ML15023A039

Response to Request for Additional Information (Rai)For Bottom Mounted Instrument Relief Request 52

ML15023A039
Person / Time
Site:	Palo Verde
Issue date:	01/20/2015
From:	Cadogan J Arizona Public Service Co
To:	Document Control Desk, Office of Nuclear Reactor Regulation
References
102-06992-JJC/DCE
Download: ML15023A039 (52)

Text

10 CFR 50.55a O aps John J. Cadogan Vice President, Nuclear Engineering Palo Verde Nuclear Generating Station P.O. Box 52034 Phoenix, AZ 85072 Mail Station 7602 Tel 623 393 5553 102-06992-JJC/DCE January 20, 2015 ATrN: Document Control Desk U.S. Nuclear Regulatory Commission Washington, DC 20555-0001

References:

1. Arizona Public Service Company (APS) letter number 102-06879, Palo Verde Nuclear Generating Station Unit 3, Docket No. STN 50-530, American Society of Mechanical Engineers (ASME) Code,Section XI, Request for Approval of an Alternative to Flaw Removal, Flaw Characterizationand Successive Examinations - Relief Request 52, dated May 16, 2014 [Agencywide Documents Access And Management System (ADAMS) Accession No. ML14142A029]

2. APS letter number 102-06880, Palo Verde Nuclear Generating Station Unit 3, Docket No. STN 50-530, Transmittalof ProprietaryDocuments for Relief Request 52, dated May 16, 2014 (ADAMS Accession No. ML14141A545)

3. Nuclear Regulatory Commission (NRC) letter Palo Verde Nuclear Generating Station, Unit 3 - Request for Relief from ASME Code,Section XI Requirements Regarding Half-Nozzle Repair and Flaw Evaluation as an Alternative to Flaw Removal and Flaw Characterizationfor Flaw in Bottom Mounted Instrument Nozzle Penetration No.3, dated April 10, 2014 (ADAMS Accession Number ML14093A407)

4. NRC letter Palo Verde Nuclear GeneratingStation, Unit 3 - Request for Additional Information Re: Relief Request 52, Alternative to ASME Code,Section XI Requirements for Flaw Evaluation, Flaw Characterization,and Successive Examinations, dated December 4, 2014 (ADAMS Accession No. ML14330A510)

5. APS letter number 102-06991, Palo Verde Nuclear Generating Station Unit 3, Docket No. STN 50-530, Response to Request for Additional Information (RAI) for Unit 3 Bottom Mounted Instrument Relief Request 52, (Proprietary Version) dated January 16, 2015

Subject:

Palo Verde Nuclear Generating Station (PVNGS)

Unit 3 Docket No. 50-530 Response to Request for Additional Information (RAI) for Unit 3 Bottom Mounted Instrument Relief Request 52 (Non-Proprietary Version)

AOq7 A member of the STARS (Strategic Teaming and Resource Sharing) Alliance Callaway

• Diablo Canyon - Palo Verde - Wolf Creek

102-06992-JJC/DCE ATTN: Document Control Desk U.S. Nuclear Regulatory Commission Response to Request for Additional Information (RAI) for Unit 3 Bottom Mounted Instrument Relief Request 52 (Non-Proprietary Version)

Page 2 On May 16, 2014, pursuant to 10 CFR 50.55a(a)(3)(i), Arizona Public Service Company (APS) requested the Nuclear Regulatory Commission (NRC) approve Relief Request 52 (References 1 and 2).

Relief Request 52 was submitted to obtain NRC approval for operation of Unit 3 beyond the current operating cycle based on analyses that justify continued operation for the remainder of licensed operating life. The request was in response to the identification of leakage in Unit 3. Specifically, on October 6, 2013, APS identified evidence of leakage in the annulus of the Palo Verde Nuclear Generating Station (PVNGS) Unit 3 reactor vessel (RV) bottom mounted instrument (BMI) nozzle penetration 3.

Previously, APS submitted Relief Request 51 on November 8, 2013, which was verbally approved by the NRC staff on November 21, 2013, and formally approved on April 10, 2014 (Reference 3). NRC approval of Relief Request 51 permitted operation of Unit 3 through the end of the current operating cycle based on ASME code-compliant repairs and the one cycle analyses completed by APS prior to restart of Unit 3.

On December 4, 2014, NRC staff requested additional information (RAI) from APS to clarify information provided in the Relief Request 52 (Reference 4).

This letter transmits a non-proprietary version of the complete set of responses to the RAIs. A proprietary version of the responses was sent by separate correspondence (Reference 5).

Should you need further information regarding this submittal, please contact Thomas N. Weber, Nuclear Regulatory Affairs Department Leader, at (623) 393-5764.

No commitments are being made to the NRC by this letter.

Sincerely, .

JJC/DCE Enclosure - Response to Relief Request 52 Request for Additional Information (Non-Proprietary Version) cc: M. L. Dapas NRC Region IV Regional Administrator B. K. Singal NRC NRR Project Manager for PVNGS M. M. Watford NRC NRR Project Manager C. A. Peabody NRC Senior Resident Inspector for PVNGS

Enclosure Response to Relief Request 52 Request for Additional Information (Non-Proprietary Version)

Enclosure Response to Relief Request 52 Request for Additional Information (Non-Proprietary Version)

Introduction Pursuant to 10 CFR 50.55a(a)(3)(i), Arizona Public Service Company (APS) requested the Nuclear Regulatory Commission (NRC) approve Relief Request 52 (References 1 and 2). Specifically, the relief request proposed a half-nozzle repair and a flaw evaluation as alternatives to the requirements for flaw removal of IWA-4421, flaw characterization of IWA-3300, and successive examinations of IWB-2420.

On December 4, 2014, NRC staff requested additional information (RAI) from APS to clarify information provided in the relief request (Reference 3).

The relief request was submitted regarding the discovery of leakage on October 6, 2013. Specifically, APS identified evidence of leakage in the annulus of the Palo Verde Nuclear Generating Station (PVNGS) Unit 3 reactor vessel (RV) bottom mounted instrument (BMI) nozzle penetration 3. The leakage was identified during planned visual examinations of Unit 3 BMI nozzle penetrations conducted at the beginning of the Unit 3 Refueling Outage (3R17). The examinations were required, pursuant to American Society of Mechanical Engineers (ASME) Code Case N-722-1, Additional Examinations for PWR PressureRetaining Welds in Class 1 Components Fabricatedwith Alloy 600/82/182 Materials,in accordance with 10 CFR 50.55a, Codes and Standards.

APS submitted Relief Request 51 (Reference 4) on November 8, 2013, for use through the current 18th operating fuel cycle, which was verbally approved on November 21, 2013, and formally approved by NRC staff on April 10, 2014 (Reference 5). The relief request was based on the implemented ASME code compliant half-nozzle repair and analyses completed prior to startup to support operation through Unit 3 Cyclel8, one operating cycle. Relief Request 51 did not address the successive examination requirements of Section Xl IWB-2420 since the duration of Relief Request 51 does not include the periods of successive examinations.

APS in Relief Request 52 performed more detailed analyses to demonstrate acceptability of the proposed alternative for the remainder of the Unit 3 licensed operating life. These analyses consisted of a fracture mechanics flaw evaluation of a postulated maximum flaw that could exist in the remnant J-groove weld and structural evaluations of the remnant nozzle. Relief Request 52 also includes in its scope justification for continued operation without successive examinations of the flaw required by IWB-2420.

The NRC RAIs for Relief Request 52 focused on details of the evaluations in the six supporting documents, Attachments 1 through 6, provided by APS in Reference 2 which are listed below:

Attachment 1 - ASME Section Xl End of Life Analysis of PVNGS Unit 3 RV BMI Nozzle Repair 1

Enclosure Response to Relief Request 52 Request for Additional Information (Non-Proprietary Version)

Attachment 2 - Corrosion Evaluation for Palo Verde Unit 3 Reactor Vessel BMI Nozzle Modification Attachment 3 - Weld Residual Stress Analysis for PVNGS UNIT 3 RV BMI Nozzle Repair Attachment 4 - ASME Section III End of Life Analysis of PVNGS Unit 3 RV BMI Nozzle Repair Attachment 5 - Palo Verde Unit 3 - BMI Nozzle Crack Growth Analysis Attachment 6 - Natural Frequencyand StructuralIntegrity Analysis for PVNGS Unit 3 RV BMI Nozzle Repair The responses to the RAIs are divided into two groups. The first group is provided in the body of this enclosure and a second group of responses is provided as an attachment to this enclosure [Attachment - Responses to RAIs for APS PVNGS Unit 3 BMI Nozzle

1. 3 Repair, AREVA Document ANP-3375Q1NP (Non-Proprietary)],portions of which include proprietary information.

