On integrating Monte Carlo calculations in and around near-critical configurations - I. Methodology

Monte Carlo with variance reduction (VR) is employed to calculate radiation-induced responses in a variety of fixed source problems. In eigenvalue problems, Monte Carlo is used without VR (apart from implicit capture) for in-core integral responses (k(eff,) reactivity coefficients, burn-up effects, etc.). More differential in-or ex-core responses are either treated in the same way thus limiting the range of solvable problems, or by decoupling. We evaluate an all-Monte Carlo approach developed to calculate differential in-or ex-core responses without decoupling. The ex-core problems involve responses in a GEN III PWR. The in-core problems study the neutron flux and Zr-96(n,gamma) rate at the surface of a control rod in the VERA Benchmark. Comparison is made with an empirical approach involving analog Monte Carlo in-core with VR ex-core. The paper consists of two parts: part I tests the methodology; part II compares with PWR GEN II and III ex-core decoupled results. (C) 2022 Elsevier Ltd. All rights reserved.

Automated summary

Monte Carlo with variance reduction is utilized to calculate radiation-induced responses in fixed source problems. A new all-Monte Carlo approach is evaluated for calculating differential in-core and ex-core responses without decoupling. The results are compared with an empirical method involving analog Monte Carlo in-core with VR ex-core.