Feasibility of Albedo-corrected parameterized equivalence constants for nodal equivalence theory

Abstract

The conventional Simplified Equivalence Theory (SET) is based on the single assembly lattice calculation with net-zero current boundary condition. However, SET has a problem that it can't reflect the actual node interface current on the equivalence constants so that it shows discrepancy with the reference value. For more accurate reactor core analysis, the conventional SET was modified by introducing Albedo-corrected Parameterized Equivalence Constants (APEC). The equivalence constants are functionalized using lattice calculation results from the several boundary conditions. The equivalence constants are updated during iterative whole-core calculation without compromising the computing time. The correction of discontinuity factors (DFs) are not considered in this study yet. The test calculation for two-dimensional PWR small core showed that APCE provided much accurate results that keff value error reduced by up to 25% and the normalized assembly power distribution error reduced by 84 % for maximum and 71 % for RMS value.