Irradiation creep of 11Cr–0.5Mo–2W,V,Nb ferritic–martensitic, modified 316, and 15Cr–20Ni austenitic S.S. irradiated in FFTF to 103–206 dpa

The irradiation creep of 11Cr–0.5Mo–2W–0.2V–0.05Nb ferritic–martensitic (PNC-FMS), modified 316 (PNC316) and 15Cr–20Ni base austenitic S.S. were determined by the gas pressurized capsule irradiation test using MOTA in FFTF. The pressurized capsules and open tubes were irradiated at 678–943 K to a peak dose of 206 dpa. The irradiation creep coefficients were derived from the diametral change differences between the capsules and open tubes, accounting for the stress-induced swelling. The creep compliance B0 and creep-swelling coupling coefficient D for PNC-FMS were found to be 0.43–0.76×10−6 MPa−1 dpa−1 and 0.85–2.5×10−2 MPa−1 for volumetric swelling, respectively. For both PNC316 and 15Cr–20Ni base S.S. the irradiation creep properties were very similar. B0 and D range from 0.55 to −1.5×10−6 MPa−1 dpa−1 and from 1.2 to −2.8×10−3 MPa−1, respectively.