Assessment of the $^{153}$Eu and $^{154}$Eu neutron capture cross sections from the Integral Data Assimilation of spent nuclear fuel experiments

Abstract

International audienceThe purpose of this paper is to make the most of a large set of used nuclear fuel experiments for determining integral trends on the $^{153}$Eu(n,$\gamma$) and $^{154}$Eu(n,$\gamma$) reactions cross sections. The assimilation of the integral trends is based on a linear least-square fitting procedure relying on the Bayes’ theorem.Realistic uncertainties are obtained thanks to a marginalization technique. The method is applied to the $^{153}$Eu and $^{154}$Eu capture cross sections recommended in the evaluated nuclear data library JEFF-3.1.1. Our results indicate an underestimation of both capture cross-sections of approximately 4.9% and 7.1%, respectively. For $^{153}$Eu, our study suggests to increase the capture resonance integral from I$_0$=1409 barns to I$_0$=1502 $\pm$ 68 barns. This trend is consistent with the capture resonance integral I$_0$=1560 barns obtained from recent time-of-flight measurements carried out at the Renssealer Polytechnic Institute. The trend obtained in this work on $^{154}$Eu capture cross section is also consistent with a recent analysis carried out on ENDF/B-VII.1, for which $^{154}$Eu capture cross section is very similar to JEFF-3.1.1, therefore confirming its underestimation