CORROSION BEHAVIOR OF NUCLEAR GRADE ALLOYS 690 AND 800 IN SIMULATED HIGH TEMPERATURE AND HIGH PRESSURE PRIMARY WATER OF PRESSURIZED WATER REACTOR

Abstract

The corrosion behaviors of nuclear grade commercial alloys 690 and 800 were studied by in situ electrochemical measurements using a self-built high temperature and high pressure water loop system,combining with SEM observation and XPS analysis.The results show that the corrosion potentials of alloys 690 and 800 decrease gradually with immersion time increasing,while the immersion time has no obvious impact on the result from electrochemical impedance spectroscopy(EIS).A large number of needle-like oxides have been found on the surface of alloy 690 after being exposed to high temperature and high pressure water for 408 h.For alloy 800,except needle-like oxides,many particle oxides are also observed.For alloy 690,Cr is rich at inner side of oxide film,while it is rich at outer side of oxide film for alloy 800.Alloy 690 shows better corrosion resistance than alloy 800 in high temperature and high pressure water.After immersion experiment,the contents of Ni~(2+),Cr~(3+) and Fe~(3+) ions in the test water solutions are 0.1×10~(-6),0.1×10~(-6) and 0.3×10~(-6),respectively.