Extension of the Hauser-Feshbach fission fragment decay model to multichance fission

The Hauser-Feshbach fission fragment decay model, (HFD)-D-3, which calculates the statistical decay of fission fragments, has been expanded to include multichance fission, up to neutron incident energies of 20 MeV. The deterministic decay takes as input prescission quantities-fission probabilities and the average energy causing fission-and postscission quantities-yields in mass, charge, total kinetic energy, spin, and parity. From these fission fragment initial conditions, the full decay is followed through both prompt and delayed particle emissions, allowing for the calculation of prompt neutron and gamma properties, such as multiplicity and energy distributions, both independent and cumulative fission yields, and delayed neutron observables. In this work, we describe the implementation of multichance fission in the (HFD)-D-3 model, and show an example of prompt and delayed quantities beyond first-chance fission, using the example of neutron-induced fission on U-235. This expansion represents significant progress in consistently modeling the emission of prompt and delayed particles from fissile systems.