2CAN112403, Affidavit for Corrosion Evaluation of ANO-2 RVCH CEDM Idtb Weld Nozzle Penetration Repair, Document Number 51-9384397-001

Affidavit for Corrosion Evaluation of ANO-2 RVCH CEDM Idtb Weld Nozzle Penetration Repair, Document Number 51-9384397-001

ML24316A004
Person / Time
Site:	Arkansas Nuclear
Issue date:	10/31/2024
From:	Entergy Operations
To:	Office of Nuclear Reactor Regulation
Shared Package
ML24316A002	List: 2CAN112403, Affidavit for Corrosion Evaluation of ANO-2 RVCH CEDM Idtb Weld Nozzle Penetration Repair, Document Number 51-9384397-001 ML24316A003
References
2CAN112403
Download: ML24316A004 (1)

Text

Attachment 6 to 2CAN112403 Affidavit for "Corrosion Evaluation of ANO-2 RVCH CEDM IDTB Weld Nozzle Penetration Repair," Document Number 51-9384397-001 (2 pages)

A F F I D A V I T

1.

My name is Philip A. Opsal. I am Manager, Product Licensing for Framatome Inc. (formally known as AREVA Inc.), and as such I am authorized to execute this Affidavit.

2.

I am familiar with the criteria applied by Framatome to determine whether certain Framatome information is proprietary. I am familiar with the policies established by Framatome to ensure the proper application of these criteria.

3.

I am familiar with the Framatome information contained in Engineering Information Record 51-9384397-001, entitled, Corrosion Evaluation of ANO-2 RVCH CEDM IDTB Weld Nozzle Penetration Repair, referred to herein as this Document. Information contained in this Document has been classified by Framatome as proprietary in accordance with the policies established by Framatome for the control and protection of proprietary and confidential information.

4.

This Document contains information of a proprietary and confidential nature and is of the type customarily held in confidence by Framatome and not made available to the public. Based on my experience, I am aware that other companies regard information of the kind contained in this Document as proprietary and confidential.

5.

This Document has been made available to the U.S. Nuclear Regulatory Commission in confidence with the request that the information contained in this Document be withheld from public disclosure. The request for withholding of proprietary information is made in accordance with 10 CFR 2.390. The information for which withholding from disclosure is requested qualifies under 10 CFR 2.390(a)(4) Trade secrets and commercial or financial information.

6.

The following criteria are customarily applied by Framatome to determine whether information should be classified as proprietary:

(a)

The information reveals details of Framatomes research and development plans and programs or their results.

(b)

Use of the information by a competitor would permit the competitor to significantly reduce its expenditures, in time or resources, to design, produce, or market a similar product or service.

(c)

The information includes test data or analytical techniques concerning a process, methodology, or component, the application of which results in a competitive advantage for Framatome.

(d)

The information reveals certain distinguishing aspects of a process, methodology, or component, the exclusive use of which provides a competitive advantage for Framatome in product optimization or marketability.

(e)

The information is vital to a competitive advantage held by Framatome, would be helpful to competitors to Framatome, and would likely cause substantial harm to the competitive position of Framatome.

The information in this Document is considered proprietary for the reasons set forth in paragraphs 6(b), 6 (c), 6(d), and 6(e) above.

7.

In accordance with Framatomes policies governing the protection and control of information, proprietary information contained in this Document has been made available, on a limited basis, to others outside Framatome only as required and under suitable agreement providing for nondisclosure and limited use of the information.

8.

Framatome policy requires that proprietary information be kept in a secured file or area and distributed on a need-to-know basis.

9.

The foregoing statements are true and correct to the best of my knowledge, information, and belief.

I declare under penalty of perjury that the foregoing is true and correct.

Executed on October 31, 2024.

Philip A. Opsal Manager, Product Licensing, Framatome Inc.

Philip A Opsal to 2CAN112403 Affidavit for "PWSCC Evaluation for Alloy 600 in ANO-2 CEDM Penetration No. 71 IDTB Weld Repair," Document Number 51-9384385-001 (2 pages)

A F F I D A V I T

1.

My name is Philip A. Opsal. I am Manager, Product Licensing for Framatome Inc. (formally known as AREVA Inc.), and as such I am authorized to execute this Affidavit.

2.

I am familiar with the criteria applied by Framatome to determine whether certain Framatome information is proprietary. I am familiar with the policies established by Framatome to ensure the proper application of these criteria.

3.

I am familiar with the Framatome information contained in Engineering Information Record 51-9384385-001, entitled, PWSCC Evaluation for Alloy 600 in ANO-2 CEDM Penetration No. 71 IDTB Weld Repair. referred to herein as this Document.

Information contained in this Document has been classified by Framatome as proprietary in accordance with the policies established by Framatome for the control and protection of proprietary and confidential information.

4.

This Document contains information of a proprietary and confidential nature and is of the type customarily held in confidence by Framatome and not made available to the public. Based on my experience, I am aware that other companies regard information of the kind contained in this Document as proprietary and confidential.

5.

This Document has been made available to the U.S. Nuclear Regulatory Commission in confidence with the request that the information contained in this Document be withheld from public disclosure. The request for withholding of proprietary information is made in accordance with 10 CFR 2.390. The information for which withholding from disclosure is requested qualifies under 10 CFR 2.390(a)(4) Trade secrets and commercial or financial information.

6.

The following criteria are customarily applied by Framatome to determine whether information should be classified as proprietary:

(a)

The information reveals details of Framatomes research and development plans and programs or their results.

