Dissolution behaviour of spent nuclear fuel at highly alkaline conditions: Phenomenological synthesis report

This report gives a summary of literature data pertaining to the dissolution behaviour of spent nuclear fuel in generic geological disposal conditions, with special attention to the highly alkaline systems that are dominated by the presence of Ordinary Portland Cement (OPC). It contains a description of the spent fuel alteration and dissolution mechanisms, leading to the release of radionuclides. The report focuses on the release of radionuclides that are incorporated in the UO2 matrix. Both results found in the open literature and results generated in the framework of the Belgian R&D programme are presented. The available information shows that the dissolution behaviour of spent fuel in a system dominated by the presence of OPC (contact with high pH cement water) is similar to the dissolution expected in other conditions (contact with near-neutral pH ground waters), both in terms of mechanisms and in terms of the resulting dissolution rate.