Six-Group Representation of the Energy Spectra of Delayed Neutrons from Fission

Group parameters (abundances and half-lives) and group spectra have been derived from the nuclear data and fission yields of the individual precursors for six delayed-neutron groups and for the fissionable nuclides 232Th, 233U, 235U, 236U, 238U, 237Np, 239Pu, 240Pu, 241Pu, 242Pu, and 252Cf. The results can be combined into a calculation of the resulting delayed-neutron energy spectrum at any cooling time and for any mixture of the above-mentioned nuclides.The validity of the method is checked in various ways such as comparing total neutron yields and group yields with the corresponding experimental quantities and comparing neutron spectra for half-life groups 2, 3, and 4 with integral experimental measurements. The outcome of these tests puts confidence in using the spectra obtained for applications within nuclear technology.