(b)

Use of the information by a competitor would permit the competitor to significantly reduce its expenditures, in time or resources, to design, produce, or market a similar product or service.

(c)

The information includes test data or analytical techniques concerning a process, methodology, or component, the application of which results in a competitive advantage for Framatome.

(d)

The information reveals certain distinguishing aspects of a process, methodology, or component, the exclusive use of which provides a competitive advantage for Framatome in product optimization or marketability.

(e)

The information is vital to a competitive advantage held by Framatome, would be helpful to competitors to Framatome, and would likely cause substantial harm to the competitive position of Framatome.

The information in this Document is considered proprietary for the reasons set forth in paragraphs 6(b), 6 (c), 6(d), and 6(e) above.

7.

In accordance with Framatomes policies governing the protection and control of information, proprietary information contained in this Document has been made available, on a limited basis, to others outside Framatome only as required and under suitable agreement providing for nondisclosure and limited use of the information.

8.

Framatome policy requires that proprietary information be kept in a secured file or area and distributed on a need-to-know basis.

9.

The foregoing statements are true and correct to the best of my knowledge, information, and belief.

I declare under penalty of perjury that the foregoing is true and correct.

Executed on October 31, 2024.

Philip A. Opsal Manager, Product Licensing, Framatome Inc.

Philip A. Opsal to 2CAN112403 Affidavit for "ANO-2 CEDM Number 71 IDTB Weld Repair One-Cycle Justification,"

Document Number 32-9384450-000 (3 pages)

to 2CAN112403 Affidavit for "ANO-2 CEDM Penetration 71 Modification As-Left J-Groove Weld One Cycle Justification," Document Number 32-9384449-000 (3 pages)

0 to 2CAN112403 Affidavit for "OCJ IDTB Weld Anomaly Assessment at CEDM Nozzle No. 71 at ANO 2,"

Document Number 32-9384443-000 (3 pages)

1 to 2CAN112403 Corrosion Evaluation of ANO-2 RVCH CEDM IDTB Weld Nozzle Penetration Repair Document Number 51-9384465-001 NON-PROPRIETARY (27 pages)

20004-028 (03/26/2024)

Page 1 of 27 Framatome Inc.

Engineering Information Record Document No.:

51 9384465 -

001 Corrosion Evaluation of ANO-2 RVCH CEDM IDTB Weld Nozzle Penetration Repair EXPORT CONTROLLED INFORMATION Contains technology subject to U.S. export controls governed by the Export Administration Regulations (15 CFR Part 730 et seq.) and/or the Department of Energy Regulations (10 CFR Part 810). Diversion contrary to U.S. law is prohibited.

Export Classification US EC: N Part 810 EAR ECCN: N/A Controlled Document

20004-028 (03/26/2024)

Document No.: 51-9384465-001 Corrosion Evaluation of ANO-2 RVCH CEDM IDTB Weld Nozzle Penetration Repair Page 2 Safety Related? YES NO Does this document establish design or technical requirements? YES NO Does this document contain assumptions requiring verification? YES NO Does this document contain Customer Required Format?

YES NO Signature Block Name and Title Signature and Date Role Scope/Comments John Neil Engineer IV P

All Trevor Eggleston Engineer I M

All Sarah Davidsaver Advisory Engineer R

All Craig Wicker Materials and Fracture Mechanics Supervisor A

All Mike Epling Project Manager PM Approval of Customer References Role Definitions:

P/R/A designates Preparer (P), Reviewer (R), Approver (A);

LP/LR designates Lead Preparer (LP), Lead Reviewer (LR);

M designates Mentor (M);

PM designates Project Manager (PM)

 





 

 






 






 





 


 



Controlled Document

20004-028 (03/26/2024)

Document No.: 51-9384465-001 Corrosion Evaluation of ANO-2 RVCH CEDM IDTB Weld Nozzle Penetration Repair Page 3 Record of Revision Revision No.

Pages/Sections/

Paragraphs Changed Brief Description / Change Authorization 000 All Initial Issue. The Proprietary version of this document is 51-9384397-000 001 All The Proprietary version of this document is 51-9384397-001 Controlled Document

Document No.: 51-9384465-001 Corrosion Evaluation of ANO-2 RVCH CEDM IDTB Weld Nozzle Penetration Repair Page 4 Table of Contents Page SIGNATURE BLOCK................................................................................................................................ 2 RECORD OF REVISION.......................................................................................................................... 3 LIST OF TABLES..................................................................................................................................... 5 LIST OF FIGURES................................................................................................................................... 6 1.0 PURPOSE..................................................................................................................................... 7 2.0 ASSUMPTIONS............................................................................................................................ 7 2.1 Assumptions Requiring Verification................................................................................... 7 2.2 Justified Assumptions........................................................................................................ 7

3.0 BACKGROUND

............................................................................................................................ 8 3.1 Contingencies..................................................................................................................11 3.1.1 Shallow Cut Contingency Case........................................................................11 3.1.2 Overbore Contingency Case............................................................................11 4.0 INDUSTRY OCCURRENCES OF EXPOSED CARBON/LOW ALLOY STEEL BASE METAL........................................................................................................................................11 5.0 CORROSION OF LOW ALLOY STEEL EXPOSED TO RCS.....................................................12 5.1 General Corrosion...........................................................................................................12 5.1.1 General Corrosion Experimental Data..............................................................13 5.1.2 Oxygen Concentration in the Modified Area.....................................................13 5.1.3 Pressure Boundary Leakage (Wastage)..........................................................14 5.1.4 General Corrosion Rates..................................................................................14 5.1.5 Long Term General Corrosion Projection.........................................................15 5.2 Crevice Corrosion............................................................................................................16 5.3 Galvanic Corrosion..........................................................................................................17 5.4 Stress Corrosion Cracking..............................................................................................17 5.5 Hydrogen Embrittlement..................................................................................................18 6.0 CORROSION OF ALLOY 690 AND FILLER METAL ALLOY 52M.............................................18 6.1 General Corrosion...........................................................................................................18 6.2 Crevice Corrosion............................................................................................................18 6.3 Galvanic Corrosion..........................................................................................................18 6.4 Low Temperature Crack Propagation.............................................................................19 6.5 Stress Corrosion Cracking..............................................................................................19 7.0

