Radioactive waste radionuclides

Means, J.L., Crerar, D.A., and Duguid, J.O., Migration of radioactive wastes Radionuclide mobilization by complexing agents, Science (Washington, DC), 200, 1477, 1978. 

McKinley 1. and Scholtis A. (1992) A comparison of sorption databases used in recent performance assessments. In Disposal of Radioactive Waste Radionuclide Sorption from the Safety Evaluation Perspective, Proceedings of an NEA Workshop, Interlaken, Switzerland, 16—18 October 1991, NEA-OECD, Paris, France, pp. 21-55. 

Means, J. L., D. A. Crerar, and J. O. Duguid (1978), Migration of Radioactive Wastes Radionuclide Mobilization by Complexing Agents, Science 200, 1477-1481. 

Arthur WJ, Janke DH. 1986. Radionuclide concentrations in wildlife occurring at a solid radioactive waste disposal area. Northwest Sci 60(3) 154-165. 

Arthur WJ, Markham OD, Groves CR, et al. 1987. Radionuclide export by deer mice at a solid radioactive waste disposal area in southeastern Idaho. Health Phys 52(l) 45-53. 

Essington EH, Fowler EB, Polzer WL. 1981. The interactions of low-level, liquid radioactive wastes with soils 2. Differences in radionuclide distribution among four surface soils. Soil Sci 132(1) 13-18. 

Janke DH, Arthur WJ. 1985. Radionuclide transport by cottontail rabbits at a radioactive waste disposal area. Northwest Sci 59(3) 221-229. 

Kennedy WE, Cadwell LL, McKenzie DH. 1985. Biotic transport of radionuclides from a low-level radioactive waste site. Health Phys 49(1) 11-24. 

Bryan, G. W., Preston, A. and Templeton, W. L. (1966). Accumulation of radionuclides by aquatic organisms of economic importance in the United Kingdom, page 623 in Disposal of Radioactive Wastes into Seas, Oceans and Surface Waters, IAEA Publication No. STI/PUB/125 (International Atomic Energy Agency, Vienna). 

Nuclear power produces spent fuel that contains radionuclides that will emit radiation for hundreds and thousands of years. At present, they are being stored underground indefinitely in heavy, shock-proof containers. These containers could be stolen or may corrode with time, or leak as a result of earthquakes and tremors. Transportation and reprocessing accidents could cause environmental contamination. One solution is for the United States to go to breeder reactors, as has been done in other countries, to reduce the level and amount of radioactive waste. 

By combining the findings of Cacchione, Drake and the results reported here, a coherent model can be proposed to explain the deposition inventory of the radionuclides. The down-canyon current transports large quantities of sediment toward the radioactive waste disposal site at 4000 m. Within the upper canyon, fine material is transported the furthest. Near the mouth of the canyon, sediment erosion of the walls occurs due to the down-canyon currents meeting a proposed opposing on-shore bottom current. The eroded material from the walls is transported and the finer material is deposited in eddies formed where the two currents meet. 

Schell, W. R., and Sugai, S., Radionuclides at the U. S. Radioactive waste disposal site near the Farallon Islands, Health Physics, 39 475-496 (1980). 

Sorption can significantly diminish the mobility of certain dissolved components in solution, especially those present in minor amounts. Sorption, for example, may retard the spread of radionuclides near a radioactive waste repository or the migration of contaminants away from a polluting landfill (see Chapters 21 and 32). In acid mine drainages, ferric oxide sorbs heavy metals from surface water, helping limit their downstream movement (see Chapter 31). A geochemical model useful in investigating such cases must provide an accurate assessment of the effects of surface reactions. 

Radioactive substances (radionuclides) are known health hazards that emit energetic waves and/or particles that can cause both carcinogenic and noncarcinogenic health effects. Radionuclides pose unique threats to source water supplies and chemical processing, storage, or distribution systems because radiation emitted from radionuclides in chemical or industrial waste systems can affect individuals through several pathways by direct contact with, ingestion or inhalation of, or external exposure to, the contaminated waste stream. While radiation can occur naturally in some cases due to the decay of some minerals, intentional and nonintentional releases of... 

Disposal of spent nuclear fuel and other radioactive wastes in the subsurface and assessment of the hazards associated with the potential release of these contaminants into the environment require knowledge of radionuclide geochemistry. Plutonium (Pu), for example, exhibits complex environmental chemistry understanding the mechanism of Pu oxidation and subsequent reduction, particularly by Mn-bearing minerals, is of major importance for predicting the fate of Pu in the subsurface. 

Owing to their high surface area and affinity for many ions, Fe oxides are used in water treatment processes (see Chap. 21). Coprecipitation of radionuclides with Fe oxides at pH > 10 can be used to decontaminate low level, radioactive waste. 

High concentration of nontargeted ionic contaminants may reduce the efficiency of the 3M Empore extraction disk. Due to the high loading capabilities of the Empore membranes, the radionuclide concentration on the filters must be monitored to ensure that the membranes do not exceed the limits for low-level radioactive waste. 

Ceramicrete is an ex situ stabilization technology that uses chemically bonded phosphate ceramics to stabilize low-level radioactive waste and hazardous waste containing radionuclides and heavy metals. The technology mixes phosphates with acidic solution, causing an exothermic reaction similar to that used in forming concrete. But while concrete is based on relatively weak hydrogen and van der Waals bonding, Ceramicrete uses a combination of ionic, covalenf and van der Waals bonds to stabilize contaminants. 

The reactors at Oklo and Bangombe provide great confidence in the feasibility of radioactive waste isolation. The reactors operated for 800 000 years and after two billion years, most of the radionuclides (except for iodine that has migrated away completely) and/or their decay products have migrated only a few metres. 

Our results show that coprecipitation of the REE with phosphate removed Ce, Pr, Nd, Sm, and Eu more easily from the brine than other REE. This finding might be of importance for the mobility of trivalent Am and Cm in a radioactive waste salt repository, because for these elements, owing to their almost identical ionic radii, an almost analogous geochemical behaviour is expected as for Sm and Nd (Choppin 1983 Krauskopf 1986). These radionuclides would, in the case of a leaking HLW salt repository, probably be retained when phosphate minerals are present in the backfill material. 

Radioactive waste management is a quite mature field of application of basic geoscientific disciplines. As we will discuss in forthcoming sections, the long-term performance and henceforth the safety of radioactive waste disposal systems, deeply relies on the basic principles that control the release, mobility, and transport of the chemical elements in the geosphere. In the context of radioactive waste disposal, the waste matrix constitutes the innermost of the barriers that may control the release and ulterior transport of radionuclides through the ground-water systems. 

Equilibrium thermodynamics is one of the pillars supporting the safety analyses of radioactive waste repositories. Thermodynamic constants are used for modelling reference porewaters, calculating radionuclide solubility limits, deriving case-specific sorption coefficients, and analysing experimental results. It is essential to use the same data base in all instances of the modelling chain in order to ensure internally consistent results. 

Review work for future updates of our data base should focus on iron compounds and complexes. The iron system is thought to be of crucial importance for characterizing the redox behaviour of radioactive waste repositories. Preliminary applications have indicated that the lack of data for the iron system is a source of major uncertainties associated with the definition of an oxidation potential. Hence, there is little use in developing sophisticated redox models for radionuclides as long as the dominant redox processes in a repository are poorly known. 

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