Uncertainty analysis for fission product inventories based on covariance data of fission product yields in JENDL-4.0 and ENDF/B-VIII.0

ABSTRACT

The uncertainties of fission product (FP) inventories in lattice physics depletion and cooling calculations were compared from the viewpoints of generation approaches of FP yield (FPY) covariance matrix and the numerical difference in FPY uncertainties between JENDL-4.0 and ENDF/B-VIII.0. The individual influences of major parent heavy nuclides were also confirmed. Single mass chain (SMC) and generalized least square (GLS) approaches were used to generate the covariance matrix of independent FPYs (IFPYs). It was shown that the FP inventory uncertainty based on the GLS approach was nearly identical or smaller than that based on the SMC approach. A significant difference in uncertainties of ¹⁰⁹Ag, ¹³⁵I, ¹³⁵Xe, and ¹⁴⁷Sm inventories was observed between JENDL-4.0- and ENDF/B-VIII.0-based uncertainty analysis results. The breakdown of individual influences of major parent heavy nuclides revealed that such discrepancies were due to differences in cumulative FPY (CFPY) uncertainty in ¹⁰⁹Ag and ¹⁴⁷Sm and the modification of IFPY uncertainty in ¹³⁵I and ¹³⁵Xe, which were obtained by calculating the covariance components using the GLS approach. Consequently, this study provided a crucial perspective regarding the difference in CFPY uncertainty and modification of IFPY uncertainty due to covariance matrix generation.

KEYWORDS:

• Uncertainty analysis
• fission product yield
• covariance matrix
• single mass chain approach
• generalized least square approach
• random sampling
• JENDL-4.0
• ENDF/B-VIII.0
• CASMO5

Acknowledgments

The author would like to thank SAKAI Tomohiro in the Nuclear Regulation Authority for useful suggestions on target FPs to be focused on and CHIBA Go and HONTA Keisuke in Hokkaido University for helpful discussions regarding the SMC and GLS approaches used in this work.

Disclosure statement

No potential conflict of interest was reported by the author(s).