. NZXXP-A-287-bis .
! OECD NUCLEAR ENZRGY AGENCY
NEACRI? members' reports on national activities on fission product decay data
flhe attached report has.,now been received from Japan7
_- ..
December '15.76 9614000.: Planned Works on Fission Product Decay Data in Japan
Japanese Nuclear Data Committee
R. Nakosimcr, T. ,Yoshida, and t?. Tasaka
ABSTRACT
The measurements of fission product decay data are planned mainly at Research
Reactor Institute of Kyoto University, Japan Atomic Energy Research institute, and
University of Tokyo. Decay properties of some specific fission product nuclides have been studied radio-chemically at Kyoto University. Radio-chemical studies of fission product nuclides have also been done at Japan Atomic Energy Research Institute.
The evaluation works on fission product decay data by Decay Heat Nuclear
Data Evaluation Working Group of Japanese Nuclear Data Committee cure in progress.
The works of this working group consist of compilation of new experimental data, esti- mation by theoretical point of view, and summation calculation of decay heat. Theo-
retical investigation is also in progress at Tohoku University.
~1. Plan of Experiments on Fission Product Decay Data
1..1 Kyoto University (communicated by K. Okono)
Main subject on the fission products is the measurements of the half-lives and
the gamma-rays of short I ived nucl’ides. Radio-chemistry group has applied e!ectro-
phonetic separation method to the short lived fission product nuclides. The procedure
.and the results moy be seen in Nuclear Science and Technology.
Preliminary test experiments by on-line isotope separator ore now going on.
lonizction of fission product from 252Cf source ( - 15O/~lc .i) has been done by helium- iet
method. Main studies using this separator are those on delayed-neutron precursors crnd
on nuclear spectroscopy of fission product nuclides. The extensive studies are expected
to start from early 1978.
1.2 Japan Atomic Energy Research Institute (T. Tomuro and Z. Matumoto) 235 Plan of decay heat mecsurement for thermal neutron fission of U is reported
by Tamuro and Motumoto (see Appendix), Expected accuracy is 10% for the cooling
time from 20 set to 1000 set and 5% for the longer cooling time, ,
. .
1.3 University of Tokyo (M. Akiyama, Y. Qkaand 5. An ; sponcered by PNC)
The program aims to measure the Y-ray and P-ray decpy heats from fast fission
products of U-235, U-238 and Pu-235’. The decay heat data are obtained from the time-
dependent Y-ray and p-ray spectra from the .irradiated samples. The r-ray and/J -ray
spectra are unfolded from the pulse-height di;tributions. The pulse-height distributions
are measured at selected times from 5 set to 2 days after fission. The 3”+ x 3” or
Y’$‘xS’ N a I scintillator and 77cc Ge(Li) detector are used for )‘-ray.measurement and
the thin plastic scintillator for p-ray. The samples are formed by electiodepositing the
fissile material onto nickel foil. U-235 and Pu-239 samples are 30pg/cm2 thick and
13mm diameter and U-235 sample is 100)lg/cm2 thick and 13mm diameter. The samples
are irradiated in a pneumatic rabbit facility of the fast source reactor “YAYOI” of the 0 University of Tokyo. The fast neutron flux in this facility is about 3 x 10” n/(cm*..sec) at the maximum power. Expected uncertainties for the experiments are of 5%.
The preliminary experiments were performed in February, 1976 in order to
examine the measuring systems and the irradiation conditions. Measurements of the time
dependent r-ray and P-ray spectra of fission products are planned early in 1977.
2. Evaluation Works of Fission Product Decay Data
2.1 Revision of Decay Data Library
In order to revise the old decay data library made by Tosaka, the compilation
of new experimental data and the theoretical estimation of non-existing data are now
underway. The first revised version of the decay data will be completed in mid 1977.
A computer code has been developed for compiling the experimental decay data
and level scheme information deduced from reaction data. It is possible to take out the
,infoimation on half-lives, betas or gammas easily from this nuclear structure data file.
