Formation and characterization of hydride blisters in Zircaloy 4 cladding tubes

Arthur Hellouin de Menibus (1, 2) , Quentin Auzoux (3) , Ousmane Dieye (3) , Pascal Berger (4) , Sophie Bosonnet (2) , Eddy Foy (4) , Vincent Macdonald (1, 3) , Jacques Besson (1) , Jérôme Crépin (1)

1 CDM - Centre des Matériaux
2 SRMA - Service des Recherches Métallurgiques Appliquées
3 SEMI - Service d'Etudes des Matériaux Irradiés
4 LEEL - UMR 3685 - Laboratoire d'Etudes des Eléments Légers

This article is focused on the formation of hydride blisters in zirconium alloys an experimental and theoretical 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 optimized based on thermo-diffusion calculations, that take into account the hysteresis in the hydrogen solubility limit, to obtain a high blister 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 δδ-hydride phase close to the external surface over one third of the blister depth. Thermo-diffusion calculations showed these half thickness blisters should grow in only a few days in PWR conditions. Eventually, the Diffusion Equilibrium Threshold (DET) was defined as a criterion that limits the blister growth, and emphasizes that the hysteresis in the hydrogen solubility limit in zirconium must be taken into account to model hydrogen thermo-diffusion in zirconium alloys.

Domaines: Matériaux

Arthur Hellouin de Menibus, Quentin Auzoux, Ousmane Dieye, Pascal Berger, Sophie Bosonnet, et al.. Formation and characterization of hydride blisters in Zircaloy 4 cladding tubes. Journal of Nuclear Materials, 2014, 449, pp.132-147. ⟨10.1016/j.jnucmat.2014.03.006⟩. ⟨hal-00980723⟩