Responses to NRC RAI Questions NRC RAI-1 As indicated in Relief Request 52, Item 6, the requested duration of the proposed alternative is for the remainder of the Unit 3 licensed operating life, which expires on November 25, 2047. The NRC approves relief requests on an interval-by-interval basis (10-year inservice inspection (ISI) interval). Therefore, please modify the requested duration of the proposed alternative of Relief Request 52 to indicate "the remaining life of the third inservice inspection interval" or justify the current description.

APS Response As requested, APS hereby modifies the relief request duration to extend through the end of the Unit 3 third inservice interval, which expires January 10, 2018. The APS ASME Code Section Xl flaw evaluations included in Relief Request 52 were performed to qualify the reactor vessel bottom head for the effects of the remnant J-groove weld flaw for the remainder of the PVNGS Unit 3 licensed operating life, which expires on November 25, 2047. This relief request will be resubmitted with the updated ISI program prior to commencement of the Unit 3 fourth interval ISI Program and similarly for subsequent intervals.

2

Enclosure Response to Relief Request 52 Request for Additional Information (Non-Proprietary Version)

NRC RAI-2 For each attachment supporting Relief Request 52, please summarize the major areas that were different from the previous submittals supporting relief for one operating cycle.

APS Response Six supporting attachments were provided in Relief Request 52. A summary of the major areas from Relief Request 52 that are different from Relief Request 51 for Attachments 1 through 4 is provided in the attachment to this enclosure.

Discussion of Attachments 5 and 6 is provided below:

The one cycle justification of Relief Request 51 (Reference 4) uses a bounding estimate of primary water stress corrosion cracking (PWSCC) crack growth for all of the RV BMI nozzles to reach their critical crack length given similar flaw characteristics as those present in BMI nozzle 3. The analysis utilized the steepest penetration angle BMI and corresponding residual stresses (Dominion Report C-7789-00-2, Palo Verde Bottom Head Instrumentation Nozzle Stress Analysis, dated July 26, 2004, provided in Reference 6) to demonstrate that the nozzle remnant would maintain its structural integrity during one operating fuel cycle. Based on the referenced flaw evaluation, and the nozzle engagement to the RV bore, it was deemed that generation of loose parts was not anticipated within one operating fuel cycle.

The current submittal (Relief Request 52) evaluates the projected growth (for the remainder of the Unit 3 licensed operating life) of the cracks in the nozzle and within the region of structural attachment to the J-groove weld to determine their crack length and the structural frequency of the degraded remnant nozzle. These evaluations are performed in reports submitted under Attachments 5 and 6 of Relief Request 52.

Together these two analyses demonstrate that the observed cracking in the remnant nozzle should not generate a loose part and that the structural integrity of the remnant nozzle is maintained throughout the remaining life of the plant.

NRC RAI-3 Please refer to the attachment to this enclosure.

NRC RAI-4 Please refer to the attachment to this enclosure NRC RAI-5 Please refer to the attachment to this enclosure 3

Enclosure Response to Relief Request 52 Request for Additional Information (Non-Proprietary Version)

NRC RAI-6 Section 2.0, "Assumptions," of Attachment 2 of Relief Request 52 lists four assumptions used in the corrosion evaluation, which require plant-specific verification. Please provide your verification based on PVNGS plant-specific information.

APS Response The first two assumptions address plant operating conditions during which industry experience shows carbon and low alloy steel corrosion rates may be more elevated.

The percentage of time at both shutdown and start-up conditions is tracked by Engineering Study 13-MS-B041, Alloy Steel Corrosion Analysis Supporting Alloy 600/690 Nozzle Repair/Replacement,which is already in place for half-nozzle repairs to other primary system components. These percentages will be determined for Unit 3 from the time the half-nozzle repair was implemented at BMI nozzle 3 until the end of the remaining Unit 3 licensed operating life. This ongoing tracking will ensure that Assumptions 1 and 2 of the corrosion evaluation for the Unit 3 reactor vessel BMI nozzle 3 penetration remains bounding.

The third and fourth assumptions are related to plant chemistry controls that have been and will continue to be used to minimize various corrosion mechanisms. The reactor coolant chemistry for PVNGS Unit 3, fuel cycles 16 and 17 was reviewed per the requirements set forth in Reference 7. The PVNGS Chemistry Program maintains the reactor coolant chemistry per the Electric Power Research Institute (EPRI) PressurizedWater Chemistry Guidelines and the PVNGS Technical Requirements Manual (TRM) in accordance with chemistry procedure 74DP-9CY04, Systems Chemistry Specifications. This chemistry review verifies the third and fourth assumptions of the corrosion evaluation for the Unit 3 reactor vessel BMI nozzle 3 penetration based on PVNGS plant-specific information.

NRC RAI-7 Please refer to the attachment to this enclosure NRC RAI-8 Please refer to the attachment to this enclosure NRC RAI-9 Please refer to the attachment to this enclosure NRC RAI-10 Please refer to the attachment to this enclosure NRC RAI-11 Please refer to the attachment to this enclosure NRC RAI-12 Please refer to the attachment to this enclosure 4

Enclosure Response to Relief Request 52 Request for Additional Information (Non-Proprietary Version)

NRC RAI-13 Section 6.2, "Thermal Analysis," of Attachment 4 of Relief Request 52, states that bulk fluid temperatures correspond to RPV inlet temperatures. Please explain why the temperatures at the RPV inlet (near top of reactor vessel) are applicable at the bottom of the RPV.

APS Response The geometry of the reactor coolant flow paths through the four (4) inlet nozzles, the core support barrel (CSB) annulus, the flow skirt baffle and into the bottom head in-core instrument (101) guide structures is illustrated in Updated Final Safety Analysis Report (UFSAR) Figures 4.1-1 and 4.4-7. As shown in these figures, the forced flow from the cold leg nozzles on the RV is met by the solid cylindrical portion of the CSB which diverts the total flow downward toward the bottom of the RV and through the flow baffle that surrounds the BMI nozzles and then turns upward through the lower core support structure and into the core.

Reactor coolant from the cold legs flows rapidly down into the RV over the small portion of the CSB that is directly heated by the operating core. Based on the geometry of the annulus area the cold leg flow travels over 26 feet per second such that there is limited heat transfer to the bulk fluid. Once past this area, the reactor coolant passes through the flow baffle which thoroughly mixes the turbulent fluid as it enters the bottom portion of the RV. Thus, the bulk fluid temperature at the bottom of the RV would essentially remain at the nominal cold leg nozzle inlet temperature.

NRC RAI-14 Please refer to the attachment to this enclosure NRC RAI-15 Please refer to the attachment to this enclosure NRC RAI-16 Please refer to the attachment to this enclosure NRC RAI-17 Please refer to the attachment to this enclosure NRC RAI-18 Please refer to the attachment to this enclosure NRC RAI-19 Please refer to the attachment to this enclosure 5

Enclosure Response to Relief Request 52 Request for Additional Information (Non-Proprietary Version)

References:

1. Arizona Public Service Company (APS) letter number 102-06879, Palo Verde Nuclear Generating Station Unit 3, Docket No. STN 50-530, American Society of MechanicalEngineers (ASME) Code, Section Xl, Request for Approval of an Alternative to Flaw Removal, Flaw Characterizationand Successive Examinations - Relief Request 52, dated May 16, 2014 [Agencywide Documents Access And Management System (ADAMS) Accession No. ML14142A029]

2. APS letter number 102-06880, Palo Verde Nuclear Generating Station Unit 3, Docket No. STN 50-530, Transmittalof ProprietaryDocuments for Relief Request 52, dated May 16, 2014 (ADAMS Accession No. ML14141A545)

3. Nuclear Regulatory Commission (NRC) letter Palo Verde Nuclear Generating Station, Unit 3 - Request for Additional Information Re: Relief Request 52, Alternative to ASME Code, Section X1 Requirements for Flaw Evaluation, Flaw Characterization,and Successive Examinations,dated December 4, 2014 (ADAMS Accession No. ML14330A510)

