What are Vitrified High-Level Wastes (VHLW)?
High-level wastes (HLW) are the highly radioactive liquid residues which are generated when spent nuclear fuel is reprocessed to extract the plutonium it contains. Japan has been shipping spent fuel to reprocessing plants in France and the U.K. for many years. Under the terms of the contracts, the HLW must be returned to Japan for disposal. The current industrial practice is to condition these wastes for storage, transport and disposal by converting them into solid glass blocks through a process called vitrification. In this process, HLW is blended with glass-forming materials and melted at a high temperature (about 1150C). The melt is then poured into thin-walled (5 millimeter-thick) stainless steel canisters and slowly cooled until it hardens. This product is referred to as vitrified high-level waste (VHLW). Because HLW generates considerable heat from radioactive decay, the VHLW canisters will remain quite hot for decades after they are produced. During normal conditions of storage
