Nonstatistical fluctuations in the Cl35(n,p)S35 reaction cross section at fast-neutron energies from 0.6 to 6 MeV

Abstract

The lack of experimental data on the $^{35}\mathrm{Cl}(n,p)^{35}\mathrm{S}$ reaction above 100 keV has led to nuclear data evaluations that are relatively unconstrained at fast neutron energies. As a result, efforts to explore, develop, and potentially certify next generation reactor designs that incorporate chloride salts as a coolant material have been hindered. In this paper, we report partial cross section data for the $^{35}\mathrm{Cl}(n,p)^{35}\mathrm{S}$ and $^{35}\mathrm{Cl}(n,\ensuremath{\alpha})^{32}\mathrm{P}$ reactions at incident neutron energies between 0.6 MeV and 6 MeV. The measurement was performed using the pulsed beam of neutrons at the unmoderated WNR spallation neutron source at the Los Alamos Neutron Science Center, with the outgoing charged particles detected by the LENZ experimental setup, consisting of annular silicon detectors. Nonstatistical fluctuations in the $^{35}\mathrm{Cl}(n,{p}_{0})$ cross section were observed up to around 3 MeV, and the magnitude of the cross section was systematically lower than all available data evaluations at energies above 1 MeV. Modifications to the ENDF/B-VIII.0 data evaluation are suggested to better reproduce the energy averaged experimental data.