Keywords: fissile materials, active neutron methods, passive neutron methods, portable pulsed neutron generator, differential die-away technique, He-3 counters, active control, passive control, nuclide composition, nuclear waste, nuclear energy, nuclear power plants, nuclear safety
System of combined active and passive control of fissile materials and their nuclide composition in nuclear wastes
New methods of non-destructive control must be developed and existing ones must be improved in order to solve the problem of control of fissile materials (FMs) in vessels with nuclear wastes, and to provide safe operation of nuclear power plants. This paper considers the application of active methods of control on the basis of DD or DT pulsed neutron generators. These methods are more comprehensive and sensitive than traditional passive methods for detection of neutron and gamma radiation from nuclear materials, such as U-235 and Pu-239. As a particular method for FM control we use a technique of differential die-away of neutrons, detected by He-3 proportional counters. Calculations performed for 60 litres containers showed the high sensitivity of detection of induced fission neutrons (up to 10 mg of U-235) in a graphite matrix and much lower sensitivity of detection for a container with an iron matrix.