ML20106E828
| ML20106E828 | |
| Person / Time | |
|---|---|
| Site: | Limerick  |
| Issue date: | 04/15/2020 |
| From: | David Helker Exelon Generation Co |
| To: | Document Control Desk, Office of Nuclear Reactor Regulation |
| References | |
| Download: ML20106E828 (41) | |
Text
200 Exelon Way Kennett Square, PA 19348 www.exeloncorp.com April 15, 2020 U.S. Nuclear Regulatory Commission Attn: Document Control Desk Washington, DC 20555-0001 Limerick Generating Station, Unit 1 Renewed Facility Operating License No. NPF-39 NRC Docket No. 50-352
Subject:
Submittal of Analytical Evaluation of Core Spray Injection Nozzle-to-Safe End Weld (N5A)
In accordance with the American Society of Mechanical Engineers (ASME) Code,Section XI, 2007 Edition with 2008 Addenda, IWB-3134(b) ("Review by Authorities"), Limerick Generating Station, Unit 1, is submitting an analytical evaluation associated with the Core Spray Injection nozzle-to-safe end weld (N5A).
As discussed in the attached report, an analytical evaluation was performed to disposition an indication associated with the Core Spray Injection nozzle-to-safe end weld (N5A). The indication is circumferentially oriented, measured by ultrasonic testing to be approximately 2.0 inches long, 0.3 inches through wall, and has a surface separation distance of 0.35 inches from the inside surface. The indication is located in the weld material. This is an embedded flaw and does not display any characteristics of an IGSCC flaw. Instead, this is likely a construction flaw that is now more clearly visible due to the change in ultrasonic examination technology. The nozzle-to-safe end weld is a dissimilar metal weld joining the SA508 CL 2 low alloy steel nozzle to the SB166 safe end with an Alloy 82 weld with an Alloy 182 butter.
As concluded in this evaluation, the required safety factors will be maintained during operation with this indication over the next five operating cycles, by which time the weld/ indication will be examined in accordance with BWRVIP-75A requirements.
There are no regulatory commitments in this letter.
Submittal of Analytical Evaluation April 15, 2020 Page 2 If you have any questions concerning this letter, please contact Tom Loomis at (610) 765-5510.
Respectfully, David P. Helker Sr. Manager, Licensing Exelon Generation Company, LLC
Attachment:
Evaluation of Unit 1 DCA-319-1 N5A Flaw Identified in IR 04332524 cc: Regional Administrator, Region I, USNRC USNRC Senior Resident Inspector, Limerick Generating Station Project Manager USNRC, Limerick Generation Station R. R. Janati, Commonwealth of Pennsylvania
Attachment Evaluation of Unit 1 DCA-319-1 N5A Flaw Identified in IR 04332524
Engineering Change Print Date:
04/08/2020 EC Number :
0000631225 000 Status/Date :
CLOSED 04/07/2020 Facility :
LIM Type/Sub-type:
EVAL MECH Page:
1 EC
Title:
EVALUATION OF UNIT 1 DCA-319-1 N5A FLAW IDENTIFIED IN IR 04332524 Mod Nbr :
KW1: SR KW2: KW3: KW4: KW5:
Master EC :
N Work Group :
Temporary :
N Outage :
N Alert Group:
A5252NESDM Aprd Reqd Date:
04/17/2020 WO Required :
N Image Addr :
Exp Insvc Date:
Adv Wk Appvd:
N Alt Ref. :
Expires On :
01/01/2023 Auto-Advance:
Y Priority :
Auto-Asbuild :
N Caveat Outst:
N Department :
Discipline :
Resp Engr :
TODD SWOYER Location :
Milestone Date PassPort Name Req By 110-PREPARE EC 04/05/2020 E060449 SWOYER TODD APPROVED 120-REVIEW EC 04/07/2020 E060449 SWOYER TODD APPROVED Todd Swoyer signing for Emmanuel Rosa per telecon. The following are the independent reviewer comments:
This Independent Review used procedure CC-AA-103-100, Attachment "D", to verify that the above response conforms to all applicable design, configuration control, codes and licensing basis requirements. The inputs were found to be correct and appropriate.
The design method used is appropriate and the output is reasonable for the given inputs. The results support the stated purpose.
All reviewer comments have been satisfactorily resolved and incorporated.
210-DEPT RVW-01 04/05/2020 E060449 SWOYER TODD APPROVED The following is an email from Ron Janowiak from corporate, dated 04/04/20 at 15:09, performing an indepdent review of the fracture mechanics portion of this technical evaluation.
Based upon e-mail correspondence provided to me between Limerick Engineering and Structural Integrity Associates (SIA)(Richard Mattson and DJ Shim) dated April 3, 2020, I was asked to perform an independent review (i.e. sanity check) of the conclusion reached by SIA that a surface flaw bounded an embedded flaw of the same dimensions (as noted by SIA in that correspondence). The surface flaw was the subject of Limerick evaluation LGS-12Q-301 (December 2007) entitled "Flaw Evaluation of Limerick Unit 1 Core Spray Nozzle N5 Weld." SIA performed that evaluation. The size of that flaw was documented as approximately 2.1 inches long and 0.695 inches deep.
The recently discovered embedded flaw has the dimensions of 1.97 inches long and 0.323 inches deep, which is both shorter and shallower than that previously evaluated. It is my understanding that Limerick Engineering intends to use the 2007 analysis as technical justification for the recently discovered embedded flaw.
Engineering Change Print Date:
04/08/2020 EC Number :
0000631225 000 Status/Date :
CLOSED 04/07/2020 Facility :
LIM Type/Sub-type:
EVAL MECH Page:
2 During my independent review, I discussed with DJ Shim his unverified analysis (back-of the envelope) for the embedded flaw. We agreed that a surface flaw bounds an embedded flaw from a fracture mechanics perspective. My review of the ASME BPV Section XI, Appendix C, code provisions reached this same conclusion in my independent review. It was also noted that the embedded flaw is smaller in both length and depth than the surface flaw. The internal surface flaw also experiences system pressure on the crack face that an embedded flaw does not, thus increasing the stress intensity factor for the surface flaw; the embedded flaw obviously does not experience system pressure.
I also understand that the loads used in the previous analysis did not chan change; however, it was not within the scope of my independent review to confirm this.
300-APPROVE EC 04/07/2020 E074144 MCCORMICK RORY APPROVED 800-ATTR CLOSED 04/05/2020 E060449 SWOYER TODD CLOSED Units Fac Unit Description LIM 01 UNIT ONE Systems Fac System Description LIM 918 RX VESSEL AND INTERNALS
EC 631225, Rev. 0 Page 1 of 3 This Engineering Technical Evaluation is being prepared in accordance with Procedure CC-AA-309-101, Revision 15.
Document Number: EC 631225, Rev. 0
Title:
EVALUATION OF UNIT 1 DCA-319-1 N5A FLAW IDENTIFIED IN IR 04332524 Reason for evaluation/scope:
============
Per IR 04332524, during 1R18 NDE technicians performed an automated phased-array ultrasonic testing (PAUT) examination of component DCA-319-1 N5A per work order 4941659-04 for the Augmented Inservice Inspection (ISI) program. DCA-319-1 N5A is the 10 inch diameter weld that connects the carbon steel reactor vessel nozzle to the Inconel safe end on the N5A nozzle (Az. 60 Deg), which is the 'B' core spray injection line.
The automated PAUT examination revealed a subsurface indication recorded approximately 11.6" clockwise from top dead center. The indication is located in the weld material adjacent to the upstream weld fusion line. This is an embedded indication, typical of a fabrication indication, it is not ID connected, and does not display any characteristics indicative of intergranular stress corrosion cracking (IGSCC). The 1R18 examination determined that the indication exceeds the allowable a/t value of Table IWB-3514-2, which is unacceptable for continued service, and must be accepted by analytical evaluation in accordance with ASME Section XI, IWB-3132.3. The examination results are included in this evaluation as Attachment 01.
This Engineering Technical Evaluation is written to evaluate the N5A weld for continued service.
Detailed evaluation:
=====
DCA-319-1 N5A has previously been identified at LGS with a subsurface flaw connected to the inside surface of the pipe (see IR 00709152), which required evaluation in accordance with ASME Code, section IWB-3600, using a detailed stress analysis for acceptance. This analysis was completed by Structural Integrity Associates (SIA) under document LGS-12Q-301 (See Attachment 2) and qualified a surface flaw measuring 2.1 inches long and 0.695 inches deep on the DCA-319-1 N5A weld.
