RA-20-0280, Submittal of IWB-3640 Analytical Evaluation Performed to Accept an ASME Section XI Code Rejected Sub-Surface Flaw

Submittal of IWB-3640 Analytical Evaluation Performed to Accept an ASME Section XI Code Rejected Sub-Surface Flaw

ML20272A194
Person / Time
Site:	Oconee
Issue date:	09/14/2020
From:	Snider S Duke Energy Carolinas
To:	Document Control Desk, Office of Nuclear Reactor Regulation
References
RA-20-0280
Download: ML20272A194 (17)

Text

Steve Snider

( ., DUKE Vice President ENERGY Nuclear Engineering 526 South Church Street, EC-07H Charlotte, NC 28202 980-373-6195 Steve.Snider@duke-energy.com RA-20-0280 September 14, 2020 U.S. Nuclear Regulatory Commission ATTN: Document Control Desk Washington, DC 20555-0001 Oconee Nuclear Station, Unit 3 Docket No. 50-287 Renewed License No. DPR-55

Subject:

Oconee Unit 3, Submittal of IWB-3640 Analytical Evaluation Performed to Accept an ASME Section XI Code Rejected Sub-Surface Flaw Pursuant to the 2007 Edition through the 2008 Addenda of the American Society of Mechanical Engineers (ASME) Boiler and Pressure Vessel Code,Section XI, IWB-3134, Duke Energy is submitting an Analytical Evaluation performed to accept an ASME code rejected sub-surface flaw identified on the 3B1 high pressure injection (HPI) nozzle-to-safe end weld during the 28 th refueling outage (O3R28) for Oconee Nuclear Station (ONS), Unit 3 in the Spring 2016. The May 2016 Analytical Evaluation for the code rejected flaw was performed in accordance with the 2007 Edition through the 2008 Addenda of the ASME Boiler and Pressure Vessel Code,Section XI, IWB-3640 and is being submitted for information only.

The Enclosure contains the HPI nozzle weld flaw evaluation per ASME Code,Section XI, IWB-3640 requirements.

This submittal contains no regulatory commitments. Please refer any questions regarding this submittal to Art Zaremba, Manager - Nuclear Fleet Licensing, at 980-373-2062.

Sincerely, Steve Snider Vice President - Nuclear Engineering

Enclosure:

High Pressure Injection (HPI) Nozzle Weld 3-RC-212-53V Flaw Evaluation

U.S. Nuclear Regulatory Commission Page 2 RA-20-0280 cc: (w/ Enclosure)

Ms. Laura Dudes Administrator, Region II U.S. Nuclear Regulatory Commission Marquis One Tower 245 Peachtree Center Avenue NE, Suite 1200 Atlanta, GA 30303-1257 Mr. Shawn Williams NRC Project Manager Oconee Nuclear Station Mr. Jared Nadel NRC Senior Resident Inspector Oconee Nuclear Station

Enclosure to RA-20-0280 Enclosure High Pressure Injection (HPI) Nozzle Weld 3-RC-212-53V Flaw Evaluation

I; Structural Integrity Associates, Inc. File No.: 1600492.301 Project No.: 1600492 CALCULATION PACKAGE Quality Program Type: 1:8] Nuclear

• Commercial PROJECT NAME:

Oconee Unit 3 HPI IWB-3600 Flaw Evaluation CONTRACT NO.:

03021365 00001 CLIENT: PLANT:

Duke Energy Oconee Nuclear Generating Station, Unit 3 CALCULATION TITLE:

HPI Nozzle Weld 3-RC-212-53V Flaw Evaluation per ASME Code,Section XI, IWB-3640 Requirements Project Manager Preparer(s) &

Document Affected Revision Description Approval Checker(s)

Revision Pages Signature & Date Signatures & Date 0 1 - 12 Initial Issue Preparers:

A A-2 Chris Lohse Wilson Wong 5/9/16 5/9/16 Checkers:

