NL-08-1301, GE-NE-0000-0080-0259-R2, Hatch 2 Nuclear Plant, Shroud Repair Replacement of Upper Support Stress Analysis Report.

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GE-NE-0000-0080-0259-R2, Hatch 2 Nuclear Plant, Shroud Repair Replacement of Upper Support Stress Analysis Report.
ML082490745
Person / Time
Site: Hatch Southern Nuclear icon.png
Issue date: 06/30/2008
From:
GE-Hitachi Nuclear Energy Americas
To:
Office of Nuclear Reactor Regulation
References
DRF: 0000-0078-8059, Rev 1, eDRF Section 0000-0080-0259, Rev 2, NL-08-1301 GE-NE-0000-0080-0259-R2
Download: ML082490745 (42)
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Edwin I. Hatch Nuclear Plant - Unit 2 Request for Authorization Under the Provision of 10 CFR 50.55a(a)(3)(i) for Modification of the Core Shroud Stabilizer Assemblies Enclosure 4 GE-NE-000-0080-0259-R2; Hatch 2 Nuclear Plant Shroud Repair Replacement of Upper Support Stress Analysis Report (Nonproprietary)

HITACHI ,..I-n-,uwr energy General Electric- Hitachi Nuclear Energy 6705, Vallecitos Road Sunol, CA 94586 GE-N E-0000-0080-0259-R2 eDRF Section 0000-0080-0259, Rev.2 Class I DRF: 0000-0078-8059, Rev.1 June 2008 Hatch 2 Nuclear Plant Shroud Repair Replacement of Upper Support Stress Analysis Report

HITACHI GE-NE-0000-0080-0259-R2 Non-Proprietary Version IMPORTANT NOTICE REGARDING THE CONTENTS OF THIS REPORT Please Read Carefully A. Disclaimer The only undertakings of the General Electric-Hitachi Company (GEH) respecting information in this document are contained in the contract between the company receiving this document and GEH. Nothing contained in this document shall be construed as changing the applicable contract. The use of this information by anyone other than a customer authorized by GEH to have this document, or for any purpose other than that for which it is intended, is not authorized. With respect to any unauthorized use, GEH makes no representation or warranty, and assumes no liability as to the completeness, accuracy or usefulness of the information contained in this document, or that its use may not infringe privately owned rights.

B. Non-Proprietary Notice This is a non-proprietary version of the document GE-NE-OO00-0080-0259-R2, Revision 2, from which the proprietary information has been removed. Portions of the document that have been removed are identified by white space within double square brackets, as shown here (( I].

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GE-NE-0000-0080-0259-R2 0 ýHITACHI Non-Proprietary Version Revision Control Sheet Revision No. Date -.Description Rev. 0 Jan 26, 2008 Initial submittal Rev. 1 June 6, 2008 Report revised to incorporate SNC comments. Major changes are identified below. In addition, some minor/editorial changes were also made.

" Throughout the report, "support block" changed to "support" to be consistent with Figure 1 and the title of the drawing (Reference 3.b of Section 8).

" Section 4, Table 4 Stabilizer Support Assembly drawing added.

" Section 5 - Bullets added for the tie rod nut to tie rod threaded-connection FEA, replacement upper support design relative to bulk flow blockage, and stresses in the shroud flange.

" Section 5.1.4 - revised to add the bulk flow blockage assessment.

" Section 5.1.6 - New Section added for the shroud flange stresses evaluation in the modified EDM pocket.

  • Section 5.3.3 - New Section added for the replacement tie rod nut/tie rod threaded-connection FEA.
  • Section 6 - The stress results section modified to include results of the maximum plastic strains in the tie rod nut and the tie rod threads.

" Section 7 - Modified to include a conclusion of the tie rod nut to the tie rod threaded-connection FEM.

" Section 8 - Stabilizer Support Assembly Drawing (Ref. 3.i) added.

Rev. 2 June 17, 2008 Report revised to incorporate the final SNC comments.

Major changes are identified below. In addition, some minor/editorial changes were also made.

0 Section 4, Table 4-1 -More detailed material specifications included.

  • Section 5.1.4 - Sentence about the transverse stiffness revised.

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HITACHI GE-NE-0000-0080-0259-R2 Non-Proprietary Version Table Of Contents 1.0 Intro d uctio n a n d Ba c kg ro u nd ...................................................................................................................... 1 2 .0 Sc o p e ....................................................................................................................................................................... 1 3.0 Replacem ent Hardw are Design Features ....................................................................................... 1 4.0 Replacement Hardware Materials and Properties .................................................................... 2 5.0 Stru c tu ra l An a ly s is ............................................................................................................................................. 3 5.1 Design Basis Loads and Load Com binations ........................................................................... 4 5.1.1 Effect of TPO RIPDs on the Tie Rod Loads ........................................................................ 4 5.1.2 Effect of Replacement Upper Support Stiffness on the Tie Rod Loads ............... 4 5.1.3 Effect of Replacement Upper Support Stiffness on the Tie Rod Seismic Loads... 4 5.1.4 Effect of Replacement Upper Support on Flow Induced Vibration and Bulk Flow Blo c ka g e .................................................................................................................................................. 4 5.1.5 Effect of the TPO Tie Rod Loads on the Reactor Pressure Vessel Stresses ............. 5 5.1.6 Effect of Replacement Upper Support on the Shroud Flange ................................ 5 5 .2 Qu a lific a tio n Crite ria .................................................................................................................................... 5 5.2.1 IGSCC Criteria for X-750 and XM -19 .................................................................................... 5 5.2.2 ASM E Code Allow able Stress Lim its .................................................................................... 6 5 .3 An a ly s is Me th od s .......................................................................................................................................... 8 5.3.1 Replacem ent Upper Support Stress Analysis ........................................................................ 8 5.3.2 Replacement Support Analysis ................................ 8 5.3.3 Replacement Tie Rod Nut/Tie Rod Threaded-connection Finite Element Analysis

