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Report No.

Model design of a compact delayed gamma-ray moderator system using $$^{252}$$Cf for safeguards verification measurements

Rodriguez, D.; Rossi, F.; Takahashi, Toon; Seya, Michio; Koizumi, Mitsuo

Delayed gamma-ray spectroscopy is an active-NDA technique used to determine the composition of HRNM samples by peak-ratio comparison of GRs above 3-MeV from the short-lived fission products. Filtering out the passive GRs from long-lived FPs reduces the DGS signal, so thermal neutrons are used to induce more fission events from fissile nuclides. We are developing a compact system to moderate $$sim$$ 2-MeV neutrons that are easier to moderate than 14-MeV neutrons from DT generators. This work describes the ideal moderator optimization for a $$^{252}$$Cf source that results in $$25.9times10^{-4}$$ cm$$^{-2}$$ $$n_{source}^{-1}$$ passing through the sample space with $$geq$$ 70% of those below 1-eV. Practical modifications resulted in $$leq$$ 20% reductions compared to the optimized design. Evaluations of DGS signals and backgrounds conclude that only a 21-MBq $$^{252}$$Cf source is required.



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Category:Chemistry, Inorganic & Nuclear



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