Kevin L. Wong 5/9/16 Page 1 of 12 F0306-01R2

SJ Structural Integrity Associates, lnc.,s; Table of Contents

1.0 INTRODUCTION

.........................................................................................................3 2.0 TECHNICAL APPROACH ..........................................................................................3 3.0 ASSUMPTIONS AND DESIGN INPUTS ...................................................................4 3.1 Piping Loads and Load Combinations...............................................................4 3.2 Thermal Transients ............................................................................................5 4.0 EVALUATION .............................................................................................................5 4.1 Allowable Flaw Size Determination..................................................................5 4.2 Crack Growth Consideration .............................................................................7

5.0 CONCLUSION

..............................................................................................................8

6.0 REFERENCES

..............................................................................................................9 APPENDIX A PHASED ARRAY ULTRASONIC EXAMINATION RESULTS [3, PDF PG. 4].................................................................................................... A-1 List of Tables Table 1: Loads at Flaw Location [9].......................................................................................10 Table 2: Stress Determination at Indications Location...........................................................10 Table 3: Stress Ratios and Allowable Flaw Depth-to-Thickness Ratios for a Non-Flux Weld Using Limit Load Analysis ..........................................................................11 Table 4: Material Properties for Alloy 600 (N06600) [10] .....................................................11 Table 5: Fatigue Crack Growth Transients and Cycles ..........................................................12 File No.: 1600492.301 Page 2 of 12 Revision: 0 F0306-01R2

SJ Structural Integrity Associates, lnc.,s;

1.0 INTRODUCTION

During phased array ultrasonic testing (PAUT) of Weld 3-RC-212-53V on the 3B1 HPI nozzle at Oconee Unit 3, a planar sub-surface flaw was identified in the Alloy 82 nozzle-to-safe end weld [3].

This indication was previously identified in 2014 and found to be acceptable [2]. However, using a higher resolution technique in 2016, the indication now measures larger than the acceptance standards as defined by ASME Code Section XI, IWB-3500 [1].

The indication was measured with several different angles with varying sizing dimensions. As such, the maximum flaw length (1.47) and maximum flaw through-wall depth (0.19) measured from any angle will be used for the flaw evaluation [3].

The objective of this calculation is to perform a flaw evaluation to the requirements of ASME Code,Section XI, IWB-3640 [1] considering the stresses and material properties at the location of the indication to determine the maximum Code allowable flaw size and acceptability for continued operation due to crack growth. The Section XI Code-of-record for Oconee is the 2007 Edition with 2008 Addenda [4].

2.0 TECHNICAL APPROACH The following technical approach will be used to perform the flaw evaluation.

1. Determine the stresses at the flaw location. Since the indications are in the circumferential direction [3], the stresses required are the axial stresses.

2. Determine the allowable flaw size using ASME Code,Section XI rules for austenitic stainless steel piping in IWB-3640 and Appendix C. The 2007 Edition of the ASME Code,Section XI states that the evaluation procedures and acceptance criteria in Nonmandatory Appendix C are applicable to piping 4 inch NPS or larger [1]. The 2013 Edition of ASME Code,Section XI [5]

states that the evaluation procedures and acceptance criteria in Nonmandatory Appendix C are applicable to piping 1 inch NPS or larger. There are no differences in the formulas, margins, or acceptance criteria in Nonmandatory Appendix C between the two versions, and as such, the 2007 Edition with 2008 Addenda can be used for the evaluation of the HPI Nozzle-to-safe end weld.

3. Assess the crack growth to ensure the as-found flaw will not reach the allowable flaw size determined in Step 2 before the end of the 10 year evaluation period. Since the flaw is a subsurface flaw as defined below in Section 4.0, there is no stress corrosion crack growth and only fatigue crack growth (FCG) is considered.

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SJ Structural Integrity Associates, lnc.,s; 3.0 ASSUMPTIONS AND DESIGN INPUTS Geometry (Dimensions taken from nozzle to safe end weld)

Pipe outside diameter (OD) = 3.5 inches [6, Figure 1]

Pipe inside diameter (ID) = 2 inches [6, Figure 1, with cladding]

Pipe thickness = 0.75 inches [6, Figure 1, with cladding]

Note that the PAUT lists a component thickness of 0.77 inches, but the use of 0.75 inches for the thickness is conservative for calculation of stresses.

