Delayed neutron energy spectra of 87Br, 88Br, 89Br, 90Br, 137I, 138I, 139I, and 186Te

In prior publications, the authors reported measurements of the energy spectra of delayed neutrons for the isotope-separated fission product precursors 93Rb, 94Rb, 95Rb, 96Rb, 97Rb, 143Cs, 144Cs, and 145Cs. Such studies of delayed neutron energy spectra have important applications in reactor physics, primarily relating to the fundamental role played by delayed neutrons in the kinetic behavior of nuclear reactors. Measurement of the energy spectra of delayed neutrons for the isotope-separated, fission product precursors 87Br, 88Br, 89Br, 90Br, 137I, 138I, 139I, and 136Te are reported for an energy range up to 1,213 keV and with lower cutoff energies of 11.1, 11.1, 29.9, 48.9, 14.2, 23.3, 29.9, and 48.9 keV, respectively. These data were obtained at the TRISTAN Isotope Separation On-Line facility using H2 and CH4 gas-filled proportional counters. The data for each of the bromine, iodine, and tellurium isotopes show good qualitative agreement with the published 3He ionization chamber data at energies above ∼200 keV. In addition, they provide definitive spectral information down to their respective cut-off energies