Radiation portal monitors used for interdiction of illicit materials at borders include highly sensitive
neutron detection systems. The main reason for having neutron detection capability is to detect fission
neutrons from plutonium. Most currently deployed radiation portal monitors (RPMs) use neutron
detectors based upon 3 He-filled gas proportional counters, which are the most common large area neutron detector. This type of neutron detector is used in the RPMs installed in international locations made by TSA and others, and in the Ludlum and Science Applications International Corporation RPMs deployed primarily for domestic applications. There is a declining supply of 3 He in the world and, thus, methods to reduce the use of this gas in RPMs with minimal changes to the current system designs and sensitivity to cargo-borne neutrons are being investigated.
Alternative Neutron Detection Testing