4. APS letter number 102-06794 Palo Verde Nuclear Generating Station Unit 3, Docket No. STN 50-530, American Society of Mechanical Engineers(ASME)

Code,Section XI, Request for Approval of an Alternative to Flaw Removal and Characterization- Relief Request 51, dated November 8, 2013 (ADAMS Accession No. ML13317A071)

5. NRC letter Palo Verde Nuclear Generating Station, Unit 3 - Request for Relief from ASME Code, Section X1 Requirements Regarding Half-Nozzle Repair and Flaw Evaluation as an Alternative to Flaw Removal and Flaw Characterizationfor Flaw in Bottom Mounted Instrument Nozzle Penetration No.3, dated April 10, 2014 (ADAMS Accession Number ML14093A407)

6. APS letter number 102-06797, Palo Verde Nuclear Generating Station Unit 3, Docket No. STN 50-530, Response to Request for Additional Information -

American Society of Mechanical Engineers (ASME) Code,Section XI, Request for Approval of an Alternative to Flaw Removal and Characterization- Relief Request 51, dated November 18, 2013 (ADAMS Accession No. ML13323A763)

7. Westinghouse Owners Group Topical Report WCAP-1 5973-P, Low-alloy Steel Component CorrosionAnalysis Supporting Small-DiameterAlloy 600/690 Nozzle Repair/ Replacement Program,Revision 1 (ADAMS Accession No. ML041540232) 6

Enclosure Response to Relief Request 52 Request for Additional Information (Non-Proprietary Version)

Attachment Responses to RAIs for APS PVNGS Unit 3 BMI Nozzle #3 Repair, AREVA Document ANP-3375Q1 NP (Non-Proprietary Version)

A AREVA ANP-3375Q1NP Responses to RAIs for APS PVNGS Unit 3 Revision 0 BMI Nozzle #3 Repair January 2015 AREVA Inc.

(c) 2015 AREVA Inc.

Copyright © 2015 AREVA Inc.

All Rights Reserved

AREVA Inc. ANP-3375Q1NP Revision 0 Resoonses to RAIs for APS PVNGS Unit 3 BMI Nozzle #3 Renair Paaei ReSDonses to RAls for APS PVNGS Unit 3 BIVII Nozzle #3 Repair Pacie i Nature of Changes Section(s)

Revision or Page(s) Description and Justification 0 All Initial Issue

AREVA Inc. ANP-3375Q1NP Revision 0 Responses to RAIs for APS PVNGS Unit 3 BMI Nozzle #3 Repair Page ii Contents Page LIST OF TABLES ........................................................................................................... IV LIST OF FIGURES ......................................................................................................... IV NOMENCLATURE ................................................................................................... V

1.0 INTRODUCTION

AND

SUMMARY

................................................................... 1-1 2.0 REQUESTS FOR ADDITIONAL INFORMATION (RAIS) AND RESPONSES .................................................................................................... 2-1 2 .1 RA I-1 ....................................................................................................... 2 -1 2 .2 RA I-2 ....................................................................................................... 2 -2 2.2.1 Statement of RAI-2 ....................................................................... 2-2 2.2.2 Response to RAI-2 ....................................................................... 2-2 2 .3 RA I-3 ....................................................................................................... 2 -4 2.3.1 Statement of RAI-3 ....................................................................... 2-4 2.3.2 Response to RAI-3 ....................................................................... 2-4 2 .4 R A I-4 ....................................................................................................... 2 -5 2.4.1 Statement of RAI-4 ....................................................................... 2-5 2.4.2 Response to RAI-4 ....................................................................... 2-5 2 .5 R A I-5 ....................................................................................................... 2-9 2.5.1 Statement of RAI-5 ....................................................................... 2-9 2.5.2 Response to RAI-5 ....................................................................... 2-9 2 .6 R A I-6 ..................................................................................................... 2 -12 2 .7 R A I-7 ..................................................................................................... 2 -1 3 2.7.1 Statement of RAI-7 .................................................................... 2-13 2.7.2 Response to RAI-7 ..................................................................... 2-13 2 .8 R A I-8 ..................................................................................................... 2 -16 2.8.1 Statement of RAI-8 ..................................................................... 2-16 2.8.2 Response to RAI-8 ..................................................................... 2-16 2 .9 R A I-9 ..................................................................................................... 2 -18 2.9.1 Statement of RAI-9 ..................................................................... 2-18 2.9.2 Response to RAI-9 ..................................................................... 2-18 2 .10 RA I-10 ................................................................................................... 2 -19 2.10.1 Statement of RAI-10 ................................................................... 2-19 2.10.2 Response to RAI-10 ................................................................... 2-19 2 .11 RA I-1 1................................................................................................... 2 -2 0 2.11.1 Statement of RAI-11 ................................................................... 2-20 2.11.2 Response to RAI- 1 ................................................................... 2-20

AREVA Inc. ANP-3375Q1NP Revision 0 Responses to RAIs for APS PVNGS Unit 3 BMI Nozzle #3 Repair Page iii 2 .12 RA I-12 ................................................................................................... 2 -2 1 2.12.1 Statement of RAI-12 ................................................................... 2-21 2.12.2 Response to RAI-12 ................................................................... 2-21 2 .13 R A I-1 3 ................................................................................................... 2 -2 3 2 .14 R A I-14 ................................................................................................... 2 -2 4 2.14.1 Statement of RAI-14 ................................................................... 2-24 2.14.2 Response to RAI-14 ................................................................... 2-24 2 .15 R A I-1 5 ................................................................................................... 2 -2 5 2.15.1 Statement of RAI-15 ................................................................... 2-25 2.15.2 Response to RAI-15 ................................................................... 2-25 2 .16 R A I-16 ................................................................................................... 2 -2 8 2.16.1 Statement of RAI-16 ................................................................... 2-28 2.16.2 Response to RAI-16 ................................................................... 2-29 2 .1 7 RA I-17 ................................................................................................... 2 -3 0 2.17.1 Statement of RAI-17 ................................................................... 2-30 2.17.2 Response to RAI-17 ................................................................... 2-30 2 .18 RA I-18 ................................................................................................... 2 -3 1 2.18.1 Statement of RAI-18 ................................................................... 2-31 2.18.2 Response to RAI-18 ................................................................... 2-31 2 .19 R A I-1 9 ................................................................................................... 2 -3 2 2.19.1 Statement of RAI-19 ................................................................... 2-32 2.19.2 Response to RAI-19 ................................................................... 2-32

3.0 REFERENCES

.................................................................................................. 3-1

AREVA Inc. ANP-3375Q1 NP Revision 0 Responses to RAIs for APS PVNGS Unit 3 RMI Nozzle #3 Repair Paae iv List of Tables Table 2-1: Stress Intensity Factors at Uphill Position 21 ............................................. 2-6 Table 2-2: LE F M A na lysis ........................................................................................... 2 -7 Table 2-3: Uphill Position 21 EPFM Results based on Code Case N-749 Section 3 .1 ............................................................................................................. 2 -8 Table 2-4: Downhill Position 21 EPFM Results based on Code Case N-749 S e ctio n 3 .1 ................................................................................................ 2-8 Table 2-5: Maximum SI Range at the Inside Node of Path "HDPATH1" (unit: psi) .... 2-26 Table 2-6: Maximum SI Range at the Inside Node of Path "HDPATH2" (unit: psi) .... 2-27 Table 2-7: Maximum SI Range at the Inside Node of Path "HDPATH3" (unit: psi) .... 2-27 List of Figures Figure 2-1: Residual Stress Field and Stress Intensity Factors ................................. 2-11 Figure 2-2: Residual Hoop Stresses (psi) .................................................................. 2-14 Figure 2-3: Residual Hoop Stresses Greater Than or Equal to [ ] .................... 2-15 Figure 2-4: Deformation under Design Conditions with Un-deformed Edges ............ 2-22

AREVA Inc. ANP-3375QINP Revision 0 Responses to RAls for APS PVNGS Unit 3 BMI Nozzle #3 Repair Paae v Nomenclature Acronym Definition APS Arizona Public Service Company ASME American Society of Mechanical Engineers BMI Bottom Mounted Instrumentation EPFM Elastic-Plastic Fracture Mechanics LEFM Linear Elastic Fracture Mechanics NRC United States Nuclear Regulatory Commission PVNGS Palo Verde Nuclear Generating Station RAI Request for Additional Information RV Reactor Vessel RTNDT Reference Temperature for Nil-Ductility Transition WRS Welding Residual Stress SI Stress Intensity SCF Stress Concentration Factor FSRF Fatigue Strength Reduction Factor CFUF Cumulative Fatigue Usage Factor

AREVA Inc. ANP-3375Q1NP Revision 0 Responses to RAIs for APS PVNGS Unit 3 BMI Nozzle #3 Repair Page 1-1

1.0 INTRODUCTION

AND

SUMMARY

Arizona Public Service Company (APS) submitted Relief Request 52 (Reference [1])

with six supporting attachments to the Nuclear Regulatory Commission (NRC). The NRC has issued a set of Requests for Additional Information (RAIs) on this submittal.

