Sensitivity and uncertainty analyses of reactivities for PWR cells with UO2UO2 and MOX fuels

•The improved method has been used to calculate sensitivity coefficients relative to infinite dilution cross-sections.•Two types of reactivities are considered: Doppler reactivity and coolant void reactivity.•The reactivity uncertainty is larger than the eigenvalue uncertainty.•The uncertainty of coolant void reactivity is much greater than Doppler reactivity.•The verification was performed by comparing our results SCALE code.

The purpose of this paper is to apply our improved method for calculating sensitivities and uncertainties of reactivity responses for UO2UO2 and MOX(ThO2–UO2MOX(ThO2–UO2 and PuO2–UO2)PuO2–UO2) fueled pressurized water reactor cells. The improved method has been used to calculate sensitivity coefficients relative to infinite dilution cross-sections with self-shielding effect taken into account. Two types of reactivities are considered: Doppler reactivity and coolant void reactivity. For each type of reactivity, the sensitivities are calculated for small and large changes of reactivity. The results have demonstrated that the sensitivities are dependent on the changes of reactivity, and the reactivity variation uncertainty is larger than the eigenvalue uncertainty. In addition, the uncertainty of coolant void reactivity is much greater than Doppler reactivity especially for large changes of reactivity because the contribution of U-238 inelastic scattering becomes large. The sensitivity coefficients and uncertainties of both reactivities were verified by comparing with SCALE code results using ENDF/B-VII library and good agreements have been found.