  Recent measurements of the reactor antineutrino emission show that there
exists a spectral excess (the "bump") in the 5-7 MeV region when compared to
the Huber-Muller prediction based on the conversion method. Analysis within an
alternate prediction technique, the summation method, suggests that the bump
could be due to excess contributions from a certain few of the beta-decaying
fission products. However, it has been shown that when updated fission yield
values are used in the summation method, the predicted excess vanishes. In the
present preliminary study, fission yields for nuclides suspected of causing the
neutrino spectral bump are investigated using gamma-ray spectroscopy of U-235
and Pu-239 samples freshly irradiated using the High Flux Isotope Reactor. For
several of the suspect nuclides, the derived fission yields are consistent with
JEFF3.3 fission yield library. The exception is the case of Cs-140 from Pu-239,
where the discrepancy between the fitted and expected values suggests a
potential error in the fission yield library. This highlights the importance of
using accurate nuclear data libraries in the analysis of the reactor
antineutrino spectra, and the need for ongoing efforts to improve these
libraries.
