Uncertainty analysis for the steady-stated BEAVRS benchmark problem at ARO and ARI situations

In this paper, the capability of uncertainty propagations of the nuclear-data to the reactor-physics calculations has been implemented in our home-developed code NECP-UNICORN based on the statistical sampling method (SSM). The "two-step" scheme has been applied in NECP-UNICORN to perform the uncertainty analysis for the reactor-physics calculations. For the lattice calculations, the nuclear-data uncertainties are propagated to the few-group constants; then for the core simulations, the uncertainties of the multiplication factor and power distributions introduced by the few-group constants' uncertainties can be quantified. Applying the NECP-UNICORN code, uncertainty analysis has been performed to the BEAVRS benchmark problem at the Hot Zero Power (HZP) conditions, with situations of All Rod In (ARI) and All Rod Out (ARO). From the numerical results, it can be observed that for the multiplication factors of the core simulations, the relative uncertainties are about 5.1‰ for the ARO situation and 5.0‰ for the ARI situation, which are the same magnitude of the relative uncertainties of the fuel assemblies; for the radial power distributions, the relative uncertainties can up to be 4.27% as the maximum value and 2.08% as the RMS value for the ARO situation, and 6.03% as the maximum value and 2.37% as the RMS value for the ARI situation.