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Deep geological repository
The deep geological repository concept involves the encapsulation of used nuclear fuel in long-lived engineered casks which are then placed and sealed within excavated rooms in a naturally occurring geological formation at a design depth of 500 to 1000 metres below ground surface. It involves the construction of a vault within stable, low permeability bedrock using conventional mining methods. The bedrock and other engineered barriers would provide a high level of long-term safety.
Additional recommended knowledge
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.
To examine the feasibility of this method, the Waste Isolation Pilot Plant (WIPP) in the United States was authorised 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. But this project is widely opposed and is a hotly debated topic 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.
Of these countries, Belgium, Canada, Finland, France, Germany, Sweden, Switzerland, the United Kingdom, have all 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.
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.
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, since its Parliament decided that this is acceptably safe, using the KBS-3 technology. In Germany, there is a political discussion about the search for an Endlager (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. Actually this place is used to store radioactive waste non-permanently. There is also a proposal for an international HLW repository in optimum geology - Australia or Russia are possible locations. However, when the proposal for a global repository for Australia (which has never produced nuclear power, and has one research reactor) has been raised domestic political objections have been loud and sustained, making such a dump in Australia unlikely. The Australian government is having a hard enough time convincing its people that nuclear is the way to go, so it is doubtful the Australian public would ever allow the country to be a global HLW dumping ground.
But despite a long-standing agreement among experts that geological disposal can be safe, technologically feasible and environmentally sound, a large part of the general public remains skeptical. One of the challenges facing the supporters of these efforts is to demonstrate confidently 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.
Repository plans by country
|This article is licensed under the GNU Free Documentation License. It uses material from the Wikipedia article "Deep_geological_repository". A list of authors is available in Wikipedia.|