Characterization of stochastic uncertainty in the 1996 performance assessment for the Waste Isolation Pilot Plant

The 1996 performance assessment (PA) for the Waste Isolation Pilot Plant (W IPP) maintains a separation between stochastic (i.e. aleatory) and subjecti ve (i.e. epistemic) uncertainty, with stochastic uncertainty arising from t he possible disruptions that could occur at the WIPP over the 10,000-yr reg ulatory period specified by the US Environmental Protection Agency (40 CFR 191, 40 CFR 194) and subjective uncertainty arising from an inability to un iquely characterize many of the inputs required in the 1996 WIPP PA. The ch aracterization of stochastic uncertainty is discussed, including drilling i ntrusion time, drilling location, penetration of excavated/nonexcavated are as of the repository, penetration of pressurized brine beneath the reposito ry, borehole plugging patterns, activity level of waste, and occurrence of potash mining. Additional topics discussed include sampling procedures, gen eration of individual 10,000-yr futures for the WIPP, construction of compl ementary cumulative distribution functions (CCDFs), mechanistic calculation s carried out to support CCDF construction, the Kaplan/Ganick ordered tripl e representation fur risk, and determination of scenarios and scenario prob abilities. Published by Elsevier Science Ltd.