RESULTS OF THE PERFORMANCE ASSESSMENT FOR THE CLASSIFIED TRANSURANIC WASTES DISPOSED AT THE NEVADA TEST SITE (1)

摘要

Most transuranic (TRU) wastes are destined for the Waste Isolation Pilot Plant (WIPP). However, the TRU wastes from the cleanup of U.S. nuclear weapons accidents are classified for national security reasons and cannot be disposed in WIPP. The U.S. Department of Energy (DOE) sought an alternative disposal method for these "special case" TRU wastes and from 1984 to 1987, four Greater Confinement Disposal (GCD) boreholes were used to place these special case TRU wastes a minimum of 21 m (70 ft) below the land surface and a minimum of 200 m (650 ft) above the water table. The GCD boreholes are located in arid alluvium at the DOE's Nevada Test Site ( NTS). Because of state regulatory concerns, the GCD boreholes have not been used for waste disposal since 1989. DOE requires that TRU waste disposal facilities meet the U.S. Environmental Protection Agency’s (EPA’s) requirements for disposal of TRU wastes, which are contained in 40 CFR 191. This EPA standard sets a number of requirements, including probabilistic limits on the cumulative releases of radionuclides to the accessible environment for 10,000 years. The DOE Nevada Operations Office (DOE/NV) has contracted with Sandia National Laboratories (Sandia) to conduct a performance assessment (PA) to determine if the TRU waste emplaced in the GCD boreholes complies with the EPA’s requirements. Sandia has completed the PA using all available information and an iterative PA methodology. This paper overviews the PA of the TRU wastes in the GCD boreholes [1]. As such, there are few cited references in this paper and the reader is referred to [1] and [2] for references. The results of the PA are that disposal of TRU wastes in the GCD boreholes easily complies with the EPA's 40 CFR 191 safety standards for disposal of TRU wastes. The PA is undergoing a DOE Headquarters (DOE/HQ) peer review, and the final PA will be released in FY2001 or FY2002.