Materials The nozzle to safe end weld is Alloy 82 weld metal [7] with elastic material properties used for finite element analysis shown in Table 4.

Operating Conditions Max Transient Internal Pressure = 3,192 psig [14, Table 4]

Design Temperature = 650°F [8, PDF pg36]

3.1 Piping Loads and Load Combinations The nozzle piping loads used in the evaluation are obtained from Reference [9] at the Alloy 600 weld.

These loads are summarized in Table 1. Safe Shutdown Earthquake is assumed to be 2X the Operating Basis Earthquake. The following Service Level load combinations are assumed to perform the flaw evaluation:

Primary Loads:

Service Level A/B (Normal/Upset): Deadweight (DW) + Operating Basis Earthquake (OBE)

Service Level C/D (Emergency/Faulted): DW + Safe Shutdown Earthquake (SSE)

From Table 1, the resultant moments for the primary and thermal loads for the various Service Levels are shown below. Even though only axial stress is needed, the moments are conservatively calculated using the SRSS of all three directions. Service Level B loads are conservatively used for both Service Level A and B.

Service Level A/B (Normal/Upset Condition, N/U) 7,182 in-lbs.

Service Level C/D (Emergency/Faulted Condition, E/F) 10,420 in-lbs.

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SJ Structural Integrity Associates, lnc.,s; 3.2 Thermal Transients In order to perform FCG analysis, stresses from thermal transients must be obtained. A previous SI calculation package [11] analyzed thermal transients on the Oconee HPI nozzle, but used material properties for Alloy 690 on the nozzle to safe end weld since the weld was changed to Alloy 52. Since the nozzle to safe end weld in the 3B1 nozzle in Unit 3 is Alloy 82, the material properties were modified to the values shown in Table 4. The model was regenerated with the new material properties using the HPI_GEOM.INP input file [11] in ANSYS 8.1 [12]. All thermal transient analysis (transient input files taken directly from [11]) and post processing was performed in ANSYS 14.5 [13] to take advantage of faster solving and post processing capabilities. First order stress coefficients (linear) are generated from mapped stresses through the weld (Path 2 in Reference [11]) using the GenStress.mac SI macro for use in FCG analysis. The GETPATH.TXT file contains the path information for stress extraction. The stress coefficients are output to *_STRS_COE_P1.CSV files, where

• is the transient number. The number of cycles for each transient for 60 years of operation are obtained from Reference

[14, Table 4], and shown in Table 5. These are scaled to 10 years by dividing the values by 6.

4.0 EVALUATION Flaw Characterization Based on the exam results in Appendix A, the following bounding flaw dimensions will be used for Flaw No. 1:

Maximum flaw length (l) = 1.47 inches Maximum flaw depth (2a) = 0.19 inch (a = 0.095 inch)

Flaw depth-to-thickness ratio (a/t) = 0.095/0.75 = 0.1266 or 12.67%

Flaw aspect ratio (all) = 0.095/1.47 = 0.065 Bottom of flaw to inside surface (S) = 0.06 Type of flaw: 0.06 (S) > 0.038 (0.4a), subsurface flaw Determination of Stresses The bending stresses were calculated from the bending moments shown in Table 1 using the equation from C-2500 [1]. Pressure stresses were also calculated based on the maximum pressure in Section 3.0 and using the equation from C-2500 [1]. The resulting stresses for the various load combinations are shown in Table 2.

4.1 Allowable Flaw Size Determination For a non-flux weld [7], Figure C-4210-1 of ASME Code,Section XI, Appendix C, allows the use of limit load techniques of C-5000 to determine the allowable flaw size [1].

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SJ Structural Integrity Associates, lnc.,s; For a limit load evaluation of a circumferential flaw, Article C-5000 points to Tables C-5310-1 through C-5310-5, which provide the allowable flaw depth-to-thickness ratios (a/t) as a function of the stress ratios and ratio of flaw length-to-pipe circumference ( f/ D). These tables are only valid if primary membrane stress is less than a factor times the material flow stress.

