Prompt emission calculations for 239Pu(nth,f) with the DSE model code and a pre-neutron fragment distribution Y(A,TKE) based on the four-dimensional Langevin model.

The request for new and/or more accurate data of independent fission product yields (FPY) and other distributions of pre- and post-neutron fragments constitutes a priority on an international level. The prompt emission model codes nowadays employed are refined enough to answer this request with the condition of using reliable distributions Y(A,TKE) of pre-neutron fragments. Up to now in the majority of cases such distributions were determined by experimental data. Y(A,TKE) from theoretical calculations can extend the use of prompt emission model codes to fissioning systems for which the experimental information is very scarce or completely missing. Such Y(A,TKE), recently obtained from four-dimensional Langevin model calculations in the frame of multi-modal fission, is tested by its use (as input) in the deterministic prompt emission model code DSE, for the case of ²³⁹Pu(n_th,f). The obtained prompt emission results (e.g. prompt neutron multiplicity distributions ν(A), ν(TKE)) succeed to describe the experimental data and the independent FPY agree with the experimental data, too. Although visible differences between these results and those obtained with a an experimental Y(A,TKE) distribution exist. The present investigations have also emphasized other interesting aspects, e.g. concerning the pre-neutron fragments which contribute to the pronounced peaks and dips in the structure of both the mass yield Y(A_p) and the isotonic yield Y(N_p) of post-neutron fragments, in connection with the role played by the even–odd effect in fragment charge, as well as how the position and magnitude of pronounced peaks and dips are influenced by the Y(A,TKE) distribution. Independent FPY separately for each number "n" of emission sequences leading to the last residual fragment Y(A_p = A-n), reported for the first time, have shown how and which of these components contribute to the structure of total Y(A_p). The crucial role of the energy partition in fission is revealed again by showing that a good choice of the R_T parameterization can lead to very close results to those obtained with a TXE partition based on modeling at scission. On the contrary the use of an unique R_T value for all fragmentations can alter -in some fission cases—the sawtooth shape of ν(A) and its agreement with experimental data, despite the refinement of the prompt emission treatment itself and of a reliable Y(A,TKE) distribution employed in calculations. [ABSTRACT FROM AUTHOR]