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. It is operated by EG ampersand G under contract to the US Department of Energy (DOE). There are ten production buildings on plant site with neutron based criticality alarm systems. These systems have been in operation for the past seventeen years. Changes in the interpretation of A.N.S.I. standards and DOE 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 A.N.S.I. 8.3 and provided information for saturation and survivability for a fission event of up to 1X1017 fissions in 80 microseconds. A rigorous testing and calibration program has been developed and is in place. Neutron sensitivity is certified at a nearby reactor which is traceable to N.I.S.T