Distribution of Fission Yields for Fission Spectrum Neutron-Induced Fission of Uranium-238

The mass-yield distribution for the neutroninduced fission of 238U by degraded fission spectrum neutrons with an average energy of 1.52 MeV has been measured radiochemically for 26 mass chains in the region A = 89 to 153. Germanium-lithium gamma-ray spectroscopy coupled with beta-particle counting techniques was used to determine the absolute activities of each nuclide measured. The absolute cumulative fission yield of mass chain 140 (140Ba - 140La) was determined to be 6.07 ± 0.24%, and all other reported yields were measured relative to that value. Measured yields ranged from a maximum of 6.33 ± 0.55% for 103Ru on the light mass wing and 6.54 ± 0.28% for 133I on the heavy mass wing to a minimum of 0.030 ± 0.007% for 121Sn in the valley region. Results from this investigation provide a consistent set of cumulative mass yields from 238U fission induced by a well-characterized neutron spectrum.