Illustration of sampling-based approaches to the calculation of expected dose in performance assessments for the proposed high level radioactive waste repository at Yucca Mountain, Nevada.

Abstract

A deep geologic repository for high level radioactive waste is under development by the U.S. Department of Energy at Yucca Mountain (YM), Nevada. As mandated in the Energy Policy Act of 1992, the U.S. Environmental Protection Agency (EPA) has promulgated public health and safety standards (i.e., 40 CFR Part 197) for the YM repository, and the U.S. Nuclear Regulatory Commission has promulgated licensing standards (i.e., 10 CFR Parts 2, 19, 20, etc.) consistent with 40 CFR Part 197 that the DOE must establish are met in order for the YM repository to be licensed for operation. Important requirements in 40 CFR Part 197 and 10 CFR Parts 2, 19, 20, etc. relate to the determination of expected (i.e., mean) dose to a reasonably maximally exposed individual (RMEI) and the incorporation of uncertainty into this determination. This presentation describes and illustrates how general and typically nonquantitive statements in 40 CFR Part 197 and 10 CFR Parts 2, 19, 20, etc. can be given a formal mathematical structure that facilitates both the calculation of expected dose to the RMEI and the appropriate separation in this calculation of aleatory uncertainty (i.e., randomness in the properties of future occurrences such as igneous and seismic events) and epistemic uncertainty (i.e., lack of knowledge about quantities that are poorly known but assumed to have constant values in the calculation of expected dose to the RMEI).

Toward a more rigorous application of margins and uncertainties within the nuclear weapons life cycle : a Sandia perspective.

“…However, not all high-consequence issues have requirements that explicitly state a confidence that includes uncertainties. Some high-consequence issues of national importance (e.g., nuclear power safety [Helton and Breeding 1993]; geologic disposal of transuranic radioactive wastes, WIPP [Helton et al 1999]; and geologic disposal of highlevel radioactive wastes, Yucca Mountain [Helton and Sallaberry 2007]) involve decisions that are tied to some measure of central tendency (mean or median) and are simply "informed" by the required treatment of uncertainties.…”

Ideas underlying quantification of margins and uncertainties(QMU): a white paper.

“…Sandia has led the application of such methodologies in quantitative risk assessments of nuclear power (Breeding et al, 1992;Helton and Breeding, 1993) and in development of the quantitative performance assessment for the Waste Isolation Pilot Plant (WIPP) (Helton et al, 2000a(Helton et al, , 2000b. Sandia has recently been named the lead technical laboratory for the Yucca Mountain repository, essentially to apply the same decision methodologies there that were applied to WIPP (Helton and Sallaberry, 2006). In our view, QMU is a customized form and application of these past RIDA methodologies to a class of decision problems that are needed for the nuclear stockpile lifecycle.…”

“…The traditional approach to separated aleatory and epistemic uncertainty quantification in NRC and WIPP QRAs has been a second-order probability technique (see Helton, 1993Helton, , 1994Helton, , 1999Helton, , 2003Helton and Breeding, 1993;Helton and Burmaster, 1996;Helton et al, , 2000aHelton et al, , 2000bOberkampf, 2004, 2005;and Helton and Sallaberry, 2006). This is also called "probability of frequency," as mentioned above.…”