Threshold stress of hydride reorientation in zirconium alloy nuclear fuel cladding tubes: A theoretical determination

One of the most critical issues affecting the integrity of nuclear fuel cladding tubes is hoop stress-induced hydride reorientation from the circumferential to the radial direction. The theoretical prediction of the threshold stress for the hydride reorientation is a long-standing but unrealized objective of material design engineers in the nuclear industry. In this paper, we propose a criterion to determine the threshold stress based on the thermodynamic model. The results obtained this way agree very well with experimental observations. Multiple factors, such as crystallographic texture, grain-boundary structure and distribution, grain morphology and size, the hydride-matrix misfit strain, hydrogen content, the chemical composition, the temperature and the mechanical strength and anisotropy of the zirconium matrix, simultaneously control the difficulty level of hydride reorientation. Strengthening only the radial basal pole texture of the zirconium alloy tube is not enough to effectively enhance the threshold stress of hydride reorientation; other factors, especially the grain-boundary structure and distribution, also need to be considered. The model presented in this study elucidates the mechanism of stress reorientation of hydrides and offers new insight on how to further increase the resistance to hoop stress-induced hydride reorientation in nuclear fuel cladding tubes (c) 2022 Elsevier B.V. All rights reserved.