[

]...............................................20

8.0 CONCLUSION

S..........................................................................................................................20

9.0 REFERENCES

............................................................................................................................22 APPENDIX A : [

]............................................................................................. A-1 Controlled Document

Document No.: 51-9384465-001 Corrosion Evaluation of ANO-2 RVCH CEDM IDTB Weld Nozzle Penetration Repair Page 5 List of Tables Page Table 5-1: Combined General Corrosion Rates for [

]........................................................................................14 Controlled Document

Document No.: 51-9384465-001 Corrosion Evaluation of ANO-2 RVCH CEDM IDTB Weld Nozzle Penetration Repair Page 6 List of Figures Page Figure 3-1: Existing Configuration of ANO-2 RVCH CEDM Penetration #71 [3]......................................9 Figure 3-2: Repair Configuration of ANO-2 RVCH CEDM Penetration #71 [3]......................................10 Figure 5-1: Shortest Distance from Crevice Edge through RVCH Base Metal [3]..................................16 Document

Document No.: 51-9384465-001 Corrosion Evaluation of ANO-2 RVCH CEDM IDTB Weld Nozzle Penetration Repair Page 7 1.0 PURPOSE This document evaluates potential corrosion concerns arising from the final configuration of the inside diameter temper bead (IDTB) weld repair of control element drive mechanism (CEDM) Nozzle #71 at Arkansas Nuclear One Unit 2 (ANO-2) [1, 2, 3], as required by Section 4.7.6 of Reference [2]. The evaluations performed herein are applicable for one cycle (18 months from the time of the repair) as defined in Reference [2]. The materials with potential corrosion concerns evaluated within this document include the exposed low alloy steel (LAS), SA-533 Grade B Class 1, of the RV closure head (RVCH) as well as the new materials, which include the Alloy 52M IDTB weld, the Alloy 690 replacement CEDM half-nozzle, the [

] replacement CEDM nozzle guide, and the Alloy 52M fillet weld joining the replacement nozzle to the replacement guide [

] In evaluating the potential corrosion concerns, this document will provide an estimate of the expected corrosion rate of the exposed LAS affected by the repair. The only corrosion mechanism that is not to be evaluated in this document is primary water stress corrosion cracking (PWSCC) of the remaining original Alloy 600 nozzle, which is evaluated separately in Reference [4].

The repair contingencies given in Reference [3] are discussed in Section 3.1.

2.0 ASSUMPTIONS 2.1 Assumptions Requiring Verification There are no assumptions requiring verification.

2.2 Justified Assumptions 1.

It is assumed that ANO-2 will maintain reactor coolant system (RCS) primary water chemistry in accordance with EPRI PWR Primary Water Chemistry Guidelines during the life of the repair. The utility has confirmed adherence to Revision 7 [5] of the guidelines (see Appendix A).

2.

The corrosion rate calculated in Section 5.1.4 is assumed to be conservative, based on the following:

Controlled Document

Document No.: 51-9384465-001 Corrosion Evaluation of ANO-2 RVCH CEDM IDTB Weld Nozzle Penetration Repair Page 8

3.0 BACKGROUND

Since 2000, several RVCH nozzles at U.S. pressurized water reactors (PWRs) have reported indications which have been attributed to PWSCC. During the Fall 2024 outage (2R30), as a part of the ultrasonic test (UT) examination for the in-service inspection at ANO-2, an axial indication was discovered in the outer portion of the nozzle of Control Element Drive Mechanism (CEDM) penetration #71 on the RVCH. Subsequently, an outside diameter surface dye penetrant test (PT) in the area of the UT indication confirmed a surface breaking indication on the J-groove weld.

Entergy Nuclear Corporation (Owner) contracted Framatome to repair the nozzle [2]. Framatome previously performed a similar repair process at ANO-2 for CEDM penetration #46 during the Fall 2021 (2R28) outage

[8]. The corresponding corrosion evaluation for that modification is Reference [9].

The current configuration is shown in Figure 3-1. Framatome will perform an IDTB weld repair of this nozzle, as shown in Figure 3-2. [

]

This repair method will create a crevice between the clearance fit Alloy 690 lower half-nozzle and the LAS of the RVCH base metal in the bore (Location A, Figure 3-2) and counterbore (Location B, Figure 3-2) regions. The crevice will extend from the original nozzle J-groove welds (considered non-structural following this repair) on the inner surface of the RVCH to the new IDTB weld, exposing the existing LAS material to the RCS. [

]

Subsequent to the IDTB weld modification of ANO-2 RVCH CEDM penetration #71, corrosion concerns for the new configuration must be evaluated. These include:

x Existing SA-533 Grade B Class 1 material, now exposed to the RCS.

x The new Alloy 690 (SB-167, UNS N06690) half-nozzle, partially replacing the existing Alloy 600 nozzle.

x The new Alloy 52M (UNS N06054) IDTB weld, securing the nozzle and forming the new pressure boundary.

x The new [

] CEDM guide, threaded to the end of the replacement nozzle.

x The new Alloy 52M (UNS N06054) intermittent fillet weld, preventing rotation of the CEDM guide.

