Improved modeling of neutron-induced reactions on chlorine isotopes aided through new $(n,p)$ and $(n,\alpha )$ measurements at LANSCE

Renewed interest in neutron-induced reactions on chlorine isotopes has led to a surge of new measurements. Much of this effort has been spurred to inform on the many modern applications in which chlorine plays an important role, e.g., molten salt reactor design and reaction rate calculations for nuclear astrophysics. In this work, we report new ${}_{35}\mathrm{Cl}(n,p)$ and ${}_{35}\mathrm{Cl}(n,\alpha )$ partial and total cross sections measured at the Los Alamos Neutron Science Center using the LENZ [Low-Energy ($n,Z$)] experimental setup, complementary to those published previously. The data span incident neutron energies from 300 keV to 12 MeV, extending beyond the previous study, and are consistent in magnitude and fluctuation. We also report on an effort at LANL to reanalyze the ${}_{35}\mathrm{Cl}(n,X)$ system in the fast (statistical) energy range under a Hauser-Feshbach formalism, including the latest data. The leading results are an overall reduction in neutron absorption in the fast-energy range compared to base (global) optical model values, due to the low level density of the compound (${}_{36}\mathrm{Cl}$) system, but a net increase in cross section at the higher energies ($>10\mathrm{MeV}$) modeled through an enhanced preequilibrium component, an energy range potentially relevant for fusion applications. The cross-cutting impacts of these results on some of the referenced applications are discussed, including extensions of the analysis to neighboring isotopes. The calculations described here provide a foundation for a future update to the ENDF/B nuclear data library.