Uncertainty quantification of sodium-cooled fast reactor based on the UAM-SFR benchmarks: From pin-cell to full core

Abstract

To quantify the uncertainties in the neutronics calculations of sodium-cooled fast reactor (SFR), a series of sensitivity and uncertainty (S&U) analysis were performed on two typical SFRs, which were a large-size MOX-fueled core and a medium-size metallic fueled core. The analysis was done from the pin-cell level to full core level to investigate the uncertainty propagation in the two-step neutronics calculation scheme. The responses analyzed contained the kinf, homogenized cross-sections, sodium void reactivity (SVR), Doppler constant (KD) and control rod worth (CRW) at the sub-assembly level, and the keff and power distribution at the full core level. The direct numerical perturbation method was used to get the relative sensitivity coefficients and the ‘Sandwich Rule’ was used to get the relative uncertainties. The results showed that the relative uncertainties propagated linearly from pin-cell to full core for the kinf and keff. Relative uncertainties of reactivity like SVR were much bigger than the ones of kinf and keff. However, the relative uncertainty of power distribution was smaller than other responses. Differences were observed in the S&U analysis between the MOX fueled and metallic fueled SFRs. Softer spectrum of the large-size MOX fueled core caused bigger uncertainty compared to the metallic fueled core.