Controlled Document

Document No.: 51-9384465-001 Corrosion Evaluation of ANO-2 RVCH CEDM IDTB Weld Nozzle Penetration Repair Page 9 Figure 3-1: Existing Configuration of ANO-2 RVCH CEDM Penetration #71 [3]

Controlled Document

Document No.: 51-9384465-001 Corrosion Evaluation of ANO-2 RVCH CEDM IDTB Weld Nozzle Penetration Repair Page 10 Figure 3-2: Repair Configuration of ANO-2 RVCH CEDM Penetration #71 [3]

Controlled Document

Document No.: 51-9384465-001 Corrosion Evaluation of ANO-2 RVCH CEDM IDTB Weld Nozzle Penetration Repair Page 11 3.1 Contingencies Two repair contingency cases have been developed by Framatome in Reference [3].

3.1.1 Shallow Cut Contingency Case

[

] Execution of this contingency will not affect the conclusions of this document (see Section 8.0).

3.1.2 Overbore Contingency Case

[

] Execution of this contingency will not affect the conclusions of this document (see Section 8.0).

4.0 INDUSTRY OCCURRENCES OF EXPOSED CARBON/LOW ALLOY STEEL BASE METAL The carbon or LAS components in the pressurizer (PZR), reactor vessel (RV), and steam generator (SG) exposed to pressurized water reactor (PWR) RCS primary coolant are clad with either stainless steel or nickel-base alloy to prevent corrosion of the base metal. Throughout the operating history of domestic PWRs, there have been many cases where a localized area of the carbon or LAS base metal has been exposed to the PWR RCS primary coolant due to damage to the cladding or a repair configuration. Several instances are listed in Reference [10], which includes repairs over the last approximately 20 years. Details of some examples are listed below (see Reference [10] unless otherwise noted):

1960s Yankee-Rowe RV - Surveillance capsules fell from holder assemblies to the bottom of the vessel, releasing test specimens and other debris, leading to perforations in the cladding.

1990 ANO Unit 1 PZR - A leak was detected at the PZR upper-level tap nozzle within the steam space in December 1990. The repair consisted of removing the outer section of the nozzle followed by welding a new section of nozzle to the OD of the PZR. (LER 313-1990-021) 1991 Oconee-Unit 1 SG - A misdrilled tubesheet hole in the upper tubesheet of one SG, during plugging operation in 1991, led to exposure of a small area of unclad tubesheet to primary coolant. (Note: This area of the tubesheet has since been patched and is no longer exposed to coolant). (ONS-1 generators were subsequently replaced in 2004 [11].)

1994 Calvert Cliffs-Unit 1 PZR - Two leaking heater nozzles in the lower head of the PZR were partially removed and the penetrations were plugged in 1994. (LER 317-1994-003) 1997 Oconee-Unit 1 OTSG manway - During the end-of-cycle (EOC) 17 refueling outage, a degraded area was observed in the bore of the 1B once through steam generator (OTSG). Subsequent inspection revealed a

[

] long circumferential damaged area to the cladding surface of the manway opening. The exposure of the base metal was confirmed by etching. (ONS-1 generators were subsequently replaced in 2004 [11].)

2001 CRDM repairs at Oconee Unit 2, Oconee Unit 3, Crystal River Unit 3, Three Mile Island Unit 1, and Surry Unit 1. (LER 270-2001-002, 287-2001-003, 302-2001-004, 289-2001-002, 280-2001-003) 2002 CRDM repairs at Oconee Unit 1 and Oconee Unit 2. (LER 269-2002-003, 270-2002-002)

Controlled Document

Document No.: 51-9384465-001 Corrosion Evaluation of ANO-2 RVCH CEDM IDTB Weld Nozzle Penetration Repair Page 12 2003 CRDM/CEDM repairs at St. Lucie Unit 2 and Millstone Unit 2, half nozzle repairs of STP-1 bottom mounted instrument nozzles, half nozzle repairs of PZR instrument nozzles at Crystal River Unit 3. (LER 389-2003-002, 498-2003-003, 302-2003-003) 2005 Half-nozzle modification for the TMI-1 PZR vent nozzle.

2013 Half-nozzle repair on RV bottom-mounted instrument nozzles after a leak was identified at Palo Verde Generating Station, Unit 3. (LER 2013-001-01) 2017 Half-nozzle repair on RV head instrument nozzle after a leak was identified at Limerick Generating Station, Unit 2. (LER 2017-004-01) 2017 Catawba Unit 2, SG D hot leg channel head visual inspection identified an area of missing and/or thin cladding [12].

2020 Half-nozzle repair on reactor pressure vessel instrument nozzle after a leak was identified at Peach Bottom Atomic Power Station Unit 2. (LER 2020-002-00) 2021 Half-nozzle repair on RVCH CEDM nozzle after a leak was identified at ANO-2 [9].

2023 Nozzle repair on PZR thermowell after a boric acid leak was identified at Palo Verde Nuclear Generating Station Unit 1. (LER 50-528/2023-002-00)

In most of these instances, carbon or LAS base metal was exposed to primary coolant in a localized area. Each plant returned to normal operation with the base metal exposed; in the case of Yankee-Rowe, the vessel operated for approximately 30 years with the base metal exposed.

