Geologic disposal evaluations

The result of this effort was an ATW roadmap released by DOE just this week. It concluded that ATW would require a six-year, 281 million R D effort for open technical issues. ATW could complement geologic disposal, and any decision to pursue ATW would follow evaluation of technical, costs, and nonproliferation issues. Whether or not this effort leads to any ATW international collaboration, we are eager to expand international collaboration on nuclear waste issues in general. 

Release rate data from actual radioactive waste forms is needed to evaluate the safety of emplacing nuclear wastes in geologic media. However, in addition to waste form development studies, such as the leach test just described, a comprehensive program was started to obtain release data from candidate waste forms for geologic disposal. 

Siegel M. D. and Erickson K. E. (1986) Geochemical sensitivity analysis for performance assessment of HEW repositories effects of speciation and matrix diffusion. Proceedings of the Symposium on Groundwater Flow and Transport Modeling for Performance Assessment of Deep Geologic Disposal of Radioactive Waste A Critical Evaluation of the State of the Art. Sandia National Eaboratories, Albuquerque, NM, pp. 465-488. 

In several countries formal environmental and safety assessments for deep geological disposal have been carried out (e.g., Sweden, Finland, and Switzerland) or are in progress (e.g., Canada). For the most part, national programs have concentrated on research and development activities to evaluate the safety and feasibility of various design options, the selection of suitable disposal sites, and optimization studies covering safety, environmental, industrial, and economical issues. It is generally estimated that disposal facilities for long-lived waste will not be operational before about 2010-2020. 

Heimann, R.B. (1987) A statistical approach to evaluating durability of a simulated nuclear waste glass, in The Geological Disposal of High-Level Radioactive Wastes (ed. D.G. Brookins), Theophrastus Publ., S.A., Athens, Greece, pp. 181-205. 

Rochelle, C. A., Bateman, K. Macgregor, R., Pearce, J., Savage, D Wetton, P. 1998. The Evaluation of Chemical Mass Transfer in the Disturbed Zone of a Deep Geological Disposal Facility for Radioactive Wastes. IV. The Kinetics of Dissolution of Chlorite and Carbonates at Elevated pH. Nirex Report NSS/R368. 

A comprehensive method to inventory inactive waste disposal sites should integrate all available historic, engineering, geologic, land use, water supply, and public agency or private company records in order to develop a complete and accurate site profile. Detailed information on site contents may not be available but areas of potential impact can be evaluated. Where people or drinking water supplies are affected, further investigation is indicated. 

Because of the ultimate return of waste by-products from disposal sites to the environment, consideration of the toxicity of the wastes is essential. The toxicity of many wastes is not well known and the assigned values are often arbitrary. One approach to this problem of waste classification is to consider the level at which toxicity occurs, i.e. as parts per thousand, million, billion, etc. In evaluating waste for disposal by landfill, the toxicity of the waste should also be related to its decomposition/decay rate. Geologic conditions in many areas may be unsuitable for landfill disposal of some wastes that have slow decomposition/decay rates and contain constituents that are toxic in low concentrations. These wastes may require destructive treatment, deep-well disposal, or shipment to a site with unique geologic conditions that may make it suitable for landfill disposal of the wastes. 

One of the more difficult problems relating to fission-reactor waste disposal is the evaluation of the suitability of a particular site for the long-term storage of actinide by-products from fuel reprocessing. Current U. S. plans call for underground storage in containers placed in a stable geologic environment. 

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