Corrosion Control for Internal Structure of Nuclear Reactor Based on Radiation Induced Surface Activation Phenomenon

点击翻译按钮获取中文摘要

When a semiconductor film is irradiated by γ-ray, excited electrons are transferred to a base metal in contact with the film, resulting in a drop of corrosion potential. This study proposes a corrosion mitigation method based on radiation induced surface activation(RISA) phenomena by supplying γ-rays from outside the material, or based on a self-excited methodology activating the film and/or the base metal. The results of the study revealed that electrons in the oxide film were activated by γ-ray irradiation and transferred from the oxide to the adjacent base metal. This made the corrosion potential of the metal less noble through a process in which the radiation induced a surface activation phenomenon, even in Zirconium oxide (ZrO_2) films which had large band gap energies. The mitigating method for the corrosion of metals was developed by utilizing this effect. The method involved external γ-rays irradiation introduced by activation of oxide films and/or base metals corrosion potential of ZrO_2 coated SUS304L was shifted down to the range between 90 mV and 300 mV vs. SSE by γ-ray irradiation. The corrosion potential was further shifted down to 600 mV when a CoCr intermediate layer was inserted between the ZrO_2 spray coating film and the SUS304L base metal. Iron specimens with a spray coating film of TiO_2,ZrO_2, and Al_2O_3 were immersed in a 3 wt% sodium chloride aqueous solution. Pitting and general corrosion were suppressed on all three specimens irradiated with γ-rays.These results clearly show that the corrosion potential of stainless steel could be less noble up to a level of -600 mV vs. SSE with this methodology and these processes would have a remarkable effect in mitigating the corrosion of stainless steels used in internal structures of nuclear reactors.