Research on Candidate Materials for Fuel Cladding in Supercritical Water Cooled Reactor

Abstract

Modified AL-6XN austenitic steel and new types of 9%Cr and 12%Cr reduced activation ferritic- martensitic (RAFM) steels were developed as candidate materials for fuel cladding in supercritical water cooled reactor (SCWR) with focus on mechanical properties and corrosion behaviors in supercritical water (SCW) at 650 °C and 25 MPa up to 1000 h. The results indicated that modified AL- 6XN exhibited superior mechanical properties over AL-6XN and good corrosion resistance with a very thin oxidation layer and no nodular corrosion morphologies was observed in SCW. However, the aging treatment degraded mechanical properties of modified AL-6XN greatly. The ultimate tensile strength of 9%Cr and 12%Cr RAFM steels reached 443 MPa and 365 MPa at 600 °C, respectively. The ductile brittle transition temperature of 9%Cr and 12%Cr RAFM steels were -25 °C and -90 °C, respectively. 9%Cr and 12%Cr RAFM steels exhibited enhanced mechanical properties, but presented poor corrosion resistance in SCW due to the absence of corrosion-resistant elements. In order to obtain better corrosion resistance and mechanical properties, the content of Ni and Mo should be increased up to 1% in modified 12%Cr ferritic-martensitic steel in further studies.