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

Korean Radioactive Waste Society (한국방사성폐기물학회)
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The Method for Evaluating Unsaturated Hydraulic Conductivity of the Bentonite-buffer Using Relative Humidity

상대습도를 이용한 벤토나이트 완충재의 불포화 수리전도도 평가방안

  • Received : 2013.10.28
  • Accepted : 2014.01.09
  • Published : 2014.03.30
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Abstract

Unsaturated hydraulic conductivity of the bentonite-buffer was evaluated using the relative humidity data. The method for calculating unsaturated hydraulic conductivity was deduced from the general analytical equation representing the movement of water in unsaturated media, which was applied to the experimental results of water infiltration tests for identifying the behavior of unsaturated hydraulic conductivity according to the water saturation. Unlike the saturated condition, the hydraulic gradient and water flux were irregularly changed, and the unsaturated hydraulic conductivity was increased with increasing the experimental time. Swelling of bentonite grains due to the water absorption increased the volume and size of pore within bentonite, resulting in the increase of water velocity and unsaturated hydraulic conductivity. This result suggested the necessity of further investigation on the correlation between the swelling degree of bentonite-buffer and unsaturated hydraulic conductivity. The method used in this study can be useful technique for evaluating long-term hydraulic performance of bentonite-buffer in the radioactive waste disposal system.

상대습도 데이터를 이용하여 벤토나이트 완충재 블록의 불포화 수리전도도 변화를 평가하였다. 불포화 매질에서의 물의 흐름을 나타내는 일반적인 분석해를 통해 상대습도를 통한 불포화 수리전도도 계산방안을 도출하였고, 이를 실제 수행한 실내 물 유입 실험 결과에 적용하여 포화가 진행됨에 따라 변화하는 완충재 불포화 수리전도도 양상을 확인하였다. 일반적인 포화 상태와는 확연히 다르게 수두 구배와 물의 유출량이 시간에 따라 불규칙하게 변화하는 결과를 나타냈으며, 벤토나이트 완충재의 불포화 수리전도도는 시간에 따라 증가하는 경향을 보였다. 수분 흡수로 인한 벤토나이트 입자 팽창 때문으로 인한 매질 내 공극의 부피 및 크기 확대가 불포화 수리전도도값의 증가를 야기하는 것으로 판단되었고, 이러한 결과는 완충재 블록의 팽창 정도와 수리전도도의 상관성에 관한 추후 연구의 필요성을 제시하였다. 본 연구에서 수행된 불포화 수리전도도 평가 방안은 방사성폐기물 처분 시 완충재의 장기적인 수리학적 성능평가에 유용한 기술로 사용될 수 있을 것이다.

Keywords

References

  1. Power Reactor and nuclear fuel development corporation, "Research and development on geological disposal of high level radioactive waste", PNC TN1410 93-059 Tokai, Japan (1992).
  2. H. Coulon, A. Lajudie, P. Debrabent, R. Atabek, M. Jordia, and R. Andre Japan, "Choice of French clays as engineered barrier components for waste disposal", Scientific Basis for Nuclear Waste Management, pp. 813-824 (1987).
  3. J.O. Lee, W.J. Cho, and S. Kwon, "Thermal-hydromechanical properties reference bentonite buffer for a Korean HLW repository", Journal of Korean Society for Rock Mechanics, 21(4), pp. 264-273 (2011).
  4. J.W. Choi, H.J. Choi, and J.Y. Lee, HLW Disposal System Development, Korea Atomic Energy Research Institute Report, KAERI/RR-2765/2006 (2006).
  5. W.J. Cho, J.O, Lee, K.S. Chun, andH.S. Park,"Analysis of Functional Criteria for Buffer Material in a Highlevel Radioactive Waste Repository", Journal of the Korean Nuclear Society, 31(1), pp. 116-132 (1999).
  6. W.J. Cho, J.O. Lee, and C.H. Kang, "Hydraulic conductivity of compacted soil-bentonite mixture for a linear material in landfill facilities", Environmental Engineering Research, 7(3), pp. 121-127 (2002). https://doi.org/10.4491/eer.2002.7.3.121
  7. H. Darcy, Les Fontaines Publiques de la Ville de Dijon, Dalmont, Paris (1856).
  8. L.A. Richards, "Capillary conduction of liquids through porous mediums", Physics, 1(5), pp. 318-333 (1931). https://doi.org/10.1063/1.1745010
  9. D.G. Fredlund and H. Rahardjo, "Soil mechanics for unsaturated soils", John Wiley & Sons Inc., NY, p. 517 (1993).
  10. J.O. Lee, W.J. Cho, and S. Kwon, "Suction and water uptake in unsaturated compacted bentonite", Annals of Nuclear Energy, 38, pp. 520-526 (2011). https://doi.org/10.1016/j.anucene.2010.09.016
  11. J.H. Lee, M. Lee, H.J. Choi, and J.W. Choi, "Temperature Effect on the Swelling Pressure of a Domestic Compacted Bentonite Buffer", Journal of the Korean Nuclear Society, 8(3), pp. 207-213 (2010).
  12. Korea Atomic Energy Research Institute, Thermalhydro-mechanical Properties of Reference Bentonite Buffer for a Korean HLW Repository, KAERI Technical Report, p.33, KAERI/TR-3729/2009 (2009).
  13. Y.J. Cui, C. Loiseau, and P. Delage, "Microstructure changes of a confined swelling soil due to suction controlled hydration. In: Juca, J.F.T., de Campos, T.M.P., Marinho, F.A.M. (Eds.)", Proceedings of the 3rd International Conference on Unsaturated Soils, pp. 593-598, Recife, Brazil (2002).