction system to give a better understandingof the different factors which play an important role* The data we»reviewed by different authors and discussed in the conferences
on Solvent-Extraction Chemistry14^ 4^. The present s t a t u s of the aainae x t r a c t i o n system has a l s o been given by MARCUS and KERTES 4 In t h e i rbook on 'Ion Exchange and Solvent a t t r a c t i o n of Metal Complexes'. Sea»of the f ac tors which play an important cola i n the araint extract ionsysten and the extract ion of act inldaa « i l l be mentioned b r i e f l y .
138. E.L. SMITH and J.E. FAGS, J. Soc. Chen. 2nd* (London), & , 48 (194»).139. F.L. MOORS, 'Liquid-Uqjaid Extraction with JIigh-mol«cular--«»iäri
Amines', HAS-HS 3107, Satloml Acadeaçr of Soianoaa, NuoVmrScionoa Series, Office of Technical Services, Sspartoant ofComaexce, 1fe8his«ton 2% D.C. (196O).
140. CF. COLBMAH, Nuel* Sel. Sng e 12» 274 ( i96j) .141. W.E. KBDBR and A.S. WIISOB, » ic i . Soi. Wr» XL* 287 (19«3).142. Y. MAHOÜS, Cham. Eav., &t W (I96j).143. CF. GGUUAS, 'ATOMIC BRBBffiT HCTIE»', g, 3 (19&()*
1 1 7
5.1.1 Anîne extraction systera
5«1.1 (a) acid-base reaction
The reaction be 'Meen an aminé dissolved in an organic diluentand an aqueous solution of an aciâ can be srepreeented by equation (12)
org vThe subscript (org) designate the organic phase ana one or two of thealkyl groups represented by 'R* can be replaced by K atoms. In dilutesolution of low dielectric constant diluent the anmcniun salt will beion paired anä can be represented by equation (13)
T7hers X represents the anion of the acid. 'îhss order of extractionCl" < Br"*< l"< CloT i* decided by the aqueous phase interactions
4She order of extraction of acids by anting claao being primary >secondary > tertiary*
5.1.1 (b) Giganio diluent
The diluent i s not ' inert' , but interacts with the anooniu»
salt tlirough i t s chemical properties and dielectric properties. Siffer-
144. W. !M4E8, Aotinides Bsv., 1 , 71145. H.A.C. acKACY., T.V. HEÄLY, 2»L. JESKEJS and A. NAÏ101Î
•Solvent Extraction Chemistry of Metals', Proc* Int* Conf.,Harwell, Ëidcot, Berks, Sept. 1965. McMillan, London (1966).
146. D. DYES8K3, J.O. UL38&ZJS and 3. EÏBBERC (B8s.), 'SolventExtraction Cîhenistry1, Proo. Int. Conf., ICSEÜ, Gothenburg,1966, NcBth-Solland Publ. Co., Amsterdam (1967).
1 1 3
ences in the magnitude of extraction duo to diluent interactionsmay be very large* e.g. the extraction of hydrogsn bromide bysolutions of trilaurylaraino Sût, in various Stluente, ÜULLEH and
150 R
DIAMOND *" observed a change of more than ICr in the extractionbetween chloroform and eyolohexane as diluents. In general, forthe acid estimation the higher the dielectric constant of ihe
diluent, the better ie the extxaction.
5*1.1 (o) Degree of association of ammonium salt
properties ol' the diluent, the m turc? of the atmnoniiamcation or the anion and their concentrât loss determine whether thesalt ia dissociated, Ion paired, or s t i l l more highly aggregated inthe organic phase» In a hi^i dielectric constant neüiura, such asnitxobensene» an ammoniwa aalt with a large an ion may be conrpletelydiseociated over a wide range of concentration, 'file expression forthis type of behaviour i s given by equation (14)
BJ3 H3 oHorg H20
(14)
An example of such extraction was shown by BUCHKE. end DIAMOND in
the case of perchloric acid extraction with TLA i n nitrobenzene.
