Thermal creep of hydride Zircaloy-4 plates under dry storage conditions

Dry storage is one of the most realistic options for interim storage until fuel reprocessing or final disposal. During dry storage, the fuel cladding temperature rises up around 400 .deg. C due to poor heat conductivity of inert gases surrounding the cladding tubes as compared to water in wet storage. Under these conditions, creep and hydride effects are important degradation mechanisms for spent nuclear fuel cladding. However, in Korea, there are few experimental results on not only in-pile but also out-of-pile spent nuclear fuel cladding to understand degradation mechanisms and to determine the domestic safety criteria. Plate creep tests were carried out up to rupture on Zircaloy-4 tensile specimen under the stresses 140 MPa and 160 MPa at 400 .deg. C. The results obtained were as follows: (1) The more stress applied, the shorter creep rupture time was and the smaller secondary creep rates were. (2) Secondary creep rates of hydride specimens were higher than those of as-received specimens. (3) Creep rupture time of hydride specimens was shorter than that of as-received specimens