Alloy 800H under supercritical water conditions: a flow reactor study of corrosion and hydrogen evolution

Hydrogen evolution and corrosion rates for an Alloy 800H flow-through reactor operating under supercritical water conditions were determined. Experiments were performed in the temperature range of 650 to 750 °C both with deoxygenated feed water, with an O2 concentration of less than 10 μg L−1 (ppb), and with a high oxygen concentration of around 20 mg L−1 (ppm). Effective rate constants for hydrogen evolution during the corrosion of an Alloy 800H were calculated to be 2.52×10−11, 2.88×10−11 and 4.30×10−11 mol cm−2 s−1, for the reactor temperatures of 650, 700 and 750 °C, respectively.