$\beta$-Decay Studies of Mass 104 Isotopes Using MTAS

Approximately 8\% of the heat produced in a nuclear reactor comes from decay chains of fission products. $\gamma$ radiation emitted in these decays is commonly referred to as “decay heat.” In order to model decay heat, accurate knowledge of $\beta$-feeding intensities and following gamma radiation is needed. This includes ground-state feeding, excited-state feeding, as well as $\beta$-delayed neutron emission. Previous high-precision measurements suffer from low detection efficiency and are thus susceptible to the so called pandemonium effect resulting in inaccurate decay patterns. The Modular Total Absorption Spectrometer (MTAS) achieves a high detection efficiency for $\gamma$ rays by utilizing one ton of NaI scintillators. In addition to being sensitive to $\gamma$ rays associated with the pandemonium effect, total absorption spectroscopy with MTAS allows for the measurement of ground-state to ground-state feeding intensities and $\beta$-delayed neutron emission branching ratios. $\beta$-feeding intensities of $^{104}$Nb, $^{104}$Mo, and $^{104}$Tc were measured with MTAS at Argonne National Laboratory's CARIBU facility. The results of these measurements as well as a comparison to previous measurements will be presented here.