..................................................................................................................................................................... 9 5.4 Other Components in the Replacement Upper Support Assembly ............................. 10 5.5 Fatigue Analysis Of Replacement Upper Support Assembly ........................................... 10 6 .0 Stre ss/S tra in Re s u lts ....................................................................................................................................... 10 7.0 Co n c lu s io n ........................................................................................................................................................... 14 8 .0 Re fe re nc e s ........................................................................................................................................................... 15 Page iii

HITACHI GE-NE-0000-0080-0259-R2 Non-Proprietary Version List of Figures Figure 1. Identification of Replacement Upper Support Components .......................................... 16 Figure 2. Finite Element Model of the Upper Support Including the Lower Support ............... 17 Figure 3. Upper Support Finite Element Model Boundary Conditions ............................................ 18 Figu re 4 . Su pp o rt FEM................................................................................................................................................... 19 Figure 5. Maximum Tensile Principal Stress Plot for Upper Support Normal Loading Co n d itio n s ....................................................................................................................................................... 20 Figure 6. Stress Intensity Plot for Upper Support Normal Loading Condition ............................ 21 Figure 7. The linearization paths for Upper Support Normal Condition Loads .......................... 22 Figure 8. Stress Intensity Plot for the Upper Support Upset Seismic Loading Condition .............. 23 Figure 9. Replacement Upper Support - Linearization Plots for the Upset Condition Loads ...... 24 Figure 10. Stress Intensity Plot for Upper Support Upset Thermal Loading Condition ........... 25 Figure 11. Replacement Upper Support - Linearization Plots for Upset Thermal Condition ...... 26 Figure 12. Stress Intensity Plot for Upper Support Emergency Loading Condition ........ 27 Figure 13. Replacement Upper Support - Linearization Plot for Emergency Condition .............. 28 Figure 14. Stress Intensity Plot for Upper Support Faulted Loading Condition .......................... 29 Figure 15. Replacement Upper Support - Linearization Plots for Faulted Condition ............ 30 Figure 16. Stress Intensity Plot for the Support in the Faulted Loading Condition .................. 31 Figure 17. Linearization Plot for the Support in the Faulted Condition .......................................... 32 Figure 18. Tie Rod Nut / Tie Rod Threaded Connection- Finite Element Model ......................... 33 Figure 19. Replacement Tie Rod Nut/Tie Rod Threaded Connection - Plot of Maximum Total Tensile Principal Strain in Nut Threads .................................................................................... 34 Figure 20. Replacement Tie Rod Nut/Tie Rod Threaded Connection - Plot of Maximum Total Principa l Stra in in the Tie Rod Threads ............................................................................................ 35 Page iv

HITACHI GE-NE-0000-0080-0259-R2 Non-Proprietary Version List of Tables Table 4-1 Components in the Replacement of Upper Support Assembly ..................................... 2 Table 4-2 Material Properties Used in This Evaluation .......................................................................... 3 Table 5-1 Comparison of Original and TPO Condition Tie Rod Loads (Ibs/tie rod) ..................... 4 Table 5-2 IGSCC Allowable Limit for X-750 and XM-19 Components (Ref 4 and 8) ................... 5 Table 5-3 ASME Code Allowable Stress Limits @ 550 OF (Non-Threaded Components) ......... 6 Table 5-4 ASME Code Allowable Stress Limits @ 550 OF (Threaded Components) ..................... 7 Table 6-1 Maximum Tensile Principal Stresses (psi) and Strains in the Normal Sustained Co nd itio ns fo r IGSCC Criteria ............................................................................................................ 11 Table 6-2 Stress Intensity for Upper Support - ASME Code Compliance ....................................... 12 Table 6-3 Stress Intensity Values for Support - ASME Code Compliance ................................... 12 Table 6-4 Stress Intensities for other Components in the Replacement Assembly ................. 13 Ta b le 6-5 Cu m ulative Usa g e Fa cto rs ....................................................................................................................

1 14 Page v

HITACHI GE-NE-0000-0080-0259-R2 Non-Proprietary Version

1.0 INTRODUCTION AND BACKGROUND

GE-Hitachi Nuclear Energy (GEH) had provided core shroud repairs using tie rods to BWR plants including Hatch 1 and 2 stations. In the spring of 2006 outage at Hatch1 (HIR22),

during an in-vessel visual inspection (IVVI), indications were observed in the shroud repair tie rod upper supports made of Alloy X-750 at two of the four shroud tie rod repair locations (Reference 1). The indications emanated from the sharp corner between the horizontal and vertical legs of the upper support and ran outwardly, at approximately 300 to the horizontal.

The cracking mechanism was determined by metallographic and Scanning Electron Microscope (SEM) techniques to be Inter-granular stress corrosion cracking (IGSCC). Alloy X-750 material is susceptible to IGSCC if subjected to sustained, large peak stress conditions.

As a result of the cracking at Hatch 1, detailed finite element stress analyses of the Hatch 2 original tie rod repair upper support and the nut, mode of Alloy X-750, were also performed by GEH. Although IGSCC susceptibility for the Hatch 2 original upper support was identified based on the maximum calculated stress exceeding the BWRVIP-84 criterion, continued operation was justified for at least one more operating cycle, and documented in the Hatch 2 shroud tie rod repair operability evaluation report (Reference 2). However, as a long-term solution to mitigate the potential for IGSCC, Southern Nuclear Corporation (SNC) decided that the upper support and tie rod nut of the shroud repairs at all four azimuth locations be replaced with new and improved replacement hardware designs that are more robust from the standpoint of IGSCC. This report documents the analyses of the replacement shroud repair hardware to be installed at Hatch 2 station.

