IX
LISTA DELLE FIGURE
Figura 1.1 IRIS Logo... 8
Figura 1.2 IRIS Integral Layout ... 12
Figura 1.3 Layout of IRIS Vessel Courses ... 13
Figura 1.4 Lower Core Support Structure and Upper Core Support Assembly ... 14
Figura 1.5 Westinghouse EMD IM/P Basic Components ... 15
Figura 1.6 Pressurizer ... 16
Figura 1.7 Neutron Radial Reflector ... 18
Figura 1.8 ISIS Reactor Module... 20
Figura 1.9 Mockup of IRIS Helical Coil steam Generator ... 20
Figura 1.10 Layout of Steam Generator Modules ... 22
Figura 1.11 Plan and 3D view of an IRIS SG module ... 23
Figura 1.12 Elevation view of SGs located within the reactor vessel ... 24
Figura 1.13 Single Helical Tube Routing... 26
Figura 1.14 Helical Tube Extrenity 3D Isometric View ... 26
Figura 1.15 Helical Tube Bending Machine for tube Bundle preparation ... 26
Figura 1.16 Header Tapered extensions fit-up for Internal Bore Welding... 27
Figura 1.17 Internal Bore Welding set in position ... 28
Figura 1.18 Internal Bore Welding set Outline Configuration... 28
Figura 1.19 Solid Piece Header in the as finished condition... 29
Figura 1.20 Solid Piece Internal/External Profiling & Shaping ... 29
Figura 1.21 Steam Generator inspection system ... 31
Figura 1.22 Scheme of the ultrasonic probe... 31
Figura 1.23 Brushing Device... 31
Figura 1.24 Scheme of the ISI Probe assembly bolted on the steam nozzle ... 33
Figura 1.25 Mockup of Steam Generator Inspection System... 33
Figura 2.1 Causes of steam generator tube plugging in the U.S. by year... 35
Figura 2.2 Sketch of recirculating steam generator (UTSG) with indicated problems ... 37
Tabella 2.2 Units reporting steam generator problems worldwide (1992) ... 37
Figura 2.3 Sludge deposited on top of the tubesheet... 40
Figura 2.4 Sketches of some support plate hole designs. (a),(b) drilled without flow holes; (c) broached-trefoil; (d) broached-quatrefoil; (e) egg crate... 41
Figura 2.5 Some degradation problems at tube support plate ... 41
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Figura 2.7 Number of steam generator tubes plugged per year (1993)... 44
Figura 2.8 Sleeving Techniques ... 46
Figura 2.9 NDT techniques for heat exchanger Tubing ... 55
Figura 2.10 IRIS probe for ultrasonic test ... 57
Figura 3.1 The engineering problem of a crack in a structure... 59
Figura 3.2 Cracked plate at a fixed displacement (a) and at a fixed load (b) ... 62
Figura 3.3 Fracturing at costant displacement... 62
Figura 3.4 Fracturing at costant load... 62
Figura 3.5 Graphical representation of instability energy criterion... 65
Figura 3.6 Difference in G for fixed grip and costant load conditions beyond instability ... 65
Figura 3.7 Trend of R-curve for plane strain and plain stress ... 66
Figura 3.8 Definition of the coordinate axis ahead of a crack tip ... 67
Figura 3.9 The three modes pf loading that cam be applied to a crack ... 67
Figura 3.10 Stress normal to the crack plane in Mode I... 70
Figura 3.11 A first approximation to the crack tip plastic zone ... 71
Figura 3.12 First-order and second-order estimates of plastic zone size... 72
Figura 3.13 The Irwin plastic zone correction... 73
Figura 3.14 Effect of thickness on plastic zone shape... 74
Figura 3.15 Dimensionless plastic zone shapes from the Von Mises yield criterion ... 74
Figura 3.16 J-curves for different stresses and typical trend of JR-curve ... 77
Figura 3.17 Schematic J resistance curve for a ductile material ... 79
Figura 3.18 Contour integrals. (A) Elastic body; (B) Body with crack; (C) Path independence contour…...81
Figura 3.19 Effect of the strain hardening exponent on the HRR integration constant... 84
Figure 3.20 Angular variation of dimensionless stress for n=3 and n=13... 84
Figura 3.21 Blunting causes the stresses to deviate from the HRR solution... 85
Figura 3.22 Effect of plasticity on the crack tip stress fields ... 85
Figura 3.23 The Marc System ... 87
Figura 3.24 Closed Contour Used in the Evaluation of the J-Integral... 88
Figura 3.25 Numerical Evaluation for J-Integral (Virtual crack advance)... 89
Figura 3.26 Collapsed two-dimensional element ... 91
Figura 3.27 Crack tip elements for elastic and elastic-plastic analysis ... 91
Figura 3.28 Collapsed three-dimensional element ... 91
Figura 3.29 Linearization of stresses... 92
Figura 3.30 Determination of crack shape factor Q ... 93
Figura 3.31 Corrective factor for membrane stress for internal cracks ... 93
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Figura 3.33 Corrective factor for bending stress for internal cracks ... 94
Figura 3.34 Corrective factor for bending stress for edge cracks... 94
Figura 4.1 IRIS SG Thermal Resistances (Relative Contributions)...106
Figura 4.2 Device for collapse test (preliminary scheme)... 107
Figura 4.3 Tube with Initial Ovality Referred to Outer Diameter... 108
Figura 4.4 Axial Loading Conditions... 111
Figura 4.5 Mechanical Stresses IRIS Tube (Design Load) t = 2.11mm... 113
Figura 4.6 Mechanical Stresses SG U-Tube (Design Load) t = 1.040 ... 113
