Development and Preliminary Verification of a Thermal-Hydraulic Multi-Scale Coupled Code

On the basis of best estimate thermal-hydraulic system code RELAP5, sub-channel code COBRA-1V, and commercial Computational Fluid Dynamics (CFD) code CFX, a thermalhydraulic multi-scale coupled code RECOX has been developed. The coupling strategy was designed to keep the integral structure of each code and minimize modifications of code source. Under the Parallel Virtual Machine (PVM) environment, an external control code has been developed to perform codes spawn, data exchange and mapping, time step coordination, etc. Two test cases including single phase blowdown and temperature fluctuation transient have been carried out to evaluate the coupling between codes. Compared with stand-alone simulations very good agreement was achieved. Then in order to demonstrate the coupled analysis capability of RECOX, an asymmetry transient in a simple two loops system which is similar to the nuclear power plant was simulated. The result is correct and reliable, although further verification of coupled code with related experiment is needed. Finally, some potential improvements of coupling and future work were presented.