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Abstract not provided.

The U.S. Department of Energy (DOE) is responsible for disposing of a variety of radioactive and mixed wastes, some of which are considered special-case waste because they do not currently have a clear disposal option. It may be possible to dispose of some of the DOE`s special-case waste using greater confinement disposal techniques at the Nevada Test Site (NTS). The DOE asked Sandia National Laboratories to investigate this possibility by performing system configuration analyses. The first step in performing system configuration analyses is to estimate the characteristics of special-case waste that might be destined for disposal at the NTS. The objective of this report is to characterize this special-case waste based upon information available in the literature. No waste was sampled and analyzed specifically for this report. The waste compositions given are not highly detailed, consisting of grains and curies of specific radionuclides per cubic meter. However, such vague waste characterization is adequate for the purposes of the system configuration task. In some previous work done on this subject, Kudera et al. [1990] identified nine categories of special-case radioactive waste and estimated volumes and activities for these categories. It would have been difficult to develop waste compositions based on the categories proposed by Kudera et al. [1990], so we created five groups of waste on which to base the waste compositions. These groups are (1) transuranic waste, (2) fission product waste, (3) activation product waste, (4) mobile/volatile waste, and (5) sealed sources. The radionuclides within a given group share common characteristics (e.g., alpha-emitters, heat generators), and we believe that these groups adequately represent the DOE`s special-case waste potentially destined for greater confinement disposal at the NTS.

The Department of Energy`s Nevada Operations Office (DOE/NV) has disposed of a small quantity of transuranic waste at the Greater Confinement Disposal facility in Area 5 of the Nevada Test Site. In 1989, DOE/NV contracted with Sandia National Laboratories to perform a preliminary performance assessment of this disposal facility. This preliminary performance assessment consisted of analyses designed to assess the likelihood of complying with Environmental Protection Agency standards for the disposal of transuranic waste, high level waste, and spent fuel. The preliminary nature of this study meant that no other regulatory standards were considered and the analyses were conducted with specific limitations. The procedure for the preliminary performance assessment consisted of (1) collecting information about the site, (2) developing models based on this information, (3) implementing these models in computer codes, (4) performing the analyses using the computer codes, and (5) performing sensitivity analyses to determine the more important variables. Based on the results of the analyses, it appears that the Greater Confinement Disposal facility will most likely comply with the Environmental Protection Agency`s standards for the disposal of transuranic waste. The results of the sensitivity analyses are being used to guide site characterization activities related to the next iteration of performance assessment analyses for the Greater Confinement Disposal facility.

Both the US Environmental Protection Agency (EPA) and the US Nuclear Regulatory Commission (NRC) have promulgated regulations regarding the performance of geologic repositories for the disposal of high-level nuclear waste. One of the responsibilities of the US Department of Energy (DOE) is to demonstrate compliance with the appropriate regulations. The DOE will most likely use extensive numerical modeling to show compliance with the various quantitative requirements. These analyses will then be evaluated by the NRC. There are different levels of evaluation: peer review, conservative estimates,used of existing models/codes, and development of models/codes by the NRC. The intensity of the review will vary from analysis to analysis, depending on the importance of the analysis, the acceptability of the conceptual model behind the analysis and the solution technique used, and the potential for increasing confidence in the system description, should the NRC decide to develop its own models/codes. An appropriate level of review can be determined by applying these four criteria in a specific manner. 24 refs.