The analysis proved the acceptability of the indication found in 1998 for continued operation until March 2008. Weld DCA-319-1 N5A was mechanically stress improved in 1R05 (1994). Reference BWRVIP 2007-367. The analysis did not take credit for performing mechanical stress improvement process (MSIP) on the weld. MSIP is utilized to produce compressive residual stresses in the component, which has been
EC 631225, Rev. 0 Page 2 of 3 effective in mitigating crack growth. The analysis also conservatively assumed the plant has been at full power since 1998. Thus, for crack growth analysis the number of hours as well as the number of cycles of operation is computed accordingly.
A linear elastic fracture mechanics analysis was performed for the observed indication to compute the crack propagation due to stress corrosion and fatigue crack growth rate.
The fatigue crack growth rate was evaluated for the 10 years of operation followed by 10 years of stress corrosion crack growth to project the total indication size. The projected indication size was compared to the allowable flaw size calculated from IWB-3610. The analysis concluded the indication identified in 1998 would be below the allowable flaw size in March 2008. The analysis is included as Attachment 2 to this EC.
During a 2008 ultrasonic testing performed of DCA-319-1 N5A, the flaw was found to be subsurface and not connected to the ID. The previously identified and evaluated flaw is the same flaw at the same location as identified in IR 04332524. Therefore, there is only one flaw in DCA-319-1 N5A.
This technical evaluation will compare the ID-connected flaw identified in IR 00709152 to the subsurface flaw identified during 1R18 (Ref IR 04332524) to show how the flaw evaluation in Attachment 2 is applicable to the newly identified flaw.
- The flaw identified in IR 04332524 is a subsurface flaw with a length of 1.97 inches, depth of 0.323, and separation of 0.361 inches to the surface (See ). The flaw evaluated in Attachment 2 is 2.1 inches long, 0.695 inches deep, and connected to the ID Surface. The subsurface flaw is both shorter and shallower than the previously evaluated flaw in Attachment 2.
- A surface flaw bounds an embedded/subsurface flaw from a fracture mechanics perspective. The subsurface flaw does not experience system pressure on the crack face like an internal flaw does. This would decrease the stress intensity for the subsurface flaw.
- The crack growth due to IGSCC is not needed for a subsurface flaw since it is not exposed to a water environment like an ID-connected flaw is. However, this technical evaluation does not take credit for removing the amount of crack growth due to SCC.
- Based on review of calculation SR-1600-2 and LEAM-MUR-0049, the moment loading used in Attachment 2 along with the design temperature and pressure remain unchanged for the current plant configuration. The loads used within the analysis were taken from SR-1600-2 because the Unit 1 configuration matches Unit 2. Therefore, there are no changes required to the inputs used in the previous flaw evaluation.
In summary, the subsurface flaw identified in IR 04332524 is bounded by the SIA flaw evaluated in Attachment 2 (LGS-12Q-301). The flaw is acceptable for ten years of service based on the crack growth evaluation in Attachment 2. This is conservative for a subsurface flaw since crack growth due to SCC is not required.
EC 631225, Rev. 0 Page 3 of 3 The subsurface flaw is indicative of a fabrication defect and is not service induced. The NDE data was sent to EPRI to perform an independent review of the PAUT data from DCA-319-1 N5A. EPRI concluded that the PAUT data from DCA-319-1 N5A shows an embedded fabrication flaw. Also, the EPRI conclusions discuss the relationship of the flaw size between the 2008 and 2020 examination techniques. The 2008 examination results were not used for this technical evaluation. The SIA flaw evaluation included as to this EC use the 1998 examination results to size the flaw.
Assignment 04332524-02 was generated to Programs to include the requirement for a ten-year inspection interval for the DCA-319-1 N5A nozzle to safe-end weld.
Refinement of the crack growth evaluation for the subsurface flaw can be performed to increase the inspection internal, if desired.
Administrative considerations:
This Engineering Technical Evaluation by Engineering (T. Swoyer and R. McCormick) on 4/05/20 was screened per HU-AA-1212, Revision 9. This evaluation is of Low risk consequence (potential adverse reduction in safety margin). It has been determined to have a risk rank of 1, and it does not require supplemental review. Per procedure, since this evaluation is safety related components, an independent review is required.
Conclusions/findings:
======
The results of the analysis presented in the SIA flaw evaluation included in Attachment 2 applies to the subsurface flaw identified in IR 04332524. The indication found is acceptable for continued service based on the requirements of ASME Code,Section XI.
A ten-year inspection interval is required based on this analysis.
References:
=
- 1. Issue Report 04332524, Dated 04/03/2020
- 2. CC-AA-309-101, Revision 15
- 3. HU-AA-1212, Revision 9
- 4. ASME Section XI, 2001 Edition with 2003 Addenda
- 5. SR-1600-2, Revision 0A
- 6. LEAM-MUR-0049, Revision 0 Attachments:
==
- CNF-002 Flaw Examination Results - LGS-12Q-301, SIA Flaw Evaluation - EPRI Letter See milestones for preparer, reviewer, and approver.
to EC 631225, Rev. 0 Page 1 of 2 HITACHI Customer Notification Form (CNF)
Project:
Li1R18 CNF No.: ICNF-002 Project No.: 200714 Component DCA-319-1 NSA Date:
April3,2020 Identification:
Subject:
Subsurface Unacceptable Indication Data Sheet:
Examination Tvoe:
Work Order Number:
N/A Phased Array UT 494165904 Conditions Found:
The Automated inspection of the above listed weld revealed a subsurface indication that was recorded @ approximately 11.6" CW from Top Dead Center. The indication is located in the weld material adjacent to the upstream weld fusion line. This indication was recorded in previous examinations and was found to be acceptable. The examination during this outage found the indication parameters now exceed the allowable alt% to table IWB-3514-2. See page 2 for the Flaw Evaluation Sheet.
Pre ared B :
Title:
Andre' Rachal UT Level Ill Received B
Title:
u II Page 1 of2 to EC 631225, Rev. 0 Page 2 of 2 8 HITACHI ASME Section XI Flaw Evaluation Sheet Project: Li1Rl8 Weld ID : DCA-319-1 N5A Indication : 1 Measured Rounded Measured Rounded Flaw Through Wall=
0.323 0.3
'7 nominal =
1.31 1.3 Flaw Length "I"=
1.97 2.0
'7 measured=
1.30 1.3 Surface Separation S =
0.361 0.35 ASME Section XI, 2007 Edition, 2008 Addenda Tobie IWB-3514-2, Austenitic Steels lnservice Examinations 2.0" T a/1 Surface%
Subsurface %
Surface%
Subsurface %
0.00 10.0 10.0 0.05 10.2 10.2 10.30 10.30V 0.10 10.4 10.4 0.15 10.5 10.5 0.20 10.7 10.7 0.25 10.9 10.9 0.30 11.1 11.1 0.35 11.2 11.2 0.40 11.4 11.4 0.45 11.6 11.6 0.50 11.7 11.7 Allowed Allowed 10.30 10.30 a=
0.150 all value=
0.075 Y=
1.000 Flaw is Subsurface Allowed alt=
10.3%
alt=
11.5%
Flaw is unacceptable by the referenced Table.
Revised: 9/27 /13 Comments: ASME Section XI rounding performed in accordance with IWA-3200 and ASTM E29.
All measurements converted from metric to US standard for evaluation.
2.0" table was used for a more conservative allowable alt.
Flaw is reiectable to the 1.0" and 2.0" tables
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Lower Tip-(.939") S-Dimensi~ closest to the inside surface
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Page 2 of2 to EC 631225, Rev. 0 Page 1 of 24 fi Structural Integrity VAssociates, Inc.
