Water vapor oxidation behaviors of nuclear graphite IG-110 for a postulated accident scenario in high temperature gas-cooled reactors

• Published in: Carbon (New York) 2020-08, Vol.164 (C), p.251-260
• Main Authors: Cho, Yi Je, Lu, Kathy
• Format: Article
• Language: English
• Subjects: Accidents; Atmosphere; Graphite; High temperature; High temperature gas cooled reactors; Nuclear engineering; Nuclear reactors; Nuclear safety; Oxidation; Oxidation tests; Oxidizing agents; Pore formation; Porosity; Reactors; Temperature dependence; Water vapor
• ISSN: 0008-6223; 1873-3891
• DOI: 10.1016/j.carbon.2020.04.004

Water leakage in accidental conditions of high temperature gas-cooled reactors is one of the most critical problems that can compromise the integrity of different nuclear components. In this study, oxidation behaviors of nuclear graphite IG-110 in water ingress accidental conditions were investigated. Mass loss and oxidation rates were evaluated after oxidation tests at temperatures up to 1400 °C in an Ar-20 vol% H2O mixed atmosphere. The activation energy decreased from 318.6 to 148.9 kJ/mol with temperature, indicating two different oxidation regimes. The cross-sections of the oxidized samples were systematically characterized. The corresponding logarithmic porosity profiles showed a temperature dependency. Pore formation moved toward near-surface regions with increasing temperature and preferential binder oxidation, with filler particle degradation. Furthermore, oxidant concentration profiles and oxidation depths were estimated using a theoretical model and compared with the experimental results. This work provides important benchmark data and safety analysis guidance for the accident scenario in high temperature gas-cooled reactors. [Display omitted]