Figura 4.7 Mechanical Stresses IRIS Tube (Operating Conditions) t = 2.11mm... 114
Figura 4.8 Mechanical stresses SG U-Tube (Operating Conditions) t = 1.040... 114
Figura 4.9 IRIS SG Temperature profiles ... 115
Figura 4.10 Temperature profiles across IRIS SG tube and U tube ... 115
Figura 4.11 Thermal Stresses IRIS Tube (Operating Conditions) t = 2.11mm... 116
Figura 4.12 Thermal Stresses SG U-Tube (Operating Conditions) t = 1.040 ... 117
Figura 4.13 Thermo-Mechanical Stresses IRIS Tube (Operating Conditions) t = 2.11mm.... 118
Figura 4.14 Thermo-Mechanical Stresses SG U-Tube (Operating Conditions) t = 1.040 ... 118
Figura 4.15 Voltage Distribution of a NDT at tube support plate... 121
Figura 4.16 Crack Distribution... 122
Figura 4.17 Schematic illustration for circumferential cracked pipe ... 123
Figura 4.18 Location of circumferential crack in IRIS tube... 123
Figura 4.19 Schematic illustration for axial cracked pipe ... 124
Figura 4.20 Location of axial crack in IRIS tube ... 124
Figura 4.21 Finite element domain along the half semi-elliptical crack front... 125
Figura 4.22 Circumferential crack distant from tube ends ... 125
Figura 4.23 Axial crack distant from tube ends ... 126
Figura 4.24 Circumferential crack near tube-to-header connection ... 126
Figura 4.25 Secondary-side pressure applied on free crack surfaces ... 126
Figura 4.26 Coarse mesh (5086 elem) and refined mesh (7268 elem) around crack tip... 127
Figura 4.27 Stress-strain curve for Inconel 690TT ... 129
Figura 4.28 Stress-strain curve for Incoloy 800 ... 129
Figura 4.29 Normal stress for tube with axial load (Tube round, t = 2.11 mm)... 131
Figura 4.30 Normal stress for tube without axial load (Tube round, t = 2.11 mm)... 131
Figura 4.31 Equivalent Von Mises Stress (Tube round, t = 2.11 mm)... 132
Figura 4.32 Normal stresses vs Distance from crack front for difference thickness... 132
Figura 4.33 Crack opening vs Distance from crack tip for difference thickness ... 133
Figura 4.34 Welded joint near Tube-to-Header connection ... 136
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Figura 4.36 Stress distribution on inner surface at Tube-to-Header connection ... 137
Figura 4.37 J-R curves for Alloy 690 Heat A and Heat B in water... 138
Figura 4.38 SIF vs time to failure in Stress Corrosion Cracking ... 139
Figura 4.38 SIF vs time to failure in Stress Corrosion Cracking ... 139
Figura 5.1 IRIS system nodalization ... 141
Figura 5.2 IRIS SG Header... 142
Figura 5.3 Secondary Side Elevations... 142
Figura 5.4 IRIS SG RELAP Model-Detail of Tube Bundle Geometry and Secondary Side Fouling Model...142
Figura 5.5 Primary-Secondary pressure profiles along tube bundle... 144
Figura 5.6 Internal-External temperature profiles along tube bundle... 145
Figura 5.7 Input Pressure trend for Structural analysis -LOL/TT- ... 148
Figura 5.8 Input Temperature trend for Structural analysis -LOL/TT- ... 149
Figura 5.9 SIF vs. Time for crack distant from Tube ends -LOL/TT- ... 150
Figura 5.10 Max Tresca Stress vs. Time for crack distant from Tube ends -LOL/TT-... 150
Figura 5.11 SIF vs. Time for crack near Tube-to-Header connection -LOL/TT- ... 151
Figura 5.12 Max Tresca Stress vs. Time for crack near Tube-to-Header connection -LOL/TT- ...151
Figura 5.13 Feed Line Break Layout... 153
Figura 5.14 Input Temperature trend for Structural analysis -FLB- ... 154
Figura 5.15 Input Pressure trend for Structural analysis -FLB- ... 155
Figura 5.16 SIF vs. Time for crack distant from Tube ends -FLB-... 156
Figura 5.17 Max Tresca Stress vs. Time for crack distant from Tube ends -FLB- ... 156
Figura 5.18 SIF vs. Time for crack distant from Tube ends -FLB-... 157
Figura 5.19 Max Tresca Stress vs. Time for crack near Tube-to-Header connection -FLB- . 157 Figura 5.20 Locked Rotor Layout ... 159
Figura 5.21 Input Temperature trend for Structural analysis -LR-... 159
Figura 5.22 Input Pressure trend for Structural analysis -LR- ... 160
Figura 5.23 SIF vs. Time for crack distant from Tube ends -LR-... 161
Figura 5.24 Max Tresca Stress vs. Time for crack distant from Tube ends -LR- ... 161
Figura 5.25 SIF vs. Time for crack distant from Tube ends -LR-... 162
Figura 5.26 Max Tresca Stress vs. Time for crack near Tube-to-Header connection -LR- ... 162
Figura 6.1 Design Response Spectrum for SSE ... 165
Figura 6.2 Two reactor vessel support: cylindrical skirt and conical skirt... 167
Figura 6.3 Finite Elements Models of Integral RPV for seismic analysis... 170
Figura 6.4 3D Model e Stick Model of steam generator ... 171
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Figura 6.6 Spectrum analysis results for cylindrical skirt ... 173
Figura 6.7 Design response spectra for SG module seismic analysis ... 174
Figura 6.8 Design response spectra for SG Tube seismic analysis ... 174
Figura 6.9 Spectrum analysis of Tube (conical skirt)... 175
Figura 6.10 Spectrum analysis of Tube (cylindrical skirt) ... 175