This report provides the answers for RAI-2 (for Attachments 1-4) through RAI-5, RAI-7 through RAI-12, and RAI-14 through RAI-19.

AREVA Inc. ANP-3375QINP Revision 0 Responses to RAIs for APS PVNGS Unit 3 RMI Nozzle #3 Renair Paae 2-1 2.0 REQUESTS FOR ADDITIONAL INFORMATION (RAIs) AND RESPONSES The NRC RAIs from Reference [2] are addressed in Section 2.1 through 2.19. For RAIs answered in this document the NRC RAI is reproduced and the AREVA/APS response is provided.

2.1 RAI-1 Please refer to the enclosure to the APS letter.

AREVA Inc. ANP-3375Q1NP Revision 0 Responses to RAIs for APS PVNGS Unit 3 BMI Nozzle #3 Repair Page 2-2 2.2 RAI-2 2.2.1 Statement of RAI-2 For each attachment supporting Relief Request 52, please summarize the major areas that were different from the previous submittals supporting relief for one operating cycle.

2.2.2 Response to RAI-2 Six supporting attachments (References [3], [4], [5], [6], [7], and [8]) were provided in Relief Request 52.

A summary of the major areas from Relief Request 52 that are different from Relief Request 51 for Attachments 1 through 4 is provided below.

Discussion of Attachments 5 and 6 is provided in the enclosure to the APS letter. - "ASME Section Xl End of Life Analysis of PVNGS3 RV BMI Nozzle Repair."

The fracture mechanics analysis justifying one operating cycle was performed in Relief Request 51, supported by AREVA Document 32-9212942-001 and subsequent RAI responses (ADAMS Accession numbers ML13323A763 and ML13325A098). Major differences from the current submittal (Relief Request 52) include:

• Relief Request 51 (one cycle justification) utilized a closed form solution for a corner crack in a nozzle to determine the applied stress intensity factors while the current submittal calculates the stress intensity factors with a detailed 3D finite element model for the specific BMI nozzle #3 configuration, which includes the boat sample that removed a portion of the degraded J-groove weld and nozzle material from the affected region.

" Relief Request 51 uses a conservative estimate of fatigue crack growth for one cycle based on past experience with similar configurations. The current submittal performs a detailed fatigue crack growth analysis based on the PVNGS specific design transient stresses and associated cycles for the remaining life of the plant.

AREVA Inc. ANP-3375QINP Revision 0 Responses to RAIs for APS PVNGS Unit 3 BMI Nozzle #3 Repair Page 2-3 - "Corrosion Evaluation for Reactor Vessel BMI Nozzle Modification."

The corrosion evaluation for Relief Request 51 was performed for the remainder of Unit 3 licensed operating life and is the same document provided as Attachment 2 in Relief Request 52. - "Weld Residual Stress Analysis for PVNGS3 RV BMI Nozzle Repair."

Relief Request 51 utilized a conservative residual stress evaluation performed by Dominion Engineering of a Palo Verde typical RV bottom head with four different types of BMI penetration angles (Report C-7789-00-2, 07/26/2004).

The current submittal performs a PVNGS specific residual stress evaluation for PVNGS Unit 3 BMI # 3 inclusive of boat sample removal. - "ASME Section III End of Life Analysis of PVNGS3 RV BMI Nozzle Repair."

The Section III analysis provided in Relief Request 51 [ 1 was performed by comparing the repair weld configuration to the ASME Code sizing and reinforcement requirements and by explicitly evaluating primary stresses.

Secondary and peak stresses (fatigue) were deemed to be acceptable for one operating cycle by comparison to the original analysis and a similar repair analysis (STP Repair, see [ ] The Section III End of Life Analysis provided in Relief Request 52 (AREVA Doc 32-9220625) is a full finite element model (FEM) analysis which explicitly evaluates primary/secondary/peak stresses, including fatigue.

AREVA Inc. ANP-3375Q1NP Revision 0 Responses to RAIs for APS PVNGS Unit 3 BMI Nozzle #3 Repair Page 2-4 2.3 RAI-3 2.3.1 Statement of RAI-3 Section 2.1, "Stress Intensity Factor Solution," of Attachment 1 of Relief Request 52 proposed an extrapolation rule for estimation of the stress intensity factor (SIF or K1) associated with a flaw size larger than the largest flaw in the finite element method (FEM) model of the PVNGS, Unit 3 bottom head and BMI nozzle. Please discuss the extent of using this extrapolation rule (e.g., 30 percent of the crack front profiles used the extrapolation rule to obtain their K,values) to demonstrate that the calculated crack growth based on the AKI values are still valid.

2.3.2 Response to RAI-3 For this application, the extrapolation procedure was not needed and therefore not utilized to obtain the K,values. The calculated maximum fatigue crack growth was

[ J inches (Table 6-2 of Reference [3]), which means that all the K,values utilized in the calculation of AKI were interpolated between modeled crack fronts 1 I and 2 1 ] which are 0.25 inches apart.

AREVA Inc. ANP-3375Q1NP Revision 0 Responses to RAIs for APS PVNGS Unit 3 BMI Nozzle #3 Repair Page 2-5 2.4 RAI-4 2.4.1 Statement of RAI-4 Section 2.4.1, "Screening Criteria," of Attachment 1 of Relief Request 52 mentioned use of the failure mode criteria (linear elastic fracture mechanics (LEFM), elastic plastic fracture mechanics (EPFM), and limit load analysis) of the ASME Code, Section Xl, Appendix C, "Evaluation of Flaws in Piping," in the current reactor pressure vessel (RPV) application. Applying the failure mode criteria for piping to RPV does not appear to be justified. The NRC staff determined the criteria separating the LEFM and EPFM regions in ASME Code Case N-749, "Alternative Acceptance Criteria for Flaws in Ferritic Steel Components Operating in Upper Shelf Temperature Range," with the NRC staffs modification acceptable. The NRC staffs position on use of ASME Code Case N-749 is provided in the Attachment for your information. Please address the impact of using the proposed Appendix C criteria instead of ASME Code Case N-749 with the NRC staffs modification to the results of this ASME Code, Section Xl end-of-life evaluation.

2.4.2 Response to RAI-4 The impact of using ASME Code Case N-749 including the NRC staffs modification was evaluated. It was determined that the conclusion of the ASME Code, Section X1 end of life evaluation submitted in Relief Request 52 is not impacted by the proposed methodology of ASME Code Case N-749 as modified by NRC staff. Therefore, no changes to the submitted analysis are necessary.

Code Case N-749 (Reference [9]) states that its methodology is applicable to ferritic steel components on the upper shelf of the Charpy energy curve when the metal temperature exceeds the upper shelf transition temperature, Tc. The NRC staff modification to Code Case N-749 defines Tc as T, = 170.40 F + 0.8 1 4 RTNDT.

The RTNDT of the bottom head at PVNGS Unit 3 is -60 0F, which results in T, = 170.40 F + 0.814(-600 F) = 122 0 F.