CALCULATION PACKAGE File No.: LGS-12Q-301 Project No.: LGS-12Q PROJECT NAME: Flaw Evaluation of Limerick Unit I Core Spray Nozzle N5 Weld Contract No: GSA No. 01002562 CLIENT: Exelon Nuclear PLANT: Limerick Unit I CALCULATION TITLE: Flaw Evaluation of Core Spray Nozzle N5 Nozzle-to-Safe-End Weld Document Revision 0
oPlt. 01. 005 S\\lpi)ril'l AM\\1s*s l=or 1)(11-11, *I NSA WC.\\cl W,c-.~*"
Affected Pages I - 15 Al - Al 1 Computer Files I - 19 Al - Al I Computer Files Revision Description Original Issue Use Revised Design Input Change Fatigue Crack Growth Law Project Mgr.
Approval Signature &
Date G. A. Miessi 12/18/07 G. A. Miessi 12/21/07 Preparer(s)
& Checker(s)
Signatures &
Date G. A. Miessi 12/18/07 S. S. Tang 12/18/07 G. A. Miessi 12/21/07
/.J"-/~-
- s. S. Tang 12/21/07 Page I of 19 SI Form F2001R2a to EC 631225, Rev. 0 Page 2 of 24 Table of Contents I
INTRODUCTION.................................................................................................................... 3 2
TECHNICAL APPROACH...................................................................................................... 3 3
DESIGN INPUT....................................................................................................................... 3 3.1 Design and Operating Conditions............................................................................................. 3 3.2 Component Dimensions............................................................................................................ 3 3.3 Material Properties.................................................................................................................... 4 3.4 Flaw Characterization............................................................................................................... 4 3.5 Applied Stresses........................................................................................................................ 4 4
ASSUMPTIONS....................................................................................................................... 7 5
CALCULATIONS.................................................................................................................... 7 5.1 Allowable Flaw Size Calculation.............................................................................................. 7 5.2 Stress Intensity Factors Calculation.......................................................................................... 8 5.3 Fatigue Crack Growth Analysis................................................................................................ 8 5.4 Stress Corrosion Crack Growth Analysis................................................................................. 9 6
CONCLUSIONS AND DISCUSSIONS................................................................................ 18 7
REFERENCES........................................................................................................................ 19
, APPENDIX A pc-CRACK OUTPUT FILE........................................................................................... Al List of Tables Table I: Core Spray Nozzle N5 Loads and Stresses.................................................................................. 5 Table 2: Design Transients....................................................................................................................... 11 Table 3: Allowable Flaw Size Calculations............................................................................................. 12 Table 4: Fatigue Crack Growth Results................................................... :............................................... 13 Table 5: Stress Corrosion Crack Growth Results.................................................................................... 14 List of Figures Figure I: Core Spray N5 Nozzle Assembly............................................................................................... 6 Figure 2: Applied Stress Intensity Factor................................................................................................ 15 Figure 3: Fatigue Crack Growth Results.................................................................................................. 16 Figure 4: Stress Corrosion Crack Growth Results................................................................................... I 7
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Structural Integrity V
Associates, Inc.
File No.: LGS-12Q-301 I
Revision: 1 Page 2 of -19 to EC 631225, Rev. 0 Page 3 of 24 1 INTRODUCTION A flaw evaluation is performed to dispbsition a flaw in the core spray nozzle-to-safe-end weld of the N5 core spray nozzle at Limerick Unit 1. The circumferential flaw, which is approximately 2.1 inches long and 0.695 inches deep, was first reported during the 1998 refueling outage. At the time, the indication was reported as a subsurface and found to be acceptable per the ASME Code,Section XI acceptance standards of Table IWB-3510-1. The weld is a dissimilar metal weld joining the low alloy steel nozzle to the Alloy 600 safe-end with an Alloy 82 weld and Alloy 182 weld butter.
2 TECHNICAL APPROACH The flaw evaluation consists of the following tasks:
Perfonn a flaw evaluation based on the guidelines of ASME B&PV Code,Section XI, IWB-3610 to calculate the allowable flaw size for the core spray nozzle weld. Applied stresses due to the moment loading from the piping design analysis are used. Given that the material of the dissimilar weld is Alloy 182, a nickel based austenitic steel, the flaw acceptance criteria for austenitic steel, based on limit load, was utilized based on Paragraph IWB-3641 of Reference l.
Determine the stress intensity factors at the flaw and perform stress corrosion and fatigue crack growth analyses to compare end-of-evaluation period flaw size to the allowable flaw size computed above. The evaluation period is 10 years.
3 DESIGN INPUT 3.1 Design and Operating Conditions The design and operating conditions of the core spray system are provided by Reference 2.
Design Temperature= 582°F Design Pressure = 1250 psig Nonna! Operating Temperature = 546°F Normal Operating Pressure= 1000 psig Due to power uprate, the pressure and temperature data has changed. The following new values are provided by Reference 3:
Nonna! Operating Temperature= 553°F Normal Operating Pressure= 1053 psig 3.2 Component Dimensions The geometry and some dimensions of the core spray nozzle N5 assembly are shown in Figure 1, which is obtained from Reference 4. Reference 5 provides more dimensions of the assembly. The nozzle safe-end
.=:r Structural Integrity VAssociates, Inc.
File No.: LGS-12Q-301 I
Revision: l Page 3 of 19 to EC 631225, Rev. 0 Page 4 of 24 where the indication was discovered is a 14-inch OD pipe [4, 5). The nominal dimensions of the safe-end (nozzle side) are:
Nominal Outer Diameter = 14.25 in.
Nominal Wall Thickness = 1.31 in.
The measured thickness at the core spray nozzle-to-safe-end weld is 1.48 inches (7).
3.3 Material Properties The core spray nozzle to safe-end weld butter containing the indication is fabricated from Alloy 182 per Reference 4. As shown in Figure 1, the different materials of the core spray nozzle assembly are as follows [4]:
Component Material N5 Nozzle Forging SA-508 Class 2 N5 Safe-End Forging Alloy 600 (SB 166)
Weld Alloy 82 Weld Butter Alloy 182 Nozzle ID Cladding Type 309/308L Stainless Steel The design allowable stress, Sm, of the weld metal is taken to be the same as that of Alloy 600, the base metal of the safe-end. At the normal operating temperature of 553°F (2, 3], Sy is equal to 30,100 psi and the ultimate strength Su is 80,000 psi [6]. Therefore, the flow stress, a 1, defined as (Sy+ Su)/2 is equal to 55,050 psi.
3.4 Flaw Characterization The flaw examination report summarized in Reference 7 indicates that the flaw is a 2.1 inches long circumferential flaw which is 0.695 inches deep. The thickness at the flaw location is reported as 1.48 inches; therefore, the flaw depth to thickness ratio is 0.47.
3.5 Applied Stresses The applicable loads at the location of the indication are provided by Reference 8 which contains stress results from a piping analysis of the core spray piping system. It should be noted that a note on Page 8 of Reference 2 states that the Reference 8 piping analysis, which is for Limerick Unit 2, is applicable to Unit
- 1. Bending moments due to deadweight, seismic loadings and thermal expansion are extracted from the piping analysis at the node representing the pipe to safe-end weld (Node 75) as shown in the isometric drawing of the core spray system [9]. The bending moments and calculated stresses at the flaw location are shown in Table 1. The stresses were calculated using the nominal thickness instead of the larger measured thickness for conservatism.
The stresses due to through-wall thermal gradients (~T1 and ~T2) are added to the calculated stresses.
The core spray nozzle is protected by a thermal sleeve and is expected to experience less severe through-wall thermal gradients than specified with the design transients. The through-wall thermal gradients at the fi Structural Integrity V
Associates, Inc.
File No.: LGS-12Q-301 I
Revision: I Page 4 of 19 to EC 631225, Rev. 0 Page 5 of 24 nozzle-to-safe-end weld are also expected to be less than those at the pipe to safe-end location. The corresponding thennal transient stress, shown in Table 1, are calculated simply as or= Ea.1T/(1-v2)
- where, Eis Young's modulus a is the coefficient of thennal expansion.
!), T is conservatively taken as the temperature difference between the reactor pressure and the HPCI at the injection time. For all the other transients, the maximum at the pipe-to-safe-end weld is conservatively used.
The core spray nozzle to safe-end weld is near the tapered transition of the safe-end and is likely subjected to the effects of the thermal gradients TA and Ts which have not been included in this analysis. The maximum sum of,1 T 1, !), T 2 and T A-T 8 from the piping analysis is 3 57°F versus the.1 T of 451 °F used for the maximum transient in this evaluation. It is believed that the stresses computed from Ea,1 Tare conservative.
