Corrosion of Metals and Alloys in High Radiation Fields

Degradation in the properties of structural materials in high-energy proton accelerators will occur as a result of the radiation environment during routine accelerator operations. The potential for such degradation must be included in design and service life assessments of the materials and components. Structural materials in the window, target/blanket, and reflector regions of high-energy proton accelerators will be exposed to a mixed proton–neutron flux that will change the materialʹs exposure environment and cause displacement damage and implant spallation products in the exposed metal. The effects of implantation and displacement damage on materials behavior have been studied on a more or less continuous basis for decades, while radiation effects on corrosion and corrosion related degradation processes has received relatively little attention. The high radiation fields will accelerate corrosion, enhance hydrogen uptake and permeation, and promote corrosion fatigue through environmental changes induced by radiolysis and the deposition of spallation products. Aluminum alloys are particularly susceptible to radiation-induced acceleration of corrosion, and may experience a decreased resistance to fatigue damage. The irradiation fields and the (n, p) reactions associated with tritium production will enhance the uptake and permeation of tritium through austenitic stainless. These radiation-induced effects must be considered in any realistic assessment of material performance in the APT target/blanket region. This paper rationalizes the impact of high radiation fields on corrosion, hydrogen embrittlement, and corrosion fatigue, and relates that impact to radiation-induced changes in chemical reactivity, hydrogen fugacity, and surface chemistry.