Nuclear Waste Vitrification

Because of its disordered structure, glass was identified in the 1950s as an excellent material for confining the wide range of elements present in fission product solutions arising from reprocessing of spent nuclear fuel. Glass can actually host most of the radioactivity generated in nuclear power plants. After two decades of research in this area, industrial vitrification lines have been commissioned in most countries involved in nuclear energy. In nuclear containment glass, radionuclides generally form chemical bonds with the glass constituent atoms. The preferred glass formulations are mixed alkali aluminum borosilicates because they combine the possibility of incorporating of a wide range of radioactive elements with a relative ease of synthesis and long-term stability. Vitrification furnaces have been developed for this application. The elements to be immobilized are mixed at high temperature with glass-forming additives to form a glass melt which, after cooling, becomes a chemically durable glass material with low radiation sensitivity. The debate on safe management of high-level waste has converged on deep geological disposal. In addition to thermal and radiation stability issues, the demonstration of long-term glass stability considers the surrounding environment as a key component constraining glass performance.