Improvement of compatibility of advanced ferritic steels with super critical pressurized water toward a higher thermally efficient water-cooled blanket system

Various oxide dispersion strengthened (ODS) steels which have high Cr concentrations with and without Al addition were made by mechanical alloying method. Corrosion measurement was done in the closed system of super critical pressurized water (SCPW) at 783 K with the pressure of 25 MPa. In order to evaluate the mechanical properties and the effect of thermal aging, a miniaturized Charpy V notch (MCVN) test and tensile test were performed before and after aging at 773 K up to 1000 h. The susceptibility to stress corrosion cracking (SCC) of high Cr-ODS steels was evaluated by slow strain rate test (SSRT). The SSRT was performed in a simulated boiling water reactor (BWR) condition with high temperature oxygenated (8-10 ppm) water at 561 K and at a pressure of 7.8 MPa. Strain rates were ranging from 1 x 10-4 to 3 x 10-7 s-1. The high Cr-ODS steels showed a better resistance to corrosion than SUS316L stainless steel in SCPW. The 14Cr and 16Cr-ODS steel did not suffer from aging embrittlement at 773 K for 1000 h. The ODS steels showed no susceptibility to SCC at strain rates from 1 x 10-4 to 3 x 10-7 s-1