A study on hoop directional creep behaviors of hydrided Zr based nuclear fuel cladding tube

Regarding the degradation of the mechanical properties of Zr based nuclear fuel cladding tubes under long term dry storage condition, the mechanical tests which can simulate the degradation of the mechanical properties properly are needed. Especially, the degradation of the hoop directional mechanical properties by creep mechanism seems to be dominant under long term dry storage condition. Accordingly, in this paper, hoop directional creep tests are performed in order to evaluate the hoop directional creep behaviors of hydrided fuel cladding under a hoop loading condition with Zr based fuel cladding tube, alloy A, in the temperature range from 350 .deg. C to 550 .deg. C. First of all, the hoop loading grips for the hoop directional creep test are designed in order that a constant curvature of the specimen was maintained during the creep deformation, and the graphite lubricant is to be used to minimize the friction effect between the outer surface of the die insert and the inner surface of the specimen. The specimens for the hoop directional creep test are also designed to limit the deformation within the gauge section and to maximize the uniformity of the strain distribution. As a result, it was revealed that creep rupture times of hydrided Zr based fuel cladding were much shorter than those of non hydrided fuel cladding. In this paper, the secondary creep rate with increasing hydrogen content are drawn, and then kinetic data such as pre exponential factor and activation energy for the creep process are also drawn in the temperature range from 350 .deg. C to 550 .deg. C