147. A.S. KPJiTES and Ï . MARCUS (Eda.) , 'Solvent attraction Sesearch',
Proc. In t . Oonf. ICSSC, Israel , 196&, Wilsy-Interflciane* 1969•
14B. Y. MARCUS and A«S. KBRTBS, 'Ion Exchange and Solvent Extraction
of Efetal Complexes•» ïïiley-Intorociônce 1968.
149. B.M» DIAMOND and D.G. T|U(SC, 'Bxtraotion of Inorganic Compounds
into Orgnnle Solvents' , Progress in Inorganio Ch©nii«try, Vol .11,
(fed^P.A. CO3T0H, Inter Science Publ. 3.Y., ( i 960) .
150. W. ffflldER and H.!J. BIATfOHB, J. Pliya. Chora., 22' 3469 (1966).
~w- ^ . • f e & Ä a * " ^ „ir _
1 1 9
If the diluent haa & low dielectric constant and l i t t l e cheaicalsolvating ability* the ammonium salt may associate to larger aggre-gates beyond the ioa pair, suoh a behaviour being represented byequation (15)
« yote
• » * • » * * • V
value of the slope n in a log-log plot of organic phase acidconeentsatloa (K-NH* X^ ) versus £-B . a ^ enables one to
distinguish between .
i ) the existent» o£ non-dissociated ion pairs (nl i ) ihelr dissociation n < 1
i i i ) their asBooiation n > 1
1)
The degree of aggregation of the amonlum salt 1B usually determinedfrom the slope of the extraction curve, measured by different techniqueslike the two-phase titrotioi» or use of radioactive tracers, l ightscattering studies, vapour-pressure or freeainy-point meaauremente e tc .
5.1.1 (d) Third-phase formation
The splitting of the organic phase during acid or metalextraction whioh is a distinct tt&tase of the organic phase i s calledthird-phase foznation. Addition of a long-chain alcohol prevents tiiathird-phase foroation, but often reduces the extractive capacity ofthe amine extractanta. The literature data on thtrd-phast formationla confined to qualitative statements concerning specific systeas and
conditions for the elimination of the third-phase4
151 J.J. and B*». DIAMOND, J. Phys. Cham., ^2., 15^5 (1965)
1 20
(e) EjcceBB acid extraction
The add concentration in ths aqueous phase at which excessacid begins to extiact into ttie organio solutions of alkyl ammoniumsalta depends on the nature of the acid and on the organic diluent*Perchloric acid and hydroiodic acid axe almost «inextxaetable intoan organic solution off alkyl ammonium sa l t of these acids even atvery high aqueous acid concentrations. Hydrochloric acid and nitricacid as© extracted beyond the amount necesoary to neutralice theamise» An acid to aaine ratio of as hiph a value as three has beenobserved.
5.1.1 (f) Extraction of matais
An aqueous solution oontalnicg hydratad rastal ion representedby H+n and X** a Konobasle liga ne!, will have a aeriss of difforest
to the equation (16)
mX" MX'n-m (16)
usually only one of these complexes reacts with the »oleculea or theextxi&ctant R.SX (one to three of lä» alkyl radicals my be replacedby hydrogen) and forms only one neutral complex which contains onemetal ion. Ä neutral salt Is extracted according to equation (17)
•vw ao,(17)
anl an anionlc oouplex reacts according to equation (18)
1 2 1
Equations (17) anå (18) being equivalent, the overall extractionequilibrium can te described by equation (19)
" ( R 4 H ) . (19)
Th» extmcticn coefficient, Eft i s defined as the ratio of the totalmetal concentration in the two phases
At couetant liganà activity in the aqueoue phase, and under coaditiooswhere both the activity of the SBtal in the aqueous phase and theactivity of the extractant in the organic phase are proportional totfae.lr concentration i t follows that
a (21)
org
Thus» -Ote slope of a log-log plot of E vermis the concentration of
the extxaotant indicates the ratio of the extractant to the metal in
the extracted complex.
5.1.2 attraction of trlvalent «otinides
152The •xp^pierioe gaintd with solid anion exebangers " pointedoat that trivalent aetlnidos were not expeeted to be easily transferredfjcea nitrio or bydxocdlorle *ci« into oxt»nio solutions of slkyla»-moniura s a l t s . Conosntxateâ lithium <Morids or nitrate solutions, which
152. E.K. HULET, ».6. GUTMACHEH and U.S. COOH3, J, Xnorg. Huol.
12» 350 (1961).
