RS-22-071, License Renewal Response to Commitment 10 - Evaluation of Possible PWSCC Crack Initiation and Propagation in the Steam Generator Channel Head Assembly and Tube-to-Tubesheet Welds
| ML22158A296 | |
| Person / Time | |
|---|---|
| Site: | Byron, Braidwood  |
| Issue date: | 06/07/2022 |
| From: | Constellation Energy Company |
| To: | Office of Nuclear Reactor Regulation |
| Shared Package | |
| ML22158A294 | List: |
| References | |
| RS-22-071 | |
| Download: ML22158A296 (111) | |
Text
BWXT Canada Ltd.
Page 1 of 55 ELECTRIC POWER RESEARCH INSTITUTE BYRON / BRAIDWOOD UNIT 1 FLAW TOLERANCE EVALUATION AT PRIMARY HEAD / TUBESHEET / DIVIDER PLATE TRIPLE POINT ANALYSIS REPORT (NON-PROPRIETARY)
BWXT CANADA REPORT NO.: M2004-SR-01-NP REVISION 1 OCTOBER 2021 Engineering Specification: 18-1229648-008 Prepared By:
Date: _See Electronic Signature__
D. Hartman, P. Eng.
Manager, Engineering Analysis and Qualification Verified By:
Date: _See Electronic Signature__
A. Cameron Engineering Analyst Approved By:
Date: __See Electronic Signature__
R. MacEacheron, P. Eng.
Project Engineer Approved By:
Date: _See Electronic Signature__
S. Fluit, P. Eng.
Manager, Engineering Services 2021 BWXTCANADA LTD. ALL RIGHTS RESERVED.
This document is the property of BWXT Canada Ltd. (BWXT Canada).
M2004-SR-01-NP, Rev. 1 Page 2 BWXT Canada Ltd.
INDEPENDENT DESIGN VERIFICATION BY DESIGN REVIEW NEF008 Rev. 01 Design Review Verification Criteria (as applicable)
Rev. 0 Rev. 1 Rev. 2 Rev. 3 Rev. 4 Rev. 5
- 1. Are the design inputs (including customer specification requirements and other customer supplied inputs, drawings or other analysis) correctly selected and incorporated into the design?
Yes Yes
- 2. Are the design inputs (including customer specification requirements and other customer supplied inputs, drawings or other analysis) verified?
Yes Yes
- 3. Are verified customer supplied design inputs located in either the CIS or project services database?
Yes Yes
- 4. Are assumptions necessary to perform the design activity reasonable and adequately described? Where necessary, are the assumptions identified for subsequent reverification when the detailed design activities are complete?
Yes Yes
- 5. Is the design method appropriate?
Yes Yes
- 6. Were all design inputs correctly incorporated into the design?
Yes Yes
- 7. Is the design output reasonable compared to design input?
Yes Yes
- 8. Are the necessary design inputs and verification requirements for interfacing organizations specified in the design documents or in supporting procedures or instructions?
N/A N/A Rev Verified By Date Rev Verified By Date 0
A. Cameron 2021-08-19 3
1 See Electronic Signature 4
2 5
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LIST OF REVISIONS Rev. Sec. / Page Description 0
All Original Release. See M2004-SR-01 report.
1 All Issued in conjunction with M2004-SR-01 Rev. 1. This is a non-proprietary version of that report and the contents are identical with the exception of redactions.
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TABLE OF CONTENTS 1.0 ABSTRACT...........................................................................................................................................................5
2.0 INTRODUCTION
..................................................................................................................................................7 3.0 ACCEPTANCE CRITERIA..................................................................................................................................8 4.0 LOADING CONDITIONS.....................................................................................................................................9 5.0 MATERIALS AND PROPERTIES.....................................................................................................................12 6.0 TRANSIENT STRESSES..................................................................................................................................13 7.0 FATIGUE CRACK GROWTH ANALYSIS.........................................................................................................15 8.0 PRIMARY STRESS ANALYSIS........................................................................................................................23 9.0 VERIFICATION OF ASSUMPTIONS................................................................................................................24
10.0 CONCLUSION
S.................................................................................................................................................24
11.0 REFERENCES
, DESIGN DRAWINGS AND COMPUTER CODES...............................................................25 12.0 LIST OF DETAILED ANALYSIS CALCULATIONS..........................................................................................27 13.0 FIGURES............................................................................................................................................................28
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1.0 ABSTRACT This report presents the flaw tolerance evaluation at the triple point (intersection of the divider plate, primary head and tubesheet) of the primary head assembly for the Bryon / Braidwood Unit 1 Replacement Steam Generators (RSG). The evaluation demonstrates the structural integrity of the RSG primary head wall in the presence of a postulated crack at the triple point that is hypothesized to propagate from the divider plate assembly through the cladding into the primary head wall. Both axial and circumferential flaws are considered. This report is prepared to demonstrate that cracking in the triple point region due to primary water stress corrosion cracking is not a concern; to avoid in-service Non-Destructive Examination (NDE) of this Braidwood Unit 1 RSGs are analyzed using a similar approach as EPRI Report 3002002850 [8] which was accepted by the NRC as substantiating that visual examination of divider plate to tubesheet welds are adequate to ensure structural integrity of the steam generator channel head. This evaluation is completed in accordance with the specified criteria of ASME Boiler and Pressure Vessel Code,Section XI, 2017 Edition
[4]. This is a document approved for incorporation by reference as per 10CFR50.55(a)(1)(ii)(c)(55). A code reconciliation to the 2007 Edition with 2008 Addenda and 2013 Edition is performed for the acceptance criteria.
