Abstract
The β decays of 87Br, 88Br, and 87Kr were measured with the Modular Total Absorption Spectrometer (MTAS) at 91’s Holifield Radioactive Ion Beam Facility (HRIBF). Both bromine isotopes are β-delayed neutron emitters that have large cumulative fission yields and were identified as top-priority cases for total absorption study by the Nuclear Energy Agency in 2007. Our investigations corroborate that the decay schemes of 87Br and 88Br suffer from the so-called pandemonium effect. Unique MTAS properties enable direct neutron measurements. We present MTAS-derived β-delayed neutron spectra, β-delayed neutron emission probabilities of Pn (87Br) = 2.36(24)%, and Pn (88Br) = 6.4(6)%, and the β-delayed neutron transitions intensity of 4(2)% to the first excited 87Kr state, populated in the β-neutron decay of 88Br. Incorporating new data into calculations of the electromagnetic decay heat component emitted during thermal neutron fission of 235U and 239Pu improves agreement with experimental data up to approximately 80 s after fission. The estimation of the nuclear reactor ¯νe flux results in changes of up to 1% in the expected ¯νe interactions with the detector material for 235U, 238U, 239Pu, and 241Pu.
