Water quality diagnosis method and device therefor

In a nuclear power plant, a concentration of the total organic carbon of primary coolants at an exit of a condensate desalter, an exit of a reactor water cleaning device and a condensate storage tank is measured by using a concentration measuring device. A reactor water conductivity is calculated based on the predetermined kind of organic materials having a possibility of being mixed and corresponding kind and decomposing rate of the decomposed products in the reactor, using the measuring data. The calculated value of the reactor water conductivity and the actually measured value by using an conductivity meter are compared to diagnose the kind of the mixed organic impurities and their position where the organic impurities are generated. Then, the kind of the organic material at a position corresponding to the position where the organic impurities are generated is analyzed and confirmed by using a gas chromatography. This can rapidly diagnose the source and the kind of the organic impurities. (I.N.)