Uranium symmetric/asymmetric neutron-induced fission up to 200 MeV
Joint Institute for Nuclear and Energy Research, “Sosny”, 220109, Minsk, Belarus
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The symmetric SL-mode and asymmetric lumped (S1 + S2)-mode fission cross-sections of 235U(n,F) and 233U(n,F) reactions are calculated up to MeV within a statistical model. For each U nuclide, emerging in reactions a separate triaxial outer fission barrier is assumed for the SL-mode. To reproduce the measured branching ratio of symmetric and asymmetric fission events for the 238U(n,F) reaction, more fissions coming from neutron-deficient nuclei were assumed. The damping of the triaxial collective modes contribution to the level density at the SL-mode outer saddle was essential for the branching ratio description. These assumptions allow to reproduce observed fission cross-sections of 235U(n,F) and 233U(n,F) reactions. The calculated branching ratio sensitivity to the target nuclide fissility is investigated.
© Società Italiana di Fisica and Springer-Verlag, 2004