234U(n,f) Model Description of Sub-barrier Fission Cross-section Resonances and Calculation of Prompt Neutron Emission Data

AbstractNeutron induced cross-sections of 234U are calculated, focusing on the description of sub-barrier resonances in the fission cross-section. The correlation between the resonant behaviour of fission cross-section of fertile actinides (characterizing the pre-scission stage) and the visible fluctuations of their fission fragment and prompt neutron data (characterizing the post-scission stage), already discussed for the case of 238U(n,f), is outlined and quantitatively supported in this case, too. The recently measured fission fragment distributions of 234U(n,f) at incident energies covering the range 0.2-5 MeV, allow the averaging of multi-parametric matrices provided by the Point-by-Point (PbP) model, leading to interesting behaviours of prompt neutron data. For the first time the average prompt neutron multiplicity <ν> as a function of TKE is calculated at many incident energies (En) revealing interesting facts: the slope dTKE/dν does not vary with En and the flattening of <ν> at low TKE values is more pronounced at low En. Average model parameters (like energy release, neutron separation energy from fragments, level density of fragments) as a function of TKE exhibit nice and regular behaviours that can be fitted very well. The obtained average parameter dependences on TKE allow the use of the most probable fragmentation approach (Los Alamos model with subsequent improvements) having as advantages a very short computing time compared to the PbP and Monte Carlo treatments and the possibility to extend the lower and upper limits of the TKE range