Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT) (방사성폐기물학회지)

Korean Radioactive Waste Society (한국방사성폐기물학회)
권호 표지
DOI QR코드

DOI QR Code

Evaluation of Thermal Properties for the Bentonil-WRK Bentonite

  • Received : 2023.11.15
  • Accepted : 2024.01.10
  • Published : 2024.03.30
Download PDF
⟨ Previous Next ⟩

Abstract

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℃. 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)).

Keywords

Acknowledgement

This research was supported by the Nuclear Research and Development Program of the National Research Foundation of Korea (2021M2E3A2041351), and Institute for Korea Spent Nuclear Fuel and National Research Foundation of Korea (2021M2E1A1085193).

References

  1. W.J. Cho. Radioactive Waste Disposal, Korea Atomic Energy Research Institute Report, KAERI/GP-495/2017 (2017). 
  2. M. Juvankoski. Buffer Design 2012, Posiva Oy Report, Posiva 2012-14 (2013). 
  3. D.A. Dixon, M.N. Gray, and A.W. Thomas, "A Study of the Compaction Properties of Potential Clay-Sand Buffer Mixtures for Use in Nuclear Fuel Waste Disposal", Eng. Geol., 21(3-4), 247-255 (1985).  https://doi.org/10.1016/0013-7952(85)90015-8
  4. A. Lloret, M.V. Villar, M. Sanchez, A. Gens, X. Pintado, and E.E. Alonso, "Mechanical Behavior of Heavily Compacted Bentonite Under High Suction Changes", Geotechnique, 53(1), 27-40 (2003).  https://doi.org/10.1680/geot.2003.53.1.27
  5. S. Siddiqua, B. Tabiatnejad, and G. Siemens, "Impact of Pore Fluid Chemistry on the Thermal Conductivity of Bentonite-Sand Mixture", Environ. Earth Sci., 77(1), 8 (2018). 
  6. Posiva Oy & Svensk Karnbranslehantering AB. Safety Function, Performance Targets and Technical Design Requirements for a KBS-3V Repository. Conclusions and Recommendations From a Joint SKB and Posiva Working Group, Posiva SKB Report 01 (2017). 
  7. A.M. Tang, Y.J. Cui, and T.T. Lee, "A Study on the Thermal Conductivity of Compacted Bentonite", Appl. Clay Sci., 41(3-4), 181-189 (2008).  https://doi.org/10.1016/j.clay.2007.11.001
  8. Y. Xu, D. Sun, Z. Zeng, and H. Lv, "Temperature Dependence of Apparent Thermal Conductivity of Compacted Bentonite as Buffer Material for High-Level Radioactive Waste Repository", Appl. Clay Sci., 174, 10-14 (2019).  https://doi.org/10.1016/j.clay.2019.03.017
  9. J.O. Lee, H.J. Choi, and J.Y. Lee, "Thermal Conductivity of Compacted Bentonite as a Buffer Material for a High-Level Radioactive Waste Repository", Ann. Nucl. Energy, 94, 848-855 (2016).  https://doi.org/10.1016/j.anucene.2016.04.053
  10. B.M. Das, Principle of Geotechnical Engineering, 6th ed., Thompson Engineering, Alabama (2006). 
  11. M. Kong, B.J. Kim, N.K. Kim, and J.S. Kim. Mineralogical Characteristics of Bentonil-WRK Bentonite, Korea Atomic Energy Research Institute Technical Report, KAERI/TR-9794/2023 (2023). 
  12. M.S. Lee, H.J. Choi, J.O. Lee, and J.P. Lee. Improvement of the Thermal Conductivity of a Compact Bentonite Buffer, Korea Atomic Energy Research Institute Technical Report, KAERI/TR-5311/2013 (2013). 
  13. K.L. Bristow, R.D. White, and G.J. Klutenberg, "Comparison of Single and Dual Probes for Measuring Soil Thermal Properties With Transient Heating", Aust. J. Soil. Res., 32(3), 447-464 (1994).  https://doi.org/10.1071/SR9940447
  14. X. Liu, G. Cai, L. Liu, S. Liu, and A.J. Puppala, "Thermo-Hydro-Mechanical Properties of Bentonite-Sand-Graphite-Polypropylene Fiber Mixtures as Buffer Materials for a High-Level Radioactive Waste Repository", Int. J. Heat Mass Transf., 141, 981-994 (2019).  https://doi.org/10.1016/j.ijheatmasstransfer.2019.07.015
  15. M.O. Usman and M.J. Simpson, "Assessment of the Molecular-Level Compositional Heterogeneity of Natural Organic Matter in Bentonites Intended for LongTerm Used Nuclear Fuel Storage", Org. Geochem., 152, 104166 (2021). 
  16. S. Yoon, M.J. Kim, S. Park, and G.Y. Kim, "Thermal Conductivity Prediction Model for Compacted Bentonites Considering Temperature Variations", Nucl. Eng. Technol., 53(10), 3359-3366 (2021).  https://doi.org/10.1016/j.net.2021.05.001
  17. Y.A. Cengel and A.J. Ghajar, Heat and Mass Transfer: Fundamentals and Applications, 4th ed., McGraw Hill Education, New York (2011). 
  18. M. Wang, Y.F. Chen, S. Zhou, R. Hu, and C.B. Zhou, "A Homogenization-based Model for the Effective Thermal Conductivity of Bentonite-Sand-based Buffer Material", Int. Commun. Heat Mass Transf., 68, 43-49 (2015).  https://doi.org/10.1016/j.icheatmasstransfer.2015.08.007
  19. F. Dupray, C. Li, and L. Laloui, "THM Coupling Sensitivity Analysis in Geological Nuclear Waste Storage", Eng. Geol., 163, 113-121 (2013).  https://doi.org/10.1016/j.enggeo.2013.05.019
  20. J.O. Lee, K. Birth, and H.J. Choi, "Coupled Thermal-Hydro Analysis of Unsaturated Buffer and Backfill in a High-Level Waste Repository", Ann. Nucl. Energy, 72, 63-75 (2014).  https://doi.org/10.1016/j.energy.2013.04.081
  21. J.H. Anthony, Probability and Statistics for Engineers and Scientist, 4th Revised ed., Thomson Brooks/Cole, Belmont, CA (2012).