Repositories geological

Spent nuclear fuel has fission products, uranium, and transuranic elements. Plans call for permanent disposal in underground repositories. Geological studies are in progress at the Yucca Mountain site in Nevada. Until a repository is completed, spent fuel must be stored in water pools or in dry storage casks at nuclear plant sites. 

Geologic repository Geologic repository Geologic repository... 

Regulations include guidelines on geologic conditions. Of special interest is the stabiUty of the geology against faulting, volcanic action, and earthquakes. The repository is to be located in an arid region, where the water table is quite low. The host rock is to have a suitable porosity and a low hydrauhc conductivity. 

Site characterization studies include a surface-based testing program, potential environmental impact, and societal aspects of the repository. Performance assessment considers both the engineered barriers and the geologic environment. Among features being studied are the normal water flow, some release of carbon-14, and abnormal events such as volcanic activity and human intmsion. The expected date for operation of the repository is 2013. 

Transuranic Waste. Transuranic wastes (TRU) contain significant amounts (>3,700 Bq/g (100 nCi/g)) of plutonium. These wastes have accumulated from nuclear weapons production at sites such as Rocky Flats, Colorado. Experimental test of TRU disposal is planned for the Waste Isolation Pilot Plant (WIPP) site near Carlsbad, New Mexico. The geologic medium is rock salt, which has the abiUty to flow under pressure around waste containers, thus sealing them from water. Studies center on the stabiUty of stmctures and effects of small amounts of water within the repository. 

To recovery and recycle or vitrification and disposal in deep geologic repository... 

Despite the problems of direct experimental evaluation of plutonium stability constants, they are needed in modeling of the behavior of plutonium in reprocessing systems in waste repositories and in geological and environmental media. Actinide analogs such as Am+3, Th+, NpOj and UOj2 can be used with caution for plutonium in the corresponding oxidation states and values for stability constants of these analogues are to be found also in reference 20. 

Grenthe, I. Ferri, D. Proc. OECD/NEA Workshop on Near-field Phenomena In Geologic Repositories for Radioactive Waste OECD/NEA Paris 1981. 

Transport of plutonium from a geologic repository may be considered to involve three processes ... 

I emphasized and seconded what Rai called out - namely the great need for experimental work to determine solubility data for plutonium in its various oxidation states under typical expected geologic repository conditions (e.g., pH, Eh, temperature, etc.). 

The Clinton Administration believes that the overriding goal of the Federal Government s high-level radioactive waste management policy should be the establishment of a permanent geologic repository - essential not only for the disposal of commercial spent fuel, but also for... 

A permanent geologic repository is also important to our non-proliferation goals an alternative to reprocessing. . . storage for foreign research reactor fuel. . . and an option for the disposition of surplus plutonium from nuclear weapon stockpiles. 

I have just returned from an International Conference on Geologic Repositories hosted by Secretary Richardson. The joint declaration from this conference committed to continued international cooperation on waste issues and the viability of geologic repositories as one of the preferred options for disposal of nuclear waste. 

Proliferation concerns have been and continue to be the basic cause ofthe official US. opposition to reprocessing and plutonium recycle, and have thus led to the official U.S. categorization of spent fuel as nuclear waste which should be permanently buried in geologic repositories. 

Source Clay Mineral Repository, University of Missouri, Department of Geology, Columbia, Missouri 65211-... 

Fig. 1. Schematic illustration of the ideal closed nuclear fuel cycle (NRC 2003). In real practice, the reprocessing capacity does not match the generation rate of the spent nuclear fuel. Thus, the excess SNF must be placed in interim storage or disposed of in a geological repository. Under normal circumstances, the SNF will be in interim storage for just a few years. Also, note that excess material from nuclear weapons, e.g.. highly enriched 235U and 239Pu, can be blended down to lower concentrations and used as a reactor fuel.

Fig. 3. Schematic illustration of the interface of the nuclear fuel cycle with geochemical/hydrological cycles. The geological repository is the interface for these two cycles. The principal sources of radioactivity (over the long term) are indicated by the radionuclides listed at the centre of each cycle. Total background exposures to radiation are less than 300 mrem/y. The total radiation exposure that can be attributed to the nuclear fuel cycle is less than 3 mrem/y.

Over 5001 of HLW have been vitrified in France and Germany. In the USA, the HLW at the Nuclear Fuel Services plant in West Valley Plant, New York, have been vitrified (300 two-ton canisters) and vitrification is ongoing at the Defense Waste Processing Facility (DWPF) at Savannah River, South Carolina 1600 canisters by February 2004). A vitrification plant is under construction at Hanford, Washington. Vitrification of all of the HLW in the USA will generate approximately 20 000 canisters, which are destined for disposal at the geological repository at Yucca Mountain. 

Natural systems have been studied to provide data to support the ability of geological repositories to isolate radioactive wastes (e.g.,... 

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