Nuclear waste, radionuclides

Similar demands for reference materials also arise in connection with the monitoring of radioactivity in and around nuclear installations (nuclear power plants, nuclear fuel and reprocessing plants, and nuclear waste facilities). These, in fact, are now the main applications of radionuclide reference materials. 

Fisher NS, Fowler SW, Boisson F, et al. 1999. Radionuclide bioconcentration factors and sediment partition coefficients in Arctic seas subject to contamination from dumped nuclear wastes. Environ Sci Technol33 1979-1982. 

Suchanek IH, Lagunas-Solar MC, Raabe OG, et al. 1996. Radionuclides in fishes and mussels from the Farallon Islands nuclear waste dump site, California. Health Phys 71(2) 167-178. 

A second major public concern is over nuclear wastes. Most experts believe that it is possible to dispose of these in a manner that poses little threat to the environment and human health, given the small volume of the spent fuel, the decay with time of the radionuclides, and the potential effectiveness of engineered and natural barriers. The success that is likely to be achieved is examined through Total System Performance Assessments (TSPA) (see, e.g, OCWRM, 1998). 

A large neutron cross section of 235U for fission (5.8 x 10 26 m2), a high fission yield (6%) for "Tc, and a long half-life of the resulting "Tc (2.1 x 105 yr) make this radionuclide one of the principal nuclear wastes. Fig. 1 shows radioactivity of nuclear wastes plotted against cooling time in years. Tc activity is very important in the time interval 104-106 years. 

The scope and scale of pollution from radionuclides has been greatly reduced due to (1) the cessation of aboveground nuclear bomb testing, (2) an international ban on the dumping of nuclear wastes at sea, and (3) better control of discharges from power and fuel reprocessing plants. 

UOP molecular sieves (UOP) has developed the lonsiv family of ion exchange resins for the extraction of radionuclides from wastewater. lonsiv TIE-96 is composed of a titanium-coated zeolite (Ti-zeolite) and is used to separate plutonium, strontium, and cesium from alkaline supernatant and sludge wash solutions. The technology was developed by Pacific Northwest Laboratory (PNL) for use at the West Valley, New York, nuclear waste facility. The technology is commercially available. 

Colloid influence on the radionuclide migration from a nuclear waste repository... 

The reliable long-term safety assessment of a nuclear waste repository requires the quantification of all processes that may affect the isolation of the nuclear waste from the biosphere. The colloid-mediated radionuclide migration is discussed as a possible pathway for radionuclide release. As soon as groundwater has access to the nuclear waste, a complicated interactive network of physical and chemical reactions is initiated, and may lead to (1) radionuclide mobilization (2) radionuclide retardation by surface sorption and co-precipitation reactions and (3) radionuclide immobilization by mineralization reactions, that is, the inclusion of radionuclides into thermodynamically or kinetically stabilized solid host matrices. 

The potentially important role of colloidal species in the geochemical behaviour of the polyvalent actinides has nevertheless been stated by various authors (e.g., Kim 1991 Kersting et al. 1999). The present paper discusses the role of colloids on the release of radionuclides from a nuclear waste repositoiy with regard to the processes leading to (1) colloid generation and stability (2) radionuclide interaction with aquatic colloids and (3) colloid-borne radionuclide migration. 

Release rate data for radionuclides from fully radioactive waste forms are needed to evaluate the safety of nuclear waste glass. Presently, contact with water is considered the most important release path therefore, the release properties of waste glass in water are of primary concern. 

Information on the interaction of radionuclides with ground-water in deeply-buried, high-level, long-term "waste repositories" is available at only a few locations. One is the OKLO natural reactor in Gabon which has for over 1. 7 billion years retained some of the radionuclides also present in nuclear wastes (5). Another is the Nevada test Site, where radionuclides were first deposited underground on September 19, 1967 during the 1.7 kt... 

Madic, C., Lecomte, M., Baron, P., Boullis, R 2002. Separation of long-lived radionuclides from high-active nuclear wastes. Comptes Rendus Physique 3 (7) 797-811. 

Wai, C.M. Supercritical fluid extraction of radionuclides A green technology for nuclear waste management, ACS Symposium Series 943 (2006) 161-170. 

Shaibu, B.S. Reddy, M.L.P. Prabhu, D.R. Kanekar, A.S. Manchanda, V.K. N, N -dimethyl-N, N -dibutyl tetradecyl malonamide impregnated magnetic particles for the extraction and separation of radionuclides from nuclear waste streams, Radiochim. Acta 94 (2006) 267-273. 

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