UNCERTAINTY AND SENSITIVITY ANALYSIS FOR GAS AND BRINE MIGRATION AT THE WASTE ISOLATION PILOT-PLANT - FULLY CONSOLIDATED SHALT

Uncertainty and sensitivity analysis techniques based on Latin hypercu be sampling, partial correlation analysis, stepwise regression analysi s, and examination of scatterplots are used in conjunction with the BR AGFLO model to examine two-phaseflow (i.e., gas and brine) at the Wast e Isolation Pilot Plant, which is being developed by the U.S. Departme nt of Energy as a disposal facility for transuranic waste, to provide insights on factors that are potentially important in showing complian ce with applicable regulations of the U.S. Environmental Protection Ag ency. Specific regulations include ''Petitions to Allow Land Disposal of a Waste Prohibited Under Subpart C of Part 268'' (40 CFR 268.6), wh ich implements the Resource Conservation and Recovery Act and establis hes maximum environmental concentrations for regulated chemicals such as volatile organic compounds (VOCs) and heavy metals, and ''Environme ntal Standards for the Management and Disposal of Spent Nuclear Fuel, High-Level and Transuranic Radioactive Wastes'' (40 CFR 191, Subpart B ), which places a probabilistic limit on allowable radioactive release s from a disposal facility over a 10 000-yr time period. The primary t opics investigated are (a) gas production due to corrosion of steel, ( b) gas production due to microbial degradation of cellulosics, and (c) gas migration into anhydrite marker beds in The Salado Formation, whi ch is the host unit into which the waste will be emplaced. Gas product ion and movement is of particular importance in establishing complianc e with 40 CFR 268. 6 because of its influence on the movement of VOCs. Important variables identified in the analysis include (a) initial br ine saturation of the waste, (b) stoichiometric terms for corrosion of steel and microbial degradation of cellulosics, and (c) gas barrier p ressure in the anhydrite marker beds.