Title Page
Abstract
국문 초록
Contents
Nomenclature 23
Chapter 1. INTRODUCTION 27
1.1. Background. 27
1.2. Objectives. 31
1.3. Structure of This Thesis. 33
CHAPTER 2. REFERENCE STRESS BASED J-INTEGRAL ESTIMATION OF CANISTERS WITH WIDE RANGE OF RADIUS-TO-THICKNESS RATIOS 38
2.1. Introduction. 38
2.2. Review of Engineering J-integral Estimation Method 39
2.3. Review of Existing Reference Stress Solutions for Cracked Thin-wall Canister 43
2.3.1. Axial Crack 43
2.3.2. Circumferential Crack 45
2.4. Finite Element Analysis 48
2.4.1. Axial Crack 48
2.4.2. Circumferential Crack 53
2.5. Comparison Estimation Results Using Existing Solutions with FE Results 56
2.5.1. Axial Crack 56
2.5.2. Circumferential Crack 60
2.6. Modified Reference Stress for Circumferential Cracked Canisters 62
2.6.1. Extension to Surface Crack 62
2.6.2. Extension to Wide Range of Radius-to-thickness Ratios 63
2.6.3. Applicability of Proposed Reference Stress 64
2.7. Summary and Discussion 67
2.7.1. Discussion 67
2.7.2. Summary 69
CHAPTER 3. MOVING TEMPERATURE PROFILE METHOD FOR THREE-DIMENSIONAL FINITE ELEMENT HEAT TRANSFER ANALYSIS OF CANISTER 113
3.1. Introduction 113
3.2. Review of Previous Engineering Approach for 3-D Welding Simulation 117
3.2.1. Heat Source Model 117
3.2.2. Prescribed weld temperature method 122
3.3. Proposed 3-D Heat Transfer Analysis Model for Welding Simulation 123
3.3.1. Background 123
3.3.2. Analysis Procedure 124
3.4. Validation of Proposed Method 127
3.4.1. Case 1: Simple two-pass model 127
3.4.2. Case 2: Mock-up Canister Model 130
3.5. Fracture Mechanics Analysis of Canister Considering WRS 133
3.5.1. Failure Assessment Diagram (FAD) Method 135
3.5.2. Reference Stress Solution and V-factor 140
3.5.3. Subject Canister for Assessment 144
3.5.4. Loading and Welding Residual Stress 147
3.5.5. FAD Results 151
3.6. Summary and Discussion 154
Chapter 4. Conclusion and Future Work 179
4.1. Conclusion. 179
4.2. Future Work. 183
REFERENCES 184
Table 2.1. Summary of cases of FE calculations for axial crack 71
Table 2.2. Summary of FE calculation cases for circumferential crack 71
Table 3.1. Welding information for simple two-pass model 157
Table 3.2. Coefficients of the fourth-order polynomial of the residual stress distribution 157
Fig. 1.1. Cycle of spent nuclear fuel and its storage system 35
Fig. 1.2. Domestic storage status of SNF in 2023 35
Fig. 1.3. Structure and components of a typical SNF storage canister 36
Fig. 1.4. Residual stress distribution measured in mock-up canister of Sandia National Laboratories 36
Fig. 1.5. Distribution of dry storage facilities in the U.S. and South Korea, and cooling systems for SNF dry storage 37
Fig. 1.6. Factors and mechanisms of CISCC outbreaks and examples of outbreaks at nuclear power plants 37
Fig. 2.1. Schematics of an axial cracked cylinder under internal pressure p. 72
Fig. 2.2. Typical three-dimensional FE meshes for ri/t=50 with (a) through-wall crack and (b) external surface crack.[이미지참조] 72
Fig. 2.3. Comparisons of the shape factor F for the stress intensity factors, obtained from the FE analyses with the API solution [7]; (a) through-... 73
Fig. 2.4. Schematics of a circumferential cracked cylinder under axial tension N and global bending moment M. 74
Fig. 2.5. FE meshes with circumferential (a) through-wall crack and (b) internal constant-depth surface crack. 74
Fig. 2.6. Comparisons of the shape factor G for the stress intensity factors, obtained from the FE analyses, with the API solution [20]; (a) at the... 75
Fig. 2.7. Comparison of the reference stress based J estimates with FE results for axial through-wall crack under internal pressure; (a)-(b) using the... 77
Fig. 2.8. Comparisons of the reference stress based J estimation method with the FE analyses for the cylinders with axial external surface crack... 79
Fig. 2.9. Comparisons of the reference stress based J estimation method with the FE analyses for the cylinders with axial external surface crack... 81
Fig. 2.10. Comparisons of the reference stress based J estimation method with the FE analyses for the cylinders with axial internal surface crack... 83
Fig. 2.11. Effect of the crack location on FE J and Je results for a/t=0.3 and c/t=1; (a) ri/t=5 and (b) ri/t=70.[이미지참조] 84
Fig. 2.12. Comparison of the reference stress based J estimation results with the FE results for semi-elliptical surface cracks; (a)-(b) for the... 86
Fig. 2.13. Comparison of the reference stress based J estimation results with the FE results for semi-elliptical surface cracks; (a)-(b) for the... 88
Fig. 2.14. Comparison of existing J estimation solutions with FE results for circumferential cracked cylinders under axial tension using two... 90
Fig. 2.15. Variations of Eq. (4) with ri/t for a given thickness.[이미지참조] 91
Fig. 2.16. Comparison of J estimation solutions proposed in Ref. [16] with present FE results: (a)-(b) semi-elliptical internal surface crack and... 93