The stress ratio (SR) for limit load is defined as:

SR = (crm +crb)/crf where:

O'm = primary membrane stress O'b = primary bending stress O'f = flow stress = 54.85 ksi = average of yield (cry) and ultimate tensile stress (cru) [1, C-8200]

O'y = yield stress at operating temperature, 29.7 ksi [10]

O'u = ultimate tensile stress at operating temperature, 80.0 ksi [10]

OD = 3.5 inches [6]

From Table 2, it can be seen that the primary membrane stress is less than 0.2 times the flow stress, or 10.97 ksi. Since the same pressure is used for all service levels and 0.2 is the most limiting factor, all service level tables are applicable. The determination of the stress ratios at the location of the flaw is shown in Table 3 for Service Levels A/B and C/D.

For Service Levels A and B O'm = pressure axial stress O'b = bending stress due to DW + seismic OBE For Service Level C and D O'm = pressure axial stress O'b = bending stress due to DW + seismic SSE Using the maximum flaw length of 1.47 inches, the ratio of flaw length to pipe circumference is l.47/(1t*3 .5) = 0.134. However, allowable values for a full circumferential crack are used to bound any possible crack growth. From the stress ratios for limit load analysis shown in Table 3 and the 0.75 ratio of flaw length to pipe circumference ( f/ D), the allowable flaw depth to thickness ratios are determined from Tables C-5310-1 through C-5310-5 of ASME Code,Section XI, and also shown in Table 3. Since the maximum stress ratio is less than 0.2, Table C-5310-5 for pure membrane stress allows a flaw depth-to-thickness ratio of 0.75 even for a full circumferential crack. The minimum allowable flaw depth-to-thickness ratio is 0.73 considering all Service Levels for a full circumferential crack, bounding the measured flaw length of 1.47 inches. This is equivalent to a total flaw depth (2a) of 0.73*0.75 = 0.54 inches.

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SJ Structural Integrity Associates, lnc.,s; 4.2 Crack Growth Consideration The pc-CRACK [15] software is used to compute FCG with the built in ASME elliptical subsurface crack model (model 208). The load cases and corresponding number of cycles evaluated are listed in Table 5.

The FCG law for austenitic steels in air is used in the FCG calculation (see Equation 1) since the flaw is a subsurface crack. This crack growth law is built into pc-CRACK and is based on the crack growth law for austenitic steels published in C-8410, Appendix C of Section XI of the ASME Code [1].

da

= Co (!1K )n (1) dN where:

Co = CS log10 C = 10.009 + 8.12 x10 4 T 1.13 x10 6 T 2 +1.02 x10 9 T 3 1 R ,:::; 0 S 1 1 .8 R 0 < R ,:::; 0.79 43.35 + 57.97 R R < 0.79 R = K min / K max

~K = K max K min n = 3.3 T is temperature in oF, which is taken to be the maximum temperature during the transient. The above constants provide crack growth rates in inches per cycle when K is in ksi-in1/2.

To account for weld residual stress, a constant membrane stress equal to the material yield strength of Alloy 82/182 at 650ºF (29.7 ksi) is conservatively applied. Due to variation of the curve fit for stresses that arent linear, 5 ksi was added to the maximum stress for each transient as a membrane stress.

The maximum thermal piping load listed in Table 1 was obtained by taking the largest absolute value for each thermal component from Reference [9]. The SRSS of the bounding thermal moments listed in Table 1 generate a bending stress of 8.8 ksi, which was conservatively added to the maximum stress of each transient as a membrane stress.

The file CrackGrowth.pcf contains the pc-CRACK input, and the file CrackGrowth.rpt contains the output with resulting crack growth. The resulting crack growth for a subsurface flaw with 1.47 inch File No.: 1600492.301 Page 7 of 12 Revision: 0 F0306-01R2

SJ Structural Integrity Associates, lnc.,s; length and 0.19 inch total height is a = 0.0097 over a 10 year evaluation period. The final flaw depth after FCG is 0.19+ 2*0.0097 = 0.2094. At this depth, the flaw remains classified as a subsurface flaw where 0.0503 (S) > 0.0419 (0.4a).