AREVA Inc. ANP-3375Q1NP Revision 0 Responses to RAIs for APS PVNGS Unit 3 BMI Nozzle #3 Repair Page 2-6 For all cases evaluated in Tables 6-4 and 6-5 of Reference [3] the temperatures exceed 122 0 F, so the Elastic-Plastic Fracture Mechanics (EPFM) performed is applicable as further described later in this response. Review of the digitized transients from Tables 4-6 through 4-14 of Reference [6] shows that the only transients with temperatures below 122 0 F are the heatup and cooldown transients. The limiting case for LEFM is the cooldown transient with upper bound pressure curve (Table 4-9 of Reference [6]), since this combines the upper bound pressure curve with the tensile stresses on the inner diameter caused by the through wall temperature gradient. The limiting time point below 122 0 F occurs when the fluid temperature reaches the minimum temperature of 70'F. The stress intensity factors at uphill position 21 for the upper bound cooldown at the limiting time point, and for the weld residual stresses are shown at the relevant flaw sizes in Table 2-1.

Table 2-1: Stress Intensity Factors at Uphill Position 21 L

Using the stress intensity factors in Table 2-1 an LEFM analysis is performed in Table I

2-2.

AREVA Inc. ANP-3375Q1 NP Revision 0 Responses to RAls for APS PVNGS Unit 3 BMI Nozzle #3 Repair Pagie 2-7 Table 2-2: LEFM Analysis Notes: 1. The use of KIa as a stress intensity factor limit for LEFM evaluations is no longer required by the ASME Code. It was replaced with Kjc in the IWB-3612 limit of the ASME Section Xl Code starting with the 2004 Edition including 2005 Addenda (Reference [10]).

The LEFM analysis above shows that the applied stress intensity factor for the bounding load case (Normal/Upset) at temperatures below 122°F meets the allowable stress intensity factor limit of K1c/Vl0 utilizing current LEFM acceptance criteria that is consistent with the application of Code Case N-749 (ASME approval date: March 16, 2012).

In addition, the remaining load cases with a temperature above 122 0 F, meet the Tc criteria of Code Case N-749 as modified by the NRC, which allows their evaluation with the EPFM criteria. The results of the evaluation (including residual stresses) meet the acceptance criteria of Section 3.1 of Code Case N-749, see Table 2-3 & Table 2-4 below.

AREVA Inc. ANP-3375Q1NP Revision 0 Responses to RAls for APS PVNGS Unit 3 BMI Nozzle #3 Repair Page 2-8 Table 2-3: Uphill Position 21 EPFM Results based on Code Case N-749 Section 3.1 Loading HUCD RT SISD LSP PLPU HYDRO Service Level Normal Upset Normal Faulted Normal Test Primary Safety Factor 2.0 2.0 2.0 1.5 2.0 2.0 Secondary Safety Factor 1.0 1.0 1.0 1.0 1.0 1.0 Required Margins 1.0 1.0 1.0 1.0 1.0 1.0 Acceptable by EPFM? Yes Yes Yes Yes Yes Yes Table 2-4: Downhill Position 21 EPFM Results based on Code Case N-749 Section 3.1 Loading HUCD RT SISD LSP PLPU HYDRO Service Level Normal Upset Normal Faulted Normal Test Primary Safety Factor 2.0 2.0 2.0 1.5 2.0 2.0 Secondary Safety Factor 1.0 1.0 1.0 1.0 1.0 1.0 Required Margins 1.0 1.0 1.0 1.0 1.0 1.0 Acceptable by EPFM? Yes Yes Yes Yes Yes Yes

AREVA Inc. ANP-3375Q1 NP Revision 0 Responses to RAIs for APS PVNGS Unit 3 BMI Nozzle #3 Repair Page 2-9 2.5 RAI-5 2.5.1 Statement of RAI-5 Section 4.4.2, "Applied Stresses," of Attachment 1 of Relief Request 52 states, in part, that "Residual stresses are obtained from the 3-D weld residual stress calculation documented in Reference [16]." This is different from the approach that was used to support the one-operating-cycle relief, where the residual stresses are inseparable from the combined stresses based on Calculation No. C-7789-00-2, Revision 1, "Palo Verde Bottom Head Instrumentation Nozzle Stress Analysis," by Dominion Engineering (Reference [7] of Calculation 32-9212942-001, "Palo Verde Unit 3 BMI Nozzle Repair-Section Xl Analysis for Restart"; ADAMS Accession No. ML13317A072). Please address the following:

• Since operating stresses for the prior and the current analyses are likely to stay the same, the difference in the combined stresses of the two cases reflects the difference in their residual stresses. In light of this observation, please discuss the difference in residual stresses between the prior and current analyses and demonstrate why the current analyses is better representation of the "actual" residual stresses.

• The applied stress intensity factors (SIF) due to residual stresses for four crack fronts are shown in Figure A-I, "SIFs for Uphill Side- Welding Residual Stress."

Please provide the corresponding residual stress distributions for these four crack fronts and demonstrate, based on engineering fundamentals, that the residual stress distribution could vary its shape from one crack front to another as suggested by Figure A-1.

2.5.2 Response to RAI-5 Response to First Bullet of RAI-5 There are several reasons why the development of a new weld residual stress analysis was undertaken for the current scope:

AREVA Inc. ANP-3375Q1NP Revision 0 Responses to RAIs for APS PVNGS Unit 3 BMI Nozzle #3 Repair Page 2-10

1. The referenced Dominion Engineering, Inc. (DEI) calculation No. C-7789-00-2, Revision 1, performs residual stress calculations for a representative set of nozzle locations, but none of the selected nozzle locations represents the specific geometry of interest, namely BMI nozzle #3. To remove any engineering approximation involved with using stresses from a slightly different geometry it was desirable to create a model of BMI nozzle #3, including the cavity remaining after removal of the boat sample.

2. The referenced DEI calculation provides the steady-state operating plus residual stress values typically used for Pressurized Water Stress Corrosion Cracking (PWSCC) analysis for postulated flaws in the nozzle. The current analysis assumes that the entire PWSCC susceptible J-groove weld is completely flawed and is focused on analyzing the growth of this assumed initial flaw size into the low alloy steel head which is not susceptible to PWSCC. For the low alloy steel head, crack growth is only by the fatigue mechanism. The ranges of applied stress intensity factor and the mean stress intensity factor influence the fatigue crack growth rates; the residual stresses only influence the mean stress intensity factor. Calculating residual stresses separately, without steady-state operating loads, allows the use of the detailed transient stresses from the Section III analysis to calculate the stress intensity factor ranges; the impact of residual stress on the mean stress intensity factor can be accounted for by using the principle of superposition.

3. The detailed 3D finite element calculation of the stress intensity factors requires the stress distribution over the entire crack face in order to map stresses onto the crack face; this data is not available from the numerical results presented in the referenced DEI calculation.

AREVA Inc. ANP-3375Q1NP Revision 0 Responses to RAIs for APS PVNGS Unit 3 BMI Nozzle #3 Repair Page 2-11 Response to Second Bullet of RAI-5 The behavior of the stress intensity factors shown in Figure A-1 of Reference [3] is consistent with the hoop residual stress field presented in the contour plot in Figure 6-1 of Reference [5]. The two figures are shown in a combined plot in Figure 2-1 below.

For the first two modeled crack fronts, the high tensile stresses (as indicated) result in high stress intensity factors in the crack tips in the center region of the crack fronts. For deeper cracks (i.e., crack fronts 3 and 4) the compressive zone (as indicated) decreases the stress intensity factors of the crack tips near the center.

Figure 2-1: Residual Stress Field and Stress Intensity Factors

AREVA Inc. ANP-3375Q1NP Revision 0 Responses to RAIs for APS PVNGS Unit 3 BMI Nozzle #3 Repair Page 2-12 2.6 RAI-6 Please refer to the enclosure to the APS letter.

AREVA Inc. ANP-3375Q1NP Revision 0 Responses to RAIs for APS PVNGS Unit 3 BMI Nozzle #3 Repair Page 2-13 2.7 RAI-7 2.7.1 Statement of RAI-7 Section 3.3, "Modeling Simplifications," of Attachment 3, item 3 of Relief Request 52 states that surrounding penetrations are far enough away from the modeled BMI nozzle to preclude interaction. Please demonstrate, based on testing/experimental or analytical information, that the spacing distance from the next nearest penetration is enough to preclude interaction.