Both classical techniques and FE analysis with ANSYS [5] are used in the analyses. The analysis concludes that:
- 1. All components meet the ASME Code Section XI requirements for the postulated crack under normal (including upset and test) conditions considering the end-of-life flaw size.
- 2. All components meet the ASME Code Section XI requirements for the postulated crack under emergency and faulted conditions considering the end-of-life flaw size.
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2.0 INTRODUCTION
The divider plate seat bar / weld build-up potentially has some susceptibility to primary water stress corrosion cracking (PWSCC), based on the conclusions of EPRI Report 3002002850 [8] and as discussed in Section 5.0. As a result, it is postulated that a crack may initiate in the divider plate weld build-up and then propagate into the cladding of the primary head at the triple point (intersection of the divider plate, primary head and tubesheet) due to PWSCC. It is further hypothesized that the crack can then propagate through the primary head wall thickness due to fatigue crack growth. The locations of the cracks and the triple point geometry can be seen in Figure 6. The flaw tolerance evaluation in this report considers the growth of this postulated planar flaw over the design life of the Byron Unit 1 and Braidwood Unit 1 RSGs. The analysis approach closely follows the approach used in EPRI Report 3002002850 [8], noting that only the flaw evaluation of the primary head is performed. Both axial and circumferential flaws are considered.
A postulated flaw in the divider plate weld build-up is included in a three dimensional finite element model of the primary head assembly, which can be seen in Figure 1. This postulated flaw is conservatively considered as being approximately [
]a of the steam generator radius, which is larger than considered in EPRI Report 3002002850 [8]. The flaw is modeled from near the primary head inside surface at the triple point towards the centre of the tubesheet. This finite element model is then used for all Level A to D transients to calculate the through-wall thickness stress distribution at the triple point due to pressure and thermal loading. More details on the finite element model and the thermal transient analysis are given in Section 6.0.
The initial crack size in the primary head is considered to be equal to the primary head cladding thickness in depth and the width of the divider plate weld build-up in length. This initial crack size is then considered in a crack growth analysis in accordance with ASME Boiler and Pressure Vessel Code (B&PVC),Section XI, 2017 Edition, Non-Mandatory Appendix A [4]. The stress distributions through the primary head wall thickness for all Level A and B transients are used to propagate the crack for the design life of the RSG. Self-equilibrating residual stress due to welding is also added to the stresses due to pressure and thermal loading for each transient. These stresses are used to calculate the Stress Intensity Factor (KI). Postulated circumferential and axial flaws on the inside surface of a cylinder are both considered using standard formulations from Non-Mandatory Appendix A [4]. The growth of these two crack types is modeled using a Paris Law fatigue crack growth model in accordance with Non-Mandatory Appendix A [4]. More details on the crack growth analysis are given in Section 7.0.
From the fatigue crack growth analysis, the final flaw size (af and lf) is known at the end of the RSG life. With this final flaw size, the acceptability of the flaw is assessed per the acceptance criteria of IWB-3600 [4]. The maximum stress intensity factor for each transient, including normal and emergency and faulted conditions, at the final end-of-life flaw size geometry is compared against the acceptance criteria. Details can be seen in Section 7.3.
The primary stress criteria per NB-3000 [2] are also verified with local area reduction in the primary head due to the final crack geometry. [
]a More details on the primary stress evaluation are given in Section 8.0.
The report conclusions are described in Section 10.0. The references, design drawings and computer codes used in the detailed analysis calculations included in this report are described in Section 11.0. These detailed analysis calculations are identified in Section 12.0. All figures mentioned in this report are contained in Section 13.0.
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3.0 ACCEPTANCE CRITERIA The acceptance criteria of the ASME Code Section XI, IWB-3600 [4] are used to show the pressure boundary component acceptability. The acceptability criteria for ferritic steel components, 4 in and greater in thickness is given in IWB-3610 [4]. The flaw category is Category 2, surface flaw in both the cladding and ferritic material, as per IWB-3610 [4]. A code reconciliation is given in Section 3.3 for the 2007 Edition with 2008 Addenda and 2013 Edition.
