Influence of scission neutrons on the prompt fission neutron spectrum calculations

CEA, DEN, DER, SPRC, 13108 Saint Paul lez Durance, France

^a e-mail: olivier.serot@cea.fr

Published online: 13 September 2017

Abstract

The calculation of the Prompt Fission Neutron Spectrum (PFNS) was performed using the FIFRELIN Monte Carlo code simulating the de-excitation of the whole fission fragments. This de-excitation is governed by the Hauser-Feshbach statistical model, which has the advantage to take into account the conservation laws for the energy, spin and parity of the initial and final states. In this way, the competition between prompt neutron and prompt gamma emission can be properly accounted for. Assuming that the prompt neutron emission comes only from an evaporation process of the fully accelerated fission fragments, our calculations are not able to reproduce satisfactorily the experimental data. In this context, we have added an additional source of neutrons that may arise during the sudden rupture of the neck (the so-called scission neutrons). Applied in the case of the spontaneous fission of ²⁵²Cf, our PFNS calculations show a very good agreement with the Mannhart evaluation by accounting for a 2% scission neutron contribution.