Effect of excess oxygen concentration on high-temperature strength of ODS martensitic steel

Otsuka, Satoshi   ; Ukai, Shigeharu  ; Fujiwara, Masayuki; Kaito, Takeji ; Narita, Takeshi

Oxide dispersion strengthened(ODS) martensitic steel (9CrODS steel) has been identified as an attractive candidate for advanced fast reactor (FR) fuel cladding tube because of its superior high-temperature strength and radiation resistance. Our recent activities revealed that high-temperature strength of different lots of the cladding tubes is inconsistent each other, even though the same manufacturing process was applied to these tubes. This inconsistency means a critical problem that high-strength 9CrODS steel cladding tubes can not be manufactured reliably and consistently. In this report, a microstructure control technique for consistently and reliably manufacturing high-strength 9CrODS steel cladding tubes are examined based on a series of data concerning effect of excess oxygen concentration on high temperature strength and microstructure of 9CrODS steel.