Versatility and stabilization improvements of full core neutronics/thermal-hydraulics coupling between RMC and CTF

This paper presents the versatility and stabilization improvements of high fidelity multi-physics coupling of neutronics and thermal-hydraulics. The coupling is accomplished between the Monte Carlo code RMC and the sub-channel code CTF. Target motion sampling method of RMC and the domain decomposition parallel strategy of CTF are used to decrease the memory requirement as well as to improve the calculation efficiency. The hybrid coupling method is adopted in coupled RMC/CTF code, in which CTF is invoked by RMC flexibly. For code versatility and stabilization, the HDF5 (hierarchical data format) file is used to replace text files in data transfer between two coupled codes, and the predictor-corrector method is also proposed to stabilize the coupling. The coupled code is validated as versatile by successfully testing two full-core problems with different scales. The BEAVRS full core calculation results show the efficiency improvement as a result of using the HDF5 file in the versatile coupled code, and the predictor-corrector method used in the simulation is demonstrated to be effective for stabilizing and accelerating the coupling convergence. Moreover, a modified PWR full core problem simulation indicates that the coupling between neutronics and thermal-hydraulic influences the power distribution both radially and axially, because of the Doppler broadening effect and coolant properties feedback.