Eur. Phys. J. A (2004) 21: 281-286
https://doi.org/10.1140/epja/i2003-10210-4

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

Joint Institute for Nuclear and Energy Research, “Sosny”, 220109, Minsk, Belarus

^* e-mail: maslov@sosny.bas-net.by

Abstract

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.