Measurement of the energy-differential ${}_{35}\mathrm{Cl}(n,p_0){}_{35}S$ cross section via the ratio with ${}_6\mathrm{Li}(n,\alpha ){}_{3}H$

Background: Knowledge of the neutron-induced ${}_{35}\mathrm{Cl}(n,x)$ cross sections is vital to the design and certification of molten chloride fast reactors (MCFRs) since the ${}_{35}\mathrm{Cl}(n,p_0){}_{35}S$ reaction is believed to be a significant reactor poison. However, recently published measurements are inconsistent with each other and with evaluation.

Purpose: The goal of this work is to measure the ${}_{35}\mathrm{Cl}(n,p_0)$ reaction cross section using a technique that is different from recent measurements.

Methods: The experiment was conducted at Lawrence Berkeley National Laboratory's (LBNL) 88-Inch Cyclotron using thick target deuteron breakup from a 14 MeV deuteron beam. Energy-differential ${}_{35}\mathrm{Cl}(n,p_0){}_{35}S$ cross sections were obtained via ratio with the ${}_6\mathrm{Li}(n,\alpha ){}_{3}H$ reaction using an active target experiment with a ${\mathrm{Cs}}_2{\mathrm{LiYCl}}_6$ (CLYC) scintillator.

Results: The ${}_{35}\mathrm{Cl}(n,p_0)$ reaction cross section was measured from 2.02 to 7.46 MeV. The results are consistent with Kuvin et al., confirming a roughly 50% reduction in magnitude relative to the ENDF/B-VIII.0 evaluation.

Conclusions: These data provide new insight into the role of natural Cl as an MCFR poison. The reduction of the ${}_{35}\mathrm{Cl}(n,p_0)$ reaction cross section compared to evaluation suggests that MCFR criticality is less sensitive to Cl enrichment. This may in turn reduce building and operating costs since isotope separation may not be needed.