Mechanical properties of irradiated type 304 and 316 stainless steels

Mechanical properties were investigated for irradiated type 304 and 316 Stainless Steels (SS) which are used as core structural materials in LWRs and LMRs. An irradiation test was performed with a 24MW output power at the IR2 hole of HNARO for 11 days. The specimens accumulated neutron fluences of about 8.0∼10 x 1019 n/cm2 (E>1.0 MeV) at 320 .deg C. The tension test was conducted in the range from room temperature to 700 .deg. C in the IMEF hot cell of KAERI, while employing a strain rate of 2x10-3 /sec. The tensile test results of the irradiated type 304 and 316SS showed the typical irradiation hardening and low ductility behaviors, and especially the yield strength was increased considerably. But, at a high temperature above 500 .deg. C, the irradiated tensile strength approached the un-irradiated one. The reason for it is that the irradiation defects are recovered by thermal activation. Also, the irradiated ones showed higher values in the strain hardening exponents than the unirradiated ones, and their values were nearly saturated to the un-irradiated ones when reaching 600 .deg. C