Tensile Properties of Fast Reactor Irradiated Type 304 Stainless Steel

Tension tests were performed on annealed Type 304 stainless steel specimens sectioned from Experimental Breeder Reactor-II (EBR-II) duct thimbles. The specimens had accumulated neutron fluences of up to 10.3 × 10²² neutrons (n)/cm², E > 0.1 MeV (10.3 × 10²⁶ n/m², E ×16 fJ). Irradiation temperatures for the material tested ranged from 700 to 750°F (644 to 672 K). The tests were performed at temperatures of room temperature to 1400°F (1033 K), employing strain rates of 2 × 10^-3 to 2/min (3.3 × 10^-5 to 3.3 × 10^-2/s).

At test temperatures below 800°F (700 K), the strength increased with fluence until about 7 × 10²² n/cm² (7 × 10²⁶ n/m²), beyond which no further increase was observed. The elongation decreased with fluence, reaching levels as low as 0.5 percent uniform and 1.3 percent total elongation at 700°F (644 K). High-fluence failures below 800°F (700 K) occurred by transgranular channel fracture.

At test temperatures above 1000°F (811 K), elongations were reduced to very low levels at high fluences (average total elongation (TE) = 0.03 percent). Extensive intergranular fracture at the high fluences produced the low ductility and resulted in failure of the specimens before reaching the strength characteristic of the true hardness of the material.