1 22
were only slightly aci<*fke» proved to be promising aa aquecue phasesfrom which trivalent aotîniaes and especially the traœplutoniusielements coald be extracted1^3*'5*. As high aa 10 t© 12 molar lithiumchloride solution» contai Ing only veiy dilate acid mm used fox241
to «tract ion. Increasing ecidlty of the aqueous phase decreasedthe extraction. 'Die extraction «as also dependent on the organicdiluent awl the following order was observed» n-hexam > raasitylene >xylene > toluene > benssene > carbon totrachloricte. If chloroform isaaad as the diluent, the aetinides ore almost unex tractable, iho mainadvantage of using this amins extractant i s the achievement of aseparation factor of moss than 100 between the trivalent actinideaand lenthanldae from concentrated chloride medium as the aqueousphase* Furthers i t is useful in the separation of actinides fromeach other»
MOORE ™ assumed the extraction o£ trivalent aetinldes as
species to explain the second order dependence of the extractioncoefficient on the extractant concentration according to equation (22)
ore(22)
Since there i s no direct evidence for the existence of a penta coordi-nated chloro cooplex, th« extmetant to aetal ratio of 2 , in analogyto the extraction of ferric chloride by tertiary ammonium chloridesolution was ascribed by MULLER et al as das to the extinction ofa tetrachloro complex R,NH+MCl7. Shis ion pair was assumed to associate
153. V.t* HQOEE, And. Chem.t ü » T48 (1961 ) •154. Y. IURCUS, IS, CITOB asA CE. CHOTPIH, J. Inore-
Ch«o.f 2£, 1457 (1963).
155. W. :M,LEn?, 0. DXUCKAEKTS «nA J. FÖGBR, Proc. Inte Conf.,
•Solvent Sitraotion Chemistry ©f Metels1, page 235-246»
HaoMiîîan, london (:966).
-to
1 23
ast loa iafc0 îoa ^aâsapoïoo GO
f> T,rn,„=>
A Kjaafesg ©f iuHrootâcatioso GÖK; eassriLod eat on $ho
©£ iEotaïa fey tjeitaasytoniEa oolta « ÖOTÖSQÏ sseuiantess
psopcooi for -Sfeo ojstsaetioBJ caâ tïîo o>E0iehi©!B1SES!r of tfao
. ïho ââffioalty âa oî)toi'fliï?e tSiooo ânÊ'osœatioiiD feta tteo
ef ftlto âlsfeitaittea coofflcioEife f?i12j feSio neâro aalt eoE89E°
rj ^äo os^ia&o gtîîasG orfseB f Ma QÎO foots ttoft fehs smiss oal t
ào aggsogateâ» tSie åogsee of oggse^ptiOES fepesîâiKs ©sa i to e©asoat5Eat£e2ä
tîîs tîaisâso öf oio dSluGOft* In @såos to obtain seco EOXO iaf©SES t ios
t t e vo,li€äty ef tînlo ä i s t s i t a t lon jaetbod fesa '&&O poiat of view
of Setes?rsiHiieäg Sae satas» of tlao estraeteå sgooiooe tîio âiotsiîsatlQESul©f ^ ' &a sas atiaäiea totusoB a^aooao aoiatiom soataisi ïo XiiCl» CsCl-
asâ diluto HCl ana Go!&tå©HQ ef t s i lo i i^ laa ise S^soeMe^iio (3&A.HC1)
in ûtî£&sent i i tooats a t fäisacse icatal eeaeontsaMoiias sisâ anâor retal
ifel©Hao %o eoaesBtsBaftioa soage of %fe© sroi»3 sa l t was
as ïa^ga eo pcaoît&o ia ©sios? to vasy fes €G,P?BQ of ag^ogaticn
5.2
os
Å 25 TO1»5^ solmtios of the assise ia iso-ootane was tacatedef 1*JP HCl» ÄG phases wos© separated a t aî)oat
ÖQO soluble te the organic ghaso. On cooling tbe
soliââfîod acû ira© flîtesed sut. I t TOB purified by recayatal-
iåois© tîîœoo tfeao JKOQ tesiîi ioo-ootaifô and dried by leaving ov«ni#it
1 24
l a o vacuum desiccator. A white crystalline powder ras obtained, ïhe
melting point was found to be 8JJ*C. I&e atoichiomotry of hydrochloric
acid in ÎLA.iîCl «se checked by carrying out potantioastric titzationa
in a» organic medium of a standard solution of 1&A.HC1 in cyclohexane.
