Precision spectroscopy with reactor antineutrinos

In this work we present an accurate parameterization of the antineutrino flux produced by the isotopes ${}^{235}\mathrm{U}$, ${}^{239}\mathrm{P}\mathrm{u}$, and ${}^{241}\mathrm{P}\mathrm{u}$ in nuclear reactors. We determine the coefficients of this parameterization, as well as their covariance matrix, by performing a fit to spectra inferred from experimentally measured beta spectra. Subsequently we show that flux shape uncertainties play only a minor role in the KamLAND experiment, however, we find that future reactor-neutrino experiments to measure the mixing angle ${\theta }_{13}$ are sensitive to the fine details of the reactor-neutrino spectra. Finally, we investigate the possibility to determine the isotopic composition in nuclear reactors through an antineutrino measurement. We find that with a three month exposure of a 1 ton detector the isotope fractions and the thermal reactor power can be determined at a few percent accuracy, which may open the possibility of an application for safeguard or nonproliferation objectives.