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

  • 제11권1호
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  • Pages.11-21
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  • 2013
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  • 1738-1894(pISSN)
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  • 2288-5471(eISSN)
한국방사성폐기물학회 (Korean Radioactive Waste Society)
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국산 압축벤토나이트 완충재의 첨가제 혼합을 통한 열전도도 향상

Increasing of Thermal Conductivity from Mixing of Additive on a Domestic Compacted Bentonite Buffer

  • 투고 : 2012.08.07
  • 심사 : 2012.12.27
  • 발행 : 2013.03.30
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초록

현재 고준위 방사성 폐기물 심층 처분 시스템에서 기본 완충재 물질로서 건조밀도 1.6 g/$cm^3$의 경주산 칼슘 벤토나이트를 사용하고 있으나, 열전도도가 낮은 단점이 있다. 따라서 본 연구에서는 기준 완충재의 열전도율을 0.8 W/mK에서 1.0 W/mK로 향상시키기 위한 목적으로 다양한 첨가제를 다양한 혼합 방법을 통해 배합하고 열전도도를 측정하였다. 첨가제는 CNT(Cabon Nano Tube), Graphite, Alumina, CuO 및 $Fe_2O_3$ 등을 사용하였다. 혼합 방법의 경우, 핸드 믹서기를 통한 건식혼합, 습식 Milling 혼합, 건식 Ball Mill 혼합 등을 실시하였다. Ball Mill 혼합의 경우가 가장 균일하게 혼합되었기 때문에, 값의 편차가 가장 적었고 열전도도 증가율이 가장 좋았다. 지금까지 수행된 시험에서 소량의 고열전도 물질의 첨가로 경주산 칼슘 벤토나이트의 열전도도를 1.0 W/mK 수준으로 용이하게 증가시킬 수 있음을 실험적으로 확인할 수 있었다. 결론적으로, 본 연구에서 제시된 열전도 향상 방법은, 첨가제 혼합이 벤토나이트의 기본 성질인 팽윤압과 수리전도도에 미치는 영향까지 제시된다면, 국내 고준위폐기물 처분장의 개념 설계에 유용하게 활용될 수 있을 것으로 기대된다.

The Geyoungju Ca-bentonite with dry density of 1.6 g/$cm^3$ has been considered as a standard buffer material for the disposal of high level waste in KAERI disposal system design. But it had relatively lower thermal conductivity compared with other surrounding materials, that was one of key parameters to limit the increase of the disposal density in the disposal system. In this study, various additives were selected and mixed with the Ca-bentonite in different mixing methods in order to increase the thermal conductivity from 0.8 W/mK to 1.0 W/mK. As an additive, CNT (Cabon Nano Tube), graphite, alumina, CuO, and $Fe_2O_3$ were selected, which are chemically stable and have good thermal conductivity. As mixing methods, dry hand-mixer mixing, wet milling and dry ball mill mixing were applied for the mixing. Above all, the ball mill mixing was proved to be most effective since the produced mixture was most homogeneous and showed higher increase in the thermal conductivity. From this study, it was confirmed that the thermal conductivity for the Geyoungju Ca-bentonite could be improved by adding small amount of highly thermal conductive material to 1.0 W/mk. In conclusion, it was believed that the experimental results will be valuable in the disposal system design if the additive effects on the swelling and permeability on the compact bentonite are also approved in further studies.

키워드

참고문헌

  1. Lee, J.W., Jo, W.J., "Thermal-hydro-mechanical Properties of Reference Bentonite Buffer for a Korean HLW Repository", KAERI/TR-3729/2009, KAERI (2009).
  2. Jun, G.S, Lee, J.W., Jo, W.J., Kang, M.J., Kim, S.S., "High-level waste disposal technology development /Engineered barrier development", KAERI/RR-1897 /98, KAERI (1999).
  3. Bel, J., Bernier, F., "Temperature criterion related to clay based backfill materials in the framework of a geological repository of heat producing radioactive waste", proc. ICEM'01, The 8th International Conference on Environmental management (2001).
  4. Lee, J.H., Lee, M.S., Choi, H.J., Choi, J. W., "Temperature effect on the swelling pressure of a domestic compacted bentonite buffer", J. of the Korean Radioactive Waste Society, 8(3), pp.207-213 (2010).
  5. Y.M. Tien., C.A. Chu., W.S. Chuang., "The prediction model of thermal conductivity of sand-bentonite based buffer material", France Clays in Natural & Engineered Barriers for Radioactive Waste Confinement, p.657 (2005).
  6. Beziat, A. Dardaine, M. Mouch, E., "Measurements of the thermal conductivity of clay-sand and clay-graphite mixtures used as engineered barriers for high-level radioactive waste disposal", Applied Clay science, 6, pp.245-263 (1992). https://doi.org/10.1016/S0169-1317(09)90001-1
  7. Michael, J., Gunter, B., "Influence of graphite and quartz addition on the thermo-physical properties of bentonite for sealing heat-generating radioactive waste", Applied Clay Science, 44, pp. 206-210 (2009). https://doi.org/10.1016/j.clay.2009.01.016
  8. Pacovsky, J., Svoboda, J., Zapletal, L., "Saturation Development in the Bentonite Barrrier of the Mock-up- CZ Geotechnical Experiment: Physics and Chemistry of the Earth, 32. Elsevier, pp.767-779 (2007). https://doi.org/10.1016/j.pce.2006.03.005
  9. Vasieek, R., "Mock-up-CZ Experiment, CTU prague, Faculty of Civil Enginering Centre of Experimental Geotechnics". http://ceg.fsv.cvut.cz/EN/ceg-downloads (2007).
  10. Japan Nuclear Cycle Development Institute, H12 Supporting Report2, Repository Design and Engineering Technology, p.431 (2000).
  11. Lee, J.W., Jo, W.J., Jun, G.S., Kang, C.H., "A study on the swelling characteristics of a potential buffer material : effect of ionic strength and temperature on the swelling pressure", KAERI/TR-1318/99, KAERI (1999).
  12. QTM-500, User Guide, Ver. 08, Japan, KYOTO ELECTRONICS,
  13. Coquard, R., Baillis, D., Quenard, D., "Experimental and theoretical study of the hot-wire method applied to low-density thermal insulators", International journal of Heat and Mass Transfer, 49, pp. 4511-4524 (2006). https://doi.org/10.1016/j.ijheatmasstransfer.2006.05.016
  14. Yoo, G.M., Lee, S.G., Kim, S.R., "Effect of Multi-wall Carbon nanotube Surface Treatment on the Interface and Termal Conductivity of Carbon Nanotube-based Composites", Journal of Adhesion and Interface, 11(4), pp.174-180 (2010).

피인용 문헌

  1. Numerical simulation studies on predicting the peak temperature in the buffer of an HLW repository vol.115, 2017, https://doi.org/10.1016/j.ijheatmasstransfer.2017.07.039
  2. Thermal Conductivity of Korean Compacted Bentonite Buffer Materials for a Nuclear Waste Repository vol.11, pp.9, 2018, https://doi.org/10.3390/en11092269