Water quality control device

The device of the present invention sufficiently reduces the amount of dissolved oxygen or metal oxides in a secondary system feedwater of a nuclear power plant. That is, when chemicals are supplied to the secondary system to control water quality of feedwater, the amount of the metal oxides or dissolved oxygen contained in the feedwater is directly measured. Then, it is controlled such that the chemicals are injected by an amount required for reduction of the metal oxides or removal of dissolved oxygen. With such procedures, even if the amount of the metal oxides or dissolved oxygen in the feedwater is increased when the feedwater flow rate is constant, the amount of the chemicals necessary for the reduction of the metal oxides or reaction with dissolved oxygen can be increased under control. Accordingly, it can contribute to prevent corrosion of a steam generator. (I.S.)