The Accelerator Production of Tritium (APT) project proposes to use a 1.0 GeV, 100 mA proton beam to produce neutrons via spallation reactions in a tungsten target. The neutrons are multiplied and moderated in a lead/aluminum/water blanket and then captured in ³He to form tritium. The materials in the target and blanket region are exposed to protons and neutrons with energies into the GeV range. The effect of irradiation on the tensile properties of candidate APT materials, 316L and 304L stainless steel (annealed), modified (Mod) 9Cr-1Mo steel, and Alloy 718 (precipitation hardened), was measured on tensile specimens irradiated in the Los Alamos Neutron Science Center accelerator, which operates at an energy of 800 MeV and a current of 1 mA. The irradiation temperatures ranged from 50–164°C, prototypic of those expected in the APT target/blanket. The maximum achieved proton fluence was 4.5 × 10²¹ p/cm² for the materials in the center of the beam. This maximum exposure translates to a dpa of 12 and the generation of 10,000 appm H and 1,000 appm He for the Type 304L stainless steel tensile specimens.

Specimens were tested at the irradiation temperature of 50-164°C. Less than 1 dpa of exposure reduced the uniform elongation of Alloy 718 (precipitation hardened) and mod 9Cr-lMo to less than 2%. Approximately 4 dpa of exposure was required to reduce the uniform elongation of the austenitic stainless steels (304L and 316L) to less than 2%. The yield stress of the austenitic steels increased to more than twice its non-irradiated value after less than 1 dpa. These results are discussed and compared with results of similar materials irradiated in fission reactor environments.