Structural Material Anomaly Detection System Using Water Chemistry Data, (III)In-Line Monitors for Electrical Conductivity of High Temperature Water

摘要

A method to determine the electric conductivity of water continuously and directly at elevated temperature up to 300°C was developed which can be applied as a sensor for corrosion behavior foreknowledge and diagnosis systems using water chemistry data of BWR primary coolant. Complex impedance was measured between a couple of parallel platinum electrodes installed with a constant distance and dipped in the water. By analyzing frequency dependence of the impedance, the resistivity of the water between the platinum electrodes was estimated separately from the impedance caused by surface reactions on the platinum electrodes, which was the source of error in the measurement of electricl conductivity at elevated temperature.Increase of necessary frequency to obtain the surface impedance at elevated temperature was evaded by the extrapolation of the frequence dependence of the impedance with calculations by using the data up to 100 kHz in which electric conductivity shows negligibly small dependence on the frequency of applied voltage.The measured conductivity of pure water up to 300°C showed a good agreement with the calculation based on the dissociation data of water, which shows the applicability for the in-line monitor of electrical conductivity at elevated temperature.