These data can be used not only for summation calculation but for checking the theoretical
estimation.
2.2 Theoretical Estimation of Decay Data of Fission Products
Gross theory of/S-decay was applied to estimate the half-lives and the average
P-ray energies emitted from short-lived (tvi;/ic a few minutes) fission products (communi-
cated by T. Yoshida). Reliability of the method was examined by using the co,mpiIed
data of Tobias. Simple fitting formulas were constructed to reproduce easily the calcu-
lated results as functions of Q-value (in MeV) and mass number A. For example,
(~~~)/Q~(0.471-0.0024GA)logQ-0.163+0.00417A+(0.2~-0.0015.4)/1ogQ for
odd -A nucl ides. Confidence bands for the calculated $ and gr were alsO estimated.
-2- .’
When half-life data are available, confidence of the calculated/! - and Y-ray
energies can be improved with the aid of them.
Improvement of reliability of the calculated energies for odd-odd nucl ides
requires further study including consideration of nuclear shell effect and systematic ! determination of ground state spin-parity.
The effects of neutron capture transformations for the decoy ‘heat are studied
by K. Tasaka by using the evaluated neutron capture cross sections of JNDC.
Theoretical studies of decay heat are also in progress at Tohoku University
(communicated by T. Yamamoto). These works include the fo!Iowing items.
1) Estimation of P -and r-ray energies on the basis of systematics of 9 , mox/Q. 240 2) Estimation of fission yield of Pu and 242 Pu by use of the statistical theory of
nuclear fission.
0’ 3) Study of dependence of the released energies on incident neutron energy and fissile
nucl ide .
4) Sensitivity study and evaluation of nuclear data uncertainties.
5) Summation calculations and comparisons with measurements.
-3- . .
Appendix A plan of Afterheat Measurement for thermal Neutron Fission of 235U at JAERI
Japan Atomic Energy Research institute
Tsutomu Tamuro and 2. M&moto
1. Abstract
An experimental program to measure beta and gamma ray energy release rates of 235 U fuel material is being planned. The objective of the study is to attain an 3 overall occurclcy of 10% for the cooling time from 2Osec to 10 set and 5% for the longer
cooling time. As an approach, we are devoting most of available time in the optimi-
zatidn of the experimental system and of dota processing. Preliminary measurement of
0 Gamma decoy heat using Ge(Li) spectrometers has been started. Beta heat experiment
will be considered in the next step.
2. Experimental procedures in gamma heating study
The following arrangements are being prepared :
1) Samples
Coated particle fuel of grain size of 6OO/*m has been used without loss of gaseous
fission products. The U fuel moteriol is enriched to 20% in mass number 235. Various
U targets will be used according to the purposes of measurements.
2) Irradiation and transport of samples
‘Pneumatic facilities at JRR-2, -3 and -4 are available for the irradiation of U samples
0 for 10 secb50 min. The shortest time for the transport of sample to the measuring
position is about 20 set with the JRR-4 pneumatic system. Also a 100 MeV electron
LINAC is being used for the preparation of calibration sources and for the various
test runs of measurements.
3) Gamma ray detectors :
NaI(T1) 1259x 125
5O~x’50
50+x 3
Ge (Li) 10% efficiency relative to 75$‘NaI(Tl)
2.2 keV FCVHM at 1.3 MeV
Ge (pure) 1 cqO.5 keV FYv’HM at 100 keV
-A- In our decay heat measurement, NaI(T1) and Ge(Li) or pure Ge detectors have been
prepared. These two systems hove their own merits and demerits. A large NaI(TI)
scintillation spectrometer exhibits large full energy peak efficiency c?nd its dependence
on gamma ray energy is fairly moderate. Due to lower resolution of this system, however,
we have to onolyze the pulse height distribution data by re!sponse matrix method. For a
complex spectrum,the iterative subtractions of high energy Compton tails in the response
matrix method introduce distortion in the reduced gamma ray spectrum. On the contrary,
Ge(Li) spectrometers have excelent energy resolution and gain stability’ thus enobl ing
precise’determinotion of energies and intensities of fairly complex spectra. For a very
complex spectrum, however, even the best Ge(Li) detector can hardly resolve each
gamma ray peok and we will have to process the data with a similar method like response
matrix method. Ge detectors with different efficiencies and absorber combinations ccln
0 be used for the quantitative interpretation of complex spectra.