5.0 CORROSION OF LOW ALLOY STEEL EXPOSED TO RCS As a result of the modified configuration of CEDM nozzle #71, areas of LAS base metal will be exposed to the RCS in the small gap between the new lower nozzle and the inside of the RVCH penetration bore. Several types of corrosion can occur when LAS is exposed to primary coolant.

During normal operating conditions, the primary coolant is deaerated at high temperatures (343°C [650°F] design temperature [2]) depending on the location within the RCS. Depending on the clearance between the new lower nozzle and the RVCH (see Figure 3-2, Locations A and B), the space may be [

]

The following sections discuss the possible corrosion mechanisms for the exposed LAS base metal at Locations A and B, adjacent to the new lower nozzle.

5.1 General Corrosion General corrosion is defined as deterioration of a surface by electrochemical reactions with the environment wherein the corrosion rate is uniform across the surface exposed to the environment. Stainless steels and nickel-base alloys (such as wrought Type 304, Type 316, Alloy 600, and Alloy 690 and their equivalent weld metals) have very low susceptibility to general corrosion in PWR RCS environments due to their passive oxide films.

Carbon and LASs, however, may be susceptible to general corrosion, depending on the service environment. The major factors impacting susceptibility to general corrosion in these alloy systems are flow rate, temperature, water chemistry (including boric acid concentration), and time. General corrosion rates of carbon and LAS in aerated and deaerated conditions are discussed below.

Controlled Document

Document No.: 51-9384465-001 Corrosion Evaluation of ANO-2 RVCH CEDM IDTB Weld Nozzle Penetration Repair Page 13 This discussion on general corrosion is applicable to both the LAS base metal and heat-affected zone (HAZ) associated with the IDTB weld. The general corrosion rate of carbon and LASs in a specific environment depends on the corrosion potential, which depends on the chemical composition. The corrosion potential (and hence the general corrosion rate) is insensitive to the heat treatment condition, such as the presence of an HAZ created by welding. The past exposures cited in Section 4.0 resulted from repairs involving welding, which would have produced a HAZ in the exposed carbon or LAS base metal. The base metal exposed due to cladding penetrations in Yankee-Rowe were examples of LAS HAZ exposed to the RCS.

5.1.1 General Corrosion Experimental Data Many studies [13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23] have reported corrosion rates of carbon and LASs in high temperature water. In many of the studies, the corrosion rates for carbon and LASs have been observed to be similar; this data is applicable to materials such as SA-302, SA-533, and SA-516 [14, 15, 16, 20]. The Electric Power Research Institute (EPRI) has also compiled a handbook [7] on boric acid corrosion. This handbook summarizes the industry field experience with boric acid corrosion incidents, a discussion of boric acid corrosion mechanisms, and a compilation of prior boric acid corrosion testing and results.

One evaluation was completed in response to the Yankee-Rowe incident (noted in Section 4.0); in the evaluation, ASTM A 302 Grade B LAS was exposed to primary coolant in aerated and deaerated conditions [24]. It was shown that under deaerated conditions (i.e., during operation), the corrosion rate depended on temperature, fluid velocity, boric acid concentration, and time. In that evaluation, a corrosion rate of 0.0009 ipy was used, because it bounded flow conditions both at the opening of the hole (10 ft/sec) as well as the semi-static (i.e., stagnant) conditions within the crevice, wherein ionic movement is diffusion controlled. In the same study under shutdown conditions (aerated, low temperature [~70°F]), the maximum corrosion rate was determined to be 0.0015 inch for a two-month shutdown, or 0.009 ipy [24].

[

]

Other studies have investigated the general corrosion rate of carbon and LASs in borated water. The corrosion rate at reactor startup for SA-533 GR B and SA-508 Class 2 was determined to be a maximum of 0.019 ipy, with an average of ~0.017 ipy, based on a 70-hour experiment at 350 in an aerated solution of 723 ppm boron, 1.8 ppm Li (as LiOH), and 0.4 ppm ammonia [25]1. At 200 in aerated 1% boric acid solution (1730 ppm B), the corrosion rate of the steel was 0.0147 to 0.0157 ipy [7]. At 70, the corrosion rate was shown to be significantly lower, approximately 0.002 ipy [7].

5.1.2 Oxygen Concentration in the Modified Area Oxygen level will be minimal during operation as it is strictly controlled by RCS chemistry during operating conditions. In PWRs, hydrogen is dissolved into the primary coolant water to prevent the accumulation of oxidizing products [26]. Radiological dissociation of water is effectively suppressed via the addition of hydrogen

[27]. Experiments have shown that the actual concentration of hydrogen used in PWRs is higher than that 1 Table 2 of Reference [25] appears to contain two typographical errors: the title of Table 2 reads Corrosion Rates of Low Alloy Steels in Borated Water at 300 and Note (1) of Table 2 states 773 PPM B in Test. The description of the borated water autoclave tests states that these tests were conducted at 350 with a boron concentration of 723 ppm B. Thus, it is assumed that the title of Table 2 should say Corrosion Rates of Low Alloy Steels in Borated Water at 350 and Note (1) of Table 2 should say 723 PPM B in Test.

Controlled Document

Document No.: 51-9384465-001 Corrosion Evaluation of ANO-2 RVCH CEDM IDTB Weld Nozzle Penetration Repair Page 14 required to avoid radiolysis of water [26]. The local hydrogen content is not expected to differ from that of the main coolant due to the likely high mobility of hydrogen at normal operating temperature. Oxygen may enter the RCS during shutdown, but any that becomes trapped in the modified nozzle during shutdown will quickly be consumed by corrosion of the LAS during startup.

