Plutonium detection with a new fission neutron survey meter

The search for illicit trafficking or hidden plutonium sources has become a pressing issue, especially since the breakdown of the former Soviet Union. Plutonium is extremely dangerous and hard to detect over large distances. The /spl alpha/-particles and X-rays which are emitted by plutonium isotopes can easily be shielded by the material itself or by surroundings. Besides a few /spl gamma/'s, the only penetrating radiation emitted by plutonium samples are neutrons from spontaneous fission. Therefore a special neutron survey meter with unrivaled sensitivity for fission neutrons has been newly designed. The hand-held commercially available instrument has an approximate weight of 4 kg and is battery driven. The neutron probe consists of a /sup 3/He proportional counter tube, a moderator and integrated electronics. The sensitivity is sufficient to detect plutonium masses below 100 g at a distance of 1 m within a few seconds.