Detection of shielded or hidden nuclear material

INT is going to equip a transportable container with a detection and identification system for nuclear materials. This container will be equipped with nuclear instrumentation for passive and active nondestructive measurements. For active nondestructive measurements we use a sealed tube 14 MeV neutron generator with and without a moderating assembly between the interrogating neutron source and the object of interest. Because stolen or diverted nuclear material generally may not have a fixed geometry and will not be packaged in standard containers main emphasis is on neutron measurements. With neutrons it is much easier to penetrate possible shielding material or to gain information on the existence of heavy shielding in order to prevent detection. Investigations were performed on the detection of induced fission neutrons and the time structure of the delayed neutrons was measured. In future it is suggested to perform in situ interrogation of suspected boxes with small neutron generator already available. Because the geometry and chemical form of the material inside the box is not known generally and additional shielding may be present data should be acquired for different arrangements of the material and shielding. In this way the identification of the material in a suspect object will be possible by comparison of the measurement results with previous data. Therefore to prohibit nuclear proliferation expertise and measurement systems must be provided to detect diverted or vagabonding nuclear materials quickly and with high significance.