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.