Regulatory Guide - Geological Considerations in Siting a Repository for Underground Disposal of High-level Radioactive Waste

At the present time in Canada, high-level radioactive waste is accumulating in the form of irradiated, used fuel from research reactors and nuclear power generating stations. The used fuel bundles are kept in water-filled bays at each of the reactor sites. Because water is both a radiation barrier and an effective coolant, this system provides a safe means of storage. Used fuel is also safely stored above ground in dry concrete canisters in several Canadian locations. Both of these methods require surveillance and maintenance in order to ensure their continued safety and can be seriously considered only as temporary management measures. Clearly, some means of disposing of these wastes permanently will be required. The Atomic Energy Control Board (AECB) is the federal agency responsible for regulating the development, application and use of atomic energy. As such, the AECB must be satisfied that any proposed disposal system will effectively isolate the radioactive waste and will not result in unacceptable risk to humans and to the natural environment, either at the present time or in the future. At the present time, a research program is being conducted in Canada to obtain scientific information for the assessment of a disposal concept based on the emplacement of radioactive waste in rock, deep below the surface of the earth. In August 1981, the governments of Ontario and Canada announced details of a process called "Concept Assessment" by which the acceptability of the concept would be examined. The announcement also stated that the process is expected to be completed by 1990 and that no siting for a repository would take place until after the concept had been generally accepted. The disposal concept that is being developed in Canada integrates both engineered and natural components. In essence, the plan involves physical and chemical stabilization of the waste in a resistant package, followed by emplacement in a repository deep within a body of rock that is situated in a geologically stable region. The information in this document is specifically related to the site selection phase. It is being published now to help identify the geological properties and processes that need to be addressed during site selection. This document should help to identify these geological considerations and to ensure that the concept assessment phase takes them into account in a balanced manner.