Research and development of a high-sensitivity non-destructive assay of fissile nuclide by using fast neutron direct interrogation method

Takamine, Jun ; Haruyama, Mitsuo; Takase, Misao; Yamaguchi, Satoshi

When an object including a lot of hydrogen atoms such as the cemented waste is measured by using the conventional active neutron method, radial sensitivity distribution in the region of surface and center is different more than 100 times. Then we developed the method to detect a nuclear fission neutron induced by the neutron which slowed down in the matrix itself, and so performed a position sensitivity difference of 10%. Furthermore, we understood that the background neutron in nuclear fission neutron counting area is great decrease by using SUS-304 instead of graphite as a moderator of conventional detection system. And then, this new system enabled to measure clearance level activity included in cemented waste. Besides, we modified the optimum structure of the detector bank, which enabled to measure precisely even metal compaction waste (the density is 34 g/cm). In this session, we introduce the process of the past research, applied examples, recent results of the research.