Formation and Characterization of Hydride Blisters in Zircaloy-4 Cladding Tubes

This article is focused on the formation of hydride blisters in zir-conium alloys an experimental and theoritical standpoint, and their characterization in terms of morphology, hydrides crystallographic phases, hardness and hydrogen concentration. An experimental setup was developed to grow hydride blisters on pre-hydrided Zircaloy-4 cladding tubes by thermo-diffusion. The thermal conditions were op-timized based on thermo-diffusion calculations, that take into account the hysteresis in the hydrogen solubility limit, to obtain a high blis-ter growth rate. Micro X-Ray Diffraction (XRD), nano-hardness and Elastic Recoil Detection Analysis (ERDA) showed that the blisters contain a hydrogen gradient, with pure δ-hydride phase close to the external surface over one third of the blister depth. thermo-diffusion ∗Tel.: +33 1 69 08 39 43