Mechanical Properties of 1950's Vintage Type 304 Stainless Steel Weldment Components After Low Temperature Neutron Irradiation

The reactor vessels of the nuclear production reactors at the Savannah River Site (SRS) were constructed in the 1950's from Type 304 stainless steel plates welded with Type 308 stainless steel filler using a multipass metal-inert-gas process. A mechanical properties database for irradiated material has been developed for the vessel with materials from archival primary coolant system piping irradiated at low temperatures (75 to 150°C) in the State University of New York at Buffalo reactor (UBR) and the High Flux Isotope Reactor (HFIR) to doses of 0.065 to 2.1 dpa. Fracture toughness, tensile, and Charpy-V impact properties of the weldment components (base, weld, and weld heat-affected-zone (HAZ)) have been measured at temperatures of 25°C and 125°C in the L-C and C-L orientations for materials in both the irradiated and unirradiated conditions for companion specimens. Fracture toughness and tensile properties of specimens cut from an SRS reactor vessel sidewall with doses of 0.1 and 0.5 dpa were also measured at temperatures of 25 and 125°C. The irradiated materials exhibit hardening with loss of work hardenability and a reduction in toughness relative to the unirradiated materials with a slight sensitivity to exposure. Irradiation increased the yield strength between 22% to 187% with a concomitant tensile strength increase between-9% to 29%. The irradiation-induced decrease in the elastic-plastic fracture toughness (J_D at 1 mm crack extension) is between 26% to 64%; the range of J_ICvalues are 72.8 to 366 kJ/m² for the irradiated materials. Similarly, Charpy V-notch results show a 38% to 59% decrease in impact absorbed energies. The C-L orientation shows significantly lower absorbed energies and fracture toughness parameters than the L-C orientation for both the base and HAZ components in both the unirradiated and irradiated conditions.