Uranium symmetric/asymmetric neutron-induced fission up to 200 MeV

The symmetric SL-mode and asymmetric lumped (S1 + S2)-mode fission cross-sections of U-235(n,F) and U-233(n,F) reactions are calculated up to E-n = 200 MeV within a statistical model. For each U nuclide, emerging in (n,xnf) 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 U-238(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 U-235(n,F) and U-233(n,F) reactions. The calculated branching ratio sensitivity to the target nuclide fissility is investigated.