The plant transient data showing the number of HPCI injections since September 1985 is obtained from Reference 14 and the material properties are taken at an average temperature of 300°F from Reference 6.
Table 1: Core Spray Nozzle N5 Loads and Stresses Ro Ri tnom z
(in)
(in)
(in)
(in3) 7.125 5.813 1.31 158.3 p
MX MY MZ a
Load (psi)
(ft-kips)
(ft-kips)
(ft-kips)
(ksi)
Pressure 1053 2.095 ow 1.242 0.971
-5.084 0.404 Thermal 10.944 13.764 12.491 1.656 QBE 2.749 2.603 5.118 0.483 SAM 2.645 23.955 6.100 1.885 Max Thermal 11.400 17.000 15.692 1.956 P+DW+T 4.155 Transient E
(l aT O'T a
ksi in/in/°F OF (ksi)
(ksi)
Max 29800 7.30E-06 451 107.814 112.268 All others 29800 7.30E-06 14 3.347 7.801
{'r Structural Integrity File No.: LGS-12Q-301 Revision: 1 Associates, Inc.
Page 5 of 19 to EC 631225, Rev. 0 Page 6 of 24 VELD IDENTIFICATION I. NOZZLE TD YESSEL N5 A.B
- 2. NDZ2t.E IIIO IWlDJS N5 A.B
- 3. NOZ2l£ TO SAFE ENO OCA-319-1 "_.
D<:A-321-1 H58
- 4. SAFE El(J TO PIPE DCA-319-1 flll DC.1*321-1 F'Wl CORE SPRAY PIPE STAINI.ESS STEEL SA 358 316L 0>::g::._~~o:21~~ITH REF. D\\165:
8931-M-l-811--l-C-ll4. l ffll-M-1-811-ANI-C-99.8 GE, FDI 25/73831-1 8831-!t-1-!IU-A881-C-178. l se:11-11-1-eu-**1-c-111.1
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. 79*
cm: CATtlDI!
B-11 B-11+
I 8-F*
I 8-F I
112" COIE SPRAY - 2 NOZZLES I 1.31" ll'Y JJ SHELL RING ASSEMSI.Y LDV ALLDY STEEL SASJ3 GR 8 NS NOZZLE FORGING LOV ALLOT STEEL 5AS1l8 CL 2
.19" STAINLESS STEEL CLADOING TYPE 389 FIRST LATER TYPE 388L SlllSEQUENT LAYERS
...... c, LIMERICK 1
'f:I
- 6.62"
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. 19' N5 NOZZLE ASSEMl!l. l ANO VELO OE TAILS
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~ J D!Ll "01..~
15-87-87 "IOUIIC NO BF-S-1 Figure 1: Core Spray NS Nozzle Assembly
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Structural Integrity V
Associates, Inc.
File No.: LGS-12Q-301 Revision: I Page 6 of 19 to EC 631225, Rev. 0 Page 7 of 24 4
ASSUMPTIONS I.
The flaw is assumed to be in the weld butter since Alloy 182 is known to be susceptible to SCC in BWR environment.
- 2.
The core spray nozzle (N5) under consideration was subjected to the mechanical stress improvement process (MSIP) in 1994 during refueling outage IR05. MSIP is utilized to produce compressive residual stresses in the component to which it is applied. However, no residual stress was included in this evaluation. This is believed to be a conservative approach based on data from a core spray nozzle analysis for another plant that showed beneficial compressive stresses in the weld region after weld repair and MSIP. The geometry differ somewhat but not drastically from the Limerick case: the nozzle thickness is 1.25" but its OD is 11.5" and the safe-end taper is on the ID side. Also, the MSIP at the other plant was applied over the weld whereas at Limerick it is applied on the safe-end taper [17]. Nonetheless, at each plant, verification analyses of the MSIP process are perfonned to ensure that it produces compressive axial residual stresses in the weld. Hence, ignoring any MSIP effect is believed to be conservative.
- 3.
It is assumed that the flaw has been surface connected since 1998, the year the indication was first reported. Therefore, all crack growth analyses start from 1998.
- 4.
It is conservatively assumed that the plant has been on 100% full operation since 1998. Thus, for all crack growth analysis, the number of hours as well as the number of cycles of operation is computed accordingly and, in the case of fatigue crack growth, based on specified plant design cycles.
5 CALCULATIONS 5.1 Allowable Flaw Size Calculation The material of the flawed weld butter is Alloy 182 which is a nickel based austenitic steel and the weld is a flux weld. Therefore, per the screen criteria in ASME Code,Section XI, Appendix C [I], the elastic-plastic fracture mechanics (EPFM) based methodology described in Appendix C is used in this evaluation. The technical approach consists of determining the critical flaw size ( circumferential extent and through-wall depth) in the pipe that will cause the flawed pipe to fracture by ductile crack extension.
The stress ratios are calculated as follows:
For combined loading, and, for membrane stress,
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Structural Integrity V
Associates, Inc.
Stress Ratio= ~(am+ ab - ae )
a1 SF,,
ZSFa Stress Ratio =
al File No.: LGS-12Q-301 I
Revision: I Page 7 of 19 to EC 631225, Rev. 0 Page 8 of 24
- where, Z = 1.30(1 + O.OIO(NPS-4)]
a"' and ab are the primary membrane and primary bending stresses, respectively.
ae is the secondary bending stress.
a I is the flow stress SF,, is the safety factor for bending stress NSP is the nominal pipe size The material properties of Alloy 182 are assumed to be the same as those of its Alloy 600. Given that the flaw in the weld butter is in close proximity to the nozzle, the allowable flaw size could be affected by the material properties of the low alloy (SA 508 Class 2) steel nozzle. However, the flow stress of the low alloy steel is much higher than that of Alloy 600 (72.7 ksi vs. 55. l ksi at 553°F). Therefore, using the flow stress ol Alloy 600 is conservative as it yields a smaller allowable flaw size.
The tables of Appendix C are used to detennine the allowable flaw depth-to-thickness ratio for each service level. The results of the analysis are presented in Table 3. It can be seen that the allowable flaw depth is 75~
of wall thickness, which is greater than the depth of the reported flaw depth of 47% of wall thickness. Since the stress ratios are small, the flaw length can be as long as 60% of the circumference of the nozzle.
5.2 Stress Intensity Factors Calculation A linear elastic fracture mechanics analysis is performed for the observed indication to compute the crack propagation due to stress corrosion and fatigue crack growth. The fracture mechanics model of an elliptical surface flaw in a cylinder obtained from Reference 10, is used in this evaluation. The initial flaw aspect ratio of 0.33 (0.695/2.1) is used in the calculation of the stress intensity factors.
Using the applied stresses computed in Section 3.5, the stress intensity factors due to the different load combinations are determined. In the calculation of stress intensity factors, the pressure stress is taken as the membrane stress, which is constant across the wall thickness. The stresses from the deadweight, seismic and thermal expansion moment loads are taken as linearly varying through-wall bending stresses.
The calculated stress intensity factors are presented in Figure 2.
5.3 Fatigue Crack Growth Analysis Since the indication is surface connected, the crack propagation due to fatigue crack growth (FCG) after l 0 years of operation is calculated using the fatigue crack growth rate for Alloy 182 welds exposed to BWR environment per NUREG/CR-6721 [15]. Reference 15 indicates that the fatigue crack growth rate for Alloy 600 in air may be used with a factor of2 for the Alloy 182 weld metal. An additional term to account for a BWR water environment is also prescribed by Reference 15. The fatigue crack growth law is shown below:
fi Structural Integrity
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File No.: LGS-12Q-301 I
Revision: 1 Page 8 of 19 to EC 631225, Rev. 0 Page 9 of 24
- where,
(~) =(~) +A*T \\-m(~)m dN cnv dN air r
dN air (da/dN)air = CA600 (l-0.82R)"22 (ti.K)4' 1
, m/cycle A
=4.4x10-7 T, = rise time, seconds m = 0.33 CA600 = 4.835x 10*
14 + J.622x 10*16T - 1.49 xl0' 18T2 + 4.355 x 10-21T3 T = temperature inside pipe, °C (taken as the maximum during the transient)
R = R ratio = (Kmin/Kmax)
.6.K = Kmax - Kmin = range of stress intensity factor, Mpa-m0*5 The largest rise time of 17388 seconds corresponding to the startup transient and the maximum operating temperature of 566°F (297°C) are used in this analysis.