3.1 Flaw Size A flaw size that exceeds the size requirements of IWB-3500 [4], is acceptable if the following conditions are met as per IWB-3612 [4], as specified per IWB-3610(d)(1) [4].
KI < KIC / 10 For normal conditions (including upset and test)
KI < KIC / 2 For emergency and faulted conditions Where:
KI is the applied stress intensity factor for the flaw dimensions af and lf.
KIC is the fracture toughness based on crack initiation for the corresponding crack tip temperature.
af is the end of evaluation period flaw depth lf is the end of evaluation period flaw length 3.2 Primary Stress As per IWB-3610(d)(2) [4], the primary stress limits of NB-3000 [2] must be met, assuming a local area reduction of the pressure retaining membrane equal to the area of the flaw. There are no requirements on secondary stresses or fatigue usage factors specified in IWB-3600.
3.3 ASME Code Reconciliation Exelon has Nuclear Regulatory Commission (NRC) approval to use ASME Section XI, 2007 Edition with 2008 Addenda [14] for Bryon and ASME Section XI, 2013 Edition [15] for Braidwood for in-service inspection activities. The evaluation documented in this report was compared to ASME Section XI, 2017 Edition [4]. The relevant Paragraph in Section XI, 2017 edition [4], used to evaluate the flaw, is IWB-3610 and Greater in Thickness. Upon comparing the requirements from this paragraph for the earlier Code Editions [14] [15] with the later Code Edition [4], it is concluded that there are no changes in technical requirements. Therefore, the requirements of the earlier editions (2008A and 2013E) [14] [15] are met.
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4.0 LOADING CONDITIONS 4.1 Transient Conditions The transient conditions for the Byron / Braidwood Unit 1 Replacement Steam Generators (RSGs) at 3672 MWt MUR uprate conditions are specified in the CDS [1]. These Level A and B transient conditions have been analyzed for the steam generator in B&W Canada Report 236R-SR-01 [10], which is the Analysis of Record for the Byron / Braidwood Unit 1 RSGs. As a result, the same transient analysis files are used in this analysis. [
]a The transients [
]a analyzed can be seen in Table 1.
The primary side temperature for the primary hydrotest transient has been modified from the transients in B&W Canada Report 236R-SR-01 [10] to reflect the field hydrotest minimum temperature of [
]b. The full [
]b cycles have been considered as field hydrotests. Similarly, the secondary side temperature for the secondary hydrotest transient has been modified from the transients in B&W Canada Report 236R-SR-01 [10] to reflect the field hydrotest minimum temperature of [
]b. The full [
]b cycles have been considered as field hydrotests.
The thermal and structural analysis of the [
]a.b Level A and B (normal, upset and test) transients listed in Table 1 is performed as discussed in Section 6.2. The bounding Level C and D (emergency and faulted) transients are listed in Table 2 and the structural analysis is performed as discussed in Section 6.2.
[
]a
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Table 1 Level A and B Transients for Normal (including Upset and Test) Conditions a,b
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Table 2 Level C and D Transient (Emergency and Faulted) Conditions a,b
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5.0 MATERIALS AND PROPERTIES The material designations for the components for the Byron/Braidwood Unit1 RSGs are specified in the B&W Canada Drawing 7720A035 [7] and summarized in Table 3. Details of material mechanical properties used in a specific component/assembly analysis are given in the corresponding calculation for that component/assembly. The properties are taken from the ASME B&PVC Section II, Part D [3]. The reference nil ductility temperature (RT NDT) for the primary head material is [
]b [1, Section 3.5.1]. A corrosion allowances of [
]b is considered for the shell secondary side only [6][1, Section 3.5.5].
The divider plate seat bar / weld build-up is constructed from [
]c. The chromium composition for this material is [
]a,c [3]. Based on the Section 3.7 of EPRI Report 3002002850 [8],
the resistance to Primary Water Stress Corrosion Cracking (PWSCC) is related to the chromium content of the material. Chromium contents below 24% can have PWSCC occur in nominal environments but chromium contents at 20% or higher are quite resistance to cracking. Therefore, the divider plate seat bar / weld build-up could have some susceptibility to PWSCC but its resistance would be fairly high. As a result, a crack is postulated to occur in this weld build-up due to PWSCC and as such is analyzed in this report.
Table 3 Component Materials Component Material Primary Head, Tubesheet
[
]c Primary Divider Plate Seat Bar (1)
[
]c Primary Divider Plate
[
]c Secondary Shell
[
]c Notes:
1)
[
]c The [
]c material is one of the materials listed in A-4200 [4] from which the data was derived and therefore the material properties and fracture toughness curve given in A-4300 and A-4200 [4]
respectively are applicable.
