臺灣博碩士論文加值系統

由於，用過核燃料具有長半衰期的特性，必須使其與人類文明和自然生態永久隔離，至其放射性不再對生物產生重大危害。因此，將退役核燃料以特殊容器包裹，並埋入深地層中做最終處置，是目前全球公認最佳的處置方法。
然而，深地層核燃料處置場當中的熱-水-力耦合現象(Thermal-Hydro-Mechanical Coupling, THM)，是影響處置場安全的一大變因。在進行建造前，需要進行適當的數值模擬以了解此現象對於處置場的安全影響。本研究利用有限元素軟體ABAQUS來進行處置場的熱-水-力耦合現象之模擬分析，探討用過核燃料所產生的衰變熱對於周圍溫度、水力場、應力場的影響。
本研究第四章參考SKB與Posiva所針對水平向處置法(KBS-3H)的THM現象之聯合研究報告[1]，並進行平行驗證，當中包含溫度場、孔隙水壓與飽和度場的平行驗證分析，其中，溫度場平行驗證與原始文獻的結果接近，而飽和度、孔隙水壓的驗證與原始文獻二維模型結果的差異都在兩年以內。其次，在無裂縫帶存在的情況下，本文分析的隧道頂、底部之最小主應力增量歷時與原始文獻結果相近，此外，在第五章中也會加入不同厚度、位置、熱傳導係數、彈性模數的水平裂縫帶來進行參數分析，並觀察出在裂縫帶的熱傳導係數低於母岩之情況下，裂縫帶的增厚、熱傳導係數的降低會造成處置場峰值溫度的升高，此效應也會導致隧道壁的最小主應力增量有上升的情況；而裂縫帶厚度增加、彈性模數減小會提升處置隧道岩壁的最小主應力極值；水平裂縫帶與隧道之間的距離越近，也會提升隧道壁的最小主應力極值，但若裂縫帶在一定距離之外則沒有明顯的影響。

Due to high radioactivity of the spent nuclear fuel, to deposit it properly is an important issue. The almost recommended way is to store the radioactive waste in a specially designed copper canister and isolate it permanently in an underground deposition.
However, the complex thermal-hydro-mechanical coupling (THM) crucially affects the safety of the underground deposition. Conducting a rigorous numerical analysis is necessary to understand the effect of THM processes before construct the underground deposition. In this study, using the finite element software ABAQUS simulates how the decay heat generated by the nuclear fuel influences the temperature ,stress field and degree of saturation around the periphery of deposition.
Firstly ,in chapter 4, a parallel verification simulation about the evolution of temperature ,saturation ,pore pressure field and the change in min. principal stress field in a KBS-3H deposition drift will be conducted and compared to a report completed by SKB and Posiva to ensure the accuracy of the numerical model. The results of verification simulation show some similarity with the base case in the joint research report by SKB and Posiva.
In chapter 5, a sensitivity analysis about the effect of the horizontal fracture included a series cases of different thickness, position, heat conductivity and elastic modulus will be tested. Horizontal fracture in different condition will be added into the simulation and set around the KBS-3H deposition. The results indicate that the temperature in deposition rises if the thickness of fracture increases or the heat conductivity decreases when the value of heat conductivity of the fracture is lower than the intact rock ,this effect further causes the min. principal stress in the tunnel wall to increase. The min. principal stress in the tunnel wall also be influenced by the change in thickness, elastic modulus of the fracture. The min. principal stress increases if the thickness increases or the elastic modulus decreases, but if the fracture locates some distances away from the deposition, this effect is not significant.

摘要 i
ABSTRACT ii
致謝 iv
目錄 v
圖目錄 viii
表目錄 xi
第一章 緒論 1
1.1 前言 1
1.2 研究動機與目的 1
1.3 研究主題與方法 2
1.4 論文內容 3
第二章 文獻回顧 4
2.1 用過核燃料處置概念 4
2.1.1 我國目前用過核燃料之處置現況 4
2.1.2 ＳＫＢ之深地層處置方案 4
2.2 工程壁障之相關研究及其功用 7
2.2.1 處置罐 7
2.2.2 緩衝材料 10
2.2.3 回填材料 11
2.3 處置場中T-H-M作用之相關研究 12
2.3.1 DECOVALEX 13
2.3.2 處置場熱傳分析回顧 14
2.3.3 緩衝材料飽和度歷時分析回顧 15
2.3.4 緩衝材料力學分析回顧 16
2.3.5 岩壁的應力與破壞分析回顧 17
2.3.6 應力與滲透率關係探討回顧 21
第三章 理論與數值分析方法 23
3.1 前言 23
3.2 守恆方程 23
3.2.1 流體質量連續性方程 23
3.2.2 能量守恆方程 24
3.2.3 動量守恆方程 25
3.2.4 位移與應變諧和方程 26
3.3 組成關係(constitutive relation) 27
3.3.1 廣義虎克定律 27
3.3.2 熱傳導理論 28
3.3.3 孔隙水流理論 29
3.4 有限元素法 31
3.5 依序耦合熱-水-力學分析流程 33
第四章 KBS-3H之近場熱-水-力耦合數值模擬 35
4.1 前言 35
4.2 模型幾何配置 35
4.3 材料參數介紹 39
4.3.1 熱傳分析之材料參數 39
4.3.2 水-力分析之材料參數 40
4.4 初始條件與邊界條件 43
4.4.1 熱傳導分析之初始條件與邊界條件 43
4.4.2 水-力分析之初始條件與邊界條件 45
4.5 案例介紹 48
4.6 熱傳導分析平行驗證 48
4.7 水-力分析平行驗證 54
4.7.1 飽和度場之觀察 54
4.7.2 水壓場之觀察 58
4.8 隧道之最小主應力增量值分析 62
第五章 水平裂縫帶對於處置隧道之影響分析 66
5.1 前言 66
5.2 模型幾何與參數配置 66
5.3 改變水平裂縫帶熱傳導係數、位置之溫度峰值分析 68
5.3.1 裂縫帶位於隧道邊緣處 68
5.3.2 改變裂縫帶位置 72
5.4 改變水平裂縫帶熱傳導係數之最小主應力增量分析 73
5.5 水平裂縫帶於隧道邊緣處之最小主應力增量分析 76
5.6 水平裂縫帶於不同位置處之最小主應力增量分析 77
5.7 BMT1C案例的水平裂縫帶對於處置場之影響 81
5.7.1 對處置場再飽和過程的影響之探討 81
5.7.2 對處置隧道最小主應力增量極值影響之探討 83
第六章 結論與建議 85
6.1 結論 85
6.2 建議 88
參考文獻 89

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