The core spray nozzle system was analyzed in Reference 2 for a number of design transients which are illustrated in the load histogram provided in Reference 16. The applicable design cyclic events are summarized in Table 2.
The fatigue crack growth analysis is implemented in spreadsheet "LGS-12Q-301.xls," worksheet "A-182 BWR (LGS-12Q-301 )" for 10 years of operation. The initial flaw depth of0.695" and flaw length of 2.1" are used in the evaluation. The largest stress ranges are from the HPCI injections associated with the Loss of F eedwater transients and the step changes that occur during startup. Per Reference 14, there have been only 2 such transients since 1998. The calculated maximum stress range will be used for those 2 HPCI injection transients. For simplicity, the maximum stress range from the remaining transients is conservatively used for all the rest of the cyclic transient events. Thus, the 8683 total number of design cycles for a 40-year plant Ii fe is divided by 4 to obtain the number of cycles corresponding to 10 years (2171 ). The analysis is conservatively performed for 2198 cycles of the maximum stress and 2 cycles of the HPCI injection transient.
The results of the fatigue crack growth analysis are summarized in Table 4 and illustrated in Figure 3.
5.4 Stress Corrosion Crack Growth Analysis A stress corrosion crack (SCC) growth analysis is performed to determine how much the final flaw calculated after fatigue crack growth will grow in IO years. The stress corrosion crack growth is performed after the fatigue crack growth analysis using the end-of-evaluation period flaw size from the FCG as initial flaw size for the SCC growth analysis. The initial flaw aspect ratio of0.33 (0.695/2. l) is assumed for this analysis.
BWRVIP-59 [ 13] provides stress corrosion crack growth laws for high nickel bases austenitic alloys for different reactor pressure vessel water chemistry conditions. Since flow in the core spray system is occasional, the SCC growth law for normal water chemistry is used in this evaluation, even though Limerick Unit 1 is on hydrogen water chemistry. The SCC growth law for normal water chemistry is:
.::=r Structural Integrity VAssociates, Inc.
File No.: LGS-12Q-301 I
Revision: 1 Page 9 of 19 to EC 631225, Rev. 0 Page 10 of 24
- where, da = C K " in/hr for K1 $ 25 ksiv'in dt o
I da = C1 in/hr for Kr > 25 ksi.../in dt K1 = stress intensity factor at flaw tip (ksi.../in)
C0
=
1.6 x 10"8 c, = 5.0 X 10-5 n
=
2.5 Sustained steady-state nonnal operating stresses are the only stresses that need to be considered for the SCC growth analysis. The sustained stress intensity factors calculated in Section 5.2 are used in the SCC growth analysis. The SCC growth analysis is performed with pc-CRACK' [12]. The results of the analysis are presente.d in Table 5 and illustrated in Figure 4. The flaw reaches 58% of the wall thickness in 10 years. The pc-CRACKTM output file is shown in Appendix A.
fi Structural Integrity V
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File No.: LGS-12Q-301 I
Revision: 1 Page 10 of 19 to EC 631225, Rev. 0 Page 11 of 24 Table 2: Design Transients T1nllial Tnna1
~T Max.
Max.
No.
Description Rate Pressure Cycles (OF)
(OF)
(OF)
(°F/hr)
(psi) 1 Leak test 70 100 30 60 1250 130 2
SLC Operation, Test 100 50 50 Step 0
130 3
Startup, Step 406 50 356 Step 250 10 Startup/Shutdown 4
Normal 100 546 446 100 1000 120 5
Increase to Power 546 522 24 Step 1000 300 Turbine Trip 100%
6 Bypass 522 490 32 1280 1000 10 Partial FW Heater 7
Bypass 522 512 10 300 1000 70 T-G Trip, OBE +
8 SRV 400 546 146 100 1125 50 9
T-G Trip, SRV 522 522 0
0 1000 7650 T-G Trip, All Other 10 Scrams 546 400 146 100 1125 180 11 SLC Operation 522 60 462 462 1000 10 Loss of FW Pumps, 12 Step 561 40 521 Step 1125 10 Loss of FW Pumps, 13 Ramp 40 561 521 802 1125 10 14 Reactor Overpressure 522 562 40 13091 1350 1
Improper Start of 15 Recirc. Pumps 522 268 254 Step 1000 1
16 Improper Startup 100 546 446 100 1000 I
(} Structural Integrity File No.: LGS-12Q-301 I
Revision: 1 Associates, Inc.
Page 11 of 19 to EC 631225, Rev. 0 Page 12 of 24 Table 3: Allowable Flaw Size Calculations Z factor 1/rrD 1.430 0.047 Service SFm SFb Sy Su Stress Ratio Allowable CJm Ob Ge a,
Level (ksl)
(ksi)
(ksi)
(ksi)
(ksi)
(ksi)
Combined Membrane alt A
2.095 2.771 1.656 2.7 2.3 31.2 80.0 55.6 0.149 0.146 0.75 B
2.095 2.771 1.656 2.4 2.0 31.2 80.0 55.6 0.152 0.130 0.75 C
2.095 2.771 1.656 1.8 1.6 31.2 80.0 55.6 0.159 0.097 0.75 D
2.095 2.771 1.656 1.3 1.4 31.2 80.0 55.6 0.164 0.070 0.75 SJ Structural Integrity File No.: LGS-I2Q-301 Revision: 1 Associates, Inc.
Page 12 of 19 to EC 631225, Rev. 0 Page 13 of 24 Table 4: Fatigue Crack Growth Results Cycles Kmax Kmin DeltaK R
Da/Dn Da a
a/t (ksi-in 112) (ksi-in 112) (ksi-in 112)
(in)
(in) 1 9.90 0.00 9.90 0.00 l.83E-05 l.83E-05 0.695 0.47 100 9.90 0.00 9.90 0.00 1.83E-05 l.83E-05 0.697 0.47 200 10.00 0.00 10.00 0.00 l.84E-05 1.84E-05 0.699 0.47 300 10.00 0.00 10.00 0.00 I.84E-05 1.84E-05 0.701 0.47 400 10.00 0.00 10.00 0.00 1.84E-05 l.84E-05 0.702 0.47 500 10.00 0.00 10.00 0.00 J.85E-05 1.85£-05 0.704 0.48 600 10.00 0.00 10.00 0.00 I.85E-05 l.85E-05 0.706 0.48 700 10.00 0.00 10.00 0.00 I.86E-05 I.86E-05 0.708 0.48 800 10.10 0.00 10.10 0.00 l.86E-05 l.86E-05 0.710 0.48 900 10.10 0.00 10.10 0.00 l.87E-05 1.87E-05 0.712 0.48 1000 10.10 0.00 10.10 0.00 l.87E-05 l.87E-05 0.714 0.48 1100 10.10 0.00 10.10 0.00 l.87E-05 1.87£-05 0.715 0.48 1200 10.10 0.00 10.10 0.00 l.88E-05 l.88E-05 0.717 0.48 1300 10.10 0.00 10.10 0.00 l.88E-05 I.88E-05 0.719 0.49 1400 10.20 0.00 10.20 0.00 1.89£-05 l.89E-05 0.721 0.49 1500 10.20 0.00 10.20 0.00 l.89E-05 I.89E-05 0.723 0.49 1600 10.20 0.00 10.20 0.00 1.89E-05 1.89E-05 0.725 0.49 1700 10.20 0.00 10.20 0.00 l.90E-05 l.90E-05 0.727 0.49 1800 10.20 0.00 10.20 0.00 l.90E-05 1.90£-05 0.729 0.49 1900 10.20 0.00 10.20 0.00 1.91E-05 1.91 E-05 0.731 0.49 2000 10.30 0.00 10.30 0.00 J.91E-05 1.91 E-05 0.732 0.49 2100 10.30 0.00 10.30 0.00 1.92E-05 1.92£-05 0.734 0.50 2200 147.60 0.00 147.60 0.00 7.87E-03 7.87£-03 0.752 0.51 tJ Structural Integrity File No.: LGS-12Q-301 I
Revision: 1 Associates, Inc.
