Analysis of neutron yields and energy spectra from spent molten-salt reactor fuel

The yields and energy spectra of primary neutrons emitted from spent molten-salt fuel have been analyzed as a function of cooling time. It was found that (α, n) reactions made a major contribution to neutron production in the Th-based molten-salt fuel, in contrast to the case of U-fuels for LWRs where spontaneous fission was a main contributor. One of the consequences of this was that the neutron yield continued to increase to reach a maximum 8-9 yr after irradiation, reflecting variation of the concentrations of strong α-emitters in the Th series. This peculiar characteristic requires that attention should be paid to neutron- as well as γ-shielding of storage facilities of spent molten-salt fuel. (author)