Energy Release from the Decay of Fission Products

Abstract

The total disintegration rates, rates of beta- and gamma-energy release, and gamma-ray energy spectrum, are calculated for fission products due to thermal neutron fission of U235. Information on decay schemes was largely obtained from the compilations of the Nuclear Data Group of the National Research Council to July, 1957. Total fission yields are from Katcoff and from Steinberg and Glendenin. Nuclear charge distributions are taken from Pappas’ work, which includes the effect of closed shells. Reactor operating times of 1, 10, 100, and 1000 hours are treated, and the results plotted for decay times ranging from 102 to 108 seconds. In addition, results for instantaneous operation are compared to other calculations and measurements. The present results fall below Way and Wigner’s predictions of both disintegration rate and total energy release over the entire range of decay times, though they agree satisfactorily with the Way-Wigner rule-of-thumb expressions. The present results are in very good agreement with experimental measurements. The gamma spectrum is found to vary considerably with decay time but to be only a weak function of reactor operating time. The total beta and antineutrino energies per fission are found to be 7.6 ± 0.5 and 10.0 ± 0.7, respectively.