Measurement of the average energy and multiplicity of prompt-fission neutrons from 238U(n,f) and 237Np(n,f) from 1 to 200 MeVJ. Taieb1, T. Granier1, T. Ethvignot1, M. Devlin2, R.C. Haight2, R.O. Nelson2, J.M. O'Donnell2 and D. Rochman3
1 CEA DAM, DPTA/SPN, BP. 12, 91680 Bruyères-le-Châtel, France
2 LANSCE, Los Alamos National Laboratory, MS H855, Los Alamos, New Mexico 87545, USA
3 NNDC, Brookhaven National Laboratory, Upton, NY 11973-5000, USA
Published online: 21 May 2008
Taking advantage of the neutron source of the LANCSE, it has been possible to obtain a measure of the velocity distribution and the number of prompt-neutrons emitted in the neutron-induced fission of 238U and 237Np over a broad incident neutron energy range. The mean kinetic energy was extracted and is shown as a function of the incident-neutron energy. We confirm here the observation, for both reactions, of a dip around the second-chance fission which is explained by the lower kinetic energy of the pre-fission neutrons. Such a observation is reproduced by Los Alamos model as implemented at Bruyères-le-Châtel and by the Maslov model. As far as the neutron multiplicity is concerned, a similar dip is observed.
© CEA 2008