AES characterization of oxide films formed on nickel-base alloys at Supercritical Water Reactor (SCWR) conditions

Austenitic alloys have shown good resistance to corrosion under light water reactor operating conditions. By this reason, these materials have been considered to be part of the new supercritical water reactor, one of the highly efficient, low waste production and simply designed Generation IV nuclear reactors. The water chemistry control and the material response to corrosion in operating conditions of the supercritical water reactor take an outstanding interest in order to minimize the release of corrosion products and their subsequent transformation into radioactive products. One nickel-base alloy, Alloy 690TT, and one austenitic stainless steel, Alloy 800 mod, were studied under supercritical water conditions (500 degrees C, 25MPa and 8ppm of dissolved oxygen). The effect of shot-peening surface finish was also studied on Alloy 800 mod. The corrosion rate of these alloys was evaluated by means of gravimetry. Surface analysis and subsequent depth profiles were made using Auger electron spectroscopy in order to characterize the oxide films (quantitative composition and thickness) of the different alloys as well as the influence of shot-peening on the oxidation process. According to these results, it can be concluded that shoot-peening favours the incorporation of chromium to the oxide layer in case of Alloy 800 mod, and the thickness of the oxide layer on Alloy 690TT is higher than on Alloy 800 mod. Copyright (c) 2015 John Wiley & Sons, Ltd.