Influence of Gamma Irradiation on Leaching of Simulated Nuclear Waste Glass: Temperature and Dose Rate Dependence in Deaerated Water

Elemental leaching rates from a simulated nuclear waste glass undergoing gamma irradiation in deaerated deionized water were evaluated as a function of temperature and gamma dose rate. Deaeration of the water eliminated nitric acid formation via air radiolysis, previously shown to substantially accelerate waste glass corrosion, and thus allowed the effects of water radiolysis alone to be measured. Water radiolysis resulted in enhanced reaction-layer thicknesses on glass samples as well as an approximate factor of three increase in the leach rate at 50°C. At 90°C, leach rates were indistinguishable for irradiated and unirradiated glasses. Most of the increase in glass dissolution occurred up to a gamma dose rate of ∼1 × 105 rad/h. Above this value, only minor further increases were observed. It is concluded that the observed glass corrosion enhancement was due to reaction with short-lived transient species generated by water radiolysis and that the effect is unlikely to significantly contribute to long-term waste isolation.