The t i t ra t ions WBBS carried out in benzene-aetbanol toedium in a
Bitrogen atraosphexe agalsœt atanferd potassium raethoxide* Standard
potaeDiun mothoxida «as prepared aceordiag to the procedure given in
l i tera tus© 1 5 6 * 1 5 7 .
5.2.2 Diluants
CyeloheKane* diisopropylbensene and toluene ( A . B . Graâo)
wexe used ns such* Dietfeylbenaene of commercial grade was osed after
d i s t i l l a t ion under seduced pressure.
5.3.3 Aqueous phase
A TU LiCl + 3K CaClj, solution was isade by using Chomleal
grade reagoots. Mm volunes of tbis solution «ere mixed with
one wlurae of ^km solution of 10"^ to 5 x 1Ö"5 M/t of 2/lr*An in
Q„12a HCÎ. The final sqnecus phafla «as 41Am in 6.?M LiCl, 2.7M
ana 0.013M HGl.
5.2.4 Organic phase
The emiae sa l t ma direetly welded and diesolved in
diluents . Solutions of lower coneentsation «rere prepared by dilution.158
For pre-equilibration the détai ls given by FUGSB ' nexe found to be
156. J .S . FHÎÎZ and R.Ï. KEEK, Anal. Chem., gâ, 179 (1953).157» A.H. BECKETT and E.ïï. TIIO.BY, 'Nitration In Hon-Aqueeu«
Solvents ' , 3rd edition t Ite British Drug Baaa» Ltd. ,
POOLE, DOESBT, p . J8 (i960).156. J . FÜGSS, »Apport snnutl Ï.Ï*S.B« (t96O) BHÖXEU.ES,
1 25
holpfal. ïhe experience gave the followlï^ informations»
a) \8hen the organic phase me equilibrated with aqueousphase (6.3H LiCl, 2.7a CaClg and 0.012M HCl), the acidkept on getting extracted in the organic phase evenafter three or four pre-equllibratlons with freshaqueous phase*
b) Excess acid was extineted in the organic phase "byequilibrating i t with the aqueous phase except thatthe acidity was 10 tiraes and the volume of aqueousphase waa double that of the organic phase* The extraacid was stripped by equilibrating the organic phasewitfc aqueous phase t i l l no œore change of acidity ofthe aqueous phase was observed* usually after threesuch equilibration» no moss acid was founâ to strip*
c) Å batch was tried by forcing excess sold in the organicphase whan equilibrated with an aqueous phase bavins100 tines acidity as that of the aqueous phase• Thoughafter four or five contacts with the aqueous phase» nosore stripping of acid was observed but the amount ofacid present in the organic phase was more than in thephases pre-equil2brated according to (b). These gaveerratic values of S •
Thus i t i s iopcrtant that only just sufficient excess acidshould be present in ttie pra-equilibmted organic pha«« which will notChangs the aqueous phase acidity. An alternative procedure would beto do experiments without pre-equilibration of the organic phaae andreport the data stating th* acidity At equilibrium f ran a blark experi-ment. Bat by adopting äie latter method more coraplicationa arise. Allorganic phase» nwd in the preoent investigation were pre-equlllbratedaccording to (b). ïhe pre-«quilibrated phases were titrated potent!©-
1 26
metrically in benzene-methanol inadium agaiist potaesiuiiMcothosiâe toget an idea aa to hew tnich fgee acid was present in excess to thatcombined in the form of ÏI.Â.HC1* 'She froe acid aas indicated by aseparate sîaxiraa in the Initial stages of the potentiometric titrationcurves. 'Ine following results vexe obtained.
i ) Practically no free acid was extracted below 0.01Uconcentration of Î1A.HC1 in the organic phase*
i i ) Above O.Ota amine salt concentration, pre-equilibxatedphases hod about 1G/ó f roe acid as compared to the
HC1 in TU.51C1.
