JAERI 1287 JNDC Nuclear Data Library of Fission Products Fir

JAERI 1287 2. Nuclear Data Library of Fission Products
high energies are too dense and complicated for existing gamma-ray detectors to detect and
resolve all transitions from them. The oversimplification of the high energy part leads to an
underestimation or a missing of the beta strength at high energy, and leads to an overestimation
of Ep and an underestimation of £r 40) . As is shown by solid line with (A) in Figs. 2.3.3
and 2.3.4, a full adoption of experiment-based values of Ep and Er results in an overestimation
of the beta-ray component of decay power and an underestimation of the gamma-ray component.
This defect of the preliminary version of JNDC FP DECAY DATA FILE (1980) was
revised by replacing the experimental values of Ep and Er by the theoretical values calculated
with the gross theory for all short-lived FPs with Q-values larger than 5 MeV. 96 Y has been
excluded from the group because this nuclide has a large contribution to the decay power
and needs a special consideration. The accuracy of the decay power calculation has been
greatly improved not only for 235 U as is seen in Figs. 2.3.3 and 2.3.4 (solid line with(B)) but
also for 239 Pu and 241 Pu. The final version of JNDC FP Nuclear Data Library adopted the
theoretical values of Ep and ET for all FPs whose beta decay Q-values are larger than 5 MeV
though experimental branching ratios are available for 87 nuclides of them. This is because the
theoretical values of Ep and Er for high Q-value FPs are more reliable than the experimental
sion
r/fis
(Me\
0-1
X
f(t)
power
decay
pa
1.0
0.9
0.8
0.7
0.6
0.5
0.4
0.3
0.2
10 u
\^ I I I I I I I I I I I I I I I I I I I I I
• ORNL (1980)
• SRRC(1970)
i i i i i i i i i i i i i i i i i
10 1 10 2
Cooling time , t (s)
Fig. 2.3.4 Effect of using theoretical values of Ep on the calculated results of 23S U beta
decay power. See the caption of Fig. 2.3.3 for the further details. The experimental
data are taken from the papers by ORNL (Ref. 3), and by SRRC
(Scotisch Research Reactor Center; MacMahon T.P., Wellum R., and Wilson
H.W. : J. Nucl. Energy 24 (1970) 493).
10 3