Page 13 of 19 to EC 631225, Rev. 0 Page 14 of 24 Table 5: Stress Corrosion Crack Growth Results Time K
da/dt da a
a/t (hr)
(ksi-in 112)
(in/hr)
(in)
(in) 4383 5.56E+OO l.17E-06 I. I 7£-06 0.757 0.51 8766 5.58E+OO 1.1.8E-06 l.18E-06 0.7623 0.52 13149 5.61E+OO I.19E-06 I. I 9E-06 0.7675 0.52 17532 5.63E+OO l.20E-06 l.20E-06 0.7727 0.52 21915 5.66E+OO 1.22E-06 l.22E-06 0.7779 0.53 26298 5.68E+OO l.23E-06 l.23E-06 0.7833 0.53 30681 5.71E+OO l.25E-06 l.25E-06 0.7888 0.53 35064 5.73E+OO l.26E-06 l.26E-06 0.7943 0.54 39447 5.76E+OO l.27E-06 l.27E-06 0.7998 0.54 43830 5.78E+OO I.29E-06 l.29E-06 0.8054 0.54 48213 5.81E+OO l.30E-06 l.30E-06 0.8111 0.55 52596 5.84E+OO l.32E-06 l.32E-06 0.8169 0.55 56979 5.86E+OO l.33E-06 l.33E-06 0.8226 0.56 61362 5.89E+OO I.35E-06 I.35E-06 0.8285 0.56 65745 5.92E+OO I.36E-06 I.36E-06 0.8345 0.56 70128 5.94E+OO l.38E-06 l.38E-06 0.8405 0.57 74511 5.97E+OO I.39E-06 l.39E-06 0.8465 0.57 78894 6.00E+OO l.41E-06 I.4 IE-06 0.8527 0.58 83277 6.03E+OO l.43E-06 I.43E-06 0.859 0.58 87660 6.06E+OO I.45E-06 1.45E-06 0.8652 0.58
~
Structural Integrity File No.: LGS-12Q-301 Revision: 1 Associates, Inc.
Page 14 of 19 to EC 631225, Rev. 0 Page 15 of 24 200.000 ~ - - - - - - - - - -
-~
I
--- Steady State
--Transient Max N
~
! 150.000 0 u IL
- z:.
C
~
.E 100.000 ~ - - - -
ui 0.000
~
Structural Integrity V
Associates, Inc.
0.200
-ti-Transient All
1 I
-- ---- --------- -- - --- --- -~
0.400 0.600 0.800 1.000 1.200 1.400 Crack Depth (In.)
Figure 2: Applied Stress Intensity Factor File No.: LGS-12Q-30I Revision: 1 Page 15 of 19 to EC 631225, Rev. 0 Page 16 of 24 0.760 0.750 0.740 *, -.
]: 0.730
- 1 CD C
- ,t.
~ 0.720 -k°
(,)
0.710
- 0.700 -
0.690..
0
~
Structural Integrity
~
Associates, Inc.
500 1000 1500 2000 2500 Cycles Figure 3: Fatigue Crack Growth Results File No.: LGS-12Q-301 Revision: I Page 16 of 19 to EC 631225, Rev. 0 Page 17 of 24 0.88 0.86 0.84 *
- [ 0.82 t
GI C
~
t!
0.8 0
0.74 0
fi Structural Integrity VAssociates, Inc.
10000 20000 30000 40000 50000 Time (hours) 60000 70000 80000 Figure 4: Stress Corrosion Crack Growth Results File No.: LGS-12Q-30I 90000 100000 Revision: I Page 17 of 19 to EC 631225, Rev. 0 Page 18 of 24 6 CONCLUSIONS AND DISCUSSIONS The results of the evaluation presented in this calculation package show that the indication found during the inservice inspection of the core spray nozzle in I 998 is acceptable for continued operation based on the requirements of ASME Code,Section XI. The allowable flaw depth for the observed flaw length is 75%
of pipe wall thickness.
A fatigue crack growth analysis was performed for 10 years of operation starting with the i'nitial flaw size reported in 1998. The flaw was projected to grow to 0.752" (alt= 0.5) in 10 years. The fatigue crack growth evaluation was then followed by 10 years of stress corrosion crack growth starting with the final flaw size computed by fatigue crack growth. The flaw was projected to extend an additional 0.113 inches to 0.865 inches, which corresponds to an alt of 0.58, well below the calculated allowable of 0.75.
~
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File No.: LGS-l 2Q-301 I
Revision: 1 Page 18 of 19 to EC 631225, Rev. 0 Page 19 of 24 7 REFERENCES
- 1. ASME Boiler and Pressure Vessel Code,Section XI, 2001 Edition with 2003 Addenda.
- 2. Bechtel Power Corporation, "Stress Report, ASME Section III Class I Analysis, The Core Spray Systems for Limerick Generating Station Unit I," Revision 1, 1991, SI File No. LGS-12Q-201.
- 3. E-mail from George Budock (Exelon) to Angah Miessi (SIA), "FW: Stress Report Changes," dated Mon 12/10/2007, SI File No. LGS-l2Q-202.
- 4. Nuclear Field Technical Services Drawing No BF-5-1, "NS Nozzle Assembly and Weld Details,", SI File No. LGS-12Q-203.
- 5. CBI Drawing, "Core Spray Nozzle N5," SI File No. LGS-12Q-203
- 6. ASME Boiler and Pressure Vessel Code,Section II, Part D, 1998 Edition with 1999 Addenda.
- 7. GE Hitachi Examination Summary Sheet, Report No. 601990, dated 12/08/07, SI File No. LGS-12Q-204.
- 8. Excerpts from Bechtel ME-913 Computer Program Output. "Core Spray DCA-419.DLA-210 Limerick #2," Job No. 08031, 9/22/1986, SI File No. LGS-12Q-205.
- 9. Bechtel Drawing, "Isometric Reactor Building (Drywell), Core Spray System-Unit #1," Drawing No.
SK-M-1609, Rev. T, SI File No. LGS-12Q-206.
- 10. S. Chapuliot et al., "Stress Intensity Factors for Internal Circumferential Cracks in Tubes Over a Wide Range of Radius Over Thickness Ratios," PVP-Vol. 365, ASME 1998.
- 11. ASME Section XI Task Group for Piping Flaw Evaluation, 'Evaluation of Flaws in Austenitic Steel Piping,' Journal of Pressure Vessel Technology, Vol. 108, August, 1986.
- 12. pc-CRACK TM for Windows, Version 3.1-98348, Structural Integrity Associates, 1998.
- 13. BWRVIP-59: BWR Vessel and Internals Project, Evaluation of Crack growth in BWR Nickel Base Austenitic Alloys in RPV Internals, EPRI, Palo Alto, CA: 1998. TR-108710, SI File No. BWRVIP 259P.
- 14. E-mail from George Budock (Exelon) to Angah Miessi (SIA), "Analysis on N5A Weld," dated Monday 12/10/2007 with attachment "LGS Unit l HPCI Injections thru Core Spray B Loop.doc", SI File No. LGS-12Q-202.
- 15. NUREG/CR-6721, "Effects of Alloy Chemistry, Cold Work, and Water Chemistry on Corrosion Fatigue and Stress Corrosion Cracking of Nickel Alloys and Welds," U.S. Nuclear Regulatory Commission (Argonne National Laboratory), April 2001.
- 16. E-mail from George Budock (Exelon) to Angah Miessi (SIA), "FW: ME-913 Run from Appendix E.PDF;Ul Core Spray Stress Report.PDF; Load Histogram P" dated Monday 12/9/2007 with attachment "Load Histogram Page 23.PDF", SI File No. LGS-12Q-202.
- 17. O'Donnell & Associates, Inc., "Analytical Verification of the Mechanical Stress Improvement Process for IO"Nozzle," Cale No. 2001-410-001-00, February 1989.
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File No.: LGS-12Q-30I I
Revision: 1 Page 19 of 19 to EC 631225, Rev. 0 Page 20 of 24 APPENDIX A pc-CRACK OUTPUT FILE Filename Description Pages sec.our Stress Corrosion Crack Growth Analysis A2-A5 tJ Structural Integrity File No.: LGS-12Q-301 I
Revision: 1 Associates, Inc.
Page Al of A5 to EC 631225, Rev. 0 Page 21 of 24 tm pc-CRACK for Windows Version 3.1-98348 (Cl Copyright '84 -
'98 Structural Integrity Associates, Inc.
