Chemical isotopic analysis of fission products in PWR-MOX spent fuels and computational evaluation using JENDL, ENDF/B, JEF, and JEFF

A chemical isotopic analysis of high-burn-up MOX spent fuels with a burn-up of 45 MWd/kgHM was carried out to accumulate nuclide composition data. Furthermore, computational analysis was performed using the integrated burn-up calculation code system SWAT. The differences between the amounts of fission products obtained by the chemical isotopic analysis and SWAT calculation using JENDL-3.2, JENDL-3.3, ENDF/B-VI.5, ENDF/B-VI.8, JEF-2.2, and JEFE-3.0 were evaluated as the ratios of the calculated values to the experimental ones (C/E ratios). The fission products such as ⁸⁸Sr, ⁹⁰Sr, ¹⁰⁶Ru, ¹³³Cs, ¹³⁴Cs, and ¹³⁵Cs, which are gamma and decay heat sources, neutron absorption nuclides, or burn-up indicators in spent fuels, were further investigated to improve their C/E ratios using the simplified burn-up chains of fission products using JENDL-3.3; consequently, the correction values for the fission yields or capture cross sections of the fission products were estimated using sensitivity coefficients. The C/E ratios for ¹⁵⁴Eu, ¹⁵⁵Eu, ¹⁵⁴Gd, ¹⁵⁵Gd, and ¹⁵⁶Gd markedly differed among libraries. The reason for this difference was also discussed using the sensitivity coefficient and capture cross section of each fission product, which is in their main sensitive production paths. (author)