«périmants were perfonaed at 35*C when TLA.HCl vascompletely oolable in the organic phase and thus experiments could bedon» at higher amine salt concentrations*
.2.5 Equilibration
voïut!ö3 of aqueous end prfi-equilibrated organicphases were équilibratsd in Pyrex glass tubes in a mechanical shakerfor 30 minutes at 35 ± 1*C in s thsrmoatatic bath. ïhe solutions werecentrifugea and both phases pipetted for assaying the activity*
5.2.6 Counting
241,Condition were standardised to count ^ Am in both phasesby alpha liquid scintil lation counting. I t was found essential toadd a s m i l amount of tri-n-oety! phosphine oxide (ïQPO), fine s i l i cagel, and about 100 > of dilute acid to the aqueous phase and shakethe eaaple vigorously for one to two minutes for reaching the finalraaxitszffi counting rate. All saraplea vere counted in a liquid sc int i l -lation counter unde» identical conditions, 'ihore was a good materialbalance of the activity taken and distributed in the too phases. ïhe
127
details of the liquid scintillation counter are given hy
5*3 geflulta and Discussion
She résulte of the determination of aggregation of ÏLA.HC1to higher ion associations than ion pairs in eyclohexane by equili-brating tbs amins salt solution with distil led water at 35°C anäaeaeuring the HC1 concentration In both the phases by titxation axeshown in Figure 29. A slops of leas than 1 neans dissociation of theion pair and a slops of greater than 1 indicates aggregation whilea constant value over a rang© of concentrations indicates a singlespacioa. The slops of 2.3 for the linear part of the curve shews that
ion associates existed. The recuite are in agreercent with those of150
M3LLIB and DlAWW ' who found an average association number of2.65 in 0.1M TLA.0C1 et 25°C. The negative slopes in the issper partof the curve are probably due to the notification of the solves-*i . o . the increase in the dielectric constant of the solution due tohigh TLA.HCi concentrations and thus give no indication of the degreeof aggregation*
241The results of the extraction behaviour of Ata at tracerconcentration are given in Sables X to XXV. The öata are shown in
341
Figure 30 «here A log-log plot of the distribution ratio of ^ Anversus concentration of amine salt is plotted. Hie and.!» salt incyclohexane gives a s t r å l a t line having a slope of about two through-out the acange of aolne salt concentration investigated. A similarextraction behaviour is observed in diieopropylbenaen» art dl«thyl-benzena. Cyclohöiiano containing 2$ and jf' tridecanol gave very poorextraction ana the slope ia no mots two.
I59. PHILIPPE BREZB, These annexe (1966) Univ»rsit« da Liege»
Liege, Belgium.
123
1 23
S.Ho.
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
Extraction of
ConcentrationÎLA.HC1 In
C6K12 (U^
0.0025
O.OO5O
0.010
0.015
0.020
O.O3O
O.O4O
0.060
0.080
0.10
0.15
0.20
0.25
O.5O
0.35
O.4O
TABLE X
2 4 An bv TLA
Of«
0.00022
0.00098
O.OO4O
0.0084
0.015
O.O32
O.O43
O.IO4
0.202
0.299
0.69?
1.220
2.025
2.961
4.OI3
5.131
.liCl in Qvolohexane
at 35'C
• O.OOOO3
• 0.00093
+ O.OOO5
• O.OOO9
+ 0.001
+ 0.001
+ 0.005
• 0.008
+ O.OI5
+ O.OO7
± O.OO3
+ 0.020
+ 0.012
• O.O4O
+ 0.002
+ 0.06
lïUsibcjj Oxdéterminations
6
8
7
6
4
2
5
5
4
3
2
2
2
2
2
2
1 3ü
Ö.Ho.