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6.0 TRANSIENT STRESSES 6.1 Finite Element Model A 3D half-symmetrical primary head / tubesheet / divider plate / secondary shell assembly FE model of the Byron / Braidwood Unit 1 Replacement Steam Generator is employed for transient and structural analysis.
The FE model is developed using ANSYS [5] and is documented in BWXT Canada Calculation M2004-B001.
The developed FE model is shown in Figure 1, which includes the primary head, tubesheet, divider plate, and secondary shell with a sufficient extension length. [
]a The inner perforated region of the tubesheet is represented with equivalent solid properties
[
]a. Detailed dimensions can be seen in Figure 2 to Figure 4. The materials for the model are as discussed in Section 5.0 and listed in Table 3. Figure 5 and Figure 6 show the FE model with the material colours. As shown in Figure 7, a divider plate crack from divider plate edge toward the tubesheet centre is modelled. This is the assumed crack in the divider plate to tubesheet weld due to PWSCC, as detailed in Section 2.0. This crack then propagates into the cladding and primary head wall through fatigue crack growth. [
]a A crack at the divider plate edge provides results at the triple-point that are bounding compared to a similar crack located centrally along the divider plate.
6.2 Transient Thermal and Structural Analysis The FE model described in Section 6.1 is used for the transient and structural analysis of the primary head assembly. The following is the procedure that is used. This procedure is documented in BWXT Canada Calculation M2004-B002.
[
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]a
[
]a
[
]a
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7.0 FATIGUE CRACK GROWTH ANALYSIS 7.1 Analysis Overview The following is a brief overview of Non-Mandatory Appendix A [4] as it pertains to the flaws and stresses considered in the evaluation of this report. For a more detailed description of the process for analytical evaluation of flaws, Non-Mandatory Appendix A [4] should be consulted.
The flaw shape is considered as an elliptical planar area surface flaw with the initial depth (a) of the crack This corresponds to a longer flaw than if the aspect ratio (a/l) of 0.167 as recommended by L-3211(a) [4] was used. An illustration of the surface flaw is seen in Figure 18.
The crack tip stress intensity factor is then calculated in accordance with A-3000 [4]. A 4th order polynomial is fit over the wall thickness to provide an accurate stress distribution in accordance with A-3212 [4]. An illustration of the stress distribution over the wall thickness is seen in Figure 19. The stress results through the wall thickness from each transient and each transient substep (critical time point) are read from the ANSYS results. The stresses are added to the weld residual stress (seen in Figure 22) and a 4th order polynomial stress distribution through the wall thickness is fit. The stress intensity factor is then calculated based on the following equation given in A-3411(c) [4].
KI = [(B0 + Bp) G0 + B1 (a/t) G1 + B2 (a/t)2 G2 + B3 (a/t)3 G3 + B4 (a/t)4 G4] ( a / Q)
Where B0 to B4 are the coefficients of the 4th order polynomial of the stress distribution through the wall thickness Bp is the inside surface pressure G0 to G4 are the coefficients dependent on the flaw size and specimen geometry Q is a flaw shape parameter The stress intensity factor is calculated for the circumferential flaw on the inside of a cylinder seen in Figure 20 and the axial flaw on the inside of a cylinder seen in Figure 21. The stress intensity factor is also calculated for both Point 1 (deepest point) and Point 2 (surface point) as seen in Figure 18. Note that for the circumferential flaw, the axial stress distribution through the wall thickness is used. For the axial flaw, the hoop stress distribution though the wall thickness is used.
The G0 to G4 coefficients are dependent on the specimen geometry and the flaw size. They are calculated according to A-3413(a) [4] for Point 1 and A-3413(b) [4] for Point 2. The coefficients used in these equations are calculated according to A-3532 [4] for the circumferential flaw and A-3552 [4] for the axial flaw. These coefficients are dependent on the crack size to wall thickness ratio, inside radius to wall thickness ratio and crack depth to length ratio.
With the stress intensity factor calculated based on the stress distribution for each transient substep, the stress intensity factor range ( KI) is calculated based on the maximum and minimum KI for each transient and used with the Paris Law type fatigue crack growth rate given in A-4300 [4]. The material property coefficients (C0, n) used in the crack growth rate model consider the more conservative of the growth rate for air and for light water environments. They are also dependent on the stress ratio for the transient and the
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appropriate material property coefficients are used based on the stress ratio. If the stress intensity factor range ( KI) is less than the threshold value ( Kth), no growth is considered as discussed in A-4300 [4]. The threshold values considered are given in A-4300 [4].
