Disposal Method

What then is the ideal method of disposing of high-level radioactive waste? Some of the most popular proposals discussed to date include firing the wastes into outer space, burying them deep beneath the seabed, and burying them under the southern polar ice cap. Each method has its own drawbacks, including the difficulties posed both by accidents and prohibitions set by international treaties. The most agreeable method would involve burying them deep underground, and this is currently a central feature of research and development programs throughout the world.

Underground disposal offers a number of distinct advantages. To begin with, it is less susceptible to dramatic shifts in climate, and the risk of inadvertent excavation is minimal, since the radioactive waste would be buried several hundred meters under the ground. Best of all, the remarkable condition of numerous fossils attests to the fact that subterranean burial sites are a superior form of preservation over immense time periods.

Vitrified waste is cooled for 30 to 50 years in above-ground storage facilities, after which it is inserted into metal containers called "overpacks" and buried deep underground in stable bedrock. Thereafter it is further encased in a layer of viscous shock-absorbing material. For subterranean disposal, the radioactive (vitrified) waste is first encased in artificial barriers in the form of canisters, an overpack and a buffer layer, after which it is buried underground in a manner that prevents radioactive material from leaking into the surrounding groundwater and penetrating the neighboring strata for as long as possible. The underground burial location is also chosen with a view to creating a natural barrier, so that even if radioactive material does leak from the site, the rate at which it spreads is limited by its absorption into the surrounding ground. This combination of artificial and natural barriers is thought to be sufficient to ensure the safety of the underground disposal of high-level radioactive waste.

Disposal flow

Researchers observing the earth's stratum.

Vitrification High-level radioactive waste is mixed with glass and poured into stainless steel canisters where it solidifies. Primary storage The vitrified waste is stored for 30 to 50 years to allow it to cool. Underground disposal When primary storage is complete, the waste is buried in a deep permanent repository. Once in place below ground, the vitrified waste is enclosed in a thick metal container (overpack) and surrounded by a layer of clayey bentonite (buffer).

Japan's Disposal Program

Japan's current high-level radioactive waste disposal program is planning to form a private consortium to handle the effort by the year 2000. Over the ensuing years, the consortium will be responsible for carrying out assessment studies for site selection, developing and demonstrating reliable disposal technologies, and reflecting the opinions from local communities and obtaining confirmation from the government for the selected site, which should be operational some time between 2030 and the mid-2040s.

Japan is not alone in this endeavor. Similar underground disposal programs are already underway around the world. The United States, Sweden, Switzerland, Germany and Canada are among those countries currently with underground facilities that are involved in research and development.

Plans for the disposal of high-level radioactive waste in major countries