  Earlier studies of 239Pu(n, f) have been extended to incident neutron
energies up to 20 MeV within the framework of the event-by-event fission model
FREYA, into which we have incorporated multichance fission and pre-equilibrium
neutron emission. The main parameters controlling prompt fission neutron
evaporation have been identified and the prompt fission neutron spectrum has
been analyzed by fitting those parameters to the average neutron multiplicity
nubar from ENDF-B/VII.0, including the energy-energy correlations in nubar(E)
obtained by fitting to the experimental nubar data used in the ENDF-B/VII.0
evaluation. We present our results, discuss relevant tests of this new
evaluation, and describe possible further improvements.
