Year
2013
Abstract
As a result of the global shortage of Helium-3 (He-3) gas, rationing of He-3 between 2009 and 2011 led to a lack of availability for most applications. During this period, industry and governments initiated programs to develop replacement technologies for neutron detection. While many technologies have been developed, no single technology has emerged as a direct replacement for all applications. One promising technology that has been successfully applied in applications such as neutron detection modules for radiation portal monitors is Boron-10 (B-10) lined proportional counters. These detectors have been shown to meet the neutron sensitivity, gamma discrimination, and environmental requirements of many systems with modest neutron sensitivity requirements; however, in some applications such as safeguards well counters with relatively high neutron efficiency requirements, B-10 lined detectors may not possess the necessary sensitivity. In recent years, He-3 gas has once again become commercially available, albeit in limited quantities and at significant cost. With these considerations, we propose the use of B10Plus+1 detectors, comprised of B-10 lined proportional counters filled with gas mixtures containing small quantities of He-3 gas, to improve the performance of a system while minimizing He-3 consumption and cost. The measured spectral response and neutron sensitivities of various B10Plus+ detectors are reported, and a Monte Carlo study investigating the relationship between a safeguards well counter’s Figure of Merit (FOM), B-10 coating thickness, and He-3 partial fill pressure is presented. The results of initial testing of a B10Plus+ system designed to meet the FOM requirements of the Uranium Neutron Coincidence Collar (UNCL-1) are reported.