3315 Almaden Expressway, Suite 24 San Jose, CA 95118-1557 Voice:
408-978-8200 Fax:
408-978-8964 E-mail: pccrack@structint.com Linear Elastic Fracture Mechanics Date: Fri Dec 21 04:31:36 2007 Input Data and Results File: SCC_Rl.LFM
Title:
Limerick Core Spray Nozzle NS, sec Load Cases:
Case ID: Steady State --- K vs a Depth K
0.0240 0.9150 0.0470
- 1. 2 930
- 0. 0710
- 1. 5830 0.0950 1.8270 0.1180 2.0420 0.1420 2.2360 0.1660 2.4170 0.1890 2.5870
- 0. 2130 2.7470 0.2370 2.8980 0.2600 3.0430 0.2840 3.1820 0.3080 3.3190 0.3320 3.4550 0.3550 3.5870 0.3790
- 3. 7160 0.4030 3.8420 0.4260 3.9660 0.4500 4.0870 0.4740 4.2060 0.4970 4.3220 0.5210 4. 4370 0.5450 4.5510 0.5680 4.6620 0.5920 4.7730 0.6160 4.8880 0.6390 5.0030 0.6630 5.1160 0.6870 5.2290
- 0. 7100 5.3410 0.7340 5.4520
~
Structural lntsgrity
~
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File No.: LGS-12Q-301 I
Revision: l Page A2 of AS to EC 631225, Rev. 0 Page 22 of 24 0.7580 5.5630 0.7810 5.6730 0.8050 5.7820 0.8290
- 5. 8910 0.8520 5.9990 0.8760 6.1070 0.9000 6.2220 0.9240 6.3450 0.9470 6.4690
- 0. 9710 6.5920 0.9950 6.7150
- 1. 0180 6.8380
- 1. 0420
- 6. 9620
- 1. 0660 7.0850
- 1. 0890 7.2090 1.1130 7.3330 1.1370 7.4570
- 1. 1600 7.5810 1.1840 7.7050 Stress Coefficients Case ID CO Cl C2 C3 Type Steady State 0
0 0
0 K vs a Crack Model: User Input K Versus Crack Size Crack Parameters:
Max. *crack size:
1.1000
Stress Intensity Factor--------------------
Crack Case Size Steady Sta 0.0220 0.0440 0.0660 0.0880 0.1100 0.1320 0.1540 0.1760 0.1980 0.2200 0.2420
- 0. 2640 0.2860 0.3080 0.3300 0.3520 0.3740 0.3960 0.4180 0.88213 1.2437
- 1. 52258
- 1. 75583
- 1. 96722 2.15517 2.3265 2.49091 2.647 2.79104 2.92952 3.06617 3.19342 3.319 3.44367 3.56978 3.68913 3.80525
- 3. 92287 fi Structural Integrity VAssociates, Inc.
File No.: LGS-12Q-301 I
Revision: 1 Page A3 of A5 to EC 631225, Rev. 0 Page 23 of 24 0.4400 4.03658 0. 4 620 4. 1465 0.4840 4.25643 0.5060 4.36512 0.5280 4.47025 0.5500 4.57513
- 0. 5720 4.6805 0.5940 4.78258 0.6160 4.888 0.6380 4.998 0.6600 5.10188 0.6820 5.20546 0.7040 5.31178
- 0. 7260 5.415 0.7480 5.51675 0.7700 5.62039 0.7920 5.72296 0.8140 5.82288 0.8360 5.92387 0.8580 6.026 0.8800 6.12617 0.9020 6.23225 0.9240 6.345 0.9460 6.46361
- 0. 9680 6.57662 0.9900 6.68937 1.0120 6.80591
- 1. 0340 6.92067
- 1. 0560 7.03375 1.0780 7.1497 1.1000 7. 26583 Crack Growth Laws:
Law ID:
sec Alloy182 Type:
Corrosion Model:
Paris da/dN = C * (dK) "n where dK = Krnax - Krnin dK > Kthres Kmax < Klc Materia l parameters:
C = 1.6000e-008 n =
2.5000 Kthres =
0.0000 Material Fracture Toughness Kic:
Material ID: Alloy 182 Depth Kic e
Structural lnlsgrity File No.: LGS-12Q-301 I
Revision: 1 Associates, Inc.
Page A4 of AS to EC 631225, Rev. 0 Page 24 of 24 0.0000 1.1000 25.0000 25.0000 Initial crack size=
Max. crack size=
Number of blocks=
0.7520 1.1000 1
Print increment of block=
1 Cycles Cale.
Subblock
/Time incre.
SteadySCC 87660 1
Kmax Print Crk. Grw.
Mat.
incre. Law Klc 4383 sec Alloy182 Alloy 182 Kmin Subblock Case ID Scale Factor Case ID Scale Factor SteadySCC Steady State 1.0000 Crack growth results:
Total Subblock Cycles Cycles
/Time
/Time Kmax Block:
1 4383 4383 5.56e+OOO 8766 8766 5.58e+OOO 1314 9 13149 5.6le+OOO 17532 17532 5.63e+OOO 21915 21915 5.66e+OOO 26298 26298 5.68e+OOO 30681 30681 5.7le+OOO 35064 35064 5.73e+OOO 39447 39447 5.76e+D00 43830 43830 5.78e+OOO 48213 48213 5.8le+OOO 52596 52596 5.84e+OOO 56979 56979 5.86e+DD0 61362 61362 5.89e+OOO 65745 65745 5.92e+OOO 70128 70128 5.94e+OOO 74511 74511 5.97e+OOO 78894 78894 6.00e+OOO 83277 83277 6.D3e+OOO 87660 87660 6.06e+OOO
~
Structural lntsgrlty VAssociates, Inc.
Kmin DeltaK R
O.OOe+OOO 5.56e+OOO 0.00 O.OOe+OOO 5.58e+OOO 0.00 O.OOe+OOO 5.61e+D00 0.00 O.OOe+OOO 5.63e+OOO 0.00 O.OOe+OOO 5.66e+OOO 0.00 O.OOe+OOO 5.68e+OOO 0.00 O.OOe+OOO 5.71e+OOO 0.00 O.OOe+OOO 5.73e+OOO 0.00 O.OOe+OOO 5.76e+OOO 0.00 O.OOe+OOO 5.78e+OOO 0.00 O.OOe+OOO 5.81e+OOO 0.00 O.OOe+OOO 5.84e+OOO 0.00 O.D0e+OOO 5.86e+00D 0.00 O.OOe+OOO 5.89e+OD0 0.00 O.OOe+OOO 5.92e+OOO 0.00 O.OOe+OOO 5.94e+OOO 0.00 O.OOe+OOO 5.97e+OOO 0.00 O.OOe+OOO 6.00e+OOO 0.00 O.OOe+OOO 6.03e+OOO 0.00 O.OOe+OOO 6.06e+OOO 0.00 End of pc-CRACK Output File No.: LGS-12Q-301 DaDn
/DaDt Da a
1.17e-006 1.17e-006
- 0. 757 l.18e-006 l.18e-006 0.7623 l.19e-006 l.19e-006 0.7675
- 1. 2De-006 1.20e-006 0. 7727
- 1. 22e-006 1.22e-006 0.7779
- 1. 26e-006 1. 26e-006 0.7943 1.27e-006 1.27e-006 0.7998 1.29e-006 1.29e-006 0.8054 1.30e-006 1.30e-006 0.8111 1.32e-006 1.32e-006 0.8169 l.33e-006 1.33e-006 0.8226 l.35e-006 l.35e-006 0.8285 l.36e-006 l.36e-006 0.8345 l.38e-006 l.38e-006 0.8405 l.39e-006 1.39e-006 0.8465 l.41e-006 1.4le-006 0.8527 1.43e-006 1.43e-006 0.859 1.45e-006 l.45e-006 0.8652 I
Revision: 1 Page AS of AS to EC 631225, Rev. 0 Page 1 of 7
~~~11 ELECTRIC POWER
~,-,~
RESEARCH INSTITUTE Nondestructive Evaluation (NOE) 20200406-002 April 61h, 2020 Michelle Karasek 3146 Sanatoga Rd Pottstown, PA l 9464-3418
Subject:
Independent review of encoded ultrasonic examination data from dissimilar metal weld DCA-319-1 (N5A) at Unit 1 of the Limerick Generating Station
Dear Michelle Karasek:
EPRI NOE Center staff performed an independent review of the supplied automated phased array examination data from dissimilar metal weld DCA-319-1 (N5A) at unit l of the Limerick Generating Station. The review was performed after Exelon's inspection vendor, GE Hitachi Nuclear Energy Americas (GEH), reported an embedded weld fabrication flaw. Examination data from the previous 2008 and current 2020 examinations were provided to EPRI. The location of the reported indication can be seen in the 2008 (left) and 2020 (right) UT polar views at the approximate 90° positions shown in Figure 1.
