Monte Carlo and thermal-hydraulic coupling via PVMEXEC

Successful high-fidelity coupling between a Monte Carlo neutron transport solver and a subchannel thermal-hydraulics solver has been achieved using PVMEXEC, a coupling frame-work developed for analysis of transient phenomenon in nuclear reactors. The PVMEXEC framework provides a generic program interface for exchanging data between solver kernels for different physical processes, such as radiation transport, heat conduction, and fluid flow. In this study, PVMEXEC was used to couple the in-house Monte Carlo radiation transport code, MC21, with a locally modified version of COBRA-TF. In this coupling scheme, MC21 is responsible for calculating three-dimensional power distributions and COBRA-TF for calculating local fluid temperatures and densities, as well as fuel temperatures. The coupled system was used to analyze 3D single-pin and assembly models based on the Calvert Cliffs commercial PWR. Convergence properties of the coupled simulations are examined and results are compared to simulations conducted using the existing integrated thermal feedback kernel in MC21. (author)