Tensile properties of modified 316 stainless steel (PNC316) after neutron irradiation over 100 dpa

ABSTRACT

The effects of fast neutron irradiation on tensile properties of 20% cold-worked modified 316 austenitic stainless steel (PNC316), which was improved swelling resistance and creep strength, claddings and wrappers for fast reactors were investigated. PNC316 claddings and wrappers were irradiated in the experimental fast reactor Joyo at irradiation temperatures between 400°C and 735°C to fast neutron doses ranging from 21 to 125 dpa. The post-irradiation tensile tests were carried out at room and irradiation temperatures. Elongations of PNC316 measured by the tensile tests were maintained at an engineering level, although the material incurred significant irradiation hardening and softening depending on irradiation temperature. The maximum swelling of PNC316 wrappers was about 2.5 vol.% at irradiation temperature between 400°C and 500°C up to 110 dpa. Japanese 20% cold-worked austenitic steels, PNC316 and 15Cr-20Ni, had sufficient ductility and work-hardenability even after above 10 vol.% swelling, while they had very weak plastic instabilities.

KEYWORDS:

• Neutron irradiation
• 100 dpa-over dose
• irradiation-hardening
• tensile properties
• swelling
• austenitic stainless steel

Acknowledgments

Execution of PNC316 development and irradiation programs required the active cooperation of many people at JAEA, Japanese universities and manufacturing companies (Kobe steel Ltd., and the former Sumitomo Metal Industries, Ltd.), and we wish to gratefully acknowledge their support and encouragement. The authors wish to specifically acknowledge Emeritus Professor H. Takahashi of Hokkaido University for his useful discussion and reviews on this manuscript, and Mr. S. Ichikawa, Mr. S. Sato, Mr. T. Inoue, Mr. T. Endo and Mr. M. Sekine of JAEA for specimen preparation and testing.

Disclosure statement

No potential conflict of interest was reported by the author(s).