Figure 1 Polar views showing location of reported embedded jlm1* in the N5A DMW (2008 examint1tio11 data 011 left, 2020 on right)
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- www.epri.com to EC 631225, Rev. 0 Page 2 of 7 Michelle Karasek Nondestructive Evaluation (NOE) 20200406-002 April 61h, 2020 Page2 The indication reported by GEH as an embedded weld fabrication flaw was confirmed during EPRl's independent review of the 2008 and 2020 ultrasonic examination data files. It was observed that the none of the data contains a "corner trap" response or other responses that would indicate that the reported flaw is connected to the inside surface. Therefore, EPRI concurs with the GEH examiners' characterization of the flaw as being embedded. The observed characteristics of the ultrasonic responses, along with the flaw not being connected to the inside surface, rule out stress corrosion cracking as being a likely origin of the indication.
The reported flaw was located near the safe-end side weld fusion line and is positioned along the upper boundary of the ASME Code[l] inner one-third examination volume. Figure 2 shows the side-view image of the ultrasonic response using the 45°RL examination data during both the 2008 (top) and 2020 (bottom) examinations. The focal law used to generate the 45°RL examination angle during the 2020 examination is intended to interrogate the inside surface of the component by electronically focusing the ultrasonic energy at 1.3" [34mm] of material depth.
This electronic focal depth corresponds to the inside surface of the DMW. If the reported flaw were attributed to an inside surface connected flaw, it is expected that the examination data would exhibit a "corner trap" response linking the reported ultrasonic indication to the inside surface; however, no such response is present.
Figure 2 45°RL 8-scan presentatio11 (side vitw) s/zowi11g location of t/ze reported embedded flaw (2008 examination data on top, 2020 on bottomj to EC 631225, Rev. 0 Page 3 of 7 Michelle Karasek Nondestructive Evaluation (NOE) 20200406-002 April 61h, 2020 Page3 Figure 3 shows the side view image of the ultrasonic response obtained from the 60°RL examination angle during the 2008 examination (top) and 2020 examination (bottom). The focal law used to generate the 60°RL examination angle during the 2020 examination is intended to interrogate a thickness region that is approximately 0.79" [20mm] below the outside surface of the component. This focal depth corresponds to the depth location of the reported flaw. The 60°RL examination data also displays an embedded ultrasonic indication located along the upper boundary of the ASME Code examination volume.
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Figure 3 60°RL B-sca11 presentation (side view) of showing location of the reported embedded flaw (2008 exanii1111tion data on top, 2020 on bottom)
The reported flaw indication was also detected at the same location using the 0° examination data (see Figure 4). 0° examination angles are well suited for detection of weld fabrication flaws. Since these examination angles are not well suited for detection of inside surface connected SCC flaws, the ability to readily identify the reported flaw with the 0° examination angle provides additional evidence that it is attributed to a weld fabrication related reflector.
to EC 631225, Rev. 0 Page 4 of 7 Michelle Karasek Nondestructive Evaluation (NOE) 20200406-002 April 61h, 2020 Page4 Figure 4 0° B-srnn prcsmlation (side i*iew) showing lornti011 of nrorled flaw within the weld material (2020 examination)
Figure 5 shows the C-scan (roll-out view) presentation, which is the same presentation that would be represented by a radiograph. The 2008 examination data is shown in the top image while the 2020 examination data *is shown in the bottom image. The horizontah~*epresented by the green index rulers located along the bottoms of these images correspond to the circumferential axis of the component. The vertical axis represented by the blue scan rulers along the left edges represent the longitudinal axis of the nozzle The inside-surface layer of parallel clad beads on the nozzle side are visible along the upper portion of the images while the safe-end side of the weld joint is shown on the lower portion of the images. The location of the weld is displayed as the area of slightly increased amplitude (e.g. pattern of darker blue responses) that extends for the complete 360° circumference of the roll-out views. The reported embedded flaw is clearly evident in each image as the high-amplitude (i.e. red) response located within the safe-end side of the visible weld pattern.
to EC 631225, Rev. 0 Page 5 of 7 Michelle Karasek Nondestructive Evaluation (NOE) 20200406-002 April 61h, 2020 Page5
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C-Scan (pla11 l'iew) prcsc11t11tion sliowi11g location of reported embt*dded fl,m* (2008 t'X11mi1111tion data on top, 2020 on bottom)
A comparison was also performed between the 2008 and 2020 examination data files. The 2008 examination was conducted using an encoded conventional (i.e. non-phased array) ultrasonic examination technique while the 2020 examination was performed using an encoded phased array ultrasonic examination technique. The responses between the two sets of examination data are very similar, as can be observed by comparing the ultrasonic indications present in figures I, 2, 3 and 5. As the ultrasonic indications present in the 2020 examination data do not contain any to EC 631225, Rev. 0 Page 6 of 7 Michelle Karasek Nondestructive Evaluation (NOE) 20200406-002 April 61h, 2020 Page6 "new" responses propagating out from the response present in 2008, the change in flaw size is most likely a result of differences between the examination techniques. It is evident that the phased array technique used in 2020 is capable of obtaining an improved signal-to-noise ratio when compared to the 2008 conventional ultrasonic examination technique.
Measuring the through-wall extent of fabrication related flaws is not included in the ASME Section XI, Appendix VIII, Supplement 10 qualification requirements for the examination of dissimilar metal welds. However, these qualified examination procedures often detect and are then used to measure the size of fabrication related flaws. Measuring the through-wall extent of embedded weld fabrication flaws is often times more subjective than measuring the through-wall extent of an inside surface SCC flaw as there are several different types and shapes of weld fabrication flaws. The through-wall extent of the ultrasonic indication was measured using the -
6dB drop (i.e. 50% drop) sizing method to provide Exelon with an estimated size that can be used to independently validate the reported flaw size. Any reported through-wall extent ranging from approximately 0.30" to approximately 0.35" [7.6mm to 8.9mm] should be considered valid.
Conclusions The ultrasonic indication reported as an embedded fabrication flaw by the inspection vendor was confirmed during EPRI's review of the examination data. Upon EPRI's review, it was concluded that the reported indication is not connected to the inside surface, so EPRI NOE staff concur with the inspection vendor that the reported flaw is associated with an embedded weld fabrication flaw. The examination data reviewed from 2008 and 2020 ultrasonic examinations appeared to be of high quality. The small increase in reported size of the flaw appears to be attributed to changes between the two examination techniques as no "new" responses were observed propagating outwards from the indication that was present in the 2008 examination data. By comparing the examination data sets shown in Figure 1, it is possible to see that the phased array examination technique utilized in 2020 (right) was capable of obtaining an improved signal-to-noise ratio from the flaw when compared to the conventional ultrasonic examination technique used in 2008 (left).
to EC 631225, Rev. 0 Page 7 of 7 Michelle Karasek Nondestructive Evaluation (NOE) 20200406-002 April 61h, 2020 Page7 Sincerely,
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Bret Flesner Principal Technical Leader, EPRI 20200406-002/jyb
References:
I.
American Society of Mechanical Engineers, Boiler and Pressure Vessel Code,Section XI; Rules for lnservice Inspection of Nuclear Power Plant Components c: Carl Latiolais (EPRI/NDE)
Leif Esp (EPRI/NDE)
Nathan Palm (EPRI/BWRVIP)
Steve Chengelis (EPRI)
Michael Salley (Exelon)
John O'Neil (Exelon)
Frank McKone Jr. (Exelon)
Mark Weis (Exelon)
Benjamin Jorden (Exelon)
H.J. Ryan (Exelon)
Andre Rachel (GEH)