SABLE XI
241Extraction of ~H Ant by gLA.HCl in
Concentration ofTLÀ.HG1 inDIB
o Kuiaber ofD s t 35°C de terminatiens
1
2
3
4
5
0.005
0.010
0.020
0.030
0.050
0.000094
0.00070
0.0045
0.0110
0.0392
4
3
4
2
2
TABLE XII
241Extraction of ^ Am by !CLA.HC1 i n Piethylbonzene
S.
Concentration efÏLA.UC1 InB3B (tt/h) at Kunber of
determinations
1
2
3456
78
• 0.01
0.02
0,03
O.O5
0.10
0.125
0.15
0.20
0.0006
0.0026
O.OO70
0.019
0.0730.111
0.174
O.32I
335
6
2
3
4
2
1 3 ;
ïABLSJÇin241Extraction of H Arc by SLA.HC1 in Cyeï.oh<jgeai3i? containing 2& triflecano?.
S.No.
Concentration ofÏLA.HC1 in
B at 35°Cdumber of
doterminations
1
2
3
0.05
0.10
0.20
0.006
O.O52
O.45O
duplicate
-ÖO-
-do-
E x a c t i o n of * Am by TLA.mil
S.Mo.
1
2
3
Concentration of
TU.HC1 în
0.05
0.10
0.20
in Cyclobexane
D*at 55*Ga
0.0006
0.0065
0.080
contai ni ne 5v' tridenanol
£%0Bb63? C f
de terminatione
duplicate
-do-
-do-
. gaCh-Sg-fc- j7,.
r
•o
o"1
F.f
ió2
,o"3
«ö4
X
CYCLOHEXANEDIISOPROPYLBENZENEDIETHYLBENZENE2%TRIDECANOL - C 6 H | 2
5%TRIDECANOL- C 6 H | 2
. i n • • i i 11
r-l
i i i 11
,0-2 10
CONCENTRATION OF TLAHCKM/L) FIG.-30
10
1 33
! !
* cc
e t «ai observed a slope of two foc the sen» distri-bution curve in the extraction of trivalent sctinlde3 W1^» Cm*', Bk*"*,Cf J and EB y at tracer concentrations from an aqueous phase havingsimilar composition ae in the present Investigation and by solutionsof llA.IfCl in toluene» In the oase of Pe** the slope varied betweenone and two depending on the acidity of the aqueous phase and alsowith macro concentrations of Fe , the existence of two complexes ofthe type 1 i 1 and 1 » 2 «as shown. These resulta along with speetro-photon» trie and Koman spectrosoopy observations led these authors tothe conclusion that although there was some aggregation of 2LA.HC1 inthe ocganio phase, the distribution method is s t i l l valid for deter-mining the etoichicmetry of the extracted ooapler from the experin»atalslop» and they proposed» for the trivalont actinides extraction, theion quadruple
The constant slope of tno in the present investigation of the distr i -bution curve in the entire concentration range of TLA.HU1 in eyelo-hexane for the extraction of am gives support to the ab»7« workof 'rîULLER et .el • Hers TLÂ.HG1 aggregation was nuch more than intoluene anà the distribution curve remained 1 inter in the whole concen-tration range whose the dagree of aggregation was also varying*
ïhis nay also be «xplaimd by assuolBg that the chloro-aetallato anions react with large aggregates which dissociât» as 1 t 1el«otioljrteB «ms famishing: each only om chlorid» icn to thecoordination sphere of the metal ion . Thio can be represented by
160e Y. flAHCOS, J. Inorg. Muol., ChMW, 2§, 309 (1966)*
;
1 34
equation (33)
• 2Ci"
(23)
explanation accounts for the experimental results but shouldconfirmed by independent; experiaanta.
It Ü3BÏÏ& actually difficult on the basis of the abovepicture, to explain the influence of the addition of tridacanol totho diluent on the alope of the distribution curve. If i t i s certainthat tridecanol diminishes the degree of aggregation, i t i s difficultto explain why the stoiohiometxy seems to increase*
the résulte of the extraction of * Aia by 33.A.HC1 i?> amixture of diluents i s given in Table XV. Proa therEiodynamicai andpractical peints of view» Figure 31 Bhowa thaï bînazy mixtures oftolaene atd diisopropylbenssene containing O.O M TLA.HCl behaveideally in so far as the distribution of omerieiMm is concerned.
