MCS based neutronics/thermal-hydraulics/fuel-performance coupling with CTF and FRAPCON

Abstract

A Monte-Carlo neutronics/thermal-hydraulics/fuel-performance (N/TH/FP) multi-physics coupling system has been developed based on the MCS code recently for the purpose of large-scale high-fidelity analysis of light water reactors (LWRs). The full N/TH/FP coupling overcomes the drawbacks of the previous N/TH (MCS/CTF) and N/FP (MCS/FRAPCON) coupling systems, which suffered respectively from the approximations in CTF on the fuel thermal conductivity and gap conductance, and from the approximations due to the single closed channel enthalpy model in FRAPCON. Thus, compared to the previous coupling systems, the new full coupling system benefits from the transverse cross flow between neighboring sub-channels in CTF, the burnup-dependent fuel thermal conductivity formulation in FRAPCON, and the iteratively determined fuel pellet-cladding gap thermal conductance in FRAPCON. Two applications of the full coupling systems are presented. First, a single fuel rod case is tested to verify the accuracy and efficiency of the new coupled system. Then, the simulation of the BEAVRS whole core model with three-dimensional (3D) pin-by-pin power density and T/H feedbacks exchange between different solvers is performed using the MCS based multi-physics coupling system. The obtained results demonstrate the practical capability of the Monte Carlo based steady-state multi-physics coupling code system for large-scale high-fidelity LWR analysis.