Corrosion Studies of Candidate Materials for European HPLWR

The High Performance Light Water Reactor (HPLWR) design is one of the concepts chosen for Generation IV reactors; however, the material requirements for HPLWR offer challenges because of the extreme operating temperatures and pressures. Consequently, general corrosion rates were studied in water at 300 to 650°C at supercritical pressure using weight gain measurements. Oxide thicknesses were determined from cross-section samples. The compositions of the oxide layers were analyzed using scanning electron microscopy in conjuction with energy dispersive spectroscopy. The surface layers of selected samples were analyzed also by X-ray diffraction. The test matrix included ten materials from four alloy classes: ferritic/martensitic steels, oxide dispersion strengthened (ODS) steels, austenitic stainless steels, and nickel-base alloys. A high oxidation resistance was seen in Ni-base alloy 625, austenitic stainless steels with high Cr content (>18 wt% Cr), and an ODS steel containing 20% Cr at all applied test temperatures (300 to 650°C). The oxidation rates of austenitic stainless steels with lower Cr content, 15 to 18%, increase considerably at temperatures >500°C. The oxidation rates of 9% Cr ODS steels were moderate or high at all temperatures. Ferritic/martensitic steels showed high oxidation rates at all temperatures.