Corrosion Performance of Candidate Materials for Canadian Gen IV Supercritical Water Cooled Reactor

Abstract

Nuclear power plants have been an important source of energy in many countries for the last fifty years. The Canadian supercritical water cooled reactors (SCWR), among the Generation IV reactors, are currently being designed in Canada and many other countries. It presents challenges for many scientists and engineers due to the harsh environment in which the reactor must operate and the lack of knowledge of material's performance in this corrosive conditions of high temperature and pressure. This thesis entails the corrosion testing of four candidate materials, two nickel based alloys (IN 625 and A-286) and two stainless steels (AISI 304 and AISI 310), and microstructure evaluation of samples after being exposed to supercritical water (SCW), subcritical water (SubCW), and superheated steam. Samples were ground to 600 grit finish and placed in an autoclave and a superheated steam rig to a maximum of three thousand hours and one thousand hours respectively. Procedures, based on the manufacturer's manuals, were created for the setup and operation of all the equipment. The temperature of all three tests was set to 625 o C with a pressure of 29 MPa (SCW), 8 MPa (subcritical water) or ambient (superheated steam). The surface morphology and composition were analyzed using scanning electron microscope (SEM) imaging and energydispersive X-ray spectroscopy (EDS). Results from this study show a poor corrosion performance, in terms of surface oxide formation and weight change, for A-286 and AISI 304 in all conditions due to their low chromium content. AISI 310 and IN 625, with higher chromium content, exhibit an excellent corrosion resistance in almost all conditions, except for the superheated steam test where oxide spallation may have