Research on the performance enhancement of accident tolerant fuel for eliminating core melting based on ISAA

Based on the Integrated Severe Accident Analysis (ISAA) code, this paper studies the influence of thermo-physical properties of Accident Tolerant Fuel (ATF) materials on the plant responses to severe accidents, and further proposes the requirements of eliminating core melting on ATF performance and reactor components. The equation of fuel temperature rise is derived from the steady-state heat conduction equation of fuel rods, and three fuel properties, including thermal conductivity, density and specific heat capacity, which affect core melting, are obtained. By selecting ATF with IMDP(Inert Matrix Dispersion Pellet) as the core material and SiC as the cladding material and changing different physical parameters, it is found that fuel density and cladding density have the greatest influence on the fuel temperature rise, and appropriately increased fuel density can extend the core melting time. In addition, to eliminate core melting, the ATF parameters in ISAA are modified step by step to improve the thermodynamic properties of the fuel, and the core is finally made to reach thermal equilibrium and to realize the safety of nuclear power plants without human intervention. According to the calculation results, the supporting capacity of the cladding, the supporting capacity of the core supporting plate, and the melting point of the fuel are the main factors limiting the core melting, which can be eliminated by appropriately improving these properties.