Corrosion resistance of structural materials is one of the key issues that affects feasibility of heavy metal cooled fast reactors (FR), because liquid lead-bismuth eutectic (LBE) used as coolant has high solubility against constituent element of the structural materials such as iron and chromium. Then, concept to protect the structural materials by thermodynamically stable thin oxide film formed on the surface of the structural material is under developing. Fe-Cr-Al alloy is one of the promising materials, because aluminum oxide is very stable thermodynamically.&nbsp;On the other hand, in the medical field, research on radiopharmaceuticals labeled with α-ray emitting radionuclide of astatine-211 had been carried out for cancer treatment. Astatine-211 is produced by irradiating bismuth-209 with high-energy alpha particles driven by accelerators, and higher irradiation current is required for mass production. But it has not realized yet because the bismuth target is expected to break (namely melt) by temperature increase during the high current irradiation.&nbsp;To overcome this difficulty, “Liquid Bismuth Target System” which is innovative idea is proposed to achieve higher irradiation current based on the liquid metal technology cultivated in FR development. To realize this system, development of a target window is essential to have enough strength separating liquid bismuth from the vacuum environment of the accelerator and withstand against high corrosive liquid bismuth environment. And more, it must be thin enough to minimize energy loss of the high energy alpha particles.&nbsp;Based on these requirements, authors have been carried out corrosion experiment to select promising target window material in liquid bismuth. Experiment was carried out using Fe-Cr-Al alloy, high chrome steel, and stainless steel as specimens under saturated dissolved oxygen condition and reducing condition at 773 K for 500 hours. From the post metallographic observation results, the corrosion behavior in liquid bismuth is as almost same as that in liquid lead-bismuth under saturated dissolved oxygen condition. Penetration of bismuth into the material and dissolution of constituent element of chromium and nickel into bismuth were confirmed in almost the entire exposure region of stainless steel. Although partly corrosion was confirmed near the gas-liquid interface in high chrome steel, overall corrosion was suppressed. High corrosion resistance was confirmed in Fe-Cr-Al alloy. Although the corrosion behavior under reducing condition against stainless steel and Fe-Cr-Al alloy seems to be slightly stronger than that under saturated dissolved oxygen condition, the effectiveness of Fe-Cr-Al alloy was confirmed.

Corrosion Behavior of Iron-Chrome Alloys in Liquid Bismuth

Paper Proceedings: https://asmedigitalcollection.asme.org/ICONE/ICONE28/volume/85246

2021 28th International Conference on Nuclear Engineering (ICONE28)

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