3. Preliminary measurements
To date, Ge(Li) spectrometer with a resolution of 2.2keV FWHM has been used
successfully for measurement of gamma ray spectra at cooling times longer than 30 min.
The present problems lies in the precise efficiency calibration of the Ge(Li) detector for
wide energy range.
4. Comparison with evaluation
From pulse height distributions, we con deduce real gamma roy spectra. The
reduced spectra will be compared with the corresponding spectra synthesized From the
decay data file which is being used in the summation calculation by Tasoka. Scuh an
examination ‘would be useful for the assessments of uncertainties in the experiments as
well CIS in the summation calculations.
5. Preparation of beta heat measurement
There exist several problems in the measurement of beta-ray spectrum using o
scintillation spectrometer. Optimization OF the following items are important : .I) Sample preporation
2) Contribution of gcrmmo ray
3) Distortion of the pulse height spectra
4) Efficiency and energy calibration of the detector .-.. 5) Stabil ization
_. To reduce gamma background, a Sating plastic scintillation detector will be
used in conjunction with an energy counter. Reentrant type plastic counter will be
examined to reduce the back-scattered electrons.
! 6. Schedule and future problems
Expected forget dates of the present study are the following:
Cooling time Measurement Analysis
.Gamma heating > 30 min Dec. ‘76 June ‘77
>. 20 set Mar. ‘77 Sept. ‘77
Beta heating > 30 min Mar. ‘77 Dec. ‘77
7 20 set Sept. ‘77 Mar. ‘78
In future, we will expand our project to the precise determinatians of short
0’ lived fission product nucl ides by on-line chemical separation and / or on-line’ mass
separation.
,..~ -6- . .- NEACRP-A-287
OECD NUCLEAR ENERGY AGENCY
NEACRP members' reports on national activities on fission product decay data
BlY t wo reports hav? been received to date (23rd November 1976lf * AR ATOMENERCI SWEDEN
.--Decay- --heat
Three sets of experimentc arc under way in Studovik all aiming at improving the accuracy of avail.ablo dr~u on fission product (FP) decey heat.
At the Studsvik van de Graaff machine a radiometric method is used to study the decay of FP from small irradiated uranium and plutonium specimens. Measurements are in progress to determine the residual. gsmmarediation from thermal fission of U-235 over the time fnte~al I.0 see to 35 min after fission.
The ssmplcoare irradiated in e special facility and trans- . . ported to the gammaspectrometer by means of a pngrmstic system,
The absolute number of fissions in the sample is dctertnincd by three iudepandent methods: e) by utilizing an absolute calibrated fission chamber with ~ln active vol.umc of the s&x size .a9 the samples, 5) by countiog the gs~mw,rays emitted from fission products with well. known yields 2nd decay pro- ' @arti&, c) by comparisca?.of thegamma rr.y yield cf uranium samples irradiated by the at&eSeratoranX'%~ thee 122reactor. The neutron spectrum in the chosen reactor position is ~rel.1 .thermali.zed and can be determined with high accuracy.
For decay heat determiwtion the gsmmaradiation from the fission pro&x% is measured with a well-shielded and collimated Nal(T1) scintillator of diameter and length 12.5 cm. A 4096 channel anrlyzer is used for recording the spectra. SampLetransportation, irradiation and counting times are handled by a PDP-15 computer which is also used for recording the gammaray spectra. Spectra ate auto- matically stored on magnetic tape for off-line data analysis, i.e. the transformntion from complex pulse height spectra to energy spactra, I i 1 ‘)Q , AKTIEBOLAGETATOMENEHGI
.
