  Recently, three antineutrino experiments at Daya Bay, Double Chooz, and RENO
measured the neutrino mixing angle $\theta_{13}$, each using a nuclear reactor
power plant. However, significant discrepancies were found, both in the
absolute flux and spectral shape. In the reactor, the neutrons have a range of
energies, with different neutron energies generating different fission yields.
The different fission yields may be the reason for the antineutrino spectrum
discrepancies. In our study, the neutron spectrum has been analyzed to
understand the possible reasons for the discrepancies. In comparing results
from the Huber--Muller model, we found that a spectral bump appears in the
energy region from 5--7~MeV. Nevertheless, the differences between the average
antineutrino spectrum and the only-thermal antineutrino spectrum are small.
That is, they are unable to account for this bump. However, in the energy
region of 7--8~MeV, the neutron flux induces a decrease in the antineutron
flux, and therefore, the distribution of the antineutrino spectrum is affected,
especially in the high-energy region.