5.1.3 Pressure Boundary Leakage (Wastage)

Several other incidents and investigations exist regarding the degradation of carbon and LASs due to primary coolant exposure outside the pressure boundary. Exposure occurred in an unpressurized environment whereby specimens were exposed to significantly greater concentrations of aerated boric acid solutions at varying temperatures [7, 28, 35]. The general corrosion or wastage rates observed in these types of events are orders of magnitude higher (on the order of inches per year) than those observed within the controlled environment of the RCS, wherein primary coolant is typically not aerated and boric acid concentrations do not increase. The maximum corrosion rates were observed at the point where fluid leaks from an annulus [7]; i.e., wastage is pressure boundary leak dependent.

[

] Therefore, gross wastage of LAS is not a credible mechanism for the repaired configuration and is not a concern for the exposed LAS at Locations A and B.

5.1.4 General Corrosion Rates

[

] Based on the corrosion rates for each reactor condition discussed above, the calculated combined corrosion rate is shown below and is bounding for Locations A and B.

Table 5-1: Combined General Corrosion Rates for [

]

Controlled Document

Document No.: 51-9384465-001 Corrosion Evaluation of ANO-2 RVCH CEDM IDTB Weld Nozzle Penetration Repair Page 15 5.1.5 Long Term General Corrosion Projection The corrosion rate for the exposed LAS is conservatively estimated to be [

]

The presence of manganese sulfide (MnS) in LASs and the effects of their exposure to primary coolant have been addressed elsewhere [29]. In Reference [29], which evaluated the acceptability of MnS laminations in RV head penetration weld repairs, it was concluded that MnS laminations [

]

Controlled Document

Document No.: 51-9384465-001 Corrosion Evaluation of ANO-2 RVCH CEDM IDTB Weld Nozzle Penetration Repair Page 16 Figure 5-1: Shortest Distance from Crevice Edge through RVCH Base Metal [3]

5.2 Crevice Corrosion The clearance created by the modified configuration at Locations A and B (see Figure 3-2 and Section 3.0 for additional detail) between the CEDM nozzle and the RVCH wall creates the geometry of a crevice (high aspect ratio). The environmental conditions in a crevice can become aggressive with time and can cause accelerated local corrosion. Experiments were conducted to determine the crevice corrosion rate of LAS in primary water, and the results indicate that the crevice corrosion rate for both aerated and deaerated conditions is less than the respective general corrosion rate [18, 24]. Operating experience from PWRs and Naval reactor programs shows that crevice corrosion is not normally a concern in PWR systems [21].

Several corrosion studies have examined crevice corrosion in the gaps between [

]

There is evidence that crevice corrosion is not a common concern in PWR systems, the rate of crevice corrosion has been experimentally shown to be lower than that of the general corrosion rate of carbon and LASs in primary coolant, and operating experience shows crevices becoming filled with corrosion product over time. Therefore, crevice corrosion is not expected to be a concern for the applicable period, specified to be 18 months of operation.

Controlled Document

Document No.: 51-9384465-001 Corrosion Evaluation of ANO-2 RVCH CEDM IDTB Weld Nozzle Penetration Repair Page 17 5.3 Galvanic Corrosion Galvanic corrosion may occur when two dissimilar metals in contact are exposed to a conductive solution or coupled together. The larger the electrochemical potential (ECP) difference between the two metals, the greater the likelihood of galvanic corrosion occurring. Low alloy steel is more anodic than nickel-base alloys [32] and could therefore be subject to galvanic attack when coupled and exposed to reactor coolant.

Several corrosion tests were performed to determine the influence of coupling between LAS and austenitic stainless steel. Passive austenitic stainless steels are only slightly lower on the galvanic series (i.e., more cathodic) than the passive Alloy 690 nickel-based alloys used in these modifications [32]. Therefore, galvanic corrosion studies of LAS and stainless steel give insight into the galvanic corrosion of LAS and nickel-based alloys.

Specimens made from 5% chromium steel coupled to Type 304 stainless steel were exposed to aerated water at 260°C (500°F) for 85 days (~2000 hours) with no evidence of galvanic corrosion. In the test above, the corrosion rates were not affected by coupling [22]. Results of the NRCs boric acid corrosion test program have shown that the ECP difference between ASTM A533 Grade B (LAS), Alloy 600, and Type 308 stainless steel is not significant enough to consider galvanic corrosion as a strong contributor to the overall boric acid corrosion process [33]. Additionally, galvanic corrosion rates of carbon steel coupled to stainless steel in boric acid solution in the absence of oxygen is about equal to the general corrosion rate [24].

Other investigations were performed for alloy steels coupled (i.e., welded) to stainless steels and exposed to high purity water for 1000 hours0.0116 days <br />0.278 hours <br />0.00165 weeks <br />3.805e-4 months <br /> at 546°F in steam, steam/water, saturated water, and sub-cooled water in aerated and deaerated conditions [13]. Again, the coupled specimen did not exhibit any accelerated rates of corrosion. In each of the tests described above, corrosion rates were not affected by coupling and will not affect the corrosion rates discussed in Section 5.1.

Given the lack of evidence that the corrosion rates of low alloy/carbon steel are increased when coupled to nickel-based alloys or austenitic stainless steel alloys in PWR systems, galvanic corrosion is not expected to be a concern for the applicable period, specified to be 18 months of operation.

5.4 Stress Corrosion Cracking Stress corrosion cracking (SCC) can occur only when the following three conditions are present: (1) a susceptible material, (2) a tensile stress, and (3) an aggressive environment.

