In 1976, the U.S. Department of Energy (DOE) established the National Waste Terminal Storage (NWTS) program. The objective of this program is to develop and provide the capability for the long-term disposal of high-level and transuranic nuclear wastes. The present U.S. nuclear waste disposal strategies envision the isolation of such wastes in deep underground geologic repositories. Technology development in support of the NWTS program includes the formulation and management of a strong basic science program to develop an appropriate data base to aid in understanding the key geological processes and other related phenomena involved in this undertaking. A site selection for the repository is to be made in the mid-1980's and repository operation could begin in the 1990's. Several geological environments encompassing a number of emplacement media will be examined before final site selections are made.

INTRODUCTION/BACKGROUND

Radioactive wastes are produced in a variety of ways. Major sources of such wastes are the mining of uranium ore, defense-related nuclear activities, and the operation of commercial nuclear power reactors. Other sources include the nuclear wastes generated in various research investigations and in medical diagnostics and therapy with radio-pharmaceuticals. The disposal of radioactive wastes is perceived to be a significant problem. Radioactive wastes are generally subdivided into five categories:

  1. High Level Wastes (HLW) -- These wastes are either intact nuclear fuel assemblies or the wastes generated during fuel reprocessing. The reprocessing wastes contain virtually all fission products and actinides not separated during reprocessing.

  2. Transuranic Wastes (TRU) -- These wastes also arise in reprocessing of fuel or in weapons' fabrication. They are currently defined as material containing more than 10 nanocuries of transuranic activity per gram of material.

  3. Low Level Wastes (LLW) -- These wastes contain less than 10 nanocuries of transuranic activity per gram or they may be free of transuranics altogether.

  4. Uranium Mine & Mill Tailings -- These are residues from mining and milling operations.

  5. Gaseous Effluents -- These wastes are usually released into the biosphere and thus become diluted and dispersed.

In Table I, estimates for the current U.S. nuclear waste inventories and projections through the year 2000 are given. Waste quantities are given in units of volume (thousands of cubic meters). Uranium mine and mill tailings and explicit estimates of decontamination and decommissioning (D&D) wastes are not included in the table. D&D wastes pose special technical and occupational exposure problems. The disposal requirements for this class of wastes cannot be simply specified since they will differ for particular sites and facilities. Evaluations will have to be done on a case-by-case basis. By far the most challenging aspect of the radioactive waste management problem deals with the disposal of high-level and transuranic nuclear wastes, including spent fuel elements from commercial power reactors. To develop and provide the capability for the long-term disposal of these high-level nuclear wastes, the U.S. Department of Energy (DOE) established the National Waste Terminal Storage (NWTS) program in 1976.

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