Total absorption spectroscopy study of the β decay of 86Br and 91Rb

The beta decaysof 86Br and 91Rb have been studied using the total absorption spectroscopytechnique. The radioactive nuclei were produced at the Ion Guide Isotope SeparatorOn-Line facility in Jyvaskyla and further purified using the JYFLTRAP. 86Br and 91Rb are considered to be major contributors to the decay heatin reactors. In addition, 91Rb was used as a normalization point in direct measurements of mean gamma energies released in the beta decayof fission productsby Rudstam et al. assuming that this decay was well known from high-resolution measurements. Our results show that both decays were suffering from the Pandemonium effectand that the results of Rudstam et al. should be renormalized. The relative impact of the studied decays in the prediction of the decay heat and antineutrino spectrum from reactors has been evaluated