English  |  正體中文  |  简体中文  |  Items with full text/Total items : 78111/78111 (100%)
Visitors : 30600906      Online Users : 403
RC Version 7.0 © Powered By DSPACE, MIT. Enhanced by NTU Library IR team.
Scope Tips:
  • please add "double quotation mark" for query phrases to get precise results
  • please goto advance search for comprehansive author search
  • Adv. Search
    HomeLoginUploadHelpAboutAdminister Goto mobile version

    Please use this identifier to cite or link to this item: http://ir.lib.ncu.edu.tw/handle/987654321/67994

    Title: 低放射性廢棄物最終處置場工程障壁材料於未飽和/飽和環境下之長期穩定性研究
    Authors: 張皓鈞;Chang,Hao-chun
    Contributors: 土木工程學系
    Keywords: 緩衝材料;未飽和/飽和處置環境;混凝土障壁材料;final disposal of low-level radioactive wastes;buffer material;unsaturated/saturated situations;barriers
    Date: 2015-07-23
    Issue Date: 2015-09-23 10:11:29 (UTC+8)
    Publisher: 國立中央大學
    Abstract: 低放射性廢棄物最終處置採多重障壁設施,由於處置場設計年限極長,處置場從施工階段至封閉後之服務期間,其近場環境的演化可能使障壁材料處於未飽和/飽和之狀態下,導致障壁材料性質發生變化,因此本研究藉由各種模擬試驗獲取本土化工程障壁於不同狀態下之參數,做為最終處置場設計之參考。
    ;Both concrete and buffer serve as engineered barriers for isolation of low-level radioactive wastes in a repository. As the disposal site is expected to serve a very long time, the interactions between the two barriers need to be evaluated under the potential unsaturated/saturated situations. The proposed study aims at simulating the long-term scenario of engineered barrier materials and the corresponding effects of the scenario on the expected function of the barrier materials in a final disposal site for low-level radioactive wastes.
    In this research, a migration technique was applied to accelerate the migration of calcium ions from the pore solution of concrete so as to investigate the alteration of compacted bentonite in contact with the concrete. The buffer material, was made using Black Hills bentonite from Wyoming mixed with Taitung area argillite to produce different ratios of sand-bentonite mixture as buffer. And the barrier concrete mixes were proportioned according to traditional American Concrete Institute (ACI) mix design method and Reactive Powder Concrete (RPC) with steel fiber.
    Also, concrete barrier and buffer are both subjected to extended unsaturated situation as well as saturated situation for further evaluation. High-low relative humidity cycling test was designed to investigate the extended unsaturated situation. Finally, the buffer was treated with water permeated through the concrete after the migration test so as to simulate the sequence of unsaturated and saturated scenarios to be experienced. And the buffer was then tested for the change accompanied by the saturation process.
    It was found from the accelerated migration test that the release of calcium from concrete in unsaturated situation results in reduction of swelling capacity of the contacting buffer. And the shorter the distance to the interface, the more the increases in the ratio of calcium to sodium content of buffer material.
    In case that the disposal vault remains unsaturated for extended periods, the absorption/loss of moisture causes changes in volume and weight of buffer material, which in turn result in some cracking and localized scaling off at the outer edge of compacted buffer materials. The use of crushed Taitung area argillite will decrease the change in volume and weight of buffer during the wet-dry cycling. However, due to the reactivity nature of Taitung area argillite, traces of alkali-aggregate reaction were noticed on surfaces of buffer mixed with crushed argillite as a result of long-term exposure to wet environment.
    Upon saturation of the disposal vault, the leaching of hydroxyl ions from concrete to the buffer may cause (1) dissolution of montmorillonite, and (2) precipitation of mineral such as NaAlSi2O6. Both tend to decrease the swelling capacity of the buffer.
    The addition of crushed Taitung argillite aggregate to bentonite showed less damaging effects, resulting from interactions between the contacting barriers, than pure bentonite on the buffer itself. Also, buffer material with 30% crushed aggregate can reduce the change in volume and weight of buffer subjected to high-low relative humidity cycling. On the other hand, the effect of leaching from reactive powder concrete (RPC) on the buffer is less detrimental than that from traditional concrete. Thus, RPC is considered more appropriate as barrier concrete for the final disposal of low-level radioactive wastes.
    Appears in Collections:[土木工程研究所] 博碩士論文

    Files in This Item:

    File Description SizeFormat

    All items in NCUIR are protected by copyright, with all rights reserved.

    社群 sharing

    ::: Copyright National Central University. | 國立中央大學圖書館版權所有 | 收藏本站 | 設為首頁 | 最佳瀏覽畫面: 1024*768 | 建站日期:8-24-2009 :::
    DSpace Software Copyright © 2002-2004  MIT &  Hewlett-Packard  /   Enhanced by   NTU Library IR team Copyright ©   - 隱私權政策聲明