  Detection of ~ 0.1-70 GeV prompt gamma-ray emission from the exceptionally
bright gamma-ray burst (GRB) 130427A by the Fermi-Large Area Telescope provides
an opportunity to explore the physical processes of GeV gamma-ray emission from
the GRB jets. In this work we discuss interactions of Iron and Oxygen nuclei
with observed keV-MeV photons in the jet of GRB 130427A in order to explain an
additional, hard spectral component observed during 11.5-33 second after
trigger. The photodisintegration time scale for Iron nuclei is comparable to or
shorter than this duration. We find that gamma rays resulting from the Iron
nuclei disintegration can account for the hard power-law component of the
spectra in the 1-70 GeV range, before the gamma-gamma to electron-positron pair
production with low-energy photons severely attenuates emission of higher
energy photons. Electron antineutrinos from the secondary neutron decay, on the
other hand, can be emitted with energies up to 2 TeV. The flux of these
neutrinos is low and consistent with non-detection of GRB 130427A by the
IceCube Neutrino Observatory. The required total energy in the Iron nuclei for
this hadronic model for GeV emission is approximately 10 times the observed
total energy released in the prompt keV-MeV emission.
