Preliminary thermo-mechanical coupling performance analysis of a three-lobe petal-shaped fuel rod

In this paper, an analytical model of thermal–mechanical coupling performance of three-lobe and four-lobe petal-shaped fuel rods (PSFRs) irradiation is established based on the finite element method, and the thermo-mechanical characteristics of PSFR during normal operation and RIA condition are investigated. The results show that the temperature of three-lobe PSFR is large in the middle and small on both sides in the axial direction, and the petal lobe root is the largest in the circumferential direction. During normal operation, the cladding stress increases continuously with time, and the stress in the center region is the largest. At the 200th day and the 600th day, when RIA occurs suddenly, the cladding will exceed the yield strength in 1.003 s and 0.763 s, respectively. The cladding lobe root at the center of three-lobe PSFR is the location of maximum plastic deformation. There are similarities and differences in temperature, heat flux, and stress between three-lobe and four-lobe PSFRs, but they can be substituted for each other. The above study provides guidance for practical application of three-lobe PSFR.