Meso-scale analysis of the creep behavior of hydrogenated Zircaloy-4

During dry storage, creep is the most likely degradation mechanism for spent Zircaloy fuel cladding. The fuel cladding integrity during dry storage depends on the amount of oxidation, irradiation hardening and hydrogen-uptake during in-reactor operation. In this paper, the effect of hydrogen on the creep behavior of Zircaloy-4 cladding material was investigated at different temperatures. Depending on temperature, hydrogen can be found in the sample in solid solution and/or hydride. To capture this phenomenon, a numerical mesoscale model of the hydrogenated material has been built using the Finite Element (FE) Method. The numerical setup explicitly describes the hydrides as an inclusion in a hydrogenated Zircaloy-4 matrix. The matrix creep behavior follows a combined Norton-Bailey and Norton creep rules whereas the hydrides are considered to be elastic material. The creep law was defined in FE Code ABAQUS using the user subroutine CREEP. The comparison of predicted creep behavior obtained from numerical modeling showed good agreement with the results reported in literature. The predicted creep behavior shows a significant effect of hydrides morphology. Particularly, our model is able to seize the competition between the creep strain rate enhancement induced by hydrogen in solid solution and its reduction due to precipitated hydrogen. (C) 2012 Elsevier Ltd. All rights reserved.