PRIMARY COOLANT CONDUCTIVITY STUDY

The AF NETF, a 10 MW water-cooled research reactor, monitors the conductivity of its coolant to detect erosioncorrosion of its structural systems and fuel element failure. When a gradual increase in this conductivity sent it above the defined limit, a study was initiated to identify the contaminants and examine the source and removal processes. The major contaminant, Na23, was traced to an in-leakage from the secondary to the primary coolant systems through the heat exchanger interface. Minor amounts of contaminant were introduced from a deluge tank and from residual ions remaining on the demineralizer from the factory NaOH flush. The study proved the absence of any fuel cladding defect and the presence of only an acceptably minimal structural erosioncorrosion rate. The in-leakage source was identified and corrected. The demineralizer system was found to be adequate for normal operation, but economically restrictive during the latter portion of resin life.