Comprehensive overview of the Point-by-Point model of prompt emission in fission

Abstract.

The investigation of prompt emission in fission is very important in understanding the fission process and to improve the quality of evaluated nuclear data required for new applications. In the last decade remarkable efforts were done for both the development of prompt emission models and the experimental investigation of the properties of fission fragments and the prompt neutrons and $\gamma$-ray emission. The accurate experimental data concerning the prompt neutron multiplicity as a function of fragment mass and total kinetic energy for ²⁵²Cf(SF) and ²³⁵ (n, f) recently measured at JRC-Geel (as well as other various prompt emission data) allow a consistent and very detailed validation of the Point-by-Point (PbP) deterministic model of prompt emission. The PbP model results describe very well a large variety of experimental data starting from the multi-parametric matrices of prompt neutron multiplicity $\nu (A,TKE)$ and $\gamma$-ray energy $E_{\gamma}(A,TKE)$ which validate the model itself, passing through different average prompt emission quantities as a function of A (e.g., $\nu(A)$, $E_{\gamma}(A)$, $\langle \varepsilon \rangle (A)$ etc.), as a function of TKE (e.g., $\nu (TKE)$, $E_{\gamma}(TKE)$) up to the prompt neutron distribution $P (\nu)$ and the total average prompt neutron spectrum. The PbP model does not use free or adjustable parameters. To calculate the multi-parametric matrices it needs only data included in the reference input parameter library RIPL of IAEA. To provide average prompt emission quantities as a function of A, of TKE and total average quantities the multi-parametric matrices are averaged over reliable experimental fragment distributions. The PbP results are also in agreement with the results of the Monte Carlo prompt emission codes FIFRELIN, CGMF and FREYA. The good description of a large variety of experimental data proves the capability of the PbP model to be used in nuclear data evaluations and its reliability to predict prompt emission data for fissioning nuclei and incident energies for which the experimental information is completely missing. The PbP treatment can also provide input parameters of the improved Los Alamos model with non-equal residual temperature distributions recently reported by Madland and Kahler, especially for fissioning nuclei without any experimental information concerning the prompt emission.