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The deep geological repository concept involves the placement of long-lived radioactive waste, often spent nuclear fuel, in rooms excavated deep within stable, low-permeability bedrock. The combination of waste package, engineered seals and bedrock would provide a high level of long-term safety, without relying on on-going future maintenance.
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Principles and Background
The ability of natural geologic barriers to isolate radioactive waste is demonstrated by the Oklo reactors. During their long reaction period about 5.4 tonnes of fission products as well as 1.5 tonnes of plutonium together with other transuranic elements were generated in the ore body. This plutonium and the other transuranics remained immobile until the present day, a span of about 2000 million years. This is quite remarkable in view of the fact that ground water had ready access to the deposits and they were not in a chemically inert form, such as glass.
With deep ocean disposal in stable clay in the seabed being excluded for legal and political reasons, there is a strong consensus among all major countries that the deep geological repository is the only possible permanent solution, and this is being studied extensively. Many countries are currently exploring this option to dispose of highly radioactive solid wastes deep underground in purpose built, engineered repositories. Already a number of surface and shallow repositories for less radioactive wastes are in operation.
Safety and Feasibility Assessment
To examine the feasibility of this method, the Waste Isolation Pilot Plant (WIPP) in the United States was authorized in 1998, and in early 1999 the first cubic metres of intermediate level long lived military waste were put for ever into the repository, in a deep stable layer of salt near Carlsbad, New Mexico. This was the first operation of its kind in the world.
In 1978 The U.S. Department of Energy began studying Yucca Mountain, within the secure boundaries of the Nevada Test Site in Nye County, Nevada, to determine whether it would be suitable for a long-term geologic repository for spent nuclear fuel and high-level radioactive waste. However, this project faces significant opposition and has suffered delays due to litigation by The Agency for Nuclear Projects for the State of Nevada (Nuclear Waste Project Office) and others.
In addition to the United States, Belgium, Canada, China, Finland, France, Germany, Japan, Russia, Spain, Sweden, Switzerland, and the United Kingdom support deep geologic disposal as the best method for isolating highly radioactive, long-lived waste.
Many of these countries have performed detailed studies, or characterizations, drilling numerous boreholes and exploratory shafts and ramps in underground research laboratories. All this data will be useful in determining the predicted safety performance of future nuclear waste repository sites.
Variations
Common elements of potential repository systems include the radioactive waste, the containers enclosing the waste, the tunnels housing the containers, and the geologic makeup, or type of rock, of the surrounding area. Some countries are developing their own repository systems, others are working in collaboration with other nations to develop shared technologies.
Atomic Energy of Canada Limited, for example, operates the Underground Research Laboratory (URL) at Lac-du-Bonnet, Manitoba, constructed by AECL to carry out large-scale testing, engineering demonstrations and performance-assessment-related experiments on key aspects of geological disposal.
Future plans and remaining risks
The process of selecting appropriate deep final repositories is now under way in several countries with the first expected to be commissioned some time after 2010. Sweden is well advanced with plans for direct disposal of spent fuel, as its Parliament has decided that this is acceptably safe, using the KBS-3 technology. In Germany, there is a political debate about the search for a final repository for radioactive waste, accompanied by loud protests - especially in the Gorleben village in the Wendland area, which was seen ideal for the final repository until 1990 because its location next to the border to the former GDR. This location is currently used for the temporary storage of nuclear waste. There is also a proposal for an international HLW repository in optimum geology - Australia or Russia are possible locations. However, since the proposal for a global repository in Australia (which has never produced nuclear power, and has one research reactor) was raised, domestic political objections have been loud and sustained, making such a facility in Australia unlikely.
But despite a long-standing agreement among expertscitation needed that geological disposal can be safe, technologically feasible and environmentally sound, a large part of the general public in many countries remains skepticalcitation needed. Major environmental and security problems at existing repositories such as Morsleben in East Germany have also cast doubt on the quality and objectivity of such safety assessments (cf. Beyer 2004)citation needed. One of the challenges facing the supporters of these efforts is to demonstrate that a repository will contain wastes for so long that any releases that might take place in the future will pose no significant health or environmental risk. Existing repositories in deep geological formations (e.g. Asse II and Morsleben in Germany) show that solutions to the problem of radioactive waste remain elusive and that safe and environmentally sound storage cannot be guaranteed, especially over long periods of time.citation needed
Repository plans by country
- The United States Department of Energy is pursuing a plan to construct a long term repository at Yucca Mountain.
- The Japanese government has mandated for the Japan Atomic Energy Agency to do research at Horonobe, HokkaidÅ for a long term repository.
- Canada has developed an Adaptive Phased Management plan that is a more evolutionary approach than other countries, they have not decided on a site yet. See also Nuclear power in Canada#Adaptive Phased Management
- Canada also now has a planned DGR in the works at the Bruce Power site in Tiverton, Ontario, Canada. See info at : Ontario Power Generation DGR page
See also
External links
- U.S. Department of Energy, Office of Civilian Radioactive Waste Management
- Long-Term Low and Intermediate Level Waste Management Study, Ontario Power Generation
- Study by the World Nuclear Organization
- OPG Plans for DGR
Wikipedia content modification information:
- This page was last modified on 10 October 2008, at 22:45.
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