Analysis of Heat Transfer Performance of a Fork-End Heat Pipe using MARS-KS

It is clear that spent nuclear fuels continuously release residual heat due to radioactive decay of fission products. Since the Fukushima accident, importance of removal of such decay heat using passive cooling system against a station black-out accident of a nuclear power plant cannot be overemphasized. The passive cooling system has to prevent exposure of nuclear fuels over the coolant in order to ensure the safety criterion for surface temperature of cladding. Recently, several research groups were proposed passive system using heat pipes which are generally used passive heat exchanger in various field. In this study, heat transfer performance of the scale-downed FEHP was numerically analyzed using a best-estimate thermal-hydraulic analysis code, MARS-KS 1.4. The obtained results were compared with measurement data in. Heat transfer performance of a fork-end heat pipe designed and tested by Lim and Kim was numerically analyzed using MARS-KS and compared to the experimental observation. Boiling heat transfer modes in the evaporator part of the heat pipe at relatively high load, including nucleate pool boiling and falling film boiling, seem to be properly modeled in MARS. It was supposed that the boiling regime at such temperature could not be properly modelled in MARS, which results in a considerable discrepancy in heat transfer and system temperature between experiment and simulation.