On October 1, 2010, the NRC staff began orderly closure of its Yucca Mountain activities. As part of orderly closure, the NRC staff prepared this technical evaluation report (TER), a knowledge management document. This document captures the NRC staff's technical assessment of information presented in DOE's Safety Analysis Report (SAR), dated June 3, 2008, as amended, and supporting information. The TER describes the staff's technical evaluation of the DOE SAR and, in particular, this document (TER Preclosure Volume) provides technical insights on the expected performance of the geologic repository operations area (GROA) during the period of operations (i.e., prior to permanent closure or preclosure period). The TER was developed using the regulations at 10 CFR Part 63 and guidance in the Yucca Mountain Review Plan (YMRP). The TER does not, however, include conclusions as to whether or not DOE satisfies the Commission's regulations.