An improved criticality alarm system

The Rocky Flats Plant near Golden, Colorado, is the primary facility for the production of plutonium components used in the US arsenal of nuclear weapons. There are ten production buildings on the plant site with neutron-based criticality alarm systems. These systems have been in operation for the past seventeen years. Changes in the interpretation of ANSI standards and US Department of Energy orders have precipitated an evaluation of detector sensitivity and placement criteria. As a result of this evaluation, improvements in detector design and calibration have improved detector sensitivity by a factor of six. Testing performed on the design defined a minimum sensitivity as required by ANSI 8.3 and provided information for saturation and survivability for a fission event up to 1*10/sup 17/ fissions in 80 mu s. A rigorous testing and calibration program has been developed and is in place. Neutron sensitivity is certified at a nearby reactor.<>