Delayed-neutron spectral calculation using augmented ENDF/B-V data

We have used the evaluated nuclear data files (ENDF/B-V) for 105 precursors, augmented with experimental spectral data for 29 emitters and recent model calculations for the remaining 76 emitters, in aggregate summation calculations. The equilibrium delayed neutrons and spectra in the conventional six time-groups for 11 fissionable nuclides were calculated. Normalized experimental emitter spectra for 29 emitters were supplied by G. Rudstam. Augmentation of the spectra uses data calculated with a recently developed code, BETA. Fission yields of the precursors and their Pn values are from ENDF/B-V. Results are compared where possible with corresponding group and total evaluations of aggregate measurements. The intent of these calculations is to examine the adequacy of data for inclusion in ENDF/B-VI. Most of the results, particularly with the added model parameters, are sufficiently accurate to be of direct interest to the reactor community. The total /anti/nu/sub d/ values for /sup 238/U and /sup 232/Th suggest that either an improvement in fission yields is needed or the evaluated experimental /anti/nu/sub d/ values are in significant error.