This paper demonstrates use of subsize fatigue specimens for testing highly irradiated specimens to generate reliable information for alloy development and structural design applications. Essential specimen design features needed to accomplish irradiation and stable cyclic fatigue loading at elevated temperature and in high vacuum are discussed in detail.

As examples, test results are presented for Type 316 stainless steel tested at 430 and 550°C. Comparisons are made between data generated from full-size and subsize specimens tested at 430°C with total strain ranges as high as 2% without buckling; results indicated a good reliability of the specimens and testing methods.