241The xesults of the extraction done at different Aaooncentiation (10*' to 10"T«) at constant TLA.iiCl concentation
(0.01a) In cyclohexane at 25°C aïe given in Table XVI. A plot of thenit*
concentration of Asa in •&© aqueous phaae veisjja concentration of2 * Aa in Oh» organio phase divided bj ainina salt oonoentisation i sshown in Figure 32. Xt appears that there is a leading effect whenthe conesntsation of A« i c the aqueous phase approaches the concen-tration of araine salt bat i t was not possible to get a 1 t 1 ccaplwcas tb* amoant of ^ A » required was too large for the experimentalconditions.
t
g
3
4
5
6
S M «101 âia Q ta&gfoago
©f §fy M
1 35
9o o-ö 55°@
©.018
0.014
0.012
hà
Ii
1
2
3
4
5
6
7
6
9
137
JABLS XVI
of fry O.O1M TU.BC1 InCyoloheranp a t 25"C
Concentration of
Ara in aqueousphase (M/
.-80.0 x 10
9.4 x 10"?
8.4 x 1Ö"6
8.8 x 10'5
9.3 x 10~4
2.8 x 10**3
4.3 r 10~3
7.4 x 10"3
9.4 x 10"3
Ratio of theconcentza t i on of241Am and ÏLA.HC1
i n the organic phase
f241*»7 /o
9.4 x W
8.8 x 10,-7
.-69.4 x 10
9.9 x 10~5
8.6 x 10"4
1.6 x 10~3
3.7 x 10"3
3.3 x 10"5
4.4 x 10,-3
»C» - ° » 0 1 M
1 39
0.413
Ån accurate knowledge of the fission yields and in general themaaa distribution i s of graat importance from the point of view ofunderstanding the fission prccecs i t se l f aad fission studies of *°Puare of significant interest aie t© i t s very important role in nuclearpower produetion.
227Fission yields in the neutron-Induced fission of 'Ac «eredeterciinad and reported for the f irst tiras. "Phis investigation irascarried out to cheek the hypothesis made by JESSES and FAIBKAUJ
that a sharp transition from symétrie node of fisaion to asymmetricmode takes place as on» passes from the fissioning nucleus aotiniuato thorium. I t was found that there is only a saall third peak in thesymmetric region and i t i s less than 1$ of the total yields clearlyshowing that these i s no strong dépende noe of the shape of the nass-yioid carve on the charge of tbo f l s s l o p ^ nucleus.
227In view of tiie results obtained in the fission of Ac i t nas
considered worthwhile to study the neutron lnôueeâ fission of s t i l llighter elements* Radiura-223 wee ana such isotope «rhich could be milked
227form Ac and an uppe? lirait of fiasion cross-section of about 100bazoe was reported for thie isotope. Though the studies were initiated
with th» idea of determining the mass-yield curve p i t was found that
tiie f ission cross-section is too low to enable any detailed study and
an upper l i a i t of TOO mill! ten» was obtained ftor the fission eros»-
seetion*
The present investigation on the détermination of fission yields
in the thermal neutron-induced fission of 39Pa indicates that Se(li)
âa'eectoi' i s useful for the détermination of fission yl*lâs anâ foras
a complet»ntary asihod to zctdiochsnlml method.
1 40*
f© aumoBrietf, the following general comments my be cade anilethe fission yields of ttte present «ork with the literature
values t
(a) The Mo yiald of the present work which ia 6.79 is thehighaet of a2.1, the next loses value being 6.59 determinedusing Ge(Li) detector toy Idaho Croup and 6.44 the inter-polated vulaa of the mass speotroicetrlc data of F1CEEL
111and TGiiLIKSliN . ' 19 lowest ia the radlocheoical value
108of fJlAKSBSN and XÄIfE which is 5.61.
(b) Fission yields of 5Eu and 5 I from the present investi-gation are 25-35/^ àlgher titan the rasSB spectreaetricvalues.
