Title Page
ABSTRACT
국문초록
PREFACE
Contents
CHAPTER 1. INTRODUCTION 26
CHAPTER 2. SIX STUDIES TO OPTIMIZE RADIATION SAFETY MANAGEMENT 29
2.1. Shielding Capability Evaluation of Slit-shaped Structure for Scattered X-ray using Monte Carlo Method 29
2.1.1. Summary 29
2.1.2. Background 29
2.1.3. Materials and methods 31
2.1.4. Results 35
2.1.5. Discussion 38
2.1.6. Conclusion 40
2.2. Proposal of a New Structure for Duct Shielding of Radiation Therapy Room 41
2.2.1. Background 41
2.2.2. MCNP Model 41
2.2.3. Assessment Methods 44
2.2.4. Results 44
2.2.5. Conclusion 53
2.3. Gamma Radiation Transmission Along the Multi-bend Mazes 55
2.3.1. Summary 55
2.3.2. Background 55
2.3.3. Materials and methods 57
2.3.4. Results and discussion 61
2.3.5. Conclusion 66
2.4. Estimation of Leakage Rate of Air from a Fume Hood in a Radioisotope Laboratory Using CFD Simulations 67
2.4.1. Summary 67
2.4.2. Background 67
2.4.3. Materials and methods 69
2.4.4. Results and discussion 76
2.4.5. Conclusion 81
2.5. Design of a Low-resolution Gamma-ray Spectrometer for Monitoring Radioactive Levels of Wastewater 82
2.5.1. Summary 82
2.5.2. Background 82
2.5.3. Materials and methods 84
2.5.4. Results 90
2.5.5. Discussion 94
2.6. Evaluation Activation for 50 MeV Cyclotron Irradiation Service Using Monte Carlo Method and Inventory Code 99
2.6.1. Summary 99
2.6.2. Background 99
2.6.3. Materials and methods 100
2.6.4. Results 105
2.6.5. Discussion 123
2.6.7. Conclusion 126
CHAPTER 3. DISCUSSION 127
CHAPTER 4. CONCLUSION 131
REFERENCE 132
Table 1. Input data for Report 78-Spectrum processor 33
Table 2. Cell numbers and sizes of the region of interest used in the calculations 34
Table 3. Constants a, b using calculation of the transmission factor of the slit-type shield 53
Table 4. Composition of materials used in simulation 59
Table 5. Characteristics of radionuclides commonly used in NDT 60
Table 6. Required length of the corridor to reduce the effective dose to limitation without shielding 65
Table 7. Technical parameters and mesh specifications used in pretesting 74
Table 8. Defined velocities of boundaries 75
Table 9. Time-integrated leakage rates with variable face velocities 80
Table 10. Specifications of the monitoring system 85
Table 11. Specifications of certified reference materials in cylinder-type source, certified by KRISS 87
Table 12. Activity conversion factors (ACFs) for various water tank volumes in Figure 26(b) 93
Table 13. Minimum detectable activity (MDA) for reading time 95
Table 14. Characteristics of proton beam produced by 50 MeV cyclotron using in this study 101
Table 15. Chemical composition of materials 106
Table 16. Inventory calculation results for a steel immediately after irradiation for 15 s and the evaluation of permission for self-disposal. Nuclide... 109
Table 17. Inventory calculation results for a steel 1 day and 7 days later after irradiation for 15 s, and the evaluation of permission for self-disposal 110
Table 18. Characteristics of radioactive waste generation according to irradiation conditions 124
Figure 1. Top view of the simulation model (a), and side views of a shielding wall (b). The unit of length in mm 32
Figure 2. X-ray energy spectrum used in this calculation 33
Figure 3. The transmission factors (B) according to the types of the shield on 110 kVp X-ray. In (b) and (c), steel is used for the structure 36
Figure 4. Effective dose behind the silt-shaped structure. The size of the region of interest was set to 90 cm wide and 200 cm high 38
Figure 5. Treatment room floor plan 42
Figure 6. Schematic of slit-type shielding structure (a) and details (b). All gray areas in (b) are the blocked area of the shielding structure and all... 43
Figure 7. X-ray energy spectrum emitted from LINAC 45
Figure 8. Transmission factors using 2 mm thick steel plate as distance between the steel plates is 2(a), 3(b), 4(c), 5(d), 6(e), 7(f),... 46
Figure 9. Transmission factors using a 3 mm thick steel plate as the distance between the steel plates is 3(a), 4(b), 5(c), 6(d), 7(e),... 49
Figure 10. Transmission factors using 4 mm thick steel plate as the distance between the steel plates is 4(a), 5(b), 6(c), 7(d),... 51
Figure 11. Transmission factor according to the shielding cross-sectional ratio 53
Figure 12. Schematic of NDT facility installed in a maze 56
