Average Energy of Delayed Neutrons from Individual Precursors and Estimation of Equilibrium Spectra

Average energies of the delayed neutron spectra from 34 precursors have been compiled from the literature to give a set of best values. Average energies of six-group and equilibrium spectra are calculated by summing weighted values of the individual precursors. These calculated average energies are in reasonable agreement with the rather limited experimental data. Equilibrium delayed neutron spectra are calculated by summing spectra for individual precursors. The calculated equilibrium spectra are then compared to an approximate spectrum based on a Maxwellian distribution with just one parameter, the average energy. Sets of experimental spectra for individual precursors measured at two different laboratories are compared. The Maxwellian shape gives reasonable agreement with one set. The other set has more neutrons at low energy and does not fit a Maxwellian shape.