Under normal PWR conditions (deaerated), primary water is not a particularly aggressive environment for low alloy/carbon steel unless a departure from normal operating conditions occurs [34]. This result is attributed to the characteristics of the PWR environment including its very low oxygen levels, hydrogen over pressure, and low conductivity. This service environment (i.e., deaerated with low sulfate and chloride content) does not generally support localized corrosion of low alloy/carbon steel; therefore, the likelihood of a pit or notch forming which would contribute a stress concentrator or SCC initiation site is negligible.

A review of the relevant laboratory work and field experience appears in a report prepared for the Combustion Engineering (CE) Owners Group [35]. The conclusion of this report is that, considering the environmental conditions present in a PWR, LAS and carbon steel will not be subject to SCC. In addition, there are field experiences that support these observations. Noteworthy is SCC revealed in the stainless steel cladding in charging pumps [36]. The interdendritic cracks, present in the cladding, were determined to have blunted at the clad/LAS interface with no evidence of significant general, crevice, or galvanic corrosion.

Based on experimental evidence and operating experience showing that SCC of low alloy/carbon steel is not expected based on the typical conditions found in PWR primary systems, SCC of the exposed SA-533 LAS is not expected to be a concern for the applicable period, specified to be 18 months of operation.

Controlled Document

Document No.: 51-9384465-001 Corrosion Evaluation of ANO-2 RVCH CEDM IDTB Weld Nozzle Penetration Repair Page 18 5.5 Hydrogen Embrittlement Hydrogen embrittlement in LASs results from excessive amounts of hydrogen in a metals crystal lattice. This type of damage is a mechanical/environmental failure process, which usually occurs in combination with a stress:

residual, applied, or otherwise. Hydrogen embrittlement is observed most often in plastically deformed metals or high-pressure hydrogen environments and is characterized by ductility losses and lowering of the fracture toughness [32]. High pressure hydrogen environments are not typical of PWRs. Hydrogen exists within the RCS (used as an oxygen scavenger) and is expected to accumulate at locations such as the top of the PZR. Corrosion tests on LAS in deaerated boric acid solutions indicated that the maximum concentration of hydrogen in the steel from corrosion was less than 2 ppm and did not increase with time [37]. The quantity of hydrogen that may accumulate at locations within the RCS is not expected to induce hydrogen embrittlement in materials at those locations. Additionally, lower strength, high toughness low alloy/carbon steels (such as the SA-533 Grade B Class 1 considered herein) - are not particularly susceptible to hydrogen stress cracking at normal operating temperatures [24, 32, 38].

Therefore, hydrogen embrittlement is not expected to be a concern for the exposed LAS for the life of this repair.

6.0 CORROSION OF ALLOY 690 AND FILLER METAL ALLOY 52M Several types of corrosion can potentially occur when austenitic nickel-base alloy base/weld metals are exposed to primary coolant. During operating conditions, the primary coolant is deaerated at high temperatures (343°C

[650°F] design temperature [2]), depending on the location within the RCS. With respect to the Alloy 690 CEDM half-nozzle component, the primary coolant will be [

] The following subsections discuss the potential corrosion mechanisms for the Alloy 690 base and Alloy 52M weld metal shown in Figure 3-2.

6.1 General Corrosion General corrosion is defined as uniform deterioration of a surface by chemical or electrochemical reactions with the environment. Nickel-base alloys (e.g., Alloy 600, Alloy 690, and their equivalent weld metals) are utilized in PWR and boiling water reactor (BWR) systems because they have low susceptibility to general corrosion due to the formation of a passivating film of various iron, nickel, and chromium oxides [39]. The potentially aerated environment in the RCS during shutdown will be more akin to a BWR environment. To date, there have been no reported instances of issues arising from general corrosion of Alloy 690 in BWR environments, so general corrosion is not expected to be a concern for this alloy for the applicable period, specified to be 18 months of operation.

6.2 Crevice Corrosion The modified CEDM nozzle configuration will create crevice conditions (high aspect ratio) associated with the Alloy 690 nozzle (see Figure 3-2, Locations A and B). However, these nickel-based alloys in general have an excellent resistance to general and crevice corrosion under typical PWR conditions [40, 41]. For the life of this repair, crevice corrosion is not considered a concern for Alloy 690 or the Alloy 52M filler metal.

6.3 Galvanic Corrosion Galvanic corrosion may occur when two different metals in contact are exposed to a conductive solution. As discussed in Section 5.3, galvanic corrosion between LAS and Alloy 690 or Alloy 52M in the PWR environment is not expected to be a concern for the applicable period, specified to be 18 months of operation.

Controlled Document

Document No.: 51-9384465-001 Corrosion Evaluation of ANO-2 RVCH CEDM IDTB Weld Nozzle Penetration Repair Page 19 6.4 Low Temperature Crack Propagation Low temperature crack propagation (LTCP) occurs in nickel-based alloys and is considered a form of hydrogen embrittlement. This type of damage is characterized by a reduction in fracture toughness when exposed to water (particularly hydrogenated) at low temperatures (below 150 (302)). This phenomenon starts from pre-existing sharp cracks, with hydrogen at grain boundaries, and at stress intensity levels greater than a critical value.

While RCS temperatures in the shutdown and startup conditions are low enough to induce LTCP in very high-pressure hydrogen environments, such environments are not typical of PWR systems [42]. Therefore, LTCP is not expected to be a concern for Alloy 690 or Alloy 52M for the applicable period, specified to be 18 months of operation.