5.0 CONCLUSION

A flaw evaluation was performed to the requirements of ASME Code,Section XI, IWB-3640 [1]

considering the stresses and material properties at the location of the indications to determine the Code allowable flaw size and acceptability after crack growth. The subsurface indication found during PAUT had a maximum measured width of 1.47 and depth of 0.19. The allowable flaw depth was found to be significantly larger at 0.54. Since the final flaw depth after FCG is only 0.2094 and remains classified as subsurface, the flaw is acceptable through the 10 year evaluation period.

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SJ Structural Integrity Associates, lnc.,s;

6.0 REFERENCES

1. ASME Boiler and Pressure Vessel and Boiler Code,Section XI, 2007 Edition with 2008 Addenda.

2. Email from Brian T Shalayda (Duke) to ONS OSM and Backups, CC Dick Mattson (SI), dated 4/30/2016 7:34am, SI File No. 1600492.204.

3. SI Phased Array Ultrasonic Examination Record, Examination Data Sheet No. 3-RC-212-53V, dated May 1, 2016, SI File No. 1600492.202.

4. Duke Energy Specification No. OSS-0018.0P-00-008, Rev. 1, Procurement Specification for The Repair of Simple Configuration Nozzles Containing Alloy 600/82/182 materials, SI File No.

1600103.205.

5. ASME Boiler and Pressure Vessel and Boiler Code,Section XI, 2013 Edition.

6. SI Calculation No. ONS-14Q-301, Rev. 0, HPI Nozzle Geometry and Material Properties.

7. Email from David Peltola (Duke) to Dick Mattson (SI), dated 5/3/2016 10:54am, with attachment 23-5015791-00.PDF, SI File No. 1600492.203.

8. Duke Power Calculation No. OSC-1522, Attachment 1, Reactor Coolant Loop Piping Stress Report, SI File No. ONS-14Q-202.

9. Email Attachment from David Peltola (Duke) to Dick Mattson (SI), dated 4/30/2016 12:11pm, Attachment 2 to OSR-0018-0P-00-0010 Rev 0.docx, SI File No. 1600492.201.

10. ASME Boiler and Pressure Vessel and Boiler Code,Section II, Part D, 2001 Edition with 2003 Addenda.

11. SI Calculation No. ONS-14Q-305, Rev. 0, Thermal Transient Stress Analyses of the HPI Nozzle.

12. ANSYS, Release 8.1 (w/Service Pack 1), ANSYS, Inc.

13. ANSYS Mechanical APDL, Release 14.5 (w/ Service Pack 1 UP20120918), ANSYS, Inc.,

September 2012.

14. SI Calculation No. ONS-14Q-307, Rev. 3, ASME Code Stress Range and Fatigue Usage Analysis.

15. pc-CRACK, Version 4.1 CS (Project 0900086), Structural Integrity Associates, Inc., December 31, 2013.

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SJ Structural Integrity Associates, lnc.,s; Table 1: Loads at Flaw Location [9]

Msrss, in-2" HPI Forces, lbs Moments, ft-lbs lbs FX FY FZ MX MY MZ Thermal 401.57 446.4 231.55 375.96 923.43 2571.95 33,101 DW -12.9 -287.5 -15.3 -151.4 -74.6 296.0 OBE 97.1 73.2 79.3 72.4 182.0 196.2 SSE 194.1 146.3 158.6 144.9 364.0 392.4 Primary, N/U 109.9 360.6 94.6 223.8 256.6 492.2 7,182 Primary, E/F 206.99 433.76 173.91 296.22 438.59 688.40 10,420 Table 2: Stress Determination at Indications Location Max Resultant Pressure Primary Bending Service Pressure Moment Stress ( (Jm) Stress ( (Jb)

Level (psig) (in-lbs.) (psi) (psi)

A/B 3,192 7,182 3,724 1,910 C/D 3,192 10,420 3,724 2,772 File No.: 1600492.301 Page 10 of 12 Revision: 0 F0306-01R2

SJ Structural Integrity Associates, lnc.,s; Table 3: Stress Ratios and Allowable Flaw Depth-to-Thickness Ratios for a Non-Flux Weld Using Limit Load Analysis Allowable Flaw Service Stress Ratio Allowable 2a/t Depth (2a)

Level (Limit Load) For Full Circ Flaw (inches)

