Determination of -decay feeding patterns of ⁸⁸Rb and ⁸⁸Kr using the Modular Total Absorption Spectrometer at ORNL HRIBF

Precise determination of ground-state feeding in the beta decay of fission products is an important but challenging component in modeling reactor antineutrino flux and reactor decay heat. The Modular Total Absorption Spectrometer (MTAS) is a versatile NaI(T1) detector array that determines the true beta-decay pattern free from the pandemonium effect, including precise ground-state feeding intensities. In this paper, we report MTAS results of the beta feeding intensities of Rb-88 and Kr-88, fission products with large cumulative yields in nuclear reactors. By comparing MTAS results with previous measurements, Rb-88 provides a validation of MTAS's ability to determine ground-state feedings in beta decays, while the precision of Kr-88 ground-state feeding is improved when compared with the Evaluated Nuclear Structure Data File (ENSDF). The investigation of sources that contribute to beta feeding branching uncertainties in MTAS experiments is discussed in detail. Lastly, the deconvolution of Rb-88 decay spectra suggests that MTAS can distinguish an allowed beta spectral shape from a first forbidden unique beta spectral shape.