Detector for fissionable material long objects esp. fuel rods - includes layer which selectively attenuates source neutrons

摘要

A device for the non-destructive determination of thermally fissionable nuclides is intended for use on long objects, such as fuel elements. The low-energy neutron source, the irradiation range and the detector range are all mutually spatially sepd. In the detector range the source neutrons and the fission neutrons which are used for detecting the fissionable material first have to pass through a hydrogen-rich, neutron-transporting layer of critical thickness; this layer either itself contains thermal neutron absorber or is separated by a concentrated absorption layer for thermal neutrons from the moderator, which is free from additional neutron absorbers and contains the neutron detectors. Used for new or irradiated fuel, esp. for fuel elements of water reactors and breeder reactors. The device is effective with large, esp. long fuel elements and rods.