Thermomechanical Response Simulation of FeCrAl and Zr-2 Fuel Claddings Under Neutron Irradiation

Abstract:

The representative C35M alloy among FeCrAl alloys was selected as the research object, and a small fuel rod model was established. Based on the user material (UMAT) subroutine, the radiation creep model of the C35M alloy was embedded in the subroutine. The thermomechanical coupling behavior of C35M alloy under neutron irradiation was calculated by the finite element software ABAQUS. Using Zr-2 alloy as a comparison, the evolution of the distribution of the temperature field, stress field, displacement field, and gap distance of the cladding over time of the alloys was analyzed. Results show that the temperature field and the stress field of the two alloys are basically the same. The temperature distribution is mainly affected by the coolant, while the stress field is related to the temperature and creep rate. During the simulation, the Zr-2 alloy mainly grows through irradiation, while C35M alloy shows the irradiation creep and has a little thermal expansion deformation. The gap closure rate of Zr-2 alloy is much faster than that of C35M alloy, which indicates that C35M alloy can prolong the accident response time. However, in order to adapt to the complex environment in the reactor, the material still needs to be optimized to improve its strength and creep rate.