Monte Carlo approach to sequential neutron emission from fission fragments

Abstract

We have implemented a Monte Carlo simulation of fission fragment statistical decay by sequential neutron emission. Within this approach, we calculate the center-of-mass and laboratory prompt neutron energy spectra as a function of the mass of fission fragments and integrated over the whole mass distribution. We also assess the prompt neutron multiplicity distribution $P(\nu )$, both the average number of emitted neutrons and the average neutron energy as a function of the mass of the fission fragments [respectively $\overline{\nu }(A)$ and $\langle \varepsilon \rangle (A)$]. We investigate the average total energy available for prompt γ-ray emission as a function of the mass of the fission fragments ${\overline{E}}_{\gamma }(A)$. We also calculate neutron-neutron correlations such as the full matrix $\overline{\nu }(A,\mathrm{TKE})$ as well as correlations between neutron energies. Two assumptions for partitioning the total available excitation energy among the light and heavy fragments are considered. Results are reported for the neutron-induced fission of ${}^{235}\mathrm{U}$ (at neutron energy of 0.53 MeV) and for the spontaneous fission of ${}^{252}\mathrm{Cf}$.