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The objective of this study is to identify and examine potential mechanisms of radionuclide transport as vapor at a high-level radioactive waste repository located in unsaturated fractured rock. Transport mechanisms and processes have been investigated near the repository and at larger distances. Transport mechanisms potentially important at larger distances include ordinary diffusion, viscous flow and free convection. Ordinary diffusion includes self and binary diffusion, Knudsen flow and surface diffusion. Pressure flow and slip flow comprise viscous flow. Free convective flow results from a gas density contrast. Transport mechanisms or processes dominant near the repository include ordinary diffusion, viscous flow plus several mechanisms whose driving forces arise from the non-isothermal, radioactive nature of high-level waste. The additional mechanisms include forced diffusion, aerosol transport, thermal diffusion and thermophoresis. Near a repository vapor transport mechanisms and processes can provide a significant means of transport from a failed canister to the geologic medium from which other processes can transport radionuclides to the accessible environment. These issues are believed to be important factors that must be addressed in the assessment of specfic engineering designs and site selection of any proposed HLW repository.

An analysis was performed of a Texas gulf coast hazardous waste injection well disposal system. The system was complicated by the presence of a fault which transected the injection interval. The existence of the fault presented the potential for enhanced vertical migration of the injected solutes via a tortuous path of interconnected, highly permeable sand units. Evaluation of this potential necessitated a fully three dimensional model which incorporated the arrangement of the alternating shales and sands and their associated discontinuities. Computer run time and memory limitations compelled a dissection of the problem into components, as well as the utilization of a specific mixture of conservative and realistic assumptions. The analysis indicated that within 10,000 years, the waste would advance vertically no further than one hundred feet into the overlying stratigraphy, and laterally no further than 24,000 feet from the point of injection.

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No description available.

No description available.

No description available.