Results of fission products β decay properties measurements performed with a total absorption spectrometer

β-decay properties are usually determined by measuring, with high resolution Ge crystals, the intensity and energy of γ-rays emitted after the beta decay. In the case of large Q_β, or complex de-excitation pattern, it happens that some transitions are missed due to the low efficiency of Germanium detectors for high energy gammas or high multiplicity decay cascades. This leads to an overestimation of the high energy part of the β spectra and the anti-neutrino ones. This is called the Pandemonium effect. Some of the data present in nuclear databases suffer from the distortion caused by this effect. A way to avoid the Pandemonium effect is to use a Total Absorption Spectrometer (TAS), this detector is a 4π calorimeter constituted of one large or segmented crystals and with the particularity of having a cascade detection efficiency close to 100%. A TAS device has been built and calibrated with ¹³⁷Cs, ⁶⁰Co and ^22-24Na sources. A test performed on ⁹²Rb shows that we have a good agreement between the simulated spectrum and the experimental one. The use of TAS for β-decay properties will help to assess the decay heat (or residual power) of reactors