Preclosure Criticality Analysis Process Report

The preclosure criticality analysis process described in this technical report provides a systematic approach for determining the need for criticality controls and for evaluating their effectiveness during the preclosure period of the Monitored Geologic Repository at Yucca Mountain, Nevada. This process is appropriate for analyses of the surface and subsurface facility systems including (1) waste form, canister, and waste package handling, (2) waste form aging prior to disposal, (3) waste package preparation for final disposal, and (4) waste package emplacement in the drifts prior to permanent closure. This report describes the approach, performance criteria, and process applications used for preclosure criticality analyses. This process will be used to demonstrate that preclosure criticality is prevented for normal conditions and for off-normal conditions such that no event sequence with a mean probability of occurrence greater than or equal to one chance in 10,000 during the preclosure period will result in an end-state configuration that violates the configuration-specific upper subcritical limit (Section 3).
The preclosure criticality analysis process complies with the U.S. Nuclear Regulatory Commission’s 10 CFR Part 63 rule, Disposal of High-Level Radioactive Wastes in a Geologic Repository at Yucca Mountain, Nevada1. This process also addresses the criticality safety specific review methods and satisfies the acceptance criteria found in Yucca Mountain Review Plan, Final Report2. The U.S. Department of Energy will use this process in facility and process specific reports (i.e., nuclear criticality calculations and safety analyses) developed in support of licensing activities for the Monitored Geologic Repository at Yucca Mountain, Nevada, to demonstrate the acceptability of proposed systems and facilities for preventing and controlling preclosure criticality.