Leaching of a zirconolite ceramic waste-form under proton and He ²⁺ irradiation

In the hypothesis of a nuclear waste geological disposal, zirconolite is a candidate host material for minor triand tetra-valent actinides arising from enhanced nuclear spent fuel reprocessing and partitioning. Its chemical durability has been studied here under charged particle-induced radiolysis (He²⁺ and proton external beams) to identify possible effects on dissolution rates and mechanisms in pure water. Two experimental geometries have been used to evaluate the influence of the following parameters: solid irradiation and total deposited energy. Results on the evolution of the elemental releases due to the enhanced dissolution of the zirconolite surface during charged particle-induced irradiation of water are presented. Under radiolysis, elemental releases are first kinetically controlled. When the titanium and the zirconium releases reach (or exceed) their corresponding hydroxide solubility limits, the zirconolite dissolution becomes thermodynamically controlled.