Evaluation of Power Plant Measurement of Sodium Ions in High-Purity Main Steam and Feedwater Utilizing In-Line Continuous Specific-Ion Electrodes

This paper discusses the measurement of trace-level sodium concentrations in aqueous solutions. A comparison between the specific-ion electrode analyzer and other analytical methodologies is presented. The techniques include atomic absorption spectroscopy, flame emission spectroscopy, and ion chromatography. The data were obtained over approximately a 300-day period utilizing combinations of the aforementioned analytical techniques. The evaluation was performed at Calvert Cliffs Nuclear Power Plant (CCNPP), Lusby, Md., a pressurized water reactor owned and operated by Baltimore Gas and Electric Co. (BG & E). The data revealed that significant perturbations in the indicated sodium concentrations on the specific-ion electrode analyzers existed during the study period. Based upon the comparison data obtained by other analytical methodologies, the indicated sodium level variances were not considered to be representative of the actual system concentration variances. The perturbations in the indicated sodium levels were correlated with flow-pressure fluctuations in the specific-ion electrode sample lines. In addition, the accuracy of the instrument was diminished as the actual system sodium concentration varied outside the calibration limits of the analyzer.