JAERI 1287 JNDC Nuclear Data Library of Fission Products Fir

4 JNDC Nuclear Data Library of Fission Products JAERI 1287
E, = sensible decay energy of nuclide i.
Therefore, the following nuclear data are necessary on each fission-product nuclide to calculate
the decay power of fission products by the summation method:
(1) Fission yields (yt)
(2) Decay schemes (/;-,)
(3) Half-lives (T,,2=(ln 2)11)
(4) Decay energies (E,)
(5) Neutron reaction cross sections (ai,gk-i)
(6) Fission energies.
The sensible fission energy per unit fission in item (6) is necessary on each fissionable
nuclide to calculate the fission rate from the operating power of a nuclear reactor. Different
weights Ei become necessary in Eq. (2.1.2) to calculate the different characteristics of fission
products. For example, the beta- and gamma-decay energies of each nuclide are necessary as
the weight in Eq. (2.1.2) to calculate the beta and gamma decay powers of fission products,
respectively. Beta- and gamma-ray spectral data of each nuclide are used to calculate the
beta- and gamma-ray spectra of fission products. The Q-value of each nuclide for beta decay
or electron capture decay becomes necessary to calculate the total decay power of fission
products including the antineutrino energy. Q-value is also indispensable in estimating the
unknown decay data as will be shown in Sec. 2.3.
2.2 Decay Data
The first task of our working group was to compile the decay data. When the compilation
work was started out, the 7th edition of Table of Isotopes (TOI) and Evaluated Nuclear
Structure Data File (ENSDF) had not been available yet. Therefore, we devoted ourselves to
collect the experimental information from various publications, and to put the data into our
own file named as NDFILE 27 \ This work was continued until TOI and ENSDF became
available.
Most of the adopted experimental data on the decay have been taken mainly from
Evaluated Nuclear Structure Data File (ENSDF), Nuclear Data Sheets and the 7th edition of
Table of Isotopes. Some of them not yet compiled in these issues were taken from the journals
published up to early 1980. The accumulated experimental decay data have been processed
by using a computer code PROFP 28) . Furthermore the present library contains the nuclides
with no information on the decay data or lack of some items of decay data; most of them
are short-lived nuclides or short-lived isomers which have been investigated mainly with the
on-line mass separators. For these nuclides some of items such as the mean beta- and gammaray
energies, the half-lives and so on have been estimated theoretically (see section 2.3).
The experimental data on the emission probability of delayed neutron have been adopted
for 71 precursors compiled by Rudstam in 1977 29 ^. For 23 precursors of them which were
identified experimentally but whose emission probabilities were not determined, their neutron
emission probabilities have been estimated with the help of the systematics. Many new experimental
results for many precursors have been reported since 1977, and these were reviewed
by Rudstam in 1979 30) . However, the hard time-schedule of the compilation prevented the
present library from containing the revised delayed-neutron data reviewed by Rudstam 30 ).
A preliminary calculation based on the revised delayed neutron data shows that the cumulative
yields for some nuclides are affected a little bit, but that the result of the summation calculation
is almost unchanged because of their small fission yields. The delayed neutron data will
be revised in the 2nd version of the JNDC FP Nuclear Data Library.