It has been speculated by A.C. Hayes and collaborators that the excess of antineutrinos at 5 MeV (known as ”the bump”) could be due to deficient knowledge of the antineutrino spectrum. Cumulative fission product yields play a major role in this calculation and Hayes suggested, in particular, that 238U could be an important contributor to the bump.
Nonetheless, yields from 238U were often neglected in experimental campaigns, and the evaluated values in ENDF-B/VIII.0 date back to the 1990s. In this work we introduce a new effort undertaken at the NNDC to produce updated FY recommended experimental values for fast fission of 238U. This is based on a reevaluation of results from older experiments, and the inclusion of new important datasets produced in the past 30 years. We will show the updated 238U(nfast,f) FY recommended values, and their effects on reactor antineutrino calculations.
The effect of updated 238U Fission Yields on reactor antineutrino spectra