Fuel cladding materials R&D for high burn-up operation of advanced water-cooling nuclear energy systems

Development of fuel cladding materials is crucial for high burnup (more than 100GWd/t) operation of advanced nuclear energy systems, such as advanced light water reactors and super critical pressurized water (SCPW) reactors. In order to overwhelm the requirements for the fuel claddings, materials R&D have been performed for high-Cr oxide dispersion strengthening (ODS) steels at Kyoto University. Corrosion resistance of the high-Cr ODS steels in SCPW (510°C, 25 MPa) was better than SUS316L The 19Cr-ODS steel was not susceptible to stress corrosion cracking evaluated by slow strain rate test at 3 × 10^-7/sec in hot water (288°C, 7.8 MPa). High-temperature strength was achieved by dispersing nano-sizedyttria in the steel matrix. An addition of aluminum reduced anisotropy in the tensile elongation, while it also reduced the strength. The thermal aging embrittlement does not occur at 500°C up to 4300 hr for the 16Cr-ODS steel. Heavy-ion irradiation at 500°C to 10 dpa did not result in the phase decomposition of Fe/Cr, showing no embrittlement. For better processing techniques, raw powders were characterized. It was found that the particle size of the mixed powder was reduced drastically by the ball milling for 12 hr. In this paper, the advantages of the ODS steels among the other candidate materials for the application to high burnup fuel claddings will be shown, and the recent progress of the ODS steels R&D in Japan will be shown.