Redox Control of Nuclear Glass

Vitrification is one of the recommended immobilization routes for nuclear waste, and is currently implemented on an industrial scale in several countries, notably for high-level waste. To optimize and extend the scope of nuclear waste vitrification, research is being conducted to specify suitable glass formulations and develop more effective processes. Vitrified nuclear waste often contains several multivalent species whose oxidation state can impact the properties of the melt and of the final glass. The redox control of nuclear glass is often advantageous: in many case it could improve the glass melting and increase the amount of waste in the final glass. In the glassmaking industry, the oxidation state of glass is optimized in order to improve the glass properties, notably refinement and colour. In this case the aimed redox state is obtained by the appropriate choice of raw materials. Redox control of nuclear glass is more complex because several redox species are contained in this glass. Furthermore, raw materials are partly driven by the chemical and physical properties of the waste that must be vitrified and specific constraints due to the active process. Different techniques of glass redox control developed for nuclear waste vitrification are reviewed.