Multi-cycle Analysis of VERA Benchmark with Monte Carlo Whole-core Depletion Code MCS

Abstract

This paper presents the verification and validation of UNIST in-house Monte Carlo code MCS and multi-physics analyses. The core depletion analysis (chain of ~1,373 isotopes) is one of the most compelling advances for reactor analysis, giving the level of details required to address the problems 9 and 10 of the Virtual Environment for Reactor Applications (VERA) Core Physics Benchmark by the Consortium for Advanced Simulation of Light Water Reactors (CASL). This paper describes the modelling and simulation (M&S) of the first and the second cycles of Watts Bar Unit 1 (WBN1) including the nuclide depletion and thermal-hydraulics (T/H) feedback. MCS is one of few Monte Carlo codes to have the capability for depletion calculation for both WBN1 Cycles 1 and 2. The accuracy of the MCS simulation of WBN1 Cycle 1 is within 50 ppm in critical boron concentration (CBC) for all burnup points compared to the measured data. To demonstrate the multi-cycle capability of MCS, the beginning-of-cycle (BOC) of WBN1 Cycle 2 was also simulated and compared to the solutions of VERA-CS. The comparison shows that MCS CBC at hot zero power (HZP) and hot full power (HFP) is ~28 ppm and ~18 ppm, respectively, which is lower than those of MPACT/CTF. For the other burnup steps, MCS solutions show an excellent agreement compared to VERA-CS within 30 ppm and the average bias in CBC for the entire Cycle 2 is approximately 20 ppm. These results provide confidence in MCS’s capability to perform high-fidelity multi-cycle calculations of practical PWRs.