The Basalt Waste Isolation Project (BWIP) is an ongoing research and engineering effort being conducted by Rockwell Hanford Operations (Rockwell), which is under contract to the United States Department of Energy (DOE). The objectives of this program are to assess the feasibility of and to provide the technology needed to design and construct a licensed commercial nuclear waste repository in the deep basalt formations underlying the Hanford Site. An extensive pre-conceptual design effort was undertaken during 1979 to develop a feasible concept that could serve as a reference design for both surface and underground facilities. The pre-conceptual design utilized existing technology to the greatest extent possible to offer a system design that could be utilized in establishing schedule and cost baseline data, recommend alternatives that require additional study, and develop basic design requirements that would allow evolution of the design process prior to the existence of legislated criteria. This paper provides a description of the concept developed for the subsurface aspects of this nuclear waste repository.

INTRODUCTION

The preconceptual repository design was not site specific, but was based upon a hypothetical site representative of the Columbia River basalts in that portion of the Pasco Basin underlying the Hanford Site. The subsurface facilities were located in the entablature of a major flow approximately 3,200 ft (1,000 m) below the surface. Design followed pre-specified criteria and employed a work breakdown structure to establish a working estimate format.

The repository was designed for an operating life of 23 years at an annual placement rate of 22,500 canisters containing commercially generated spent fuel aged 5 years. The basis for this estimate was storage of all generated fuel with an assumed nuclear generating capacity of 380 GW by the year 2000. In addition, 4,000 containers of low-level or contact-handled waste would be disposed of annually in a dedicated area. An experimental area was included to allow testing of equipment and placement configurations and to permit personnel training. This experimental area might also function as a test facility prior to completion of the full-scale facility.

The primary objective of the preconceptual design effort was to establish requirements for construction and operation of a repository in basalt.

The subsurface facilities of the repository were designed to be compatible with retrieval of the canisters for up to 25 years after emplacement as a design option. Backfilling of the canister storage rooms was planned before the 25-year retrieval period, but should retrieval be necessary, remining of the backfill and resupport of the storage rooms were considered feasible.

The BWIP is presently undertaking the conceptual design of a nuclear waste repository in basalt. While many of the concepts developed during the preconceptual design, such as horizontal waste emplacement, have been rejected at the conceptual stage, the overall preconceptual design gives us an idea of what a repository in basalt might look like.

SHAFTS

Five shafts were selected as the minimum practical number necessary to accomplish the functions of separate air intake and exhaust flows for the development and waste-handling systems and to provide an independent waste-handling shaft.

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