The crack growth rate for both Point 1 and Point 2 is calculated ( a and l) which is then added to initial crack size to give the new crack size at the end of the transient. This process is then repeated for each transient and each application of the transient to get the final crack size at the end of the design life. The transient order is based on dividing up the transients in to blocks which give an even distribution of the transients over the design life. The crack growth analysis is performed for the normal (including upset and test) conditions only per A-5200 [4].
The crack growth analysis is performed through encoding all of the necessary equations from Non-Mandatory Appendix A [4] into Excel. More details on this analysis approach and the tool used are given in BWXT Canada Calculation M2004-B004.
7.2 Fatigue Crack Growth Each of the paths (8 total) defined in Section 6.2 are then considered for crack growth analysis. Both axial and circumferential flaws are considered independently for each path location and therefore the hoop and axial stresses respectively are used for these flaws. All 8 paths with the two flaw types are run through the crack growth analysis. The final crack sizes for all 8 paths and both flaw types can be seen in Table 4. [
]a The maximum and minimum stresses for each transient are plotted as seen in Figure 23 to Figure 25 for the axial stress and Figure 26 to Figure 28 for the hoop stress. Note that the stresses correspond to the stress distribution through the primary head wall without any postulated crack included in the primary head wall within the FE model. The stresses are therefore the nominal stress distribution as required for linear elastic fracture mechanics. [
]a Weld residual stress is considered in the analysis due to the proximity to the primary head seam weld. This is a self equilibrating through-wall weld residual stress profile for post weld heat treated vessel plate seam welds from EPRI Report TR-100251 [9], as seen in Figure 22. [
]a With the through-wall stress distribution, including weld residual stress, the stress intensity factor range for
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each transient is calculated as described in Section 7.1, for both the deepest point (Point 1) and the surface point (Point 2). From this stress intensity factor range, the end of transient flaw depth growth ( a) and the end of transient flaw length growth ( l) are calculated. This gives the new flaw geometry and the process is repeated for the next transient. [
]a After all of the normal (including upset and test) transients have been applied, the final crack length and depth are known for each path, as seen in Table 4. The crack depth and length growth versus time can be seen in Figure 29 and Figure 30 for the circumferential and axial flaw respectively. With the final crack size, the acceptance criteria for the flaws is as discussed in Section 7.3.
Table 4: Final Crack Sizes for all Paths Figure 31 to Figure 33 show the calculated stress intensity factor range for each transient for paths 1, 2 and 4 respectively for the circumferential flaw. Similarly, Figure 34 to Figure 36 show the calculated stress intensity factor range for each transient for paths 1, 2 and 4 respectively for the axial flaw. [
]a
[
c
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]a
[
]a More details on the crack growth analysis are given in BWXT Canada Calculation M2004-B003.
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7.3 End-of-Life Flaw Size From the fatigue crack growth analysis, the final flaw size (af and lf) is known at the end of the RSG life. With this final flaw size, the acceptability of the flaw is assessed per the acceptance criteria of IWB-3600 [4] as documented in Section 3.1. The maximum stress intensity factor for each transient, including normal and emergency and faulted conditions, at the final end-of-life flaw size geometry is compared against the acceptance criteria. The results are seen in Table 5 and Table 6 for normal conditions, for the axial flaw and circumferential flaws respectively at Path 4. Similarly, Table 7 and Table 8 contain the results for emergency and faulted conditions for the axial flaw and circumferential flaws respectively at Path 4. These bound the results for all other paths.
The fracture toughness, KIC, is calculated based on the equation given in A-4200 and curve seen in Figure A-4200-1 [4]. An upper shelf fracture toughness of 220 ksi
- in0.5 is used. [
]a,c Figure 37 to Figure 39 show representative maximum stress intensity factors for each transient for paths 1, 2 and 4 respectively for the circumferential flaw. Similarly, Figure 40 to Figure 42 show the representative maximum stress intensity factor for each transient for paths 1, 2 and 4 respectively for the axial flaw. [
]a The end-of-life analysis, as seen in Table 5 and Table 6, accurately calculates the KI value considering the actual crack a/l, calculates KI values for both Pt. 1 and 2 and considers the plastic zone correction factor. Additionally, the allowable shown on these figures is applicable for most transients. A few transients or transient time points have a lower allowable based on the primary side temperature.
The maximum stress intensity factor calculation for the emergency and faulted conditions follows the same approach as the normal conditions. Considering the final end-of-life flaw geometry and the appropriate stresses from the transient analysis, as described in Section 6.2, the maximum stress intensity factor is calculated. The maximum stress intensity factor is then compared to emergency and faulted condition acceptance criteria. The transient stresses for the emergency and faulted condition consider both pressure and thermal stresses. [
]a
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As can be seen in Table 5 and Table 6, all circumferential and axial end-of-life flaws meet the acceptance criteria, for all Level A and B transients (normal and upset, including test conditions), as defined in Section 3.1. The acceptance criteria is calculated using the equation for normal conditions, as given in Section 3.1, at the appropriate transient temperature from the KIC curve given in in A-4200 [4]. As can be in Table 7 and Table 8, all circumferential and axial end-of-life flaws meet the acceptance criteria, for all Level C and D transients (emergency and faulted conditions), as defined in Section 3.1. The acceptance criteria is calculated using the equation for emergency and fault conditions, as given in Section 3.1, at the appropriate transient temperature from the KIC curve given in in A-4200 [4].