Fig. 2.17. Schematic figures to define a semi-elliptical surface crack shape: (a) internal and (b) external surface crack. 94
Fig. 2.18. Comparison of the modified reference stress based J estimates with FE results for external circumferential surface crack under axial... 96
Fig. 2.19. Comparison of the modified reference stress based J estimates with FE results for larger ri/t ratios with circumferential cracks of θ/π=0.08:...[이미지참조] 98
Fig. 2.20. Variation of the proposed g function for the optimised reference stress with the relative crack depth and radius-to-thickness ratio. 99
Fig. 2.21. Comparison of the modified reference stress based J estimates with FE results for an external circumferential crack under axial tension:... 102
Fig. 2.22. Comparison of the existing reference stress based J estimates with FE results for an external circumferential crack under global bending... 105
Fig. 2.23. Comparison of the modified reference stress based J estimates with FE results for circumferential crack under global bending moment:... 108
Fig. 2.24. Comparison of the modified reference stress based J estimates with FE results for an internal circumferential surface crack under axial... 110
Fig. 2.25. Comparison of normalized PL from the previous works[10,13]with the R6 Tresca based limit load for the axial through-wall cracked cylinders....[이미지참조] 111
Fig. 2.26. Comparison of normalized PL from the previous work[12] with the R6 Tresca and von Mises based limit loads for the axial internal...[이미지참조] 112
Fig. 3.1. Heat transfer process difference between 3-D model and 2-D axisymmetric model 158
Fig. 3.2. Start-end location effects in a 3-D analysis model 158
Fig. 3.3. Changes in temperature distribution over time (a) constant heat flux model and time-dependent heat flux model and (b) moving heat... 159
Fig. 3.4. Heat flux density function of a moving heat source model 159
Fig. 3.5. Effect of holding temperature and duration time on time-temperature history of PWT method 160
Fig. 3.6. Schematic of the proposed moving temperature profile boundary condition model 160
Fig. 3.7. Difference of cooling speed in 2-D and 3-D heat transfer analysis 161
Fig. 3.8. Temperature distribution by location over time in 3-D heat transfer analysis 162
Fig. 3.9. Welding bead temperature history and the proposed approximation method 163
Fig. 3.10. Calculation example of input temperature profile for butt weld case 164
Fig. 3.10. Thermal properties of 304 stainless steel used in welding simulation 164
Fig. 3.11. Mechanical properties of 304 stainless steel used in welding simulation 165
Fig. 3.12. Plastic strain-stress of 304 stainless steel used in welding simulation 165
Fig. 3.13. Three-dimensional finite element mesh for simple two-pass model 166
Fig. 3.14. Temperature distribution results of 2-D welding analysis of simple 2-pass model 166
Fig. 3.15. Temperature distribution results of proposed 3-D analysis for simple 2-pass model 167
Fig. 3.16. Comparison of residual stress of the experimental Results and proposed 3-D analysis for simple 2-pass model 167
Fig. 3.17. Comparison of analysis time between moving heat source model and proposed moving temperature profile model 168
Fig. 3.18. Schematic representation of the full scale mock storage canister 168
Fig. 3.19. Edge preparation prior to welding of mock-up canister model 169
Fig. 3.20. Schematic of welding procedure of mock-up canister model 169
Fig. 3.21. Experimental WRS results of mock-up canister by SNL; from (a) longitudinal weld center-line and (b) circumferential weld center-line 170
Fig. 3.22. Welding pass section of finite element analysis for mock-up canister model 171
Fig. 3.23. Temperature distribution of 2-D FE analysis using MHS model of the first and fourth passes of the 2-pass model 171
Fig. 3.24. Temperature distribution results of 2-D welding analysis of mock-up canister model 172
Fig. 3.25. Boundary conditions for mechanical analysis of mock-up canister model 172
Fig. 3.26. Comparison of residual stress of the experimental results and proposed 3-D analysis for mock-up canister model 173
Fig. 3.27. Measurement position of start, end point and residual stress of welding simulation 174
Fig. 3.28. Schematics of failure assessment diagram (FAD) method 175
Fig. 3.29. Determination method of margin in loads using FAD method 175
Fig. 3.30. Determination method of critical crack length using FAD method 176
Fig. 3.31. Calculation of critical crack length according to reference stress of axial surface crack 176
Fig. 3.32. Calculation of critical crack length according to reference stress of circumferential surface crack 177
Fig. 3.33. Weld residual stress profile of welded HAZ in the circumferential direction 177
Fig. 3.34. Calculation of critical crack length according to welding residual stress of circumferential surface crack 178