A high-temperature process used to convert highly radioactive liquid waste into glass form for long-term storage purposes. The process heats the material to 1,100^ºC, evaporating the liquid either to the glass transition temperature to form an amorphous solid that is free from a crystalline structure, or is added to molten glass. In both processes, the molten glass is loaded into steel containers. The hardened glass material is therefore free from leakage and can be stored in safe and secure underground repositories.