膨潤土在酸性環境之緩衝回填材料性能影響

Effect of Bentonite on the Performance of Buffer Backfill Material in Acidic Environment

郭俊廷(Jyun-Ting Guo)

指導教授 ： 詹穎雯

國立臺灣大學/工學院/土木工程學研究所/碩士(2021年)

https://doi.org/10.6342/NTU202102354

摘要

隨著科技日益的進步，現今社會對於能源的使用也越來越多，而對核能的應用也逐漸跟著提高，但因為現階段核融合的技術還不夠成熟，因此對現今使用核能伴隨產生的放射性廢棄物的處理便成為重大的課題。
目前各國對於放射性廢棄物大都採用「多重障壁」概念來隔離處理，利用天然地形的屏障，搭配多道人工障壁來隔絕放射性廢棄物與外界環境，讓其放射性衰減至對環境無害的程度。然而要達到上述目標需要一段很長的時間，而且近年來氣候變遷的影響，導致土壤酸化的情況日趨嚴重，位於地下的處置場可能會被因土壤酸化而使酸化的地下水入侵，而導致對以膨潤土作為主要材料的緩衝回填材料有不良的影響，本研究將探討在此酸性環境下對緩衝回填材料之性能的影響進行研究與討論。
本研究以日本進口的KUNIGEL-V1與美國進口之MX-80的純膨潤土試體進行酸性溶液對緩衝回填材料的膨脹性能，且不考慮加入其他粒料，純粹考慮純膨潤土膨脹性能在酸性溶液環境下的影響，藉由土壤基本性質試驗、單向度膨脹率試驗、定體積膨脹壓力試驗及水力傳導係數試驗，來探討此兩種膨潤土在不同初始乾密度下在酸性環境下的各項性能。結果發現，酸性溶液會使鈉型膨潤土蒙脫石礦物內的主要陽離子鈉被氫離子所取代，使蒙脫石礦物溶解，進而影響緩衝回填材料的膨脹性能及阻水性能。綜合比較下，KUNIGEL-V1與 MX-80兩種膨潤土各有優點，且兩膨潤土多數組數皆可達到國外高放規範的要求，因此在設計高放射性廢棄物處置場時，依據所需要的膨脹性能來選擇膨潤土為佳。
最後本研究根據試驗結果提出可以供工務實務設計參考的兩種膨潤土的膨脹性能預測式。

關鍵字

放射性廢棄物 ； 緩衝回填材料 ； 土壤酸化 ； 膨脹率 ； 膨脹壓力 ； 水力傳導係數 ； 預測式

並列摘要

With the increasing advancement of science and technology, today's society is using more and more energy, and the application of nuclear energy has gradually improved. However, because the technology of nuclear fusion is not mature enough at this stage, the treatment of radioactive waste that is accompanied by the use of nuclear energy today has become a major issue.
At present, most countries use the concept of "multiple barriers" to isolate and process radioactive waste. Natural terrain barriers are used with multiple artificial barriers to isolate the radioactive waste from the external environment, so that its radioactivity is attenuated to a level that is not harmful to the environment. However, it will take a long time to achieve the above goals. In recent years, the impact of climate change has caused soil acidification to become more and more serious. The disposal site located underground may be invaded by groundwater acidified by soil acidification, causing the team to use bentonite. As the main material, the buffer backfill material has adverse effects. This study will explore the impact of the buffer backfill material in this acidic environment for research and discussion.
In this study, the pure bentonite samples of KUNIGEL-V1 imported from Japan and MX-80 imported from the United States were used to investigate the swelling performance of the buffer backfill material with acidic solution, and the addition of other pellets was not considered. The swelling performance of pure bentonite was purely considered in the acid solution environment. In order to explore the performance of the two bentonites in acidic environments under different initial dry densities, through the basic soil properties test, the one-dimensional expansion rate test, the constant volume expansion pressure test and the hydraulic conductivity test. It was found that the acidic solution would replace the main cation sodium in the sodium bentonite montmorillonite mineral by hydrogen ions, dissolving the montmorillonite mineral, and then affect the expansion performance and water blocking performance of the buffer backfill material. In a comprehensive comparison, KUNIGEL-V1 and MX-80 have their own advantages, and the number of two bentonites can meet the requirements of foreign high-level radio regulations. Therefore, when designing high-level waste disposal sites, according to the needs Bentonite is better for swelling performance.
Finally, based on the test results, this study puts forward two predictive formulas for the expansion performance of bentonite that can be used as reference for the design of public works.

並列關鍵字

radioactive waste ； buffer and backfill material ； soil acidification ； swelling rate ； swelling pressure ； hydraulic conductivity ； prediction formula

參考文獻

[1] International Atomic Energy Agency (IAEA), “The principles of radioactive waste management, IAEA Safety Series No. 111-F, International Atomic Energy Agency”, 1995.

[2] International Atomic Energy Agency (IAEA), “Technical considerations in the design of near surface disposal facilities for radioactive waste, IAEA-Tecdoc-1256, International Atomic Energy Agency”, 2001.

[3] International Atomic Energy Agency (IAEA), “Classification of radioactive waste: general safety guide, IAEA Safety Standards Series No GSG-1”, 2009.

[4] SKB, “International perspective on repositories for low level waste”, SKB R-11-16, Svensk Kärnbränslehantering AB, 2011.

[5] 行政院原子能委員會網站，高放射性廢棄物最終處置，2019。