Estimated post-scram reactor coolant densities from prompt-response self-powered neutron detectors in loss-of-coolant experiments

By analysis of the output from self-powered neutron detectors (SPND) in the core of the Loss of Fluid Test (LOFT) Reactor, the authors have estimated local coolant densities in a large break loss of coolant transient. The analysis is based on interaction of gamma radiation as it passes through coolant from the core to the SPNDs. The authors estimated the post-scram temporal behavior in the vicinity of gamma production, converted this to expected SPND behavior and compared the result to observed SPND behavior. The analysis results have provided valuable information in core hydraulic behavior. Though the detectors never were installed and calibrated with the intent to obtain accurate fluid densities, the SPNDs provided spacially and temporally resolved data that is qualitatively excellent and quantitatively good.