The incorporation of fission products into glass for disposal



There is need of an economical and safe method of disposing of radioactive waste produced by nuclear reactors. A method for the incorporation of fission products into glass is being studied at Chalk River. Class containing up to 50 curies of fission products per kilogram has been made during the investigation of the process. This radioactive glass has been used in stability studies in the laboratory and in the field.

Nepheline syenite (a rock containing Na, K and Al silicates) fluxed with up to 30% by weight of lime, is used as the base for the glass. A nitric acid solution of the fission products is added to a pelletized mixture of the solids. When the mixture is heated nitric acid is evaporated near 110°C. The nitrates are decomposed in the temperature range 130–600°, and the mixture is melted to form a glass at a maximum temperature of 1350°. Two of the fission products, ruthenium and cesium, are volatilized to varying degrees from the mixture during heating and create a major contamination and containment problem.

The method of processing and results obtained are discussed. The volatilized elements have been removed from the off-gas stream by a method which permits their incorporation into glass. Scale-up of the process to treat fission product wastes from power reactors should present no great difficulty other than design of equipment for the remote processing of large quantities of radioactive material at high temperature.