Tensile Properties of 11Cr-0.5Mo-2W, V, Nb Stainless Steel in LMFBR Environment

The tensile strength of ferritic-martensitic 11Cr-0.5Mo-2W, Nb, V stainless steel (PNC-FMS), which had been developed for core component applications in LMFBR by Japan Nuclear Cycle Development Institute, was evaluated for the effects of thermal aging, sodium exposure, and neutron irradiation. The tensile strength of thermal aged specimens (∼1,023 K, ∼12,000 h) decreased at aging conditions above the initial tempering parameter, and the aging effect was considerably enhanced for the wrapper tubes tempered at lower temperatures. The tensile strength of sodium exposed specimens (∼973 K, ∼10,000 h) decreased more than aged specimens due to decarburization, and the effect of decarburization was greater in thin wall cladding tubes. Evaluation of the contribution of both thermal aging and decarburization effects on the tensile strength of cladding tubes irradiated in JOYO (∼1,013 K, ∼6,030 h, ∼29 dpa) suggested that the radiation showed smaller effect on tensile properties than thermal aging and decarburization. By using the derived correlations for thermal aging and decarburization effects, the tensile strength decrease for PNC-FMS after long period (30,000 h) in LMFBR environment was quantitatively calculated.