In this Letter, we study the impact of the inclusion of the recently measured beta decay properties of the ${}^{102;104;105;106;107}\mathrm{Tc}$, ${}^{105}\mathrm{Mo}$, and ${}^{101}\mathrm{Nb}$ nuclei in an updated calculation of the antineutrino energy spectra of the four fissible isotopes ${}^{235,238}\mathrm{U}$ and ${}^{239,241}\mathrm{Pu}$. These actinides are the main contributors to the fission processes in pressurized water reactors. The beta feeding probabilities of the above-mentioned Tc, Mo, and Nb isotopes have been found to play a major role in the $\gamma$ component of the decay heat of ${}^{239}\mathrm{Pu}$, solving a large part of the $\gamma$ discrepancy in the 4–3000 s range. They have been measured by using the total absorption technique, insensitive to the pandemonium effect. The calculations are performed by using the information available nowadays in the nuclear databases, summing all the contributions of the beta decay branches of the fission products. Our results provide a new prediction of the antineutrino energy spectra of ${}^{235}\mathrm{U}$, ${}^{239,241}\mathrm{Pu}$, and, in particular, ${}^{238}\mathrm{U}$ for which no measurement has been published yet. We conclude that new total absorption technique measurements are mandatory to improve the reliability of the predicted spectra.

• Received 19 August 2012

DOI:https://doi.org/10.1103/PhysRevLett.109.202504