Numerical Simulation of Fission Products Release Following Fuel Cladding Failure in the Lead-Based Fast Reactor

This study investigates the behavior of fission products during cladding failure in lead-based nuclear reactors, with a particular focus on the release mechanisms of solid fission products. A three-dimensional numerical model of the cladding-breach-subchannel system was developed to analyze these processes. To account for the phenomenon of deposited particles re-entering the fluid from the surface, this study proposes a torque balance-based resuspension criterion specifically designed for vertical walls. This method enables an accurate simulation of particle resuspension behavior within the Lagrangian framework. The results reveal that the release of fission products occurs in two distinct stages: the rapid depressurization stage and the equilibrium release stage. During the rapid depressurization stage, a significant pressure differential between the interior and exterior of the fuel rod drives the formation of a high-speed jet, which transports a substantial quantity of solid fission products into the coolant. The resuspension and release of deposited particles predominantly take place in this stage. However, the final release rate of resuspended particles is significantly lower than that of migrating particles, indicating that particle resuspension is a critical factor in limiting the overall release of solid fission products.