Year
1989
Abstract
Strict security measures are used to prevent diversion of special nuclear materials (SNM) from the facilities in which they are used or processed. Typical diversion scenarios call for systematic and covert removal of small quantities of SNM, hidden either on the person or in authorized shipments, from the facility. Gamma-ray monitors are used to detect excessive ionizing radiation emitted by personnel and other objects leaving such a facility. The gamma-ray monitors alarm in the presence of gamma radiation but do not identify the radionuclides emitting the radiation. The movement of radionuclides, such as in personnel undergoing in vivo medical therapy, through a gamma portal monitor may occasionally be required. Whenever such a movement alarms a gamma portal, the radionuclide causing the alarm must be precisely identified. We have designed a portable instrumentation system that automatically acquires pulse-height energy spectra from suspect emitters and then identifies the radionuclides emitting the radiation. We have built two such systems at Los Alamos National Laboratory which are used to quickly analyze radiation emitted by plant personnel, waste dumpsters, shipments, and previously unknown sources.