LAUSR

Abstract The natural circulation loops have been widely used in the design of next generation nuclear reactors and spent fuel storage facilities. However, the friction correlations for fuel bundle and grid spacers in RELAP5 code are not applicable for natural circulation flow. This paper summarizes the modeling methods in previous researches, and proposed a flow resistance model for rod bundle and grid spacers based on experimental data. A RELAP modeling method of radiation heat transfer in fuel assembly is proposed for natural circulation flow of air in the fuel assembly. The new model is verified using experimental data from the Spent Fuel Project by NRC. The results of the new model are in good agreement with the experimental data. The current model will be useful for analyzing the flow and heat transfer characteristics of natural circulation in the reactor core of next generation nuclear reactors and spent fuel storage facilities.