In secondary systems of several pressurized water reactor (PWR) plants, operation conditions under a high pH in the presence of ammonia or ethanolamine (ETA) have been used, and the suppression of corrosion has been reported.
In PWR secondary systems, Cu alloys have been used for some of the structural components. Accordingly, it is necessary to investigate the corrosion behavior of these Cu alloys under high pH conditions.
In the present paper, the corrosion behavior of Cu alloys in NH3 and ETA solutions was investigated under conditions simulating the condensate water, feed water, and main steam systems. The effects of corrosion on the integrity of the alloys were determined by a tensile test.
The corrosion of the copper alloys was accompanied with the formation of oxide in the solution containing dissolved oxygen at 70°C. On the other hand, the selective dissolution of additional elements was observed in the solution without dissolved oxygen at 220 and 280°C. There was no apparent difference in the corrosion behavior of Cu alloys in NH3 solution and ETA solution. The corrosion rate of the Cu alloys increased with the Pb content in the alloys. Effects of the corrosion during the immersion test on tensile properties of Cu alloys were not observed.