Measurement of the Ratio of Cumulative Spectra of Beta Particles from 235U and 239Pu Fission Products for Solving Problems of Reactor-Antineutrino Physics

The first cycle of measurements of the ratio of cumulative spectra of beta particles originating from the isotopes U-235 and Pu-239 undergoing thermal-neutron-induced fission was performed. It is found that the curve obtained from our present measurement of the U-235/Pu-239 ratio of beta-particle spectra lies 5% lower than the analogous curve following from the measurement of a group from Institute LaueLangevin (ILL). The present analysis reveals that this is due to an erroneous 5% overestimation of the U-235 beta-particle spectrum measured by the ILL group. As a consequence, the results obtained for the U-235 (nu) over bar (e) spectrum at the production instant via a reconstruction from the cumulative spectrum of beta particles from U-235 also turned out to be overestimated by 5%. These data explain the effect of the reactor antineutrino anomaly.

Automated summary

The first cycle of measurements was conducted for the ratio of cumulative spectra of beta particles from U-235 and Pu-239 undergoing thermal-neutron-induced fission. The results revealed a 5% discrepancy between the current measurement and a group from Institute LaueLangevin (ILL). Further analysis showed that this was due to an erroneous overestimation of the U-235 beta-particle spectrum by the ILL group, leading to a 5% overestimation in the results.