Alpha dose rate and alpha decay dose impacts on the residual alteration rate regime of HLW nuclear glasses

Magaly Tribet (1) , Caroline Marques (1) , Sarah Mougnaud (1) , Veronique Broudic (1) , Christophe Jegou (1) , Sylvain Peuget (1)

1 DPME - Département de recherche sur les Procédés et Matériaux pour les Environnements complexes

The long-term behavior of high-level nuclear glass subjected to alpha radiation by long-life minor actinides must be investigated with respect to geological disposal. This study focuses on the effects of alpha radiation on the chemical reactivity of R7T7-type glasses with pure water, mainly on the residual alteration rate regime, by considering separately the alpha dose rate and the alpha decay dose. Old SON68 glasses doped with $^(238/239)$PuO2 or $^(244)$CmO2 were studied in order to simulate high alpha dose rates corresponding to an early water ingress and also high level of alpha decay doses corresponding to long-term disposal conditions. A part of the $^(238/239)$Pu-doped glass block was annealed to fully recover the irradiation induced damage accumulated since the glass fabrication and to dissociate the effect of the alpha dose rate from the one of alpha decay dose. The glasses were then leached under static conditions in argon atmosphere at 90°C for several years. The results showed that the residual alteration rate is not impacted by the alpha dose rate parameter on a wide range of the dose rate values expected under disposal conditions, even in the eventuality of an early water ingress. It means that a SON68-type glass remained poorly sensitive to the alpha particle energy deposition at the glass-water interface. However, the residual alteration rate of the damaged $^(238/239)$Pu-doped glass was enhanced compared to the one of the annealed glass. This result is in agreement with the one obtained on the $^(244)$Cm-doped glass, and also with the literature about simplified glasses externally irradiated, indicating that the ballistic effects of the recoil nuclei are thus responsible for this increase of the residual alteration rate. A link between the glass structure and its leaching behavior is evidenced on these radioactive glasses and the role of the reactive interface is highly suspected.

Mots clés: Borosilicate glass; doped glass; alpha dose rate; alpha decay dose; leaching; residual rate; radiolysis

Domaines: Chimie inorganique

Magaly Tribet, Caroline Marques, Sarah Mougnaud, Veronique Broudic, Christophe Jegou, et al.. Alpha dose rate and alpha decay dose impacts on the residual alteration rate regime of HLW nuclear glasses. npj Materials Degradation, 2021, 5, https://doi.org/10.1038/s41529-021-00183-4. ⟨10.1038/s41529-021-00183-4⟩. ⟨cea-03298512⟩