Evaluation of Thermal Properties for the Bentonil-WRK Bentonite

• Published in: Journal of nuclear fuel cycle and waste technology (Online) Vol. 22; no. 1; pp. 9 - 16
• Main Authors: Yoon, Seok, Lee, Gi-Jun, Lee, Deuk-Hwan, Kim, Min-Seop, Kim, Jung-Tae, Kim, Jin-Seop
• Format: Journal Article
• Language: English
• Published: 한국방사성폐기물학회 01-03-2024
• Subjects: 원자력공학; Thermal conductivity; Regression analysis; Bentonil-WRK bentonite; Specific heat capacity
• ISSN: 1738-1894; 2288-5471
• DOI: 10.7733/jnfcwt.2024.008

The bentonite buffer material is a crucial component in an engineered barrier system used for the disposal of high-level radioactive waste. Because a large amount of heat from the disposal canister is released into the bentonite buffer material, the thermal conductivity of the bentonite buffer is a crucial parameter that determines the design temperature. At the Korea Atomic Energy Research Institute (KAERI), a new standard bentonite (Bentonil-WRK) has been used since 2022 because Gyeongju (KJ) bentonite is no longer produced. However, the currently available data are insufficient, making it essential to investigate both the basic and complex properties of Bentonil-WRK. Thus, this study evaluated its geotechnical and thermal properties and developed a thermal conductivity empirical model that considers its dry density, water content, and temperature variations from room temperature to 90°C. The coefficient of determination (R2) for the model was found to be 0.986. The thermal conductivity values of Bentonil-WRK were 1–10% lower than those of KJ bentonite and 10–40% higher than those of MX-80 bentonites, which were attributable to mineral-composition differences. The thermal conductivity of Bentonil-WRK ranged between 0.504 and 1.149 W·(m−1·K−1), while the specific heat capacity varied from 0.826 to 1.138 (kJ·(kg−1·K−1)).