The Hauser-Feshbach statistical model is applied to the de-excitation of primary fission fragments using input mass yields calculated with macroscopic-microscopic models of the potential energy surface. We test the sensitivity of the prompt fission observables to the input mass yields for two important reactions, ${}^{235}\mathrm{U}(n_{\mathrm{th}},f)$ and ${}^{239}\mathrm{Pu}(n_{\mathrm{th}},f)$, for which good experimental data exist. General traits of the mass yields, such as the location of the peaks and their widths, can impact both the prompt neutron and $\gamma$-ray multiplicities, as well as their spectra. Specifically, we use several mass yields to determine a linear correlation between the calculated prompt neutron multiplicity $\overline{\nu }$ and the average heavy-fragment mass $\langle A_h\rangle$ of the input mass yields $\partial \overline{\nu }/\partial \langle A_h\rangle =\pm 0.1(n/f)/\mathrm{u}$. The mass peak width influences the correlation between the total kinetic energy of the fission fragments and the total number of prompt neutrons emitted, ${\overline{\nu }}_T\left(\mathrm{TKE}\right)$. Typical biases on prompt particle observables from using calculated mass yields instead of experimental ones are $\delta \overline{\nu }=4\%$ for the average prompt neutron multiplicity, $\delta \overline{M}{}_{\gamma }=1\%$ for the average prompt $\gamma$-ray multiplicity, $\delta {\overline{\epsilon }}_n^{\mathrm{LAB}}=1\%$ for the average outgoing neutron energy, $\delta {\overline{\epsilon }}_{\gamma }=1\%$ for the average $\gamma$-ray energy, and $\delta \langle \mathrm{TKE}\rangle =0.4\%$ for the average total kinetic energy of the fission fragments.

• Received 20 December 2017

DOI:https://doi.org/10.1103/PhysRevC.97.034608