2.0 SCOPE The objective of the stress analysis presented in this report is to demonstrate that the proposed shroud repair replacement hardware (upper support, support, their associated components, and the tie rod nut) depicted in the drawings (Reference 3) satisfies the IGSCC susceptibility criteria and ASME Code requirements of the design specification data sheet (Reference 4). The shroud repair replacement hardware design, criteria for qualification, analysis approach, results and conclusions are presented in the following sections.

3.0 REPLACEMENT HARDWARE DESIGN FEATURES The replacement hardware (upper supports, support, their associated components and tie rod nut) shown in Figure 1 are fabricated in accordance with Reference 3 drawings. The major load bearing components are the upper support and the tie rod nut. These replacement components incorporate features that improve their ability to resist IGSCC.

These features are as follows:

0 Generous Fillet Radius at the Corner and Simplified Design of Upper Support.

The original support design had no stress relief specified between the bottom of the U-shaped horizontal arm that rests on the shroud flange and the vertical arm of the upper support. In the replacement upper support, a generous fillet radius has been incorporated as a stress-relief. This provision reduces the stress concentration and in turn reduces the peak stress. Also, the U-shaped horizontal arm design of the upper support was simplified to a rectangular plate. The finite element analysis of the upper support is consistent with Reference 3.a drawing. '

Hatch-2 Replacement Upper Support Stress Analysis Report Page 1 of 35

GE-N E-0000-0080-0259-R2 0 HITACHI Non-Proprietary Version

" Sharp Edges Eliminated on the Upper Support: Generous fillet radii are specified at interfaces between mating surfaces and cross section variations. This provision reduces the stress concentration, and in turn reduces peak stresses at these locations.

" Use of IGSCC-Resistant Material: The tie rod nut and the support are made of XM-19.

(References 3.b and 3.c). This mitigates the potential for the nut and the support to IGSCC. Original tie rod nut and support were made of Alloy X-750. Alloy X-750 material is susceptible to IGSCC if subjected to sustained, large peak stress conditions.

O Generous Root Radius for the ACME Threads in the Tie Rod Nut: A generous radius of R[ I] is provided for the replacement tie rod nut ACME threads to reduce peak stress (Reference 3.c). This feature along with the use of XM-19 material greatly mitigates the potential for IGSCC.

4.0 REPLACEMENT HARDWARE MATERIALS AND PROPERTIES The materials used in the shroud repair replacement hardware (upper supports, support, their associated components, and tie rod nut) and their properties are provided in Table 4-1 and Table 4-2 respectively.

Table 4-1 Components in the Replacement of Upper Support Assembly 1

Material Reference (Sect No Description (Section 8).

AMS 5542 Rev. L 1 Upper Support ASME SB-637, UNS N07750 3.a ASME SA-479, Type XM-19 2 Support ASME SA-182, Grade F XM-19 3.b ASME SA-336, Class F XM-19 ASME SA-479, Type XM-19 3 Tie Rod Nut ASME SA-182, Grade F XM-19 3.c ASME SA-336, Class F XM-19 ASME SA-479, Type XM-19 4 Top Support Bracket ASME SA-182, Grade FXM-19 3.d ASME SA-336, Class F XM-19 ASME SA-479, Type XM-19 5 Retainer Pin ASME SA-182, Grade FXM-19 3.e ASME SA-336, Class F XM-19 6 Retainer Spring ASME SB-637, UNS N07750 3.f ASME SA-479, Type XM-19 7 Socket Head Screw Cap ASME SA-182, Grade FXM-19 3.g ASME SA-336, Class F XM-19 ASME SA-479, Type XM-19 8 Dowel Pin ASME SA-182, Grade F XM-19 3.h ASME SA-336, Class F XM-19 Stabilizer Support 9 N/A (Assembly Drawing) 3.i Assembly Hatch-2 Replacement Upper Support Stress Analysis Report Page 2 of 35

GE-NE-0000-0080-0259-R2 0 ý HITACHI Non-Proprietary Version The Design Specification Data Sheet (Reference 4) calls for the use of ASME B&PV Code Section III NB and NG-3000, 2001 Edition through 2003 Addenda (Reference 5), and Code Case N-60-5 (Reference 6). The following material properties are obtained from these references and are used in the evaluations below.

Table 4-2 Material Properties Used in This Evaluation At nits Material I Ref/Table Mate Ref/Table Property Temp unts XM-19 X-750 70 OF psi 28.30E+06 Ref 7, TM-*I 30.90E+06 Ref 7, TM-4 Modulus of 300 OF psi 27.00e+06 Ref 7, TM-1 29.80E+06 Ref 7, TM-4 Elasticity, E 550 OF psi 25.60E+06 Ref 7, TM-1 28.85E+06 Ref 7, TM-4 Coefficient of 70 OF in/in OF 8.20E-06 Ref 7, TE-1 6.70E-06 Ref 7, TE-4 Thermal 300 OF in/in OF 8.70E-06 Ref 7, TE-1 7.20E-06 Ref 7, TE-4 Expansion, a 550 OF in/in OF 9.10E-06 Ref 7, TE-1 7.70E-06 Ref 7, TE-4 Ultimate Tensile 70 OF psi 90,000 Ref 7, U 160,000 Ref 6, Tbl C Strength, Su 550 OF psi 81,150 Ref 7, U 160,000 Ref 6, Tbl C 70 OF psi 55,000 Ref 7, Y-1 100,000 Ref 6, Tbl B Yield Strength, Sy 550 OF psi 38,100 Ref 7, Y-1 92,800 Ref 6, TbI B 70OF psi 33,300 Ref 7, 2A 53,300 Ref 6, Tbl A Stress Intensity, Sm 550 OF psi 29,450 Ref 7, 2A 53,300 Ref 6, Tbl A 5.0 STRUCTURAL ANALYSIS Structural analyses of the shroud repair replacement upper support, and the support were performed. Details of the analysis methods, loads and qualification criteria are provided in the following subsections. The results of these analyses are presented in Section 6.0.

