Waste geologic isolation

All the countries that produce nuclear waste have chosen the same alternative for the ultimate disposition of HLW, deep geological isolation, and they did so indepeiideiitly of one another. The United States has the most radioactive nuclear waste and the most complicated array of waste types of any nuclear country. Only in the United States can one find the same economy of scale for waste handling. Thus, it leads the world in most activities aimed at safe isolation. Ill France, Japan, and Great Britain, however, reprocessing is routinely practiced. Those countries reprocess HLW for many other countries. As mentioned above, reprocessing is not currently allowed in the United States. 

The objective of geologic isolation of radioactive wastes is to preclude their reaching the biosphere until after they have decayed to the extent that they no longer constitute a health hazard. Concern over radioactive wastes from military, industrial and research uses has elicited many lines of commentary and deep concern from many individuals. In California, the concern about waste disposal was the focal point in establishing a moratorium on the construction of new reactors until a satisfactory waste disposal technology could be demonstrated. 

If the waste is isolated in a geologic repository, the iodine form should be stable to at least 100°C and possibly at 250°C depending on the repository site. If the waste form satisfies the thermal stability requirement, the most likely release mechanism then becomes leaching in the event that groundwater contacts the immobilization form. Allard et al. (11) report log Kd values for silicate minerals ranging from -0.5 to -3.5. Fried et al. (12) found little retention of iodine (as iodide or iodate) by Los Alamos Tuff. Thus, once the Iodine has been removed by leaching, it will potentially move at the same velocity as the groundwater. 

The action that could lead to such release is placement of the wastes in geologic formations. Such action is known, in waste management terminology, as geologic isolation since its objective is to isolate the wastes from the biosphere. 

There are four candidate geologic isolation environments the sea floor, ice sheets, deep continental geologic formations, and shallow continental geologic formations. In waste manage-... 

For purposes of assessing the safety of repositories of radioactive wastes placed in geologic isolation, actinide behavior in the environment has been interpreted in terms of five steps of prediction ... 

The ingestion toxicity indices of the actinides in the wastes are shown as a function of decay time in Fig. 8.9 [P2]. Because the actinides are nonvolatile and because the wastes are expected to be geologically isolated, ingestion toxicity is probably a more important measure than inhalation toxicity. During the first 600 years the total toxicity index is controlled by the fission products, mainly Sr. It is thereafter controlled by Am and Am, followed by... 

The hydrolytic chemistry of Pu is important in that it affects the behavior and mobility of plutonium in the environment [A2] and in geologically isolated radioactive wastes that may be subjected to slow leaching by ground water. The absorption spectra of the Pu(TV) polymer is similar to that of the plutonium hydroxide precipitate Pu(0H)4 [L4]. Experimental data in Fig. 

Kiihn, K., and J. Hamstra Geologic Isolation of Radioactive Wastes in the Federal Republic of Germany and the Respective Program of the Netherlands, Proceedings of the International Symposium on the Management of Wastes from the LWR Fuel Cycle, Denver, 1976, Report CONF-76-0701, p. 580. 

Board on Radioactive Waste Management, National Research Council (1999). Discussion Papers prepared for the Workshop on Disposition of High-Level Radioactive Waste Through Geological Isolation, National Academy Press, Washington, DC. 

HLW generally refers to materials requiring permanent isolation from the environment. It frequently arises as a by-product of nuclear power generation (reprocessing streams or spent fuel) or from the isolation of fissile radionuclides from irradiated materials to be used in nuclear weapons production. When nuclear fuel from reactor operations (civilian or defense) is chemically processed, the radioactive wastes include highly concentrated liquid solutions of nuclear fission products. Typically, these waste streams are solidified either in a glass (vitrification) or in another matrix. Both the liquid solutions and the vitrified solids are considered HLW. If the nuclear fuel is not processed, it too, is considered as HLW and must be dispositioned. The path most often proposed is direct, deep geologic isolation. 

Commission of European Community, Performance Assessment of Geological Isolation Systems for Radioactive Wastes, (EWU 11777) (1988). 

National Research Council. 1999. Disposition of high-level radioactive waste through geological isolation Development, current status, and technical and policy challenges. Natl. Academy Press, Washington, DC. ... 

Consumption of transuranics in a closed fuel cycle, thus reducing the radiotoxidty and heat load, which facilitates waste disposal and geologic isolation and... 

D Alessandro, M. Gera, F. 1986. Geological isolation of radioactive waste in clay formations fractures and faults as possible pathways for radionuclide migration. Radioactive Waste Management and the Nuclear Fuel Cycle, 7(4), 381-406. 

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. 

Shurr, G.W. "The Pierre Shale, Northern Great Plains a Potential Isolation Medium for Radioactive Waste", U.S. Geological Survey Open-File Report 77-776, 1977. 

Radioactive wastes are usually stored in underground tanks or in temporary storage at reactor sites for recycling or disposal (Whicker and Schultz 1982a). For low-level wastes, containment and isolation are the preferred disposal options, including burial, hydraulic injection into deep geological strata, and ocean disposal (Table 32.10). Options for the disposal of high-level wastes include... 

This is to be achieved by deep underground disposal of the wastes, the objective of which is to isolate them from man and the biosphere until they become innocuous. This time span is short, geologically speaking, i.e. in comparison with the periods of time that many deep underground geologic formations are known to have remained stable. 

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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