Extensive work has been carried out by the US Department of Energy (DOE) in the development of a proposed geologic repository at Yucca Mountain (YM), Nevada, for the disposal of high-level radioactive waste. In support of this development and an associated license application to the US Nuclear Regulatory Commission (NRC), the DOE completed an extensive performance assessment (PA) for the proposed YM repository in 2008. This presentation describes uncertainty and sensitivity analysis results for the seismic ground motion scenario class and the seismic fault displacement scenario class obtained in the 2008 YM PA. The following topics are addressed for the seismic ground motion scenario class: (i) engineered barrier system conditions; (ii) release results for the engineered barrier system, unsaturated zone, and saturated zone; (iii) dose to the reasonably maximally exposed individual (RMEI) specified in the NRC regulations for the YM repository; and (iv) expected dose to the RMEI. In addition, expected dose to the RMEI for the seismic fault displacement scenario class is also considered. The present article is the part of a special issue of Reliability Engineering and System Safety devoted to the 2008 YM PA; additional articles in the issue describe other aspects of the 2008 YM PA.
Uncertainty and sensitivity analysis are fundamental components of the 2008 performance assessment (PA) conducted by the US Department of Energy (DOE) for the proposed high-level radioactive waste repository at Yucca Mountain (YM), Nevada [1] and [2]. The following presentation describes the uncertainty and sensitivity analysis results obtained for the seismic scenario classes [3] in the 2008 YM PA. Additional presentations describe the uncertainty and sensitivity analysis results obtained in the 2008 YM PA for the nominal scenario class [4] and [5], early failure scenario classes [6] and [7], igneous scenario classes [8] and [9], and all scenario classes collectively [10].
The uncertainty and sensitivity techniques in use are described in Section 2 of Ref. [5]. The presented uncertainty and sensitivity analysis results are obtained with the first of the three replicated Latin hypercube samples (LHSs) described in Sections 11 and 12 of Ref. [2]. This is the same LHS used in the generation of the expected dose results for the seismic scenario classes [3] and also in the generation of results for the other scenario classes under consideration [4], [5], [6], [7], [8] and [9]. Descriptions of the epistemically uncertain analysis inputs under consideration and references to additional sources of information on these variables are given in Appendix B of Ref. [2]. Further, additional information on the uncertainty and sensitivity techniques in use is available in several reviews [11], [12], [13] and [14].
The following topics are considered in this presentation for the seismic ground motion scenario class for the time interval [0, 20,000 yr]: engineered barrier system (EBS) conditions (Section 2), release from the EBS (Section 3), release from the unsaturated zone (UZ) (Section 4), release from the saturated zone (SZ) (Section 5), and dose to the reasonably maximally exposed individual (RMEI) (Section 6). Corresponding results are not presented for the time interval [0, 106 yr]. As described in Ref. [3], a sampling-based (i.e., Monte Carlo) procedure is used to propagate aleatory uncertainty for this time interval. Due to the use of this method, results were not obtained conditional on common elements from the sample space for aleatory uncertainty; as a result, sensitivity results for the effects of epistemic uncertainty analogous to those presented in 2, 3, 4, 5 and 6 are not available for the time interval [0, 106 yr]. However, the uncertainty and sensitivity results for expected dose to the RMEI are available for both time intervals (Section 7). In addition, expected dose to the RMEI for the seismic fault displacement scenario class is also considered (Section 8). The presentation then ends with a summary discussion (Section 9).
The primary focus of this presentation is on the uncertainty and sensitivity analysis results obtained for the seismic scenario classes. Summary descriptions of the models that underlie these results are given in Ref. [15] and in Section 6 of Ref. [1], and more detailed descriptions are available in the reports cited in Refs. [1] and [15] and in Appendix B of Ref. [2]. Further, an extensive description of the development process that led to these models is given in Refs. [16], [17], [18], [19], [20], [21], [22], [23], [24] and [25].