" The upper support in engagement with the shroud flange at the top and with the support at its bottom was analyzed using finite element method.

" Other associated components in the replacement upper support assembly, including the tie rod nut were evaluated using hand calculations. These components are non-Alloy X-750 and are more resistant to IGSCC.

  • The tie rod nut/tie rod threaded-connection was evaluated using finite element method to determine plastic strains in the threads of the nut and the tie rod for Normal operation tie rod load.

In addition, the following were also addressed:

  • Effect of TPO RIPDs on the tie Rod Loads.
  • Effect of the replacement upper support stiffness on the tie rod loads.

Hatch-2 Replacement Upper Support Stress Analysis Report Page 3 of 35

HITACHI GE-N E-0000-0080-0259-R2 Non-Proprietary Version

  • Effect of the replacement upper support stiffness on tie rod seismic loads.
  • Effect of replacement upper support on the shroud flange.

5.1 Design Basis Loads and Load Combinations 5.1.1 Effect of TPO RIPDs on the Tie Rod Loads The effects of the changes in RIPDsidue to TPO on the tie rod loads were considered in the present evaluations. The load combinations considered for the operating conditions are the same as the original design basis. The tie rod loads due to TPO RIPDs were calculated, and are provided below in comparison with the original design basis tie rod loads. As shown in the Table 5-1 below, the TPO tie rod loads remain essentially the same as the original design basis loads (change < 0.5%)

Table 5-1 Comparison of Original and TPO Condition Tie Rod Loads (lbs/tie rod)

.,Condition 'I Normal. Upst-Upst-ncy, a Seismic Therm'al Eeg Original ((

Cu rrent/TPO 5.1.2 Effect of Replacement Upper Support Stiffness on the Tie Rod Loads The vertical stiffness of the replacement upper support assembly was determined from the finite element model. Using the upper support stiffness, the net combined stiffness of the tie rod assembly was calculated and compared to the original design basis tie rod assembly stiffness. The increase in stiffness of the tie rod assembly with the replacement upper support was found to be < 1%. Also, adequate margins to the ASME Code stresses and conservatism in the IGSCC evaluations exist in the analyses, to offset these small increases in the tie rod loads. Hence, the effect of the increased stiffness on the tie rod loads is deemed to be negligible.

5.1.3 Effect of Replacement Upper Support Stiffness on the Tie Rod Seismic Loads The tie rod assembly stiffness due to the replacement upper support remains essentially the same as that of the original (< 1% increase). This small increase in the tie rod assembly stiffness has practically no effect on the overall dynamic characteristics of the vessel and internals primary structure model. Hence it is deemed that the seismic load for the tie rod assembly remains unchanged.

5.1.4 Effect of Replacement Upper Support on Flow Induced Vibration and Bulk Flow Blockage The bulk flow in the annulus area remains unchanged for the TPO condition with respect to the original design basis conditions. ((

1] The calculated value of transverse stiffness Hatch-2 Replacement Upper Support Stress Analysis Report Page 4 of 35

HITACHI GE-NE-0000-0080-0259-R2 Non-Proprietary Version of the tie rod is not affected by the replacement upper support since the transverse stiffness is based on the length of the tie rod between the upper and lower springs, and the location and configuration of the mid support.

Therefore, there is no effect of the replacement hardware on the flow-induced vibration characteristics of the tie rod assembly.

The impact of the replacement upper support hardware relative to bulk flow blockage was also assessed. There has been no increase in the cross sectional area of the replacement upper support relative to the original upper support design. Hence, there is no concern for bulk flow blockage with the replacement upper support hardware design.

5.1.5 Effect of the TPO Tie Rod Loads on the Reactor Pressure Vessel Stresses The tie rod loads in the TPO conditions are essentially the same as the original loads (change

< 0.5%). Thus, the effect of this small increase in the loads on the stresses at the reactor pressure vessel walls is deemed to be negligibly small.

5.1.6 Effect of Replacement Upper Support on the Shroud Flange The cross section of the horizontal leg in contact with the shroud flange ((

)) The bearing stresses in the shroud flange pocket for the Normal, Upset, Emergency, and Faulted condition tie rod loads specified in Table 5-1 were computed, and shown to be within the ASME code allowable stress limits. .

5.2 Qualification Criteria 5.2.1 IGSCC Criteria for X-750 and XM-19 In accordance with the requirement of the design specification data sheet (Reference 4), the total tensile principal stress (Pm + Pb + Q + F)is compared to the IGSCC criterion of (( I]

for 40-year life. This criterion is summarized in Table 5-2 and is more restrictive than the BWRVIP-84 criterion of 0.8Sy.

For XM-19 material, no specific criterion for IGSCC is specified in BWRVIP-84. However, the maximum plastic strain is limited to within J[ )), in accordance with Reference 8.

Table 5-2 IGSCC Allowable Limit for X-750 and XM-19 Components (Ref. 4 and 8)

Total Principal Material Allowable Limit Allowable Tensile Stress value Maximum Principal stress of the X-750 ((

(Pm + Pb + Q + F)category due to Plastic Strain <

normal sustained loads XM-19 Limited by strain Hatch-2 Replacement Upper Support Stress Analysis Report Page 5 of :35

GE-NE-0000-0080-0259-R2 0 HITACHI Non-Proprietary Version 5.2.2 ASME Code Allowable Stress Limits In accordance with the requirement of the design specification data sheet (Reference 4), the Normal, Upset, Emergency and Faulted condition allowable stress limits used in this report are in accordance with the ASME Code (Reference 5). The allowable stress limits of the ASME Code are summarized in Table 5-3 and Table 5-4 below.

