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

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 νpair 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 behaviour of experimental ratios νH/νpair as a function of heavy fragment mass number AH 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 dTKE/dν 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 behaviour 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, are for the first time well described by model calculations without any adjustment, due to our statistical model for reaction cross-section calculation including a refined fission model with sub-barrier effects.

TUDORA A.;  HAMBSCH Franz-Josef;  OBERSTEDT Stephan; 

2013-11-26

ELSEVIER SCIENCE BV

JRC83606

0375-9474,   

http://www.sciencedirect.com/science/article/pii/S0375947413007203,    https://publications.jrc.ec.europa.eu/repository/handle/JRC83606,   

10.1016/j.nuclphysa.2013.09.002,