WATER QUALITY CONTROL METHOD AND ITS DEVICE

PROBLEM TO BE SOLVED: To reduce the exposure by maintaining metal ion at specific concentration without using conventional metal ion-injecting equipment and controlling the reactor water. SOLUTION: Two water purification systems A and B are provided and the A system filter element 1 is precoated with an ion exchanger resin to provide a resin-precoater layer 2. this resin-precoated layer 2 is constituted of the mixture layer of metal type cation resin 4 and OH type anion resin 5. When necessary, H type cation resin layer 5 is applied for overcoating. Metal oxide dissolved in its solubility in A system is not captured by the cation resin already broken by the ion 7 and eluted in the reactor water. If the monitored concentration becomes higher than a predetermined concentration, it is switched to the B system. The concentration is kept almost constant by repeating this. By this, injection equipment for the supply system becomes unnecessary, excess metal ion 7 incoming is avoided because of a single system, the rise of pipe dose due to prefilming is suppressed and the exposure is reduced.