Table 5-3 ASME Code Allowable Stress Limits @ 550 OF (Non-Threaded Components)

Stress Service Level Category Allowable Limit XM-19 X-750 Components Other Than Threaded Fasteners (Ref 5, NG-3220)

Pm Sm 29,450 53,300 44-Pm + Pb 1.5 Sm 44,175 79,950 i - 4 Pm + Pb + Q 3.0 Sm 88,350 159,900 4 4 +

Normal & Shear Stress 0.6 Sm 17,670 31,980 4 4-Upset Sy 38,100 92,800 Bearing Stress 4 +

1.5 Sy (away from free edge) 57,150 139,200

-- 4 CUF 1.0 1.0 1.0 i +

Pm 1.5 Sm 44,175 79,950 Pm + Pb 2.25 Sm 66,263 119,925 Shear Stress 0.9 Sm 26,505 47,970 Emergency Bearing Stress 1.5 Sy -_-_

57,150 139,200 2.25 Sy (away from free edge) 85,725 208,800 Pm Min (2.4Sm, 0.7S) (Austenitic) 56,805 112,000 0.7S, (Ferritic)

Pm + Pb Min (3.65m, 1.05 S) (Austenitic) 85,208 168,000 Faulted 1.05Su (Ferritic)

Shear Stress 0.42 S, 34,083 67,200 2.0 Sy 76,200 185,600 Bearing Stress 3.0 Sy (away from free edge) 114,300 278,400 Hatch-2 Replacement Upper Support Stress Analysis Report Page 6 of 35

GE-N E-0000-0080-0259-R2 0 ý HITACHI Non-Proprietary Version Table 5-4 ASME Code Allowable Stress Limits @ 550 OF (Threaded Components)

Service Stress Category Allowable Limit XM-19 X-750 Threaded Structural Fasteners (Ref 5, NG-3230)

Pm (Mech. Loads) Sm 29,450 53,300 Pm (Installation Min. (1.08 Sy, 0.8 Su) at 59,400 108,000 Torque) installation temperature.

i' i Pm + Qrm Min. (0.9 Sy, 2/3 Su) 34,290 83,520 Normal &

Pm + Pb + Qm+ Qb Min. (1.2 Sy, 8/9 Su) 45,720 [ 111,360 Upset Threads Shear 0.6 Sm(Primary) 17,670 31,980 Shear 0.6 Sy (Primary + Secondary) 22,860 55,680 Under Bearing 2.7 Sy 102,870 250,560 bolt head Shanks, Tras CE Threads CUF1 k1.0 .1 1.0 01 0 1.0 Pm Same as for non-threaded components. 44,175 53,300 If Su > 100 ksi, then same as Normal, Upset Pm + Pb limits for threaded components. 66,263 111,360 Emergency Shear (Primary) Same as for Normal Upset limits 17,670 31,980 Shear (Pr +Sec) for threaded components 22,860 55,680 i -

Smaller of (2.4 Sm, 0.7 Su);

Pm 56,805 106,600 If S,>100 ksi, then 2Sm Smaller of (3.65m, 1.05S.);

Faulted Pm+Pb 85,208 159,900 If S, > 100 Ksi, then 3Sm

+/-

Shear Stress Smaller of (0.42Su, 0.6Sy) 22,860 55,680 Hatch-2 Replacement Upper Support Stress Analysis Report Page 7 of 35

HITACHI GE-N E-0000-0080-0259-R2 Non-Proprietary Version 5.3 Analysis Methods 5.3.1 Replacement Upper Support Stress Analysis A finite element analysis of the upper support was performed using the ANSYS computer program (Reference 9). The components included in the finite element model are shown in Figure 2. Only half of the upper support is modeled due to the symmetry of the geometry about the vertical mid-pane. The model was meshed using ANSYS SOLID 186, 20-noded brick elements. ((

)) The appropriate boundary conditions and the loads as shown below were applied to the finite element model.

Boundary conditions (Figure 2) o The bearing interface of the horizontal arm of the upper support with the shroud flange was modeled using contact elements with 1[

)) (per Reference 10). ((

" The gap between the upper support and the shroud head flange is conservatively not included in the model. The contact between the top surface of the upper support and the shroud head flange would reduce the stresses in the upper support.

o The shroud flange was modeled as a block, initially in contact with the upper support.

O The lower end of the upper support contacts the outer surface of the shroud. This is simulated by using rigid surface and contact elements (Figure 3).

" At the lower end the upper supports, the 'hooks' on the Support engage into the pockets machined into the upper support. This engagement is modeled in the finite element by merging the nodes.

o Symmetry boundary conditions were applied on the plane of symmetry.

Load Application o One half of the tie rod loads in the Normal, Upset-Seismic, Upset-thermal, Emergency and Faulted conditions respectively are applied along the axis of the tie rod, on the support as uniformly distributed ring loads on the edge of the circular hole.

The results of the normal condition peak stress and conformance to the IGSCC criterion is summarized in Table 6-1 below.

The stress results for all operating conditions for ASME Code conformance of the upper support are summarized in Table 6-2 below.

5.3.2 Replacement Support Analysis Afinite element analysis of the support was performed using the ANSYS computer program (Reference 9). The finite element model is shown in Figure 4. Only half of the support is modeled due to the symmetry of the geometry about the vertical mid-pane. The model was meshed using ANSYS (( 1].The appropriate boundary conditions and the loads as shown below were applied to the finite element model.

