Uncertainty quantification of LWR-PROTEUS phase II experiments using CASMO-5

Abstract

This paper presents an improved uncertainty quantification method for the validation of CASMO-5 on the spent fuel reactivity worth experiments of the LWR-PROTEUS Phase II program. For this method, we modeled with CASMO-5 the spent fuel reactivity worth measurement in the PROTEUS research reactor and the prior irradiation of the fuel in a Swiss nuclear power plant. We propagated the nuclear data uncertainties coming from cross-sections and fission yields in both fuel irradiations and reactivity worth experiment models using the SHARK-X tool. The fission yield and cross-section uncertainties have similar contributions to the uncertainty of the reactivity worth prediction. The reactivity worth probability distribution is non-normal because of the non-normal distribution of the perturbed fission yield data produced by the GEF code. The reactivity worth predictions obtained with CASMO-5 are very accurate for various moderating conditions and for all exposure conditions, even for burnup higher than 100 MWd/kg. Finally, we estimated the effects of the irradiation history specifications as well as various sources of nuclear data uncertainties on the relative reactivity worth uncertainty for a subset of the burnt fuel samples. The uncertainties due to the irradiation history specifications appear to be negligible. Scale-6.2, ENDF/B-VII.1 and JEFF-3.3 cross-sections uncertainty lead to consistent uncertainty estimates while the source of fission yield input uncertainty strongly affects the magnitude of the output.