Review of physics methodology of ATR safety analysis

At the request of EG G Idaho, the Pacific Northwest Laboratory (PNL) performed a brief review of the physics methods employed in the safety analyses for the Advanced Test Reactor. PNL determined that the general approach used by EG G was sound. Comparisons were made between the EG G results and a simplified PBL model. These demonstrated good agreement. However, the lack of spacial treatment of the moderator density reactivity coefficient and exclusion of the test loops from the reactivity model were identified as potential problems. In addition to these two concerns, a series of more minor observations were offered to assist EG G in their analyses. 2 refs., 2 figs.