Hatch-2 Replacement Upper Support Stress Analysis Report Page 8 of :35

HITACHI GE-NE-0000-0080-0259-R2 Non-Proprietary Version

" The protrusions/lugs that engage in the machined pockets in the Upper Support are simplified in the model as rectangular blocks.

O The contact between the support and upper support is modeled by the use of rigid surfaces and contact elements.

o Symmetry boundary conditions are applied on the plane of symmetry.

o One half of the tie rod loads in the Normal, Upset-seismic, Upset-thermal, Emergency and Faulted conditions (from Table 5-1) are applied as uniformly distributed ring load around the rim of the circular hole.

Results of the finite element analysis runs for the Normal, Upset Seismic, Upset Thermal, Emergency and Faulted conditions for the upper support and the support are provided in Figure 6 through Figure 17 as stress plots and the actual values are provided in Table 6-3 below.

5.3.3 Replacement Tie Rod Nut/Tie Rod Threaded-connection Finite Element Analysis The replacement Tie Rod Nut to tie rod threaded-connection was analyzed using FEM to determine the plastic deformation in the threads and by hand calculation for ASME Code evaluation.

FEA of the replacement tie rod nut to tie rod threaded-connection (ACME threads) was performed using the ANSYS computer program (Reference 9).

The axisymmetric FEA model of the Tie Rod Nut and Tie Rod threads interface is shown in Figure 18 with all the available threads in engagement. The model was composed of ANSYS The boundary conditions are as described below, and the loads specified in Table 5-1 were applied to the finite element model.

Boundary Conditions:

The tie rod nut is supported in the vertical direction as shown in Figure 18 using dimensions per Drawings Tie Rod Nut 223D5971 Rev.0 and Support 223D5969, Rev.0.

The tie rod nut and the tie rod are engaged at all the threads. Therefore, contact elements were provided between the threads of the tie rod nut and the tie rod, ((

)) All the threads in engagement were so modeled in the FEA. The outer edge of the support block-to-nut bearing interface is restrained in the radial direction. It permits the entire nut surface free to slide except at the location where it is restrained radially.

Material Properties:

Load Application:

Hatch-2 Replacement Upper Support Stress Analysis Report Page 9 of 35

HITACHI GE-NE-0000-0080-0259-R2 Non-Proprietary Version The Normal condition sustained load specified in Table 5-1 (( ] was used to determine the plastic strain in the nut and tie rod threads evaluated based on the elastic-plastic finite element analysis.

The Normal, Upset, Emergency, and Faulted condition loads in Table 5-1 were used for the ASME Code stress evaluation. The ASME Code stresses were evaluated based on hand calculations using elastic analysis methods.

The stress results of this analysis are presented in Section 6.0.

5.4 Other Components in the Replacement Upper Support Assembly The other components in the Replacement Upper Support Assembly (Items 3, 4, 5, 6, 7, and 8 of Table 4-i) are analyzed by hand calculation and the stress results are provided in Table 6-4 below. These components (except the retainer spring) are made of XM-19 material, which is more IGSCC-resistant compared to Alloy X-750. For these components the ASME code stresses are of primary importance.

5.5 Fatigue Analysis Of Replacement Upper Support Assembly Cumulative usage factor (CUF) was evaluated for the replacement components in accordance with the provisions of the Code, and using the cycles per Reference 11. The number of cycles considered is (( II cycles for plant start up and shut down, (normal load combination) (( )) cycles for seismic (upset-seismic load combination) and (( ))

cycles for thermal (upset-thermal load combination). Table 6-5 summarizes the Cumulative Usage Factors for the components in the replacement assembly.

6.0 STRESS/STRAIN RESULTS The replacement hardware components (upper support, support, tie rod nut and other associated upper support components) were evaluated for their susceptibility to IGSCC and ASME Code stresses, consistent with the acceptance criteria of the Reference 4 design specification data sheet. The maximum tensile principal stress (Pm + Pb + Q + F)for all Alloy X-750 components satisfies the R[. )) requirement for IGSCC.

The XM-19 components (the replacement tie rod nut and tie rod threads) become plastic under the sustained load. The maximum total strain (which includes the elastic and plastic strain) is R[ )) the tie rod nut threads (Figure 19) and Ji )) in the tie rod threads (Figure 20). They meet the strain limit criteria ((

)) specified in Table 5-2.

The ASME requirements for the stress and fatigue usage are satisfied for all components in the replacement upper support assembly.

Hatch-2 Replacement Upper Support Stress Analysis Report Page 10 of 35

GE-NE-0000-0080-0259-R2 0HITACHI Non-Proprietary Version Table 6-1 Maximum Tensile Principal Stresses (psi) and Strains in the Normal Sustained Conditions for IGSCC Criteria

-i Max Tensile Yield Strain L. Principal IGSCC S!

Component 0 4-, Fig Strength 25.6 x 106 0 Stress, S1 Sl/SY I SY (Pm+Pb+Q+F)

Upper Support, at X-750 Figure 5 (( 92,800*

large radius Support XM-19 38,100 Tie Rod Nut, threads XM-19 38,100 All XM-19 Top Support XM-19 components 38,100 remain in the Bracket .....

elastic range.

Retainer Spring X-750 92,800 A i- j i Hence, the Retainer Pin XM-19 38,100 strain limit in A 6- 6 -A--- +

Soc Head Cap XM-19 Table 5-2 is 38,100 satisfied.

Screws A i Dowel Pin XM-19 38,100 98 Upper Support, at the Internal threads X-750 1] 92,800 ]

at Socket Head Cap Screws

[* These values are based on the Code allowable values of Sy. The actual CMTR Sy values are expected to be higher, yielding better margin against IGSCC].

