Disposal Criticality Analysis Methodology Topical Report Revision 2

This topical report describes the approach to the risk-informed, performance-based methodology to be used for performing postclosure criticality analyses for waste forms in the Monitored Geologic Repository at Yucca Mountain, Nevada. The risk-informed, performance-based methodology will be used during the licensing process to demonstrate how the potential for postclosure criticality will be limited and to demonstrate that public health and safety are protected against postclosure criticality. The report describes the overall approach used in the methodology, presents performance criteria, and describes the general criticality scenarios. The details of the methodology and modeling approach are documented in separate model reports. The overall validation methods employed for the methods and models used for determining critical configurations, evaluating criticality, estimating probabilities, estimating criticality consequences, and estimating criticality risk are described in this report with the details included in the individual model reports.
The disposal criticality analysis methodology provides a systematic means for evaluating the following through the entire postclosure period of the repository.
(1) The combined system of a waste form, waste package, engineered barrier, and repository for effectiveness in limiting the potential for criticality in the repository
(2) The consequences of any such criticalities
(3) The impact of any consequences on the regulatory performance objectives for the repository.
The design parameters and environment within which the waste forms will reside are currently not fully established and will vary with the detailed waste package design, engineered barrier design, repository design, and repository layout. Therefore, it is not practical to present the full validation of the methodology in this report. The methodology will be fully developed and validated for design applications to which it will be applied for the repository License Application and applicable documents developed in support of licensing activities.
Revision 02 of the topical report was undertaken to incorporate the licensing requirements for disposal of spent nuclear fuel and high-level radioactive wastes in geologic repository at Yucca Mountain identified in the U.S. Nuclear Regulatory Commission’s 10 CFR Part 63 rule Disposal of High-Level Radioactive Wastes in a Proposed Geologic Repository at Yucca Mountain, Nevada, revisit Safety Evaluation Report for Disposal Criticality Analysis Methodology Topical Report1 open items addressed in Revision 01, and to update the documentation of the approach used in the disposal criticality methodology. The U.S. Department of Energy will use the accepted methodology in reports developed in support of licensing activities for the Monitored Geologic Repository at Yucca Mountain, Nevada, to demonstrate the acceptability of proposed systems for limiting the potential for postclosure criticality.
Any sample results presented in this report that were derived from analyses based on specific features of the repository design or performance, which may be subject to change, should not be taken as final. Such sample results are, however, consistent with the present state of knowledge on this subject and neither the analyses nor the sample results are expected to change significantly.