Modifications of oxidized Zircaloy-4 surface in contact with radiolysed wet air

C. Guipponi (1) , N. Millard-Pinard (2) , N. Bérerd (2, 3) , Eric Serris (4, 5, 6) , Michèle Pijolat (4, 5, 6) , Véronique Peres (4, 5, 6) , Virginie Wasselin-Trupin (7)

1 ACE
2 IPNL - Institut de Physique Nucléaire de Lyon
3 UCBL - Université Claude Bernard Lyon 1
4 LPMG-EMSE - Laboratoire des Procédés en Milieux Granulaires
5 SPIN-ENSMSE - Centre Sciences des Processus Industriels et Naturels
6 PRESSIC-ENSMSE - Procédés et REactivité des Systèmes Solide-gaz, Instrumentation et Capteurs
7 IRSN - Institut de Radioprotection et de Sûreté Nucléaire

In the framework of radioactive waste geological disposal, the long term evolution of the nuclear wastes packages and the release of the radionuclides from the wastes have to be studied. Regarding compacted wastes (cladding tubes) coming from reprocessing of spent fuel, the Zircaloy-4 (zirconium alloy) cladding tubes have been activated and oxidized in reactors. In the disposal, the radioactive waste is exposed to humid air in a first phase and to water after the resaturation phase. In order to better assess the degradation process of these nuclear waste package, the influence of wet air proton radiolysis on the behavior of surface oxidized Zircaloy-4 has been investigated. Radiolysis experiments were performed using an irradiation cell which is associated to an extracted beam. Samples are exposed to wet air, under and without radiolysis, during 12 and 24 h. The water partial pressure has been fixed at 6 and 50 mbar in order to have, respectively, localized adsorbed water molecules and a thin film of adsorbed water. Before and after each treatment, sample surfaces were characterized by X-ray Photoelectron Spectroscopy (XPS) in order to identify the elements at the topmost surface of the solid. The wet air radiolysis causes changes at the surface of oxidized Zircaloy-4 and influences the corrosion phenomenon. Indeed, an enrichment of tin and the presence of nitrogen species were observed. It could be due to the formation of tritin(II) tetrahydroxide dinitrate and a Zr4+ tetramer on the topmost oxide surface.

Mots clés: Zircaloy-4; Radiolysis; Wet air; XPS

Domaines: Génie des procédés; Chimie-Physique [physics.chem-ph]

C. Guipponi, N. Millard-Pinard, N. Bérerd, Eric Serris, Michèle Pijolat, et al.. Modifications of oxidized Zircaloy-4 surface in contact with radiolysed wet air. Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, 2012, 272, pp.222-226. ⟨10.1016/j.nimb.2011.01.070⟩. ⟨hal-00667455⟩