On the possibility of detecting fissile nuclear materials using coincident gamma rays

Almost every radiation monitor installed at the customs and border control points designed for detection of nuclear fissile materials uses gas neutron counters tracing decay neutrons. They have a low background level, but at the same time small efficiency. This work describes the nuclear fissile materials detection methodology based on the instantaneous gamma-radiation accompanying the decay. The tests results of designed and produced radiation monitors based on this principle to control pedestrian and vehicles are presented