More details on the end-of-life flaw analysis are given in BWXT Canada Calculation M2004-B003 and the analysis is performed through the analysis tool described in BWXT Canada Calculation M2004-B004.
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Table 5 Fracture Mechanics Flaw Size Acceptance for Axial Flaw, Path 4 for Normal Conditions Table 6 Fracture Mechanics Flaw Size Acceptance for Circ. Flaw, Path 4 for Normal Conditions c
c
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Table 7 Fracture Mechanics Flaw Size Acceptance for Axial Flaw, Path 4 for Emergency and Faulted Conditions Table 8 Fracture Mechanics Flaw Size Acceptance for Circumferential Flaw, Path 4 for Emergency and Faulted Conditions c
c
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8.0 PRIMARY STRESS ANALYSIS The primary stress limits of NB-3000, assuming a local area reduction to the pressure retaining membrane that is equal to the area of the flaw must be met in accordance with IWB-3610 [4]. Table 9 lists the primary stress for the Design, Test and Level C and D conditions compared to the primary stress limits.
Table 9: Primary Stress Results for Base Design
[
]a,c
[
]a,c Table 10: Prorated Primary Stress Results for Base Design c
c
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9.0 VERIFICATION OF ASSUMPTIONS There are no assumptions requiring verification made in the calculations listed in Section 12.0.
The following assumption not requiring verification is made:
1)
[
]a,c
10.0 CONCLUSION
S The postulated flaw in the divider plate, due to PWSCC, is grown into the primary head wall through fatigue crack growth considering all normal (including upset and test) transients for the full design life. Both axial and circumferential flaws are independently considered with initial depth and width equal to the cladding thickness and divider plate width respectively. Conservative inputs and stresses are used. The analyses included in this report show that both postulated flaws are acceptable for the end-of-life flaw size they produce for normal (including upset and test) conditions and emergency and faulted conditions. Additionally, the primary stresses in the primary head with the end-of-life flaws are acceptable by meeting the requirements of IWB-3600 [4] for Design and transient conditions. Therefore, the structural integrity of the Byron / Braidwood 1 replacement steam generator primary head wall has been demonstrated if a crack, initiating in the divider plate weld build-up, propagates into the cladding of the primary head at the triple point.
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11.0 REFERENCES
, DESIGN DRAWINGS AND COMPUTER CODES 11.1 References
- 1. Areva NP Document No. 18-1229648-008, Certified Design Specification for Replacement Steam Generator Byron and Braidwood Unit 1.
- 2. ASME Boiler and Pressure Vessel Code Section III, Subsection NB, 1986 Edition with No Addenda.
- 3. ASME Boiler and Pressure Vessel Code Section II, Parts C and D, 1986 Edition with No Addenda.
- 4. ASME Boiler and Pressure Vessel Code Section XI, 2017 Edition with No Addenda.
- 5. BWXT Canada List of Approved Codes for Nuclear Analysis, June 11, 2021.
- 6. B&W Canada Drawing 7720E001, Rev. 06, Steam Generator Arrangement.
- 7. B&W Canada Drawing 7720A035, Rev. 03, Materials and Parts List.
- 8. EPRI Report 3002002850, Steam Generator Management Program: Investigation of Crack Initiation and Propagation in the Stream Generator Channel Head Assembly, October 2014.
- 9. EPRI Report TR-100251, White Paper on Reactor Vessel Integrity Requirements for Level A and B Conditions, January 1993.
- 10. B&W Canada Report 236R-SR-01, Rev. 1, Exelon Byron and Braidwood Unit 1 Replacement Steam Generators MUR Power Uprate Structural Analysis Report.
- 11. B&W Canada Report 222-7720-SR-1, Rev. 4, Exelon Company Byron and Braidwood Station Replacement Steam Generator Design Condition Report.
- 12. B&W Canada Report 222-7720-SR-2, Rev. 6, Exelon Company Byron and Braidwood Stations Replacement Steam Generators Transient Analysis Report.
- 13. Welding Research Council Bulletin 175, August 1972 PVRC Recommendations on Toughness Requirements for Ferritic Materials.
- 14. ASME Boiler and Pressure Vessel Code Section XI, 2007 Edition with 2008A Addenda.
