Sensitivity and uncertainty analysis of BEAVRS core keff

Abstract

Background: The uncertainty calculation of nuclear data plays an important role in reactor core physics. Purpose: This study aims to search nuclear reaction cross section that has the greatest influence on keff calculation results so as to reduce engineering conservative margin and improve reactor safety. Method: First of all, BEAVRS (Benchmark for Evaluation and Validation of Reactor Debris) physical model of first-cycle thermal zero-power core was established by using KENO module in SCALE6.1 program. Then the TSUNAMI-3D module was used to analyze the influence of the sensitivity and uncertainty of keff on the conditions of different fuel enrichment and different temperature. Results: The results show that the total uncertainty of the BEAVRS model nuclear data to keff is 0.501 6% whilst the maximum sensitivity coefficient is 0.926 58, which is caused by the average fission neutron yield of 235U, and the largest contribution to the keff uncertainty is the 238U(n,γ) reaction cross section, accounting for 0.298 14%. The uncertainty of keff increases with the increase of the uncertainty of the 238U(n,γ) reaction cross section when the fuel enrichment degree decreases and the temperature rises. Conclusions: Therefore, attention should be paid to the 238U(n,γ) reaction cross-section information during the physical calculation of the reactor core.