Irradiation Accelerated Corrosion of 316L Stainless Steel in Simulated Primary Water.

[摘要] The objective of this work is to understand the effects of irradiation on the corrosion of 316L stainless steel in simulated primary water. 316L stainless steel samples were irradiated with a proton beam while simultaneously exposed to simulated PWR primary water to study the effects of radiation on corrosion. A 3.2 MeV proton beam was transmitted through a 37 µm thick sample that served as a ;;window” into a corrosion cell containing flowing 320˚ C water with 3 wppm H2. This design permitted radiolysis and displacement damage to occur on the sample surface in contact with the simulated primary water environment. Samples were irradiated for 4, 12, 24, and 72 hrs at dose rates between 400 and 4000 kGy/s, corresponding to damage rates of 7x10-7 to 7x10-6 dpa/s respectively. The structure and composition of the oxide films were characterized using Raman spectroscopy, STEM, and SEM.Sample areas exposed to direct proton irradiation had inner oxide films that were thinner, more porous, and were deficient in chromium when compared to unirradiated oxides. Outer oxides on irradiated samples exhibited a smaller particle size, and had a significant amount of hematite, which was not found on unirradiated samples. The presence of hematite on irradiated samples indicates an increase in electrochemical potential due to irradiation. Dissolution of chromium-rich spinels due to the elevated potential is identified as a likely mechanism behind the loss of inner oxide chromium. It is suggested that the loss of inner-oxide chromium leads to a less protective inner oxide, and a higher rate of oxide dissolution.Sample areas that were not irradiated, but were exposed to the flow of radiolyzed water, exhibited most of the same phenomena found on irradiated areas including loss of Cr and thinner more porous oxides, indicating that water radiolysis is the primary mechanism. When a sample with a pre-formed oxide was irradiated in the same conditions, the region exposed to radiolyzed water showed signs of elevated potential (hematite), but was not deficient in chromium, and did not exhibit porosity, suggesting displacement damage may still affect corrosion kinetics in an already formed oxide.

[发布机构] University of Michigan

[效力级别] Nuclear Engineering and Radiological Sciences

[关键词] Irradiation Accelerated Corrosion;Nuclear Engineering and Radiological Sciences;Engineering;Nuclear Engineering & Radiological Sciences