2.7.2 Response to RAI-7 The validity of this simplification can be verified by inspection of the residual hoop stress results using the logic described in the following discussion. The nearest penetration to BMI nozzle #3 is BMI nozzle #1, which is approximately [ ] inches away centerline to centerline. The diameter of the nozzle bores is approximately 3 inches, leaving a minimum of approximately [ ] between the nearest points of the BMI nozzle #3 bore and the BMI nozzle #1 bore. If the residual stresses drop to small tensile values (i.e., less than [ J ) or compressive values within half the distance between the two nozzles ([ J inches) then there will not be any significant interaction between residual stress fields. Figure 2-2 below (Figure B-1 of Reference

[5]) shows that the residual stresses decay very quickly moving radially away from the nozzle and weld. In the areas away from the weld there is a tensile residual stress in the stainless steel clad and stresses near zero in the head base metal. For additional clarity, Figure 2-3 plots the data such that nodes with a residual stress greater than or equal to [ are filled in circles and nodes with residual stress less than [ ]

are open circles. Moving radially away from the nozzle bore, the stresses in the head base metal are less than [ ] within approximately [ ] inches; since [ ]

inches is less than [ 1inches there will not be any significant interaction between the residual stress fields.

AREVA Inc. ANP-3375Q1NP Revision 0 Responses to RAIs for APS PVNGS Unit 3 BMI Nozzle #3 Repair Page 2-14 Figure 2-2: Residual Hoop Stresses (psi)

AREVA Inc. ANP-3375Q1NP Revision 0 R-esDonses to RAIs for APS PVNGS Unit 3 BMI Nozzle #3 ReDair Paae 2-15~

Paae 2-15 Figure 2-3: Residual Hoop Stresses Greater Than or Equal to I I

AREVA Inc. ANP-3375Q1NP Revision 0 Responses to RAIs for APS PVNGS Unit 3 BMI Nozzle #3 Repair Paqe 2-16 2.8 RAI-8 2.8.1 Statement of RAI-8 Section 4.2, "Materials," of Attachment 3 of Relief Request 52 states that ASME SA-508 material is used in lieu of ASME SA-533 Grade B Class 1. Based on the value of the modulus of elasticity at room temperature given in Table 4-3, "Room Temperature Thermal and Mechanical Properties," the ASME SA-508 class appears to be Class 2.

There have been revisions to ASME SA-508 Class 2 properties (ASME SA-508 Class 2 is now currently ASME SA-508 Grade 2 Class 1) after the construction code of record for the subject component. This revision lists different values of elastic modulus (E) and coefficient of thermal expansion (a). Please assess the impact of these differences on the resulting stresses.

2.8.2 Response to RAI-8 A comparison was made of the elastic modulus and coefficient of thermal expansion from the AREVA Welding Residual Stress (WRS) material properties database (for SA-508 Class 2) with the ASME Code properties for SA-533 Grade B Class 1. The ASME Code elastic modulus and coefficient of thermal expansion were taken from ASME Section II, Part D, 1998 Edition with Addenda through 2000 (Reference [11]).

The variation between properties is typically less than 10% over the majority of the temperature range, with some larger differences (approximately 20%) at high temperature (i.e., greater than 1000°F). Industry experience with welding residual stress simulations shows that the stresses are insensitive to variations of as much as 50% in elastic modulus and coefficient of thermal expansion. For example, quoting from Section 3 of MRP-317, "Welding Residual Stress Dissimilar Metal Butt-Weld Finite Element Modeling Handbook" (Reference [12]):

AREVA Inc. ANP-3375Q1 NP Revision 0 Responses to RAIs for APS PVNGS Unit 3 BMI Nozzle #3 Repair Page 2-17 The material property sets compared are shown in Figure 3-2 and Figure 3-3 for the coefficient of thermal expansion and the modulus of elasticity, respectively. As shown in these figures, the differences between the material property sets are not insignificant, in some cases approaching variations of 50%. However, comparison of the through-wall stress distributions considering only these property variations showed an insignificant effect on the results [11].

Given these results, it is considered likely that the range of material property data values commonly available for the materials of interest is below the threshold of sensitivity for typical welding residual stress models.

Based on the above, the differences in elastic modulus and coefficient of thermal expansion will have an insignificant impact on the weld residual stresses.

AREVA Inc. ANP-3375Q1 NP Revision 0 Responses to RAIs for APS PVNGS Unit 3 BMI Nozzle #3 Repair Page 2-18 2.9 RAI-9 2.9.1 Statement of RAI-9 Section 4.5.2, "Structural Boundary Conditions," of Attachment 3 of Relief Request 52 mentions the application of post-weld heat treatment (PWHT) of the RVBH (reactor vessel bottom head). Please provide a description of modelling the PWHT process to demonstrate that the modelling reflects what the BMI penetration nozzle #3 actually experienced.

2.9.2 Response to RAI-9 The PWHT was simulated using the steps below, which reflect the actual fabrication of the RV bottom head.

Initial Condition: The head, clad, and butter elements have cooled after the butter weld beads were deposited, and are initially at a temperature of 70 0 F. The nozzle and J-groove weld elements have not been activated.

Step 1: Apply a uniform temperature of [ J to the model and solve.

Step 2: Apply a uniform temperature of [ ] to the model and solve.

As noted in Section 3.3, item 4 of Reference [5] the simulation of PWHT does not include creep, and is therefore time independent. This is a conservative method to model PWHT since there is no credit taken for a reduction in residual stresses due to creep.

AREVA Inc. ANP-3375Q1 NP Revision 0 Responses to RAIs for APS PVNGS Unit 3 BMI Nozzle #3 Repair Page 2-19 2.10 RAI-1O 2.10.1 Statement of RAI-10 Section 4.3.1, "Design Condition," of Attachment 4 of Relief Request 52 states the design conditions were simulated on the model by applying a uniform temperature with no differential thermal growth throughout the model. The term "no differential thermal growth" needs clarification. In the actual situation, if metals of different coefficients of thermal expansion are brought up to the same temperature, there will be differential thermal growth and thermal stresses.

2.10.2 Response to RAI-10 The Design Condition stress limits are specified in Figure NB-3221-1; only the primary stress intensities (NB-3221.1, NB-3221.2 and NB-3221.3) are to be evaluated for the components under the Design Condition. Since thermal stresses resulting from the differential coefficients of thermal expansion are categorized as either secondary (Q) or peak (F) (see Table NB-3217.1), they need not be included in the primary stress intensities calculated for comparison with Design Condition limits. Therefore, the thermal stresses were eliminated by setting both the uniform body temperature and the reference temperature to [ ] OF. Thermal loads are applied in Level A and B conditions. The effect of the thermal growth differences is analyzed in those conditions and compared against Primary + Secondary Stress Intensity Range or Cumulative Fatigue limit.

AREVA Inc. ANP-3375Q1NP Revision 0 Responses to RAIs for APS PVNGS Unit 3 BMI Nozzle #3 Repair Page 2-20 2.11 RAI-11 2.11.1 Statement of RAI-11 Section 4.3.3.1, "Repair Nozzle", of Attachment 4 of Relief Request 52, states, in part, that "External Loads are defined at the juncture between the nozzle and the outside surface of the RVBH ... " Since the FEM model includes a portion of the repair nozzle that extends out some distance from the outside surface of the RVBH, please address whether the external loads have been adjusted by the appropriate moment arm, which is the distance the repair nozzle extends out from the outside surface of the RVBH.

2.11.2 Response to RAI-11 The external loads, taken from Reference [16] and listed in Table 4-15 of Attachment 4 of Relief Request 52, are reaction loads at the juncture between the nozzle and the outer surface of the vessel bottom head. Per Reference [16], the external piping loads on the nozzle weld (BMI to tube weld interface) down below are less than those given in the table. Since it is apparent that the external loads decrease as the location gets farther away from the outside surface of the reactor vessel bottom head (RVBH),

applying the external piping loads that were defined at the junction between the nozzle and the outside surface of the RVBH on the new weld build-up location (few inches below the original location) will be conservative and lead to larger stress results.

In addition, the outside end of the new Alloy 690 nozzle protrudes below the reactor vessel bottom head approximately the same length as the original Alloy 600 nozzle where it is welded to the instrument guide tube, thus no adjustments are required.

AREVA Inc. ANP-3375QINP Revision 0 Responses to RAIs for APS PVNGS Unit 3 BMI Nozzle #3 Repair Page 2-21 2.12 RAI-12 2.12.1 Statement of RAI-12 Section 4.4.1.2, "Structural Boundary Conditions," of Attachment 4 of Relief Request 52, states, in part, that "Symmetric boundary conditions are applied to the 3 faces corresponding to the cutoff sections of the model." The NRC staff is of the opinion that the surface of geometric symmetry is a preferred choice for the FEM model symmetry.

