The corrosion of materials in spallation neutron sources

Efforts to measure the real-time corrosion rates of alloy 718 during 800 MeV proton radiation at currents up to 1 mA are reported. Specially designed corrosion probes, which incorporate ceramic seals, were mounted in a water 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 manifold provided a means for controlling water chemistry, measuring dissolved hydrogen concentration, and measuring the effects of water radiolysis and water quality on corrosion rate. Real-time corrosion rate measurements during proton irradiation showed an exponential increase in corrosion rate with proton-beam current. These results are discussed within the context of water radiolysis at the diffusion boundary layer/beam-spot interface. However, additional factors that may influence these parameters, such as oxide spallation and charge build-up in the passive film, are not ruled out. Scott Lillard earned his Ph.D. in materials science and engineering from Johns Hopkins University in 1992. He is currently a technical staff member at the Materials Corrosion and Environmental Effects Laboratory, Los Alamos National Laboratory. Darryl P. Butt earned his Ph.D. in ceramic science from Pennsylvania State University in 1991. He is currently a technical staff member at the Non-Proliferation and International Security Division, Los Alamos National Laboratory.