Irradiation temperature, fluence, and heating rate effects on plastic flow and failure properties of fast reactor cladding were investigated by heating internally pressurized specimens until failure occurred. Specimens tested were from 20 percent cold-worked Type 316 stainless steel cladding, irradiated in the experimental breeder reactor II (EBR-II) at temperatures to 720°C and fluences to 10²³ neutrons (n)/cm² (E > 0.1 MeV).

A decrease of transient failure temperature with increasing irradiation temperature was observed at the “standard” heating rate of 5.6 C°/s. This effect became more pronounced for irradiation temperatures above 600°C. Transient failure temperatures also generally decreased with increasing fluence for tests performed at the standard heating rate. Irradiated and unirradiated specimens were tested at several heating rates. For equal stress, fluence, and irradiation temperature, decreasing the heating rate decreased failure temperatures by as much as 170 deg C for irradiated specimens and 150 deg C for unirradiated specimens. The data reported herein fall well within fast-flux test facility (FFTF) design limits for transient conditions and serve to confirm the material properties currently used in the design analyses.