The Heavy-Section Steel Irradiation Program conducted the Second and Third Irradiation Series to investigate the effects of irradiation on the ductile fracture toughness of seven commercially fabricated low upper-shelf welds. All seven submerged-arc welds were fabricated with copper-coated wire and Linde 80 flux and have average bulk copper contents ranging from 0.21 to 0.42% with nickel levels of about 0.6%. The preirradiation upper-shelf energies range from 74 to 111 J (55–82 ft-lb). Compact specimens up to 101.6 mm (4 in.) thick, 4TC(T), were irradiated at nominally 288°C in the Bulk Shielding Reactor at Oak Ridge National Laboratory to fluences ranging from about 4 to 12 × 1018 neutrons/cm2 (>1 MeV). Charpy V-notch and tensile specimens were included in the capsules at available locations which were subject to wide variations in irradiation temperature and fluence.
This paper presents analyses of the Charpy impact and tensile test data, including adjustments for irradiation temperature and fluence normalization which make possible comparison of the irradiation sensitivity of the different welds. Analyses revealed a dependence of yield and ultimate strength on irradiation temperature of -1.1 and -0.8 MPa/°C, respectively. Similarly, the Charpy impact energy changes due to irradiation temperature were -0.5°C/°C for transition temperature shift and -0.05 J/°C for the upper-shelf energy decrease. After adjustment to an irradiation temperature of 288°C and normalization to a fluence of 8 × 1018 neutrons/cm2, percentage increases in yield strength due to irradiation ranged from about 21 to 35% while those for ultimate strength ranged from about 13 to 20%. The Charpy transition temperature shifts ranged from 59 to 123°C while the postirradiation upper-shelf energies ranged from 58 to 79 J.