The accuracy of the determination of the total gamma.energy is expected to be about 10 X in the time intervsl a few seconds. to 30 ninutea after fission, Plana sxc under way al.90 to include b&ta decay energy measuremux.
The calorimetric measurements briefly mentioned in the pro- gress report for the last meeting have been~further delsyed by the activity at the FRITZ facility. All effort hithextn has been soncentrated on ihe construction of a. c~lorimetcr with a short time constant and actual~ meaevremcnts em not expected to start until the end of 1976.
The third set of experimwt related to decay hezt ie part of a fargi'pkogrsm fox studying the decay propertie of fission productso Jrradiated U-235 samples P,TTBused in tht: ion source of a mass ~pectroaster ellowing individual fiss
I' Fccperimcntal (I) Beta-decay power from fast fission H F Murphy and W.H Taylor (AEE Winfrith) have measured the gross beta-decay power from the products of Pu239 and U235 fission in a fast reactor (ZESRA). The irradiation period was 103sece, and detection continued for 3 x 107sece (347 days) after shut-down. The measurements are now complete and analyaia is nearly finished. Method: Thin deposits of Pu239 and U233 were irradiated with catcher foils at the centre of the Zebra core with the neutron energy spectrum close to that of fast power reactor. Fissions were monitored by absolute (alpha-calibrated) counters. The catcher foils were transferred rapidly to a scintillation detector, the current output from the photo-multiplier being a measure of beta power. Calibration wae with a standard Sr-90-Y-90 source. Various subsidiary experiments were made to obtain corrections and check for systematic errorfs.
Accuracy: Randomerrors range from + I$ at a cooling time of 20tecs through + 2% at IO5 sets, and + 3% at 20 sece, to + lC% at 107secs. The systematic error is + 3.4%.
' (ii) Determination of K and L internal conversion coefficients of 133m Xe These measurements are being carried out by P Christmas and P Cross at the National Physical Laboratory, Teddington, using an isotope separator and airabeta-ray epectrometer. Target accuracy is + I%, and the measurements should be completed in 1977. 2 Evaluation and Compilation Working group: V Barnes BNFL Windscale B S J Davies CEGBBerkeley WFJames AEE Winfrith A L Nichols AEREHarwell A Tobias CEGBBerkeley D Q 'fellis Aldermaston (i) Fission Product decay data - a comprehensive, continually updated data file of radionuclidio half-lives , ,!I and $ energies and intensities. An initial data base of two separate (pre-19741 libraries are being used, and are to be merged into one data file. They are the decay data of A Tobias (CECBRD/B/M2669) and the comprehensive 1 -library of Q Erdtmann and W Soyka (~Jiilich IOCj-AC). The recent literature and NDSare also being surveyed. The French bibliography (J.Blachot) will be used to aid FP data input.
-I- Comparisons of those data with other data files especially the US EEDF/BIV library will be made. The literature is also , continually being assessed, and it is hoped that updating vi11 occur annually from the completion date onwards. The data file will be in ENDF/BIV format. Although the first priority is FF' data, the data file Vi11 also include decay data of non FP nnclides. .
Expected completion data is late 1976, including the first round of literature evaluations.
(ii) Decay scheme calculations - to compare experimental data with decay data calculated from a more basic data set (eg spin, parity etc.) The major sources of information will be the ORNLdata file containing the various parameters of decay levels. International conversion coefficient data of Trusov, and Hager and Seltzer will be used. The program also uses the calculated (&%o) of Widmanet al, and the calculated EC/ ' of Zweifel. The i&ention is also to use data from the latest &ederer and Hollander Table of Isotopes. This work is being carried out in collaboration with the Department of Nuclear Technology, Imperial College, London. CASCADE,a computer program written by D G Vallis* is being used to compute the decay data of a parent nuclida to its daughter(s). It is hoped that a direct comparison between the computed results and experimental data will highlight discrepancies, and also reveal compilation errors in decay data files.~ The program will be applied to FP nuclides initially.
l The CASCADEprogram, D 0 Vallie AWREReport No. 0X5/74
,