Study on the mass and heat transfer characteristics of the drying process of spent nuclear fuel cladding with nitrogen assisted

Abstract

The spent nuclear fuel cladding needs to be cooled in water for a long time before being compressed. The water attached to the solid must be dried before compressing the spent nuclear fuel cladding. In this paper, based on the heat and mass transfer process inside the porous medium, a coupled heat and mass transfer model for the nitrogen-assisted drying of the waste cladding porous medium is established. The influence of nitrogen flow rate, temperature and inlet position on the heat and mass transfer characteristics of the porous medium in the nitrogen-assisted drying of waste cladding is analyzed. The results show that the calculated results of the model are in good agreement with the experimental results. According to the temperature change on the surface of the waste cladding, the gas-assisted drying process can be divided into three stages: the initial stage of drying, the accelerated drying stage and the latter stage of drying. In addition, the nitrogen flow rate has the greatest impact on the accelerated drying stage in the drying process, and the change of the nitrogen flow rate only changes the heat transfer rate between the liquid and solid phases. Nitrogen temperature affects the drying time by changing the heat transfer coefficient between the gas and liquid phases during the drying process. The inlet position of nitrogen affects the drying time by changing the convection effect between the gas and liquid phases in the drying process. The above research provides reference for the study of the heat and mass transfer characteristics and the mechanism of the drying process in the process of nuclear fuel solid waste treatment. It can also provide an important reference for the application research of key equipment in the reprocessing of spent fuel in nuclear power plants.