Feasibility study of neutral water treatment in component test loop

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The Component Test Loop (CTL) has been operated for several kinds of tests under mechanical and thermal conditions similar to reactor "Fugen". Its water chemistry has been controlled by all-volatile-treatment (AVT) for inhibiting corrosion of the loop components and piping which is composed of carbon steel. The CTL has a schedule of performing corrosion tests of main components and materials used in "Fugen". For these tests, the CTL is required to simulate water chemistry of the real reactors and to operate under neutral water condition. However, there is no experience of operating carbon steel boilers with neutral water treatment (NWT) in Japan. Therefore, preliminary tests were done to examine the possibility of NWT operation of the CTL and to make clear what kinds of apparatus to be added to the loop. Test results are as follows. (1)Throughout a period of steady state operation of the CTL with neutral water treatment, the following water chemistry was obtained at the inlet of a test section; electrical conductivity: 0.3S/cm, disolved oxygen: 150ppb, PH: 6.25, total iron: 2.5ppb, total cupper: 15-20ppb, SiO: 25ppb, organie impurity (UV value): 0.005. These values are totally close to those of the primary coolant of reactor "Fugen", and indicates that the CTL can be operated under a water condition simulating "Fugen". (2)The total iron content of 2.5 ppb under neutral water conditions is 1/4 to 1/2 times as low as that under AVT water conditions, and indicates neutral water treatment is excellent anti-corrosive treatment for carbon steel pipings. (3)It was found that cupper, SiO and organic impurities had been accumulated in the CTL through the past 10 years. Where these impurities come from and how to remove them from the loop are discussed. (4)Corrosion tests of iron, cupper and its alloy specimens showed cupper and its alloy are much corrosive than iron under the neutral water condition. 0bservation and analysis of inner surfaces ...