Replicating PWR Primary Water Conditions in Low Pressure H2-Steam Environment to Study Alloy 600 Oxidation Processes

The effects of thermodynamic parameters associated with low pressure H2-steam on the oxidation behaviour of Nickel have been investigated to simulate PWR primary water conditions. An Y2O3-ZrO2 solid state reference electrode operated between 372 and 480 °C, and exposed to variable hydrogen partial pressures, was used to obtain in-situ potential measurements to identify the Ni/NiO transition. Microstructural analyses on Alloy 600 coupons exposed to H2-steam under different oxidizing conditions showed a marked dependence of the intergranular oxidation processes, as expected for a PWR environment. Overall, the H2-steam simulated an environment that can be considered to be representative of PWR primary water.