RadiationPortalMonitors(RPMs)areusedtodetectillicittraffickingofnuclearorotherradioactive materialconcealedinvehicles,cargocontainersorpeopleatstrategiccheckpoints,suchasborders, seaportsandairports.Mostofthemincludeneutrondetectorsfortheinterceptionofpotential plutoniumsmuggling. The mostcommontechnologyusedforneutrondetectioninRPMsisbasedon 3He proportional counters.Therecentsevereshortageoft…