Hatch-2 Replacement Upper Support Stress Analysis Report Page 11 of 35

GE-N E-0000-0080-0259-R2 0 ýHITACHI Non-Proprietary Version Table 6-2 Stress Intensity for Upper Support - ASME Code Compliance Service Governing stress intensity (psi)

Level* Stress Max Stress Allowable ' Stress Remark Category intensity. Stress I Ratio

[ 53,300 See Figure 6, 7 NPm Pm+Pb 79,950 See Figure 6, 7 53,300 See Figure 8, 9 Pm Pm+Pb 79,950 See Figure 8, 9 U2 Pm+Pb+Q 159,900 See Figure 10, 11 1P 79,950 See Figure 12, 13 Pm+Pb 119,925 See Figure 12, 13 P{

F 112,000 See Figure 14, 15 Pm+Pb )) 168,000 )) See Figure 14, 15 Table 6-3 Stress Intensity Values for Support - ASME Code Compliance Governing stress intensity (psi)

Service Level* Stress Max Stress A

, Allowable Stress *Stress Ratio Category intensity Pm 29,450 Normal Pm+Pb 44,175 Pm 29,450 Upset-Seismic Pm+Pb 44,175 Upset Thermal Pr+Pb+Q 88,350 Emergency Pm 44,175 Pm+Pb 66,263 Pm 56,805 Faulted Pm+Pb 85,208 Hatch-2 Replacement Upper Support Stress Analysis Report Page 12 of 35

HITACHI GE-N E-OO00-0080-0259-R2 Non-Proprietary Version Table 6-4 Stress Intensities for other Components in the Replacement Assembly Governing Stress Intensity, psi Component Name Service Stress (material) Level* Stress Max Allowable Ratio Category Stress Stress Intensity Shear 17,670 N

Pm 29,450

+ + I-Shear 17,670 U1 Pm 29,450

+ +----. + I- -

Shear 17,670 Tie Rod Nut - (XM19) U2 I + I-Pm 29,450 Shear 17,670 E

Pm 44,175 Shear 22,860 F

Pm 56,805 Instln Pm 59,400 Shear 17,670 N

Pm 29,450 Shear 17,670 UlP Pm Top Support Bracket, 29,450 Socket Head Screw Shear 17,670 Caps (XM-19) U2 Pm 29,450

+ I ___

Shear 17,670 E

Pm 44,175 Shear 22,860 F

Pm 56,805 Retainer Pin (XM-19) All [...

Retainer Spring (X-750) Instaln Pm+Pb 79,950 Dowel Pins - (XM19) All Shear 17,670 1]

  • (N - Normal, Ul - Upset Seismic; U2-Upset Thermal, E - Emergency and F - Faulted)

Hatch-2 Replacement Upper Support Stress Analysis Report Page 13 of 35

GE-N E-0000-0080-02 59-R2 0 ýHITACHI Non-Proprietary Version Table 6-5 Cumulative Usage Factors Cumulative Component ' Usage Factor Upper Support, at the large radius Upper Support, at Socket screw threads Tie Rod Nut Support Block Top Support Bracket Retainer Pin Retainer Spring Socket Head Screw Cap

))

7.0 CONCLUSION

Based on the structural evaluation documented in the preceding sections, the shroud repair replacement upper support hardware (upper support, support, their associated components and tie rod nut) as depicted in the referenced drawings are structurally qualified in accordance with the design specification data sheet for IGSCC and ASME Code requirements.

The plastic strains in the nut and tie rod threads are also within strain limit specified in Table 5-2.

Hatch-2 Replacement Upper Support Stress Analysis Report Page 14 of 35

0 HITACHI GE-NE-0000-0080-0259-R2 Non-Proprietary Version

8.0 REFERENCES

1. GE Indication Notification Report
a. INR H1R221VVI-06-03-Rev.1 Tie Rod @1350
b. INR H1R221VVI-06-04-Rev.1 Tie Rod @2250
2. GE-NE-0000-0051-8783-R1, Edwin I. Hatch Nuclear Plant - Unit 2, Shroud Tie Rod Repair

- Operability Evaluation, March 2007.

3. Replacement Upper Support Assembly Drawings
a. Upper Support, 223D5968 Rev 0
b. Support, 223D5969 Rev 0
c. Tie Rod Nut, 223D5971 Rev0
d. Top Support Bracket, 223D5970 Rev 0
e. Retainer Pin, 147C2846 Rev 0
f. Retainer Spring, 147C2847 Rev 0
g. Socket Head Screw Cap, 147C2850 Rev 0
h. Dowel Pin, 147C2852 Rev 0
i. Stabilizer Support Assembly, 223D5967, Rev.0
4. 25A5718AA Rev 0, Hatch-2 Shroud Repair Hardware Modification, Design Specification Data Sheet, Jan 18, 2008.
5. ASME Boiler and Pressure Vessel Code,Section III, Division I, Nuclear Power Plant Components, Subsection NG, Core Support Structures, 2001 Edition through 2003 Addenda.
6. ASME Boiler and Pressure Vessel Code,Section III, Division I, Code Case N-60-5, Material for Core Support Structures.
7. ASME Boiler and Pressure Vessel Code,Section III, Division II,Part D,Materials, 2004 Edition.
8. GENE-0000-0063-5939, Assessment of SCC Crack Initiation in Hatch-2 and Pilgrim Type XM-19 Tie Rods, Feb 22, 2007.
9. ANSYS Finite Element Computer Code, Version 10.0, ANSYS Incorporated, 2004.
10. 22A4052, GE Design Specification for Core Support Structure, Reactor System.
11. 761E246 Rev 1, Hatch-2 Reactor Vessel Thermal Cycles.

