(A) study on hydride formation and plastic deformation behavior in zirconium alloy

Abstract

As the policy for final disposal of spent nuclear fuel has yet to be decided in Korea, the spent fuel has temporarily stored in the on-site wet storage. The on-site storage will be saturated with the gradual increase in the amount of the stored spent fuel due to the storage capacity. Hence, spent nuclear fuels have to be transported to temporary storages, disposal sites, or reprocessing facilities. In the light of the condition of domestic reactor operation, it needs to be expected the risk factor for safety which may happen during transportation and dry storage of spent fuels and be evaluated safety verification using experimental and empirical data on material properties of the spent fuels. It has been reported that the mechanical changes by hydrides, whose size is nano to micron size, is most important among various parameters which may be detrimental to the integrity of zirconium alloy cladding. Focused ion beam (FIB) has facilitated the microfabrication of site-specific specimen in a bulk sample. However, it is well-known that ion beam irradiation induces not only various types of defects in the metal but the formation of artifact hydrides. Here, the specimens prepared with and without FIB are analyzed using transmission electron microscopy (TEM). The formation of FIB-induced artifact hydrides is investigated and the increased strength of zirconium alloy by the artifact hydrides is identified. In addition, the mechanical properties of a bulk hydride with zirconium matrix are measured and plastic deformation mechanism is investigated by microcompression.