Determination of the creep compliance and creep swelling coupling coefficient for neutron irradiated titanium-modified stainless steels at ∼ 400C

The objective of this effort is to provide irradiation creep data and design correlations for application to fusion and breeder reactor design. Irradiation creep data from FFTF-MOTA at ∼ 400C were analyzed for nine 20% cold-worked titanium-modified type 316 stainless steels, each of which exhibits a different duration for the transient regime of swelling. One of these steels was the fusion prime candidate alloy designated PCA. The others were various developmental breeder reactor heats. The analysis was based on the assumption that the B0 + DS creep model applies to these steels at this temperature. This assumption was found to be valid. A creep-swelling coupling coefficient of D ≅ 0.6 x 10-2 MPa-1 was found for all steels that had developed a significant level of swelling. This result is in excellent agreement with the results of earlier studies conducted in EBR-II using annealed AISI 304L and also 10% and 20% cold-worked AISI 316 stainless steels. There appears to be some enhancement of swelling by stress, contradicting an important assumption in the analysis and leading to an apparent but misleading nonlinearity of creep with respect to stress