Cross-cutting R and D of ODS steels for Gen-4 and fusion nuclear systems

Full text of publication follows: (authors) High-performance nuclear materials are essential for the realization of advanced fission and fusion nuclear power plants. In this study, cross-cutting materials issues for Gen IV and fusion blanket system will be discussed with focusing on the R and D of oxide dispersion strengthening (ODS) steels, which have been developed for application to fuel cladding materials for highly efficient and high-burnup operation over 100 GWd/t of Gen IV nuclear energy system. Recent ODS steels R and D revealed that the high-Cr ODS steels, whose Cr concentration was 14-16 wt%, showed excellent properties of high strength, high-resistance to corrosion and high-resistance to irradiation embrittlement. The ODS ferritic/ martensitic steels, which contain 9-12 wt% Cr, show rather high resistance to neutron irradiation embrittlement and high strength at elevated temperatures. However, their corrosion resistance is not good enough in supercritical pressurized water and in lead at high temperatures. In order to improve corrosion resistance of the ODS steels in such environment, high-Cr ODS steels have been developed. An increase in Cr content and an addition of Al resulted in a drastic improvement of corrosion resistance in SCW and in lead, respectively, while increasing Cr content was expected to cause an enhancement of aging embrittlement as well as irradiation embrittlement. Anisotropy in tensile properties is another issue. Methodology to achieve high-performance to meet the requirements from system design of Gen IV and fusion systems is discussed. It includes new processing technologies to 1) disperse nano-sized oxide particles in high density, 2) reduce the grain size and their anisotropy. The load map of the ODS steels development towards realization of both the Gen IV and fusion nuclear systems will be shown on the bases of the cross-cutting technology development. (authors)