JAERI 1287 JNDC Nuclear Data Library of Fission Products Fir

JAERI 1287 4. Calculation of Decay Power of Fission Products 153
powers.
(3) The parameter a] for the total of beta and gamma decay powers are given as the
sum of off and off.
(4) The weights of (l//«) are used in the least-squares method where fn is the calculated
burst-fission decay power of the «-th data point.
The fitting errors are shown in Tables 4.2.3 through 4.2.11 and Figs. 4.2.1 through
4.2.27. The fitting errors for the burst fission are given in Table 4.2.3 for beta+gamma decay
power, in Table 4.2.4 for beta decay power and in Table 4.2.5 for gamma decay power.
The results for a year's irradiation are given in Tables 4.2.6 through 4.2.8 and those for the
infinite irradiation are given in Tables 4.2.9 through 4.2.11. The fitting errors for the burst
fission of 235 U by thermal neutrons are shown in Fig. 4.2.1 for beta+gamma decay power, in
Fig. 4.2.2 for beta-decay power, and in Fig. 4.2.3 for gamma decay power. The results for fast
fission of 238 U and thermal fission of 239 Pu are shown in Figs. 4.2.4 through 4.2.6 and Figs.
4.2.7 through 4.2.9, respectively. The results for a year's irradiation are shown in Figs. 4.2.10
through 4.2.18, and those for the infinite irradiation in Figs. 4.2.19 through 4.2.27.
It is seen from these tables and figures that the fitting errors are very small. The fitting
errors are especially small (± 0.03%) for the cooling times less than 10 6 s after a year's irradiation
for the beta+gamma decay power for thermal fission of 235 U. The error increases
to ± 0.3% as the wider cooling time ranges up to 10 10 s. The fitting errors are of the same
order of magnitude for fast fission of 238 U and thermal fission of 239 Pu. The fitting error
decreases with irradiation time; ± 0.5% for burst fission, ± 0.3% for a year's irradiation, and
±0.1% for infinite (10 13 s) irradiation for the above three types of fission. The maximum
fitting error for beta+gamma decay power is -0.6% at 2 X 10 7 s after burst fission of 233 U
by thermal neutron among the ten fission types.