However, symmetric boundary conditions may not necessarily be appropriate to the other two faces, especially the curved surface of the FEM model. Please justify your assumption. This justification should be expanded to include discussion of the assumed symmetric boundary conditions of the FEM model for residual stresses discussed in Section 4.5.2, "Structural Boundary Conditions," of Attachment 3 of Relief Request 52.

2.12.2 Response to RAI-12 For the Section III and the residual stress finite element models, the same symmetric boundary conditions were applied. "Symmetric boundary conditions" are often used in finite element analysis in cases where some planes in the structure exist or behave as the plane of symmetry and can save substantial computation effort. In a 3-D structural analysis involving solid elements, it is the condition that for all nodes in the symmetry plane, the out-of-plane displacement is set to zero.

The symmetry boundary condition can not only be applied on a symmetry plane but it can also be applied to a curved surface as long as the boundary nodes are correctly rotated. The FEM has been verified to ensure that the symmetry boundary condition was correctly applied so that the nodes at the constraints are set perpendicular to the cut planes. Figure 2-4 below demonstrates that nodes on the symmetry planes are "sliding" in the plane and no out-of-plane "warping" exists.

Note that the symmetric boundary conditions are also applicable to the thermal deformation as the inside surface is subjected to a uniform temperature loading that varies over time. The thermal gradients at these locations are in the radial direction, not in the circumferential direction.

AREVA Inc. ANP-3375Q0NP Revision 0 Responses to RAIs for APS PVNGS Unit 3 BMI Nozzle #3 Repair Paae 2-22 Figure 2-4: Deformation under Design Conditions with Un-deformed Edges

AREVA Inc. ANP-3375Q1NP Revision 0 Responses to RAIs for APS PVNGS Unit 3 BMI Nozzle #3 Repair Page 2-23 2.13 RAI-13 Please refer to the enclosure to the APS letter.

AREVA Inc. ANP-3375Q1NP Revision 0 Responses to RAIs for APS PVNGS Unit 3 BMI Nozzle #3 Repair Page 2-24 2.14 RAI-14 2.14.1 Statement of RAI-14 Section 6.2, "Thermal Analysis," of Attachment 4 of Relief Request 52, states that the selection process for time points of maximum and minimum temperature gradients is based on temperature gradients for certain paths as shown in Figure 6-3. In the opinion of NRC staff, an ANSYS macro may be used to consider all the time points in the thermal analysis and use those same time points to be read in the subsequent stress analysis. Selecting time points based on the critical paths in Figure 6-3 involves some judgment, and, therefore, may not capture time points of maximum/minimum thermal stresses. Please justify that selecting the time points based on temperature gradients in Figure 6-3 is at least adequate enough to capture the times of maximum/minimum thermal stresses as compared to a macro-based procedure for the time selection process.

2.14.2 Response to RAI-14 Thermal stresses develop where the thermal gradients and/or the difference in material thermal coefficients of expansion exist. Thermal analysis involves a significant number of load steps and sub-steps. Selecting all time points (i.e., load steps) in thermal analysis for structural analysis is generally impractical, if not prohibited by the overwhelming demand on computing resource. Since the P+Q (primary plus secondary) stress intensities are to be evaluated along certain path lines through the pressure-retaining wall of the structure, thermal stresses can be readily evaluated for the peaks/valleys by examining the thermal gradients between critical locations. Note that the DT plots in Appendix C of the report demonstrate that these peaks/valleys are fairly concentrated at a certain period of time. Therefore, the efforts are spent to refine those time points having thermal peaks/valleys through iterations, in order to capture the extreme stress states. Thus, the method used in this evaluation is deemed to have captured the times of maximum/minimum thermal stresses for the transients evaluated.

AREVA Inc. ANP-3375Q1NP Revision 0 Responses to RAIs for APS PVNGS Unit 3 BMI Nozzle #3 Repair Page 2-25 2.15 RAI-15 2.15.1 Statement of RAI-15 Section 7.2, "Primary plus Secondary Stress Intensity Range," of Attachment 4 of Relief Request 52, states that a post-processing routine is used to convert component stresses into stress intensities (SI) and SI ranges. Is this post-processing part of the ANSYS fatigue module mentioned in Section 7.3, "Fatigue Usage Factor Criteria," of ? If so, please provide details of internal verification performed for this ANSYS fatigue module to ensure compliance with the requirements of Title 10 of the Code of Federal Regulations (10 CFR), Part 50, Appendix B, "Quality Assurance Criteria for Nuclear Power Plants and Fuel Reprocessing Plants."

2.15.2 Response to RAI-15 The ANSYS Fatigue Module as mentioned in Section 7.3 of Attachment 4 of Relief Request 52 was used to calculate the stress intensity (SI) ranges. The ANSYS fatigue module is a part of the ANSYS program. Internal verification is assured by AREVA's Administrative Procedures that are written to ensure compliance with Appendix B.

ANSYS performs its own Appendix B verification of its products by executing thousands of verification cases, including cases that test the features of the Fatigue Module used by AREVA. AREVA, in turn, executes verification cases to ensure that the program is executing properly on the hardware being used in safety related analyses. In addition, AREVA has reviewed the user's manual for limitations on the use of this module and also checked the error notices provided by ANSYS regarding the use of this application.

Therefore, suitable verification of the proper use of this module has been performed by AREVA.

Note that the usage factor calculation itself was performed in an Excel spreadsheet after all SI ranges were obtained.

To further demonstrate that the program is working correctly, the following verification was performed.

AREVA Inc. ANP-3375Q1NP Revision 0 Responses to RAIs for APS PVNGS Unit 3 BMI Nozzle #3 Repair Page 2-26 Calculation of P+Q stress intensity (SI) ranges shall follow the concept in calculating the alternating stress intensity Salt, as specified in NB-3216 (NB-3216.2 in particular) and implemented in Step 2 of NB-3222.4(e)(5). The ANSYS fatigue module was used to calculate the SI ranges needed in Sections 7.2 for the maximum P+Q SI ranges, and in Section 7.3 for the cumulative fatigue usage factor calculations.

The accuracy of the ANSYS fatigue module in calculating the SI ranges has been verified using Excel spreadsheet. For instance, in Table 7-2, the SI ranges calculated by the ANSYS fatigue module for the inside node at paths "HDPATH1 ," "HDPATH2" and "HDPATH3" are compared with those by Excel spreadsheets as presented in Table 2-5, Table 2-6, and Table 2-7, respectively.

The linearized stresses (M+B, components) along the pre-defined paths are first obtained from the ANSYS post-processing at each time point of each transient (Normal and Upset). Then the difference of component stresses between any two time points are calculated and used to calculate the principal stresses (S1, S2 and S3). The SI range is simply the magnitude of the difference between S1 and S3 (where S1 > S2 >

S3). The highest SI range is obtained by sorting out all SI ranges.

Table 2-5: Maximum SI Range at the Inside Node of Path "HDPATHI" (unit: psi)

AREVA Inc. ANP-3375Q1NP Revision 0 Responses to RAIs for APS PVNGS Unit 3 BMI Nozzle #3 Repair Page 2-27 Table 2-6: Maximum SI Range at the Inside Node of Path "HDPATH2" (unit: psi)

Table 2-7: Maximum SI Range at the Inside Node of Path "HDPATH3" (unit: psi)

Upon examining the differences (See Table 2-5, Table 2-6, and Table 2-7) between ANSYS fatigue module results and independent calculation results, the differences are negligible due to rounding. Therefore, it can be concluded that the ANSYS fatigue module is functioning properly.

AREVA Inc. ANP-3375Q1NP Revision 0 Responses to RAIs for APS PVNGS Unit 3 BMI Nozzle #3 Repair Page 2-28 2.16 RAI-16 2.16.1 Statement of RAI-16 Table 7-2, "P+Q Membrane plus Bending SI Ranges," of Attachment 4 of Relief Request 52, Section 7.2, "Primary plus Secondary Stress Intensity Range," presents the membrane plus bending (P+Q) Stress Intensity (SI) range for HDPath5 shown in Figure 7-1, "Path Lines on Reactor Vessel Bottom Head." The NRC staff notes that this path does not have the highest P+Q SI range, but has the highest cumulative fatigue usage factor (CFUF) as shown in Table 7-4, "Cumulative Fatigue Usage Factors." This observation is contrary to those indicated by WDPathl and NZPath3, where both have the highest values of the P+Q ranges and CFUF in their respective path groupings.

