Worldwide, significant effort has been expended to develop replacement technologies for 3He-filled proportional counters used as neutron detectors and employed extensively in applications as diverse as Homeland Security portal monitoring to fundamental scientific research. Far less attention has been paid to the specific needs of safeguards measurement systems to meet mission objectives such as international obligations under the Nuclear Non-Proliferation Treaty. The measurement configuration, operational environments, and performance requirements for the typical safeguards assay system are sufficiently different from those of other applications that the new generation of neutron detectors is not generally suitable for use in demanding safeguards applications. To illustrate the performance needs for any viable replacement neutron detector technology, the operational constraints for several typical safeguards measurement systems are considered. Key attributes include achieving adequate efficiency per unit volume and minimal parasitic losses, along with gamma-ray immunity in a unit with high reliability and low maintenance.
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