(c) The laaas-yield curve of the present woife covers as axeaof «bout 206^ «hlle that of iBAKÖDKM and ÏMTE1 ° has beenreported to cover 19 /1 and thas making a difference ofabout 16 ia a total of 200.
(d) difference between the present values and radioohemioal1OB1OB
values of raiiSDSIi and YAFS'S seem to be in both the peakregions «hile the nain difference between the present valuesand the aass speotroaetric values seems to be only in thel i g i t peak region.
(e) 'fee present values seem to be close to the mass speetzoaetricvalues of FICKJ3. and «KLOT0Î5111
aaä Idaho Group11
are in gei»ral agreeirent 'aetween ttiemaalves.
( f ) Oat of the methods which are being compared, the BBSS speotro-2K)tric nethod and the radiocheoical method involving the us»of f oar-pi counting and determination of f ission yield» by
1 4 1
'absolute oethod' ore better ttian tho 'eorapariBon sethod'used in the present investigation as the 'comparison method 'Involves the uae of fission yields of "fl ana the assum-ption that the ehsrgs distribution ana gonstie relation-ships in the *•*& anS ™Pa fission ara tîie sane.
(g) Inapite of the differences in the methods mentioned above»tile agxeemnt between the psaseiat data and the raass speetro-jEetrio data aeeras to bo closer compared to the agxeeraeatbetween nass spectroaotric data and four-pi counting data*
Solvent extraction studies of Ara using high-moleculo:ardre in différant diluents wexe carried out to obtain aoree raoreinformation about the validity of the distribution raathod from thepoint of view of determining the nature of the extracted species
241studies i9Bse carried oat at tracer M concentrations and under metalloading conditions. A log-log çlot of aie distribution coefficient of* Ara versus con'oentratlon of tbe aralne salt gave a constant slope of
two in ISiQ entire concentration range of trilaasylamiEe hydrochloridein eyclohexane, although the amim aalt was feunsl to be aggregated inthe organic phase. Studies under natal leading conditions showed thattheze was s loading effect when the eoneentxetion of 4 Am in aqueousphase approaches the concentration of amine salt but i t was not possible
to get a 1 t 1 complex: es Hie amount oftoe the experimental conditions.
241km required «as too large
RECTO; EB w s a 0*413
work described in the lâissle has been planned by ae aafi•Ifte leaults ax© solely dm» to rae. In ca-sying out the experimentalwoxfc, help has been trtaa at different stL-e» of 3>r. C«L. Sao,Ur. K. Iten^n and Br. Sa^a F^ahaah. Parts of this wrak we» included
"MW
1 42
paWLâsîîod i s t t o EosrôioE3û
FISSION ® âCïîHHUS3-g279 PSOTACîïiîimi-231
Ai© vusmmwB^j $ mss
aaâ Cteniotsgr of
? | Q Œ S 9 i , 439 (1965) «
2 » FISSION fi? ay®ïilîJ-g25 BY BEâCÎCB HEDTBQHS
<îo ÏBösgo Kuol. etea.g, 2^9 26? (19S7) .
FIüSIOH YIELBS Aή HEGOIL MHGSS JJSTBHMIEIEB BI A fc
Vienna» 741
EJtTïUCÏIOö OF A&ÎBRÏGKJ?a-341 FSOïï SOSCSÏÏÎEâflS
CHLGIffiJE SCâ-USIOI® BY maAÜBTflA IK
â» 553
MÏEGÏOB
to iEOΫd® tfco worft OH s©ïvent
ubicb oao easeisâ ea% a t ïïniire^sit^ ©f liago (Belgium)
t a s obtsinoâ fsom fâis ütóvessiV ® Bontey viflo l e t t e r ïto.'Ih/ê14O
April 23o 1971.
As fe work oa aetisjit2J&-227 fissîoa raas tarr ied ©at daring Hie
pesloå fsom t t e flats© of ps«wisi©seii e l i g ib i l i t y cer t i f icate and Sisal
data of 2ogl0-&sat£@m9 perKisslOK to isasîuâe this yctóc raa,s tshen ftots
of Bcîstej vide l e t t e r K O . Ä / S I J S åateå April 23» 1971»
(lï.V. (H.C. J a i n )Studeat
ë.,.,.9-.
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