Please justify your approach.

AREVA Inc. ANP-3375Q1NP Revision 0 Responses to RAIs for APS PVNGS Unit 3 BMI Nozzle #3 Repair Page 2-29 2.16.2 Response to RAI-16 The P+Q SI ranges refer to the membrane plus bending (M+B) stress intensity ranges.

In calculating the fatigue usage factor at a particular location, either the M+B or the Total stress intensity ranges may be used, depending on which SI range is representative or conservative. For example, there are situations where the finite element model is limited in its capability to capture peak stresses near discontinuities for the calculation of total stress for use in a fatigue analysis. In these cases a stress concentration factor (SCF) or fatigue strength reduction factor (FSRF), as applicable, are applied to M+B in order to calculate the total stress which is conservative. In this particular case, an ASME fatigue strength reduction factor of [ ] is applied to the M+B stress intensity range for path "WDPathl" and "NZPath3" as shown in Table 7-3 as required by NB-3352.4(d) to represent the peak SI range at the crevice. However, for path "HDPath5" a factor of [ ] is applied to the outside node while a factor of [ ] is applied to the inside node because the inside node is away from a stress concentration region. Therefore, because it is sometimes necessary to apply factors to appropriately adjust stress results from the finite element model, the location that has the highest P+Q SI range may or may not be the location that has the highest cumulative fatigue usage factor.

AREVA Inc. ANP-3375Q1NP Revision 0 Responses to RAIs for APS PVNGS Unit 3 BMI Nozzle #3 Repair Paqe 2-30 2.17 RAI-17 2.17.1 Statement of RAI-17 of Relief Request 52 does not mention thermal stress ratchet. Did the analyses supporting nozzle repair met the requirement of NB-3222.5, "Thermal Stress Ratchet," of ASME Code,Section III?

2.17.2 Response to RAI-17 Per NB-3227.6, the limit on primary plus secondary stress intensity of 3Sm (NB-3222.2) has been placed to ensure that shake down to elastic action occurs. From the elastic analysis, it is demonstrated that the primary plus secondary stresses in all pressure-retaining components are within the stress limits (3Sm) under the plant design transients. Furthermore, results show that the stress intensity ranges are less than 2Sy (i.e., alternating stress < Sy, therefore Poisson's ratio does not need to be adjusted) for the replacement nozzle and the weld pad where 3Sm is greater than 2Sy. Since Thermal Stress Ratchet requires plastic deformation, an explicit analysis to demonstrate compliance with NB-3222.5 is not needed.

AREVA Inc. ANP-3375Q1NP Revision 0 Responses to RAIs for APS PVNGS Unit 3 BMI Nozzle #3 Repair Page 2-31 2.18 RAI-18 2.18.1 Statement of RAI-18 Section 5.4, "Growth of Single Edge Notched Plate Crack," of Attachment 5 of Relief Request 52, states that "Review of the results indicates that by path P23 the residual stresses have decayed and thus the stresses will be constant and equal to those at path P23 above that point." However, stresses in Table 5-3 decrease constantly along crack growth beyond P23. Please explain the inconsistency.

2.18.2 Response to RAI-18 It is agreed that this statement appears inconsistent. The values presented in Table 5-3 are average stresses over the length of the crack. The local stresses in the nozzle decrease in magnitude as the vertical distance from the weld increases, thus, the average stresses over the crack length continually decrease as the crack grows into lower stressed regions of the nozzle. As noted in Section 2.0 items 5.b and 5.c, the stresses utilized for calculation of the stress intensity factor are average stresses over the crack length.

AREVA Inc. ANP-3375Q1NP Revision 0 Responses to RAIs for APS PVNGS Unit 3 BMI Nozzle #3 Repair Page 2-32 2.19 RAI-19 2.19.1 Statement of RAI-19 Figure 6-4, "Remnant Nozzle First Mode," of Attachment 6, Section 6.2, "Natural Frequency Analysis," of Relief Request 52 shows the mode shape of the fundamental mode of the remnant BMI nozzle. The dynamic model has a cut-out (removal of FEM elements) to account for the actual cracks on the nozzle and weld. Similar to a cantilever beam, a cut-out (see Figure 6-4) close to the root of the nozzle will lower its first natural frequency significantly. The NRC staff considers that detaching the nodes without removing elements (i.e., the cut-out) to simulate the crack may be more realistic.

Therefore, please explain that an FEM model with detached nodes without cut-out will not increase the first natural frequency of the remnant BMI nozzle to a value close to the reported high pump exciting frequency (the higher of the reported two frequencies).

2.19.2 Response to RAI-19 While modelling the cracked area differently may serve to raise the natural frequency, the load at resonance was already applied to this limiting case model and determined to be acceptable (page 18 of the report). Therefore, even if the natural frequency does approach the pump blade frequency of [ ] Hz, the cracked configuration is acceptable based on a highly conservative analysis which considered load at resonance with minimum cross-section.

AREVA Inc. ANP-3375Q1NP Revision 0 Responses to RAIs for APS PVNGS Unit 3 BMI Nozzle #3 Repair Pagqe 3-1

3.0 REFERENCES

1. "Palo Verde, Unit 3 - ASME Code Section Xl, Request for Approval of an Alternative to Flaw Removal, Flaw Characterization and Successive Examinations - Relief Request 52," NRC ADAMS Accession Number ML14142A029, May 16, 2014.

2. Letter, Balwant K. Singal (NRC) to Randall K. Edington (APS), "Palo Verde Nuclear Generating Station, Unit 3- Request for Additional Information RE: Relief Request 52, Alternative to ASME Code, Section Xl Requirements for Flaw Evaluation, Flaw Characterization, and Successive Examinations (TAC NO.

MF4169)," NRC ADAMS Accession Number ML14330A510, December 4, 2014.

3. Attachment 1 to R.R. 52, "ASME Section XI End of Life Analysis of PVNGS3 RV BMI Nozzle Repair." (Proprietary AREVA Document [ ]/

Non-Proprietary AREVA Document 32-9222042-000)

4. Attachment 2 to R.R. 52, "Corrosion Evaluation for Palo Verde Unit 3 Reactor Vessel BMI Nozzle Modification." (Proprietary AREVA Document I ] / Non-Proprietary AREVA Document 51-9214650-000)

5. Attachment 3 to R.R. 52, "Weld Residual Stress Analysis for PVNGS3 RV BMI Nozzle Repair." (Proprietary AREVA Document [I /

Non-Proprietary AREVA Document 32-9219662-000)

6. Attachment 4 to R.R. 52, "ASME Section III End of Life Analysis of PVNGS3 RV BMI Nozzle Repair." (Proprietary AREVA Document [ ] /

Non-Proprietary AREVA Document 32-9220625-000)

7. Attachment 5 to R.R. 52, "Palo Verde Unit 3 - BMI Nozzle Crack Growth Analysis." (Proprietary AREVA Document [ ] / Non-Proprietary AREVA Document 32-9222043-000)

8. Attachment 6 to R.R. 52, "Natural Frequency and Structural Integrity Analysis for PVNGS3 RV BMI Nozzle Repair." (Proprietary AREVA Document I ] / Non-Proprietary AREVA Document 32-9220624-000)

9. Cases of the ASME Boiler and Pressure Vessel Code, Case N-749, "Alternative Acceptance Criteria for Flaws in Ferritic Steel Components Operating in the Upper Shelf Temperature Range," Section Xl, Division I.

10. ASME Boiler and Pressure Vessel Code, Section Xl, "Rules for Inservice Inspection of Nuclear Power Plant Components", 2004 Edition including Addenda through 2005.

11. ASME Boiler and Pressure Vessel Code,Section II, Part D, "Properties", 1998 Edition including Addenda through 2000.

t AREVA Inc. ANP-3375Q1NP Revision 0 Resoonses to RAIs for APS PVNGS Unit 3 BMI Nozzle #3 Renair Pane 3-2

12. "Materials Reliability Program: Welding Residual Stress Dissimilar Metal Butt-Weld Finite Element Modeling Handbook (MRP-317)". EPRI, Palo Alto, CA:

2011. 1022862.