Components of Antineutrino Emission in Nuclear Reactor

Abstract

New ${\barν_e},e$ scattering experiments aimed for sensitive searches of the $ν_e$ magnetic moment and projects to explore small mixing angle oscillations at reactors call for a better understanding of the reactor antineutrino spectrum. Here we consider six components, which contribute to the total ${\barν_e}$ spectrum generated in nuclear reactor. They are: beta decay of the fission fragments of $^{235}$U, $^{239}$Pu, $^{238}$U and $^{241}$Pu, decay of beta-emitters produced as a result of neutron capture in $^{238}$U and also due to neutron capture in accumulated fission fragments which perturbs the spectrum. For antineutrino energies less than 3.5 MeV we tabulate evolution of ${\barν_e}$ spectra corresponding to each of the four fissile isotopes vs fuel irradiation time and their decay after the irradiation is stopped and also estimate relevant uncertainties. Small corrections to the ILL spectra are considered.