An examination of criticality accident alarm coverage of the X-710, X-760 Buildings and the north half of the X-7745-R storage pad at the Portsmouth Gaseous Diffusion Plant

This report summarizes the results of an evaluation of Criticality Accident Alarm System (CAAS) coverage of the X-710 and X-760 buildings and the north half of the X-7745-R storage lot located east of the X-7725 building at the Portsmouth Gaseous Diffusion Plant. In order to evaluate coverage, the facilities were modeled using the Monte Carlo N-Particle Transport Computer Code (MCNP). MCNP was then used to simulate criticality accidents at various locations in the X-710 and X-760 buildings and the north half of the X-7745-R storage lot. The associated neutron flux at current detector locations was calculated. The neutron flux was then converted to an absorbed dose rate (in tissue) and compared with the Portsmouth criticality accident alarm set-point of 5mrad/hr. The parameters defining the simulated criticality accidents have been calculated as ''the minimum accident of concern'' as defined in ANSI Standard ANS 8.3-1986. These calculations are documented in Portsmouth report POEF-SH-31. The results of this evaluation indicate that the X-710 and X-760 buildings and surrounding roads are adequately covered by the CAAS systems that are currently in place in those buildings. The X-7745-R storage pad is also adequately covered by the CAAS in the X-7725 building