On the optimisation of the use of He-3 in Radiation Portal Monitors

Radiation Portal Monitors (RPM) are used to detect illicit trafficking of nuclear or other radioactive material concealed in vehicles, cargo containers or people at strategic check points, such as borders, seaports and airports. Most of them include neutron detectors for the interception of potential plutonium smuggling. The most common technology used for neutron detection in RPM is based on He-3 proportional counters. The recent severe shortage of this rare and expensive gas has created a problem of capacity for manufacturers to provide enough detectors to satisfy the market demand. In this paper we analyse the design of typical commercial RPM and try to optimise the detector parameters in order either to maximise the efficiency using the same amount of He-3 or minimise the amount of gas needed to reach the same detection performance: by reducing the volume or gas pressure in an optimised design.JRC.E.8-Nuclear securit