Mass Distribution in the Fission of ²³²Th by Degraded-Fission-Spectrum Neutrons

The mass-yield distribution of fission products following degraded-fission-spectrum neutron-induced fission of ²³²Th was measured by gamma spectrometry for 25 mass chains including mass 138 for the first time for fast fission. Cumulative yields for ^83gSe and ^130gSb were observed, the latter also for the first time for fast fission. In general, the yields for degraded-fission-spectrum neutron-induced fission of ²³²Th were slightly higher in the inner portions of both the heavy and light mass wings than for those from reactor-neutron-induced fission of ²³²Th. This was expected, since the average energy of degraded-fission-spectrum neutrons is slightly above that of reactor neutrons.