Prompt fission neutron emission calculations and description of sub-barrier fission cross section resonances for 234U()

Abstract

Abstract Prompt emission quantities of 234U( n , f ) (average quantities as a function of fragment mass, average quantities as a function of total kinetic energy (TKE) and total average quantities) have been calculated within the Point-by-Point model. The recently measured fission fragment distributions at incident energies (En) ranging from 0.2 MeV to 5 MeV have been used. The insensibility of the fragment pair multiplicity ν pair to the partition of total excitation energy (TXE) between complementary fully accelerated fission fragments has been confirmed. This gives confidence in the predicted total average prompt emission data as a function of En and of average quantities as a function of TKE at different incident energies of 234U( n , f ). The systematic behavior of experimental ratios ν H / ν pair as a function of heavy fragment mass number A H together with the TXE partition based on modeling at scission allow the parameterization of the excitation energy ratio E H ⁎ / TXE . This opens up the possibility to provide ν ( A ) of 234U in the absence of any experimental data. For the first time the calculation of 〈 ν 〉 ( TKE ) at many En revealed two interesting aspects: the slope d TKE / d ν does not vary with En and the flattening of 〈 ν 〉 at low TKE values is more pronounced at low incident energies. The correlation between the sub-barrier resonant behavior of the fission cross section of fertile actinides (characterizing the pre-scission stage) and the visible fluctuations of their fission fragment and prompt neutron emission data (characterizing the post-scission stage), already discussed in the case of 238U( n , f ) is outlined and quantitatively supported by 234U( n , f ), too. The pronounced vibrational resonances in the experimental fission cross section of 234U placed below 1 MeV can be described by the statistical model for reaction cross section calculation including the optical model for fission.