Features, Events, and Processes for the Total System Performance Assessment: Methods

The purpose of this methods report is to document: (1) the origin, and the methods used in the development of a comprehensive list of features, events, and/or processes (FEPs) that could potentially affect the postclosure performance of the Yucca Mountain disposal system; (2) the methodology and guidance used to screen FEPs for inclusion or exclusion from Total System Performance Assessment for the License Application (TSPA-LA) analysis; (3) the methodology and guidance used to create scenario classes; and (4) compliance with NUREG-1804 (NRC 2003. [DIRS 163274]) acceptance criteria outlined in Section 4.2.1. The conclusions drawn from this report include a list of FEPs identified for consideration in the TSPA analysis, criteria used to screen the FEPs for inclusion/exclusion in the TSPA-LA analysis, guidance to develop the scenario class designations, and, text describing compliance of these activities with the applicable acceptance criteria.
A performance assessment is required to demonstrate compliance with the postclosure performance objective for the U.S. Department of Energy (DOE) Yucca Mountain Project (YMP) as stated in 10 CFR 63.2 [DIRS 178394; DIRS 180319]. A performance assessment means an analysis that:
(1) Identifies the features, events, processes (except human intrusion), and sequences of events and processes (except human intrusion) that might affect the Yucca Mountain disposal system and their- probabilities of occurring;
(2) Examines the effects of those features, events, processes, and sequences of events and processes upon the performance of the Yucca Mountain disposal system; and
(3) Estimates the dose incurred by the reasonably maximally exposed individual, including the associated uncertainties, as a result of releases caused by all significant features, events, processes, and sequences of events and processes, weighted by their probability of occurrence.