Irradiation Effects on Hydrothermal Corrosion of SiC

2019 Fiscal Year Final Research Report

• Project/Area Number: 17H04977
• Research Category: Grant-in-Aid for Young Scientists (A)
• Allocation Type: Single-year Grants
• Research Field: Nuclear engineering
• Research Institution: Tohoku University (2018-2019); Kyoto University (2017)
• Principal Investigator: Kondo Sosuke 東北大学, 金属材料研究所, 准教授 (10563984)
• Project Period (FY): 2017-04-01 – 2020-03-31
• Keywords: 炭化ケイ素 / 腐食 / 軽水炉 / 燃料被覆管 / 格子欠陥

Outline of Final Research Achievements

SiC is expected to be a new reactor material that is resistant to accidents.　One of the reasons for this is the high chemical stability of SiC. However, it has been reported the neutron irradiation accelerated the corrosion in the hot water (coolant of the reactor). Therefore, we tried to clarify the mechanisms of the corrosion acceleration and to develop a corrosion-resistant surface. We have developed a system to evaluate the corrosion current in SiC, and have revealed the correlation between the corrosion current and various material parameters. The most significant finding is that the density of dangling-bonds localized at lattice defects such as vacancies showed a strong correlation with corrosion by using surface analysis such as KFM and ESR. Thus, the excessive amount of these defects introduced by irradiation was one of the main causes of the accelerated corrosion. We tried to deactivate the dangling-bonds of the irradiated SiC and demonstrated a corrosion protection.

Free Research Field

格子欠陥

Academic Significance and Societal Importance of the Research Achievements

得られた成果はそのまま原子炉安全性向上に貢献するが、高濃度な欠陥準位は例えば粒界などセラミックス中に一般に存在するため、セラミックスの普遍的な腐食理論（高温水、水蒸気酸化なども含む）の拡張が期待される。近年、航空機エンジンや廃棄物処理設備など高温水や水蒸気との共存がセラミックスに益々期待されているが、上述のように禁制帯中の局在準位の任意制御により、新しい防食技術に直結する知見となることが工学的にも期待される。