- 15. ASME Boiler and Pressure Vessel Code Section XI, 2013 Edition with No Addenda.
- 16. B&W Canada Calculation 236R-B02, Rev. 1, Byron and Braidwood Primary Head / Tubesheet / Shell Assembly Level A to D and Fatigue Analysis for MUR Uprate.
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11.2 Design Drawings The design drawings used in the analyses are the latest revisions and are listed in Table 11.
Table 11 List of Design Drawings B&W Canada Design Drawings Drawing No.
Rev. No.
Title 7720E001 06 ComEd Steam Generator Arrangement 7720E004 03 ComEd Primary Head & T/S D. L 7720A035 03 ComEd Materials and Parts List 7720E110 00 ComEd Tubesheet Drilling Pattern 11.3 Computer Codes The computer programs listed in Table 12 are used in the analyses.
Table 12 List of Computer Codes Program Name Program Version No. Rev. No.
Program Description System ANSYS 15.0 On-line Manuals General Purpose Finite Element Program for structural, seismic and thermal analysis of various nuclear pressure vessel components Windows 10 x64 on DP T5810 This code is qualified by BWXT for Nuclear Analysis. All User Guide limitations and computer program notifications, as applicable, have been reviewed to ensure there is no impact on this calculation. The
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12.0 LIST OF DETAILED ANALYSIS CALCULATIONS Calculation Rev.
Title M2004-B001 0
Byron / Braidwood Unit 1 Replacement Steam Generator Model Development for Tubesheet / Primary Head / Divider Plate Assembly.
M2004-B002 1
Byron / Braidwood Unit 1 Replacement Steam Generator Transient Analysis for Tubesheet / Primary Head / Divider Plate Assembly.
M2004-B003 1
Byron / Braidwood Unit 1 Replacement Steam Generator Flaw Analysis at Divider Plate Triple Point.
M2004-B004 0
Divider Plate Crack Growth Analysis Tool.
M2004-B005 0
Byron / Braidwood Unit 1 Replacement Steam Generator Limit Analysis for Tubesheet / Primary Head / Divider Plate Assembly with Postulated Primary Head Flaw The detailed engineering analysis is propriety to BWXT. They are available at BWXT Canada Cambridge office or via secure electronic data room, upon request, on a platform such as Firmex.
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13.0 FIGURES Figure 1 FE Model of Divider Plate Assembly............................................................................................................29 Figure 2 Divider Plate Assembly Model Dimensions (a)..........................................................................................30 Figure 3 Divider Plate Assembly Model Dimensions (b)..........................................................................................31 Figure 4 Divider Plate Assembly Model Dimensions (c)...........................................................................................32 Figure 5 Divider Plate Assembly with Materials.........................................................................................................33 Figure 6 Divider Plate Assembly Triple Point.............................................................................................................33 Figure 7 Exaggerated Crack Opening Displaced Shape due to Internal Pressure (psi)....................................34 Figure 8 Thermal Boundary Conditions (Applied HTCs and Temperatures).......................................................35
..........36 Figure 10 Temperature History Plot for the Heatup / Cooldown Transient...........................................................37 Figure 11 Structural Boundary Conditions..................................................................................................................38 Figure 12 Stress Plot for Transient Heatup/Cooldown (at 32060.1 sec) (a).........................................................39 Figure 13 Stress Plot for Transient Heatup/Cooldown (at 32060.1 sec) (b).........................................................39 Figure 14 Path Locations for Through-Wall Stress Distributions. View from Inlet Side.....................................40 Figure 15 Path Locations for Through-Wall Stress Distributions. View from Outlet Side..................................40 Figure 16 Path Locations at Triple Point for Through-Wall Stress Extraction. View along Divider Plate and Section at Tubesheet / Primary Head Junction..........................................................................................................41 Figure 17 Path Locations at Triple Point for Through-Wall Stress Extraction. Section through Primary Head
/ Tubesheet Juncture.......................................................................................................................................................41 Figure 18 Surface Flaw Geometry [4]..........................................................................................................................42 Figure 19 Stress Distribution Through-Wall Thickness [4].......................................................................................42 Figure 20 Circumferential Flaw Geometry on the Inside Surface of a Cylinder [4].............................................43 Figure 21 Axial Flaw Geometry on the Inside Surface of a Cylinder [4]................................................................43 Figure 22 Self Equilibrating Weld Stress Distribution [9]..........................................................................................44 Figure 23 Axial Stress Through-Wall Distribution at Path 1.....................................................................................45 Figure 24 Axial Stress Through-Wall Distribution at Path 2.....................................................................................45 Figure 25 Axial Stress Through-Wall Distribution at Path 4.....................................................................................46 Figure 26 Hoop Stress Through-Wall Distribution at Path 