CONCEPTUAL BASIS OF A SYSTEMS PRIORITIZATION METHODOLOGY FOR THE WASTE ISOLATION PILOT-PLANT

A systems prioritization methodology (SPM) is under development at San dia National Laboratories (SNL) to provide guidance to the US Departme nt of Energy (DOE) on experimental programs and design modifications t o be supported in the development of a successful compliance certifica tion application to the US Environmental Protection Agency (EPA) for t he Waste Isolation Pilot Plant (WIPP) for the geologic disposal of tra nsuranic (TRU) waste. The purpose of the SPM is to determine the proba bilities that the implementation of different combinations of experime ntal programs and design modifications, referred to as activity sets, will lead to compliance with 40 CFR 191, Subparts B and C (Environment al Radiation Protection Standards for the Management and Disposal of S pent Nuclear Fuel, High-Level and Transuranic Waste) and 40 CFR 268.6 (Petitions to Allow Land Disposal of a Waste Prohibited under Subpart C of Part 268, which implements the Resource Conservation and Recovery Act, i.e., RCRA). Appropriate tradeoffs between compliance probabilit y, implementation cost and implementation time can then be made in the selection of the activity set to be supported in the development of a licensing application. Determination of compliance probabilities for individual activity sets involves probability spaces for (1) possible outcomes of the experimental programs, (2) uncertainty in analysis inp ut given specific experimental outcomes and (3) possible future occurr ences at the WIPP, and also models for (1) fluid flow in the vicinity of the repository, (2) radionuclide release from the repository due to flowing groundwater, (3) groundwater flow and radionuclide transport in geologic formations overlying the repository, (4) radionuclide rele ase to the surface environment due to cuttings and spallings removal i n the event of a drilling intrusion and (5) transport of RCRA contamin ants in gas and brine. Descriptions are given for the conceptual struc ture of the SPM and the manner in which this structure determines the computational implementation of an example SPM application. Due to the sophisticated structure of the SPM and the computational demands of m any of its components, the overall computational structure must be org anized carefully to provide the compliance probabilities for the large number of activity sets under consideration at an acceptable computat ional cost. Conceptually, the determination of each compliance probabi lity is equivalent to a large numerical integration problem. Published by Elsevier Science Limited.