Hatch-2 Replacement Upper Support Stress Analysis Report Page 15 of 35

GE-NE-0000-0080-0259-R2 O HITACHI Non-Proprietary Version Top Support Bracket r Support Tie Rod Nut Existing Upper Stabilizer Assembly -

Figure 1. Identification of Replacement Upper Support Components.

Hatch-2 Replacement Upper Support Stress Analysis Report Page 16 of 35

GE-NE-O000-0080-0259-R2 Q HITACHI Non-Proprietary Version

))

Figure 2. Finite Element Model of the Upper Support Including the Lower Support.

Hatch-2 Replacement Upper Support Stress Analysis Report Page 17 of 35

GE-N E-OO00-0080-0259-R2 0 HITACHI Non-Proprietary Version Figure 3. Upper Support Finite Element Model Boundary Conditions Hotch-2 Replacement Upper Support Stress Analysis Report Page 18 of 35

GE-NE-0000-0080-0259-R2 0HITACHI Non-Proprietary Version

((

1]

Figure 4. Support FEM Hatch-2 Replacement Upper Support Stress Analysis Report Page 19 of 35

GE-N E-OO00-0080-0259-R2 0 HITACHI Non-Proprietary Version 11 Figure 5. Maximum Tensile Principal Stress Plot for Upper Support Normal Loading Conditions Hatch-2 Replacement Upper Support Stress Analysis Report Page 20 of 35

GE-NE-0000-0080-0259-R2 0 ýHITACHI Non-Proprietary Version 11 Figure 6. Stress Intensity Plot for Upper Support Normal Loading Condition Hatch-2 Replacement Upper-Support Stress Analysis Report Page 21 of 35

GE-N E-0000-0080-0259-R2 0 HITACHI Non-Proprietary Version

((I I]

Figure 7. The linearization paths for Upper Support Normal Condition Loads (The governing Pm occurred on the 45 deg path and the governing (Pm+Pb) occurred along the vertical path).

Hatch-2 Replacement Upper Support Stress Analysis Report Page 22 of 35

GE-NE-0000-0080-0259-R2 0 HITACHI Non-Proprietary Version 11 Figure 8. Stress Intensity Plot for the Upper Support Upset Seismic Loading Condition Hatch-2 Replacement Upper Support Stress Analysis Report Page 23 of 35

GE-N E-OO00-0080-0259-R2 0 HITACHI Non-Proprietary Version 1]

Figure 9. Replacement Upper Support - Linearization Plots for the Upset Condition Loads Hatch-2 Replacement Upper Support Stress Analysis Report Pa*ge 24 of 35

GE-NE-0000-0080-0259-R2 0 HITACHI Non-Proprietary Version Figure 10. Stress Intensity Plot for Upper Support Upset Thermal Loading Condition Hatch-2 Replacement Upper Support Stress Analysis Report Page 25 of 35

HITACHI GE-NE-OO00-0080-0259-R2 Non-Proprietary Version Figure 11. Replacement Upper Support - Linearization Plots for Upset Thermal Condition Hatch-2 Replacement Upper Support Stress Analysis Report Page 26 of 35

GE-N E-0000-0080-0259-R2 0HITACHI Non-Proprietary Version 11 Figure 12. Stress Intensity Plot for Upper Support Emergency Loading Condition Hotch-2 Replacement Upper Support Stress Analysis Report Page 27 of 35

GE-NE-OO00-0080-0259-R2 0 HITACHI Non-Proprietary Version

[r 11 Figure 13. Replacement Upper Support - Linearization Plot for Emergency Condition Hatch-2 Replacement Upper Support Stress Analysis Report Page 28 of 35

GE-N E-0000-0080-0259-R2 0 HITACHI Non-Proprietary Version 11 Figure 14. Stress Intensity Plot for Upper Support Faulted Loading Condition Hatch-2 Replacement Upper Support Stress Analysis Report Page 29 of 35

GE-NE-0000-0080-0259-R2 0 ýHITACHI Non-Proprietary Version 11 Figure 15. Replacement Upper Support - Linearization Plots for Faulted Condition Hatch-2 Replacement Upper Support Stress Analysis Report Page 30 of 35

GE-N E-0000-0080-0259-R2 0 HITACHI Non-Proprietary Version 11 Figure 16. Stress Intensity Plot for the Support in the Faulted Loading Condition Hatch-2 Replacement Upper Support Stress Analysis Report Pa~ge 31 of 355

GE-NE-0000-0080-0259-R2 0 ýHITACHI Non-Proprietary Version

((

))

Figure 17. Linearization Plot for the Support in the Faulted Condition Hatch-2 Replacement Upper Support Stress Analysis Report Page 32 of 35

GE-N E-0000-0080-0259-R2 0HITACHI Non-Proprietary Version It Figure 18. Tie Rod Nut / Tie Rod Threaded Connection- Finite Element Model Hatch-2 Replacement Upper Support Stress Analysis Report Page 3:3 of 35

GE-NE-0000-0080-0259-R2 Q HITACHI Non-Proprietary Version I)

Figure 19. Replacement Tie Rod Nut/Tie Rod Threaded Connection - Plot of Maximum Total Tensile Principal Strain in the Nut Threads for Normal Loading Condition, [I 1]

Hatch-2 Replacement Upper Support Stress Analysis Report Page 34 of 35

GE-NE-0000-0080-0259-R2 0 HITACHI Non-Proprietary Version 11 11 Figure 20. Replacement Tie Rod Nut/Tie Rod Threaded Connection - Plot of Maximum Total Principal Strain in the Tie Rod Threads for Normal Loading Condition, [I 1]

Hatch-2 Replacement Upper Support Stress Analysis Report Page 35 of 35

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