Expert judgment as input to Waste Isolation Pilot Plant performance- assessment calculations. Probability distributions of significant system parameters.

摘要

Performance-assessment calculations are being performed for the Waste Isolation Pilot Plant (WIPP), a planned underground repository in southeastern New Mexico, USA for the disposal of transuranic waste and any hazardous materials that may contaminate the waste. The performance-assessment calculations estimate the long-term radionuclide releases from the disposal system to the accessible environment. The estimation of the releases is probabilistic in nature, requiring system parameters to be described with probability distributions. Because direct experimental data in some areas are presently of insufficient quantity to form the basis for the required distributions, researchers at Sandia National Laboratories have utilized a formalized expert-judgment elicitation procedure. Expert judgment was used to estimate the concentrations in the brines in the repository rooms and drifts of the specific radionuclides and hazardous materials that may be released. The variables representing these concentrations have been shown by sensitivity analyses to be among the set of parameters making the greatest contribution to the uncertainty in WIPP model predictions. Utilizing the available information, the experts developed an understanding of the problem and were formally elicited to obtain probability distributions that characterize fixed, but unknown, quantities. The probability distributions developed by the experts have been incorporated into the performance-assessment data base and will be used in subsequent calculations.