A steady-state performance analysis of fuel rods with accident tolerant claddings for a WWER reactor

Abstract

This survey focuses on the behavior of the fuel rods with accident tolerant claddings in steady-state conditions of a working WWER–1000 reactor. Thermal–mechanical performances of fuel rods with UO₂ fuels supported by two newly recommended claddings made of FeCrAl and SiC are cross-checked against two conventional ones made of Zr4 and Zr–1 %Nb. We resort to the rigid pellet model to study temperature distribution, swelling, expansion, densification, and displacement of fuel pellet pieces. In addition, thermal and radiation creep, expansion, oxidation, as well as elastic and plastic stresses and strains of claddings are explored, too. Comparison of performances are carried out using power histories of the hottest fuel rod in four successive fuel cycles of a WWER–1000. The results indicate that the possibility of hard contact between fuel and alternative clads and therefore the creation of positive stresses due to the low creep rate is less than that of conventional clads. This privilege, however, leads to the gap thickness not being reduced during the cycle, and hence, the gap heat transfer remains significantly lower than that of their conventional counterparts. As a result, Zr–free clads keep the fuel temperature about 30 % higher than those made of Zr. This increase in fuel rod temperature undermines neutron economy, fuel burn-up and cycle safety which is worth studding for future works.