Evaluation and Testing of n + ²³⁹Pu Nuclear Data for Revision 2 of ENDF/B-V

A major revision of the ENDF/B-V evaluation of neutron-induced nuclear data for ²³⁹Pu has been completed for neutron energies between 8 keV and 20 MeV. The most important changes to the evaluation include incorporation of a comprehensive new theoretical analysis based on recent experimental data to replace part of the total cross-section file and all of the elastic and inelastic cross sections and secondary distributions, reevaluation of the prompt and total average neutron multiplicities from fission for incident energies between 0.4 and 11.5 MeV to correct discrepancies of almost 3% with new experimental data, and the replacement of all secondary neutron energy spectra from fission with improved shapes based on approximations to a new theoretical method. The results have been validated by calculating measured quantities for five fast critical assemblies. The evaluation is being distributed as Revision 2 of ENDF/B-V by the National Nuclear Data Center at Brookhaven National Laboratory.