The purpose of this document is to evaluate the potential for criticality for the fissile material that could accumulate in the near-field (invert) and in the far-field (host rock) beneath the U.S. Department of Energy (DOE) spent nuclear fuel (SNF) codisposal waste packages (WPs) as they degrade in the proposed monitored geologic repository at Yucca Mountain. The scope of this calculation is limited to the following DOE SNF types: Shippingport Pressurized Water Reactor (PWR), Enrico Fermi, Fast Flux Test Facility (FFTF), Fort St.

The objective of these calculations is to perform intact and degraded mode criticality evaluations of the Department of Energy's (DOE) Fort Saint Vrain (FSV) commercial High Temperature Gas Reactor (HTGR) spent nuclear fuel. This analysis evaluates codisposal in a 5-Defense High-Level Waste (5-DHLW/DOE SNF) Long Waste Package (WP)(CRWMS M&O 2000c, Attachment V), which is to be placed in a potential monitored geologic repository (MGR).