The corrosion of materials in spallation neutron sources

Efforts to measure the real-time corrosion rates of alloy 718 during 800 Me V proton radiation at currents up to 1 mA are reported. Specially designed corrosion probes, which incorporate ceramic seals, were mounted in a wafer manifold that allowed samples to be directly exposed to the proton beam at the Los Alamos Neutron Science Center. The water system that supplied the m anifold provided a means for controlling water chemistry, measuring dissolv ed hydrogen concentration, and measuring the effects of water radiolysis an d water quality on corrosion rate. Real-time corrosion rate measurements du ring proton irradiation showed an exponential increase in corrosion rate wi th proton-beam current. These results are discussed within the context of w ater radiolysis at the diffusion boundary layer/beam-spot interface. Howeve r, additional factors that may influence these parameters, such as oxide sp allation and charge build-up in the passive film, are not ruled out.