Figure 13. Top views of a single bend (a), double bend (b), and triple bend (c) maze layout. d1 is the width of the aisle and... 58
Figure 14. Effective dose rates versus distance from point A (d₃ in Figure 13) with the cross-section of 3x1 m(H and W) in the single-bend maze... 61
Figure 15. Effective dose rates versus distance from point A (d₃ in Figure 13) with the cross section of 3x1 m (H and W) in the double-bend maze with... 62
Figure 16. Effective dose rates versus distance from point A (d₃ in Figure 13) with the cross section of 3x1 m (H and W) in the triple-bend maze with 192Ir...[이미지참조] 63
Figure 17. Effective dose rates versus distance from point A (d₃ in Figure 13) with the various cross sections and gamma... 64
Figure 18. Effective dose comparison between this study and the formula suggested by Matsuda and Sasamoto 64
Figure 19. Geometric features for 3D fume hood model 71
Figure 20. Schematic view of variable face velocity fume hood model under investigation 72
Figure 21. Schematics of (a) computational meshes and (b) region of interest 74
Figure 22. Stream plots of air flow in inner fume hood body for 3D simulation with face velocity of 0.01 m·s-1 (a-c), 0.1 m·s-1...[이미지참조] 77
Figure 23. Fluctuation of air flow at region of interest with face velocity of 0.1 m·s-1. (a) The sum of positive y-direction velocities is stable,...[이미지참조] 78
Figure 24. Plot of accumulated leakage rates with variable face velocities at the sash opening 79
Figure 25. Accumulated leakage rates for 160 s with variable face velocities at the sash opening 80
Figure 26. Outline of real wastewater tank (a) and calculation model (b) 88
Figure 27. Count rates of 18F source including background (a) and background (b) obtained by experiment using NaI(Tl) detector[이미지참조] 91
Figure 28. Count rates of 18F source obtained by experiment using HPGe detector[이미지참조] 91
Figure 29. Specific activities measured by HPGe and count rates measured by NaI(Tl): count rates (a), (b) and full energy peaks (c), (d)... 93
Figure 30. View of the irradiation room (a) and cross-section (b) 103
Figure 31. Divided space of irradiation room. (a) is the space under the room for maintaining the gantry structure, (b) is the irradiation room, and... 104
Figure 32. Neutron energy spectrum produced by the interaction of 35 MeV protons and a 10.5 mm thick beryllium target 106
Figure 33. Neutron flux in divided space inside the irradiation room 108
Figure 34. Neutron energy spectrum in tally No. f164 in the irradiation room 108
Figure 35. Inventory calculation results to trace the specific activities of nuclides produced by irradiating a steel for 15 seconds, 1... 111
Figure 36. Inventory calculation results to trace the specific activities of nuclides produced by irradiating a steel for... 112
Figure 37. Inventory calculation results to trace the specific activities of nuclides produced by irradiating a steel... 112
Figure 38. Inventory calculation results to trace the specific activities of nuclides produced by irradiating a copper for 15 seconds, 1... 113
Figure 39. Inventory calculation results to trace the specific activities of nuclides produced by irradiating a copper for 1 hour 114
Figure 40. Inventory calculation results to trace the specific activities of nuclides produced by irradiating a copper for 8 hours 115
Figure 41. Inventory calculation results to trace the specific activities of nuclides produced by irradiating a aluminum for 15 seconds 116
Figure 42. Inventory calculation results to trace the specific activities of nuclides produced by irradiating a... 117
Figure 43. Inventory calculation results to trace the specific activities of nuclides produced by irradiating a aluminum for 5 minutes 117
Figure 44. Inventory calculation results to trace the specific activities of nuclides produced by irradiating a aluminum for 1 hour 118
Figure 45. Inventory calculation results to trace the specific activities of nuclides produced by irradiating a aluminum for 8 hours 119
Figure 46. Inventory calculation results to trace the specific activities of nuclides produced by irradiating a tungsten for 15 seconds, 1... 120
Figure 47. Inventory calculation results to trace the specific activities of nuclides produced by irradiating a tungsten for 1 hour 121
Figure 48. Inventory calculation results to trace the specific activities of nuclides produced by irradiating a tungsten for 8 hours 121