1....................................................................................46 Figure 27 Hoop Stress Through-Wall Distribution at Path 2....................................................................................47 Figure 28 Hoop Stress Through-Wall Distribution at Path 4....................................................................................47 Figure 29 Circumferential Flaw Crack Growth............................................................................................................48 Figure 30 Axial Flaw Crack Growth..............................................................................................................................49 Figure 31 Circumferential Flaw Stress Intensity Factor Range, Path 1 (Representative).................................50 Figure 32 Circumferential Flaw Stress Intensity Factor Range, Path 2 (Representative).................................50 Figure 33 Circumferential Flaw Stress Intensity Factor Range, Path 4 (Representative).................................51 Figure 34 Axial Flaw Stress Intensity Factor Range, Path 1 (Representative)....................................................51 Figure 35 Axial Flaw Stress Intensity Factor Range, Path 2 (Representative)....................................................52 Figure 36 Axial Flaw Stress Intensity Factor Range, Path 4 (Representative)....................................................52 Figure 37 Circumferential Flaw Maximum Stress Intensity Factor, Path 1 (Representative)...........................53 Figure 38 Circumferential Flaw Maximum Stress Intensity Factor, Path 2 (Representative)...........................53 Figure 39 Circumferential Flaw Maximum Stress Intensity Factor, Path 4 (Representative)...........................54 Figure 40 Axial Flaw Maximum Stress Intensity Factor, Path 1 (Representative)..............................................54 Figure 41 Axial Flaw Maximum Stress Intensity Factor, Path 2 (Representative)..............................................55 Figure 42 Axial Flaw Maximum Stress Intensity Factor, Path 4 (Representative)..............................................55
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Figure 1 FE Model of Divider Plate Assembly
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Figure 2 Divider Plate Assembly Model Dimensions (a) a,c
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Figure 3 Divider Plate Assembly Model Dimensions (b) a,c
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Figure 4 Divider Plate Assembly Model Dimensions (c) a,c
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Figure 5 Divider Plate Assembly with Materials Figure 6 Divider Plate Assembly Triple Point a,c
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Figure 7 Exaggerated Crack Opening Displaced Shape due to Internal Pressure (psi) c
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c
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Figure 11 Structural Boundary Conditions a,c
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Figure 12 Stress Plot for Transient Heatup/Cooldown (at 32060.1 sec) (a)
Figure 13 Stress Plot for Transient Heatup/Cooldown (at 32060.1 sec) (b) c c
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Figure 14 Path Locations for Through-Wall Stress Distributions. View from Inlet Side.
Figure 15 Path Locations for Through-Wall Stress Distributions. View from Outlet Side.
a a
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Figure 18 Surface Flaw Geometry [4]
Figure 19 Stress Distribution Through-Wall Thickness [4]
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Figure 20 Circumferential Flaw Geometry on the Inside Surface of a Cylinder [4]
Figure 21 Axial Flaw Geometry on the Inside Surface of a Cylinder [4]
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Figure 22 Self Equilibrating Weld Stress Distribution [9].
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Figure 23 Axial Stress Through-Wall Distribution at Path 1 Figure 24 Axial Stress Through-Wall Distribution at Path 2 c
c
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Figure 25 Axial Stress Through-Wall Distribution at Path 4 Figure 26 Hoop Stress Through-Wall Distribution at Path 1 c
c
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Figure 27 Hoop Stress Through-Wall Distribution at Path 2 Figure 28 Hoop Stress Through-Wall Distribution at Path 4 c
c
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Figure 29 Circumferential Flaw Crack Growth c
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Figure 30 Axial Flaw Crack Growth c
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Figure 31 Circumferential Flaw Stress Intensity Factor Range, Path 1 (Representative)
Figure 32 Circumferential Flaw Stress Intensity Factor Range, Path 2 (Representative) c c
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Figure 33 Circumferential Flaw Stress Intensity Factor Range, Path 4 (Representative)
Figure 34 Axial Flaw Stress Intensity Factor Range, Path 1 (Representative) c c
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Figure 35 Axial Flaw Stress Intensity Factor Range, Path 2 (Representative)
Figure 36 Axial Flaw Stress Intensity Factor Range, Path 4 (Representative) c c
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Figure 37 Circumferential Flaw Maximum Stress Intensity Factor, Path 1 (Representative)
Figure 38 Circumferential Flaw Maximum Stress Intensity Factor, Path 2 (Representative) c c
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Figure 39 Circumferential Flaw Maximum Stress Intensity Factor, Path 4 (Representative)
Figure 40 Axial Flaw Maximum Stress Intensity Factor, Path 1 (Representative) c c
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Figure 41 Axial Flaw Maximum Stress Intensity Factor, Path 2 (Representative)
Figure 42 Axial Flaw Maximum Stress Intensity Factor, Path 4 (Representative) c c