臺灣博碩士論文加值系統

經過了國際間無數年的研究與發展，技術上廣泛的一致認為深地質處置提供相對足夠的空間容納大量多年積累的高放射性廢棄物，不論現在或未來對於人類及所居住的環境將較能提供安全性的保障。但是到目前為止尚未有國家正式開始實施深地質處置場的建造，多半都還處在研究評估階段，持續多方面地研究地下處置場岩體的條件與狀況。然而大多數的研究都將地下深層岩體視為均質且等向，但在實際情況下，深層岩體其實為異質且具有異向性的。此外，多數為具有熱傳的異向性，這表示在不同方向上具有不同的熱傳導性。
因此，在本研究中我們延伸了先前Salama A.等人在2015年的研究，進行高放射性廢棄物在深地層處置場岩體的熱傳特性分析，包括考慮了圍岩的熱傳異向性。我們發現高放射性廢棄物置入深地層處置場後周圍的岩體的熱傳異向性差異可能對溫度場有明顯的影響。我們研究了岩體傾角對溫度場的影響，包括0⁰、15⁰、30⁰、45⁰、60⁰、75⁰和90⁰ 並且與等向性案例做對比參考。除了岩體傾角的考量，本研究同時考慮了不同異向性比對溫度場的影響，異向性比從1.1到1.5並且與等向性做比較。本研究與先前的研究最大的差異在於我們在異向性的數值模擬之前有進行與解析解的驗證，並且將模擬分析的結果整理製作成圖，內容為圍岩與緩衝材料在不同異向比與不同傾角下所對應的溫度與100⁰C的溫度限制的關係，提供給後人做為高放射性廢棄物岩體熱傳異向性這方面的參考。
為了確保數值模擬的可行性與準確度，在進行熱傳異向性案例的數值模擬之前，本研究與瑞典SKB公司在2009年的技術報告中所提出的解析解方法做驗證，經過驗證後結果顯示兩種方法的總體趨勢一致。因此，本研究將以相同的數值模型套用在熱傳異向性的模擬分析中。
在本研究中發現整體溫度的分布會隨著岩體傾角的方向轉動，且所有異向性的案例溫度皆高於等向性岩體的溫度，此外，當岩層傾角越大時緩衝材料的最高溫度也越高，反之亦然；同樣地，當岩層異向性比越大時緩衝材料最高溫度也越高。模擬分析之後本研究整理了不同異向性比與不同傾角所對應的緩衝材料最高溫度的圖表，並發現當異向性比從1.1增加到為1.3時，緩衝材料的最高溫度會達到100⁰C的設計限制。此圖表可提供後人研究高放射性廢棄物深層處置場的熱傳異向性的參考之用。

After numerous years of international research and development, there is a broad technical consensus that deep geological disposal which offers relatively enough space to accommodate the large volume of HLW accumulated over the years will provide for the safety of humankind and the environment now and far into the future. In addition, there is not yet an operating geological repository for high-level radioactive waste, and there remains substantial public research about the underground rock mass of geological repository. However, most studies all consider the host rock as homogeneous and isotropic. While in real cases, underground host rock is inherently anisotropic and heterogeneous. Besides, many of them are thermally anisotropic, indicating that there is a preferred direction of thermal conductivity.
Therefore, in this thesis, we extend the previous research (Salama A. et al., 2015) conducted to analyze thermal characteristics of HLW geological repositories by including the effect of anisotropy of thermal conductivity of host rock. We reveal that differences in anisotropy of thermal conductivity of host rock with direction could have clear effects on temperature fields. We also investigate the effect of dip angle on the temperature field. This includes 0⁰, 15⁰, 30⁰, 45⁰, 60⁰, 75⁰and 90⁰ in additions to the isotropic case as a reference. Furthermore, we also consider the effect of anisotropy ratio on the temperature fields. This includes ratios ranging from 1.1 to 1.5. The significant differences between this study with previous research are that we conducted the verification with analytical approach before the numerical simulation and also developed a chart for variation of peak rock wall temperature with the anisotropy ratio for different dip angles which can be used as an anisotropic case for HLW repositories reference.
In order to ensure feasibility and accuracy of the numerical model, we conduct the numerical verification with analytical approach proposed by SKB (2009) before the thermal simulation for anisotropic cases. The results of both approaches show pretty much the same overall trends. As a result, after the verification, the same numerical model is feasibly used for the next anisotropic simulation.
In this study, it is found that the temperature contours are shifted towards the direction of dip angle. The temperature of anisotropic cases are all high than isotropic one. Furthermore, the peak buffer temperature is found to be higher when the dip angle is larger and vice versa. Additionally, the peak buffer temperature is also found to be higher when anisotropic ratio is larger. Also we developed a chart of variation of peak buffer temperature with the anisotropy ratio for different dip angles and find that the peak buffer temperature meets the 100℃ design limit when anisotropy ratio is set to 1.3. The presented chart can be used as an anisotropic case for HLW repositories reference.

CONTENTS
Abstract...I
中文摘要...III
致謝...V
List of Tables...IX
List of Figures...XI
Chapter 1 Introduction...1
1.1 Background and Motivation...1
1.2 Objectives of the study...4
1.3 Layout of the thesis...5
Chapter 2 Literature Review...7
2.1 Historical overview of backfilled EBS design concept...7
2.2 Thermal properties of rock...14
2.2.1 Thermal conductivity of rocks and minerals...14
2.2.2 Conductivity anisotropy of metamorphic rocks...15
2.2.3 Rock conductivity change with temperature...18
2.3 Reference design of the buffer...22
2.3.1 Material composition...22
2.3.2 Blocks and pellets...25
2.4 Thermal conductivity and anisotropy of layered oxides ...27
2.4.1 Thermal Conductivity of Oxides...27
2.4.2 Heat Capacity of Oxides...28
2.4.3 Thermal Diffusivity of Oxides...29
2.5 Numerical investigation in anisotropic geologic repositories...32
Chapter 3 Methodology...39
3.1 Simulating Process...40
3.2 Governing Equations...41
3.2.1 Finite Difference Method of Heat Transport Law...41
3.2.2 Decay Heat...47
3.2.3Thermal Anisotropy...48
3.2.4 Effective Thermal Conductivity...50
Chapter 4 Model Construction and Verification...52
4.1 Cases Description...52
4.1.1 Example case: thermal conduction in a plane sheet...52
4.1.2 Canisters in the central part of the panel...55
4.1.3 Canisters in panel edge regions...56
4.2 Construction for Numerical Model (FLAC3D)...58
4.3 Transformation of the Parameters...58
4.4 Verification result of Numerical Model...62
4.4.1 Verification case of canisters in the central part of the panel...62
4.4.2 Verification case of canisters in panel edge regions...68
Chapter 5 Numerical Analysis...77
5.1 Thermal Anisotropy Setting...77
5.2 Results and Discussions...80
5.2.1 Temperature Distribution...80
5.2.2 Variation with peak buffer temperature for anisotropic cases...81
Chapter 6 Conclusions and Suggestions...94
6.1 Conclusion...94
6.2 Suggestions for future work...96
References...97

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