Comparison of fast neutron rates for the NEOS experiment

The fast neutron rates are compared at the site of the NEOS (Neutrino Experiment Oscillation Short baseline) experiment, a short-baseline neutrino experiment located in a tendon gallery of a commercial nuclear power plant using a 0.78-liter liquid scintillator detector. A pulse shape discrimination technique is used to identify neutron signals. The measurements are performed during the nuclear reactor-on and -off periods, and the fast neutron rates are found to be consistent with each other. The fast neutron rate is also measured at an overground site with a negligible overburden and is found to be ~ 100 times higher than that at the site of the NEOS experiment.