A 0.103 0.74 0.555 B 0.103 0.75 0.5625 C 0.118 0.73 0.54 D 0.118 0.75 0.5625 Table 4: Material Properties for Alloy 600 (N06600) [10]

Youngs Mean Thermal Specific Temperature, Thermal Conductivity, Modulus, Expansion, Heat,

°F x106 psi x10-6 in/in/°F x10-4 Btu/sec-in-°F Btu/lb-°F 70 31.0 6.80 1.99 0.114 200 30.2 7.10 2.11 0.119 300 29.8 7.30 2.22 0.123 400 29.5 7.50 2.34 0.125 500 29.0 7.60 2.45 0.127 600 28.7 7.80 2.57 0.130 700 28.2 7.90 2.69 0.133 Density, p = 0.283 lb/in3, assumed temperature independent.

Poissons Ratio, u = 0.3, assumed temperature independent.

Note: Specific Heat values are derived from the equation shown in General Note (a) of Table TCD [10], Specific Heat = TC / (TD x density).

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SJ Structural Integrity Associates, lnc.,s; Table 5: Fatigue Crack Growth Transients and Cycles 10 Year 60 Year Design Transient Evaluation Cycles [14]

Period Cycles 1A Heatup 360 60 1B Cooldown 360 60 8B Rx Trip High Temp 610 102 8C Rx Trip High Press 170 30 8HPI Activation 70 12 9 Depressurization 40 7 12 HydroTest 5 1 22A HPI Test 40 7 OBE 5 1 File No.: 1600492.301 Page 12 of 12 Revision: 0 F0306-01R2

APPENDIXA PHASED ARRAY ULTRASONIC EXAMINATION RESULTS [3, PDF PG. 4]

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tJ Structural Integrity Associates, Inc.

PHASED ARRAY ULTRASONIC EXAM/NATION RECORD Examination Data Sheet No.: 3-RC-212-53V

/WB-3500 Flaw Evaluation Planar Flaw Comparison to Acceptance Standards - ASME Section XI - 2007 Edition with Addenda Through 2008 Oconee Unit 3 Component ID: HPI 3-RC-212-53V Subsurface Subsurface (S) Depth Depth Flaw Flaw Subsurface Code Flaw No.1 Flaw Flaw Flaw OD to Top OD to Bottom Through Component Flaw Flaw Flaw Flaw Material Flaw Only Flaw Allowable Data View Start End Length of Flaw of Flaw !YM Wall Thickness  !!.  !!.!!  !!r<i ilQ!  !!.!! Y=sla ~ Table Results 1 10.30 11 .68 1.38 0.51 0.70 0,19 0,77 0.10 0.07 12.34% Subsurface Austen itic 0.07 1 12.34% 11. 24% Exceeds 2 1089 12.27 1.38 0,37 0.54 0.17 0,77 0.09 0.06 11.04% Subsurface A.Jstenitic 0.06 1 11.04% 11. 19% Acceptable 3 10.29 11 .37 1.08 0.39 0.56 0.17 0.77 0.09 0.08 11.04% Subsurface Austenitic 0.08 1 11.04% 11. 29% Acceptable 4 9.99 11.46 1.47 0.53 0.71 0.18 0.77 0.09 0.06 11.69% Subsurface Austenilic 0.06 11.69% 11.19% Exceeds

~ 0.29 0.87 0.58 0.59 0.69 0.10 0.77 0.05 0.09 6.49% Subsurface Austenitic 0.09 6.49% 11. 35% Acceplable FlawNo.3 1.27 1.76 0.49 0.57 0,70 0.13 0.77 0.07 0.13 8.44% Subsurface Austen,tic 0,13 8.44% 11.48% Acceptable Flaw #1 Data Views:

Data View #1

• Flaw #1 As depic1ed with 45' RL Data from the nozzle side of the weld Data View #2 Flaw #1 As depicted with 60" RL Data from the nozzle side of the weld Data View #3 Flaw #1 As depicted with 45' RL Data from the safe end side of the weld Da1a View #4* Flaw#1 As depicted with 45' shear wave data from the safe end side of the weld File No.: 1600492.301 Page A-2 of A-2 Revision: 0 F0306-01R2