Corrosion of nuclear waste glasses in long term tests

Abstract Field tests of vitreous nuclear waste forms are of high importance in nuclear waste management and require long-term experiments during which the governing mechanisms of glass corrosion can vary. Corrosion of glasses is a complex process evolving with time which is mainly dependent on glass composition and environmental conditions. We analyse the alternations of glass corrosion mechanisms during long-term tests focusing on an idealised model situation of a perfect homogeneous glass surface in contact with unsaturated water solutions and revealing dominant contributions from either ion exchange or hydrolysis with progressing of process. The two long-lasting mechanisms—ion exchange (IEX) and hydrolysis (HL)—control the overall release of radionuclides from the nuclear waste borosilicate glasses in contact with water with typical effective diffusion coefficients for 137 Cs via IEX of about 5 × 10 –21 m 2 /s (4.5 × 10 –12 cm 2 /day) and rates for HL of about 100 nm/y in near surface conditions. The consequences of intrinsic self-irradiation of nuclear waste glasses are also discussed.