臺灣博碩士論文加值系統

本研究針對用過核子燃料最終處置場緩衝材料之潛變行為進行實驗及數值模擬分析之相關研究。當處置場中的緩衝材料受到來自近場的熱-水-力學-化學(T-H-M-C)耦合效應的影響，會因為處置罐因自重及其他設施所施加的壓力，而造成處置孔位移，故需要進行潛變試驗及數值模擬，避免多重障壁系統受到損害。
本研究透過單軸壓密試驗及直接剪力試驗，以取得SPV200膨潤土的潛變參數。單軸壓密試驗是將膨潤土壓實後的不飽和試體，放入單軸壓密試驗儀中，垂直載重從0.6 MPa開始加載至4.8 MPa。由應變控制剪力試驗中取得應力控制剪力試驗所需的數據，以進行應力控制剪力試驗，其發現在高剪力強度下試體含水量減少且試體乾密度會增加。而應力控制剪力試驗的試體分別為含水量29.2%的壓實試體以及在剪力盒上經水壓飽和的試體。
使用ABAQUS的數值分析是模擬處置孔中的廢料罐、緩衝材料、回填材料及母岩。在第一部分由實驗室取得潛變參數輸入至ABAQUS數值模擬中，結果顯示因廢料罐自重造成的瞬時沉陷量為0.37 mm；而由直接剪力試驗取得潛變參數，顯示出角應變高於參考文獻中的數據；在數值模擬中緩衝材料預計在400年後才會完全飽和，而在廢料罐下的緩衝材料會在10萬年的時候發生潛變，故由數值模擬中的結果表示，對於潛變位移不會對處置設施造成危害；但是當緩衝材料飽和後，因回脹壓力增加導致緩衝材料及回填材料的介面會有最大向上的為位移。

The buffer material serves a major function in the multiple barrier system for containment of spent nuclear fuels in a geological respository. The deposition hole of high-level nuclear spent fuels components are affected by thermal (T), hydrological (H), mechanical (M), and chemical (C) processes from the near field, referred to as T-H-M-C coupling effects. Bentonite as buffer material is affected by T-H-M-C coupling effects, needs to keep the emplaced canister physically stable to avoid damage caused by displacements and movements initiated by the weight of the canister and stresses exerted by other components of the barrier system.
One-dimensional compression test and direct shear test were performed to determine the creep parameters of SPV200 bentonite. The unsaturated sample compacted and the loading increment for one-dimensional compression test from 0.6 MPa to 4.8 MPa were applied. The strain-controlled direct shear tests were done for obtaining the shear strength of SPV200 bentonite, such that the loading sequence for stress-controlled direct shear test can be obtained. SPV200 bentonite was found to have high shear strength as water content decreases and dry density increases. Stress-controlled direct shear test were run on compacted samples at a saturation water content of 29.2% and on sample saturated in the shear box.
Numerical simulations using ABAQUS were performed on a model incorporating all barrier components in a deposition hole, including the buffer material, the canister, the backfill, and the host rock. The instantaneous settlement caused by canister weight is 0.37 mm as the result of simulation in the first step. The creep parameters obtained from laboratory works were applied as the input for numerical simulation. The creep parameters obtained from direct shear test shows the angular strain rate is higher than the reference. The buffer material was predicted to get fully saturated in 400 years. It is shown that the buffer material under the canister moves upward due to the creep in 100,000 years of time period. And the largest vertical displacement was found to be located at the interface of buffer and backfill caused by the swelling pressure after saturation.

ABSTRACT i
摘要 iii
TABLE OF CONTENTS v
LIST OF TABLES ix
LIST OF FIGURES xi
CHAPTER 1 INTRODUCTION 1
1.1 Research Background 1
1.2 Research Objectives 2
1.3 Research Scope 3
1.4 Research Flowchart 4
CHAPTER 2 LITERATURE REVIEW 5
2.1 Design Concept for Storage of Nuclear High-Level Waste 5
2.2 Functional Requirements of Buffer Material 6
2.3 Basic Properties and Microstructure of Bentonite 7
2.4 Mechanical Behavior of Compacted Bentonite 9
2.4.1 Swelling Behavior of Compacted Bentonite 9
2.4.2 Secondary Compression of Unsaturated Bentonite 12
2.4.3 Shear strength of Compacted Bentonite 12
2.4.4 Creep Behavior of Compacted Bentonite 14
2.5 Canister Settlement 26
2.5.1 Physical Process Leading to Canister Settlement 26
2.5.2 Creep Model for Predicting Canister Settlement 31
CHAPTER 3 RESEARCH METHODOLOGY 41
3.1 Research Design 41
3.2 Material 42
3.2.1 Volclay SPV200 bentonite 42
3.2.2 Creep parameters of bentonite as buffer material 42
3.3 One-Dimensional Compression of Bentonite 43
3.3.1 Sample Preparation 43
3.3.2 Test Set-up of One-Dimensional Compression 44
3.3.3 Test program of One-Dimensional Compression 46
3.4 Direct Shear Test of Bentonite 48
3.4.1 Sample Preparation 48
3.4.2 Test Set-up of Direct Shear 53
3.4.3 Test program of Direct Shear 55
3.5 Numerical Simulation using ABAQUS 56
3.5.1 Parameters for creep of bentonite 56
3.5.2 Mechanical Properties 57
3.5.3 Element Mesh 60
3.5.4 Calculation sequence and Step 62
3.5.5 Initial Condition 64
3.5.6 Boundary Conditions 65
CHAPTER 4 RESULTS AND DISCUSSIONS 69
4.1. One-Dimensional Compression Test Result 69
4.2. Direct Shear Test Result 75
4.2.1 Strain-Controlled Direct Shear Test 76
4.2.2 Stress Controlled Direct Shear Test 81
4.2.3 Calculation of Creep Parameters 85
4.3. Numerical Simulation Analysis 90
4.4. Discussion of Experimental and Numerical Simulation on Creep of Buffer Material 97
CHAPTER 5 CONCLUSIONS AND RECOMMENDATIONS 101
5.1 Conclusions 101
5.2 Recommendations 103
REFERENCES 105

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