Overview of Computational Methods for Hydrogen Diffusion Coupled With Stress and Temperature Gradients in Zirconium Reactor Components

In order to better understand and predict hydride blister formation and hydride cracking in zirconium alloy CANDU⁽¹⁾ fuel channels, specialized computational methods are required. Hydride blister formation involves the coupled action of gradients in temperature and hydrogen concentration, while hydride cracking involves coupling of stress and concentration gradients. Hydride accumulation and crack growth in a leaking crack involves a complete coupling of concentration, stress and temperature gradients. In all cases, the action of dissolution or precipitation of hydride adds complexity to the numerical analysis procedure. Dedicated finite difference and finite element programs have been developed and applied to blister formation and uniform temperature cracking problems. On the basis of experience gained in the use of such specialized codes, a fully coupled capability has been integrated into a general-purpose finite element program. This program can more realistically address complex load and temperature histories that may be encountered during fuel channel operation. An overview of important computational features is given along with applications relevant to current experimental research and fuel channel assessments. ⁽¹⁾CANDU is a registered trademark of Atomic Energy of Canada Limited.