6.5 Stress Corrosion Cracking A comprehensive review of testing for the use of Alloy 690 in PWR systems cites numerous investigations and test results under a wide array of conditions, including both primary (high temperature de-oxygenated water) and secondary coolant environments. The first Alloy 690 SG went on-line in May 1989 with no reported failures of tubes as of the date of that publication (August 1997) [40]. To this date there have not been any reported Alloy 690 in-service PWSCC failures. More information on the PWSCC behavior of Alloy 690 can be found in MRP-258 [43].

The various test conditions of different investigations cited in the Alloy 690 literature review included temperatures to 365 (690), dissolved oxygen levels <20 ppb, tests in doped and undoped 400 (752) steam, lithium concentrations up to 20 ppm, chlorides up to 300 ppb, and various heat treatments. Reverse U-bend SCC tests within the above matrix of environmental conditions produced no PWSCC in Alloy 690. No cracking was observed in high purity water containing 16 ppm oxygen at 288 (550), even in a creviced situation. Only slight intergranular cracking of Alloy 690 mill annealed (MA) was observed in slow strain rate testing (SSRT) in 360 (680) high purity deaerated hydrogenated water.

SCC test data comparing results between Alloy 690 and Alloy 600 is available in both aerated and deaerated high temperature water. Test specimens were made from a creviced double U-bend geometry and were tested for 48 weeks at 316 (600). Various Alloy 690 material conditions were tested including MA, MA + thermal treatment (TT), MA followed by solution annealing (SA), cold working (cold rolled 40%), and gas tungsten arc weld (GTAW) welded specimens with matching filler metal. In tests with an environment of 6 ppm oxygen and pH of 10, the control alloys (including Alloy 600 and Alloy 800) readily cracked, whereas Alloy 690 showed no cracking. Additional tests were carried out under deaerated conditions (<20 ppb O2) where Alloy 690 showed no cracking. Other tests were conducted at 360 (680) in deaerated water with a pH of 10 for 60 weeks as part of the same study. Alloy 690 material test conditions included solution annealed (SA) (1010 [1850] and 1120

[2048]) and SA + thermally treated (TT) (1120 [2048] + TT (675 [1247]). Again, no cracking of Alloy 690 was reported [44].

Alloy 52M is a variant filler metal of Alloy 52 that includes a very small amount of boron and zirconium to improve weldability. The SCC resistance of weld metal Alloy 52 was identified as unaffected by a variety of test conditions, including RCS water. No cracking occurred in weld metals containing more than 22 wt% chromium

[40]. One study tested Alloy 52M in accelerated corrosion conditions using a weld mockup that simulated nozzle safe end repairs. The testing consisted of 400°C (752°F) steam plus hydrogen doped with 30 ppm each of fluoride, chloride, and sulfate anions. The hydrogen partial pressure was controlled at approximately 75 kPa with a total steam pressure of 20 MPa. This environment has been previously used to accelerate the simulated PWSCC of nickel-base alloys. After a cumulative exposure of 2051 hours0.0237 days <br />0.57 hours <br />0.00339 weeks <br />7.804055e-4 months <br /> (equivalent to 45.6 EFPY), no environmental degradation was detected on the surface of the Alloy 52M welds. Small micro-fissures on the surface of the Alloy 52M welds, stressed in tension, did not serve as initiation sites for environmental degradation, nor did they propagate during the tests [45]. This study indicates that the Alloy 52M weld metal in the proposed modification has a low susceptibility to PWSCC.

Controlled Document

Document No.: 51-9384465-001 Corrosion Evaluation of ANO-2 RVCH CEDM IDTB Weld Nozzle Penetration Repair Page 20 Some studies have indicated that Alloy 690 SCC crack growth rates (CGRs) can increase dramatically if extensive cold work (especially non-uniform cold work, such as unidirectional rolling) is present [43, 46].

Extensive cold work is not thought to generally be representative of plant components [46], and the extent of cold work to the Alloy 690 nozzle surfaces during machining is expected to be negligible with respect to SCC CGRs.

Alloy 52M is chemically very similar to Alloy 690 [47, 48] and cold work is expected to have a similar effect on SCC CGRs for this alloy. PWSCC growth tests conducted on compact tension Alloy 690 specimens found that stresses in the heavily cold worked surface layers are sufficiently large to increase the probability of PWSCC crack initiation. However, the CGR may become negligibly small or arrest completely if the bulk residual strain is low and the stress intensity factor has not increased significantly [46]. Operations introducing extensive cold work are not anticipated for the Alloy 690 replacement nozzle and/or the Alloy 52M weld for the CEDM nozzle modification.

Based on these studies examining the PWSCC of Alloy 690 and Alloy 52M weld metal, it can be concluded that these two alloys have a low susceptibility to PWSCC. Therefore, PWSCC of Alloy 690 and Alloy 52M is not considered to be a concern in the case of CEDM nozzle modification for the applicable period, specified to be 18 months of operation.

7.0

[

]

8.0 CONCLUSION

S The information provided above describes the potential corrosion mechanisms that may affect ANO-2 RVCH CEDM nozzle #71 resulting from the modified configuration shown in Figure 3-2.

Controlled Document

Document No.: 51-9384465-001 Corrosion Evaluation of ANO-2 RVCH CEDM IDTB Weld Nozzle Penetration Repair Page 21 Galvanic corrosion, hydrogen embrittlement, SCC, and crevice corrosion are not expected to be a concern for the exposed LAS base metal for the applicable period, specified to be 18 months of operation. Based on industry data and Framatomes experience, the general corrosion rate of LAS exposed to the RCS is [

] which is applicable for material at Locations A and B in Figure 3-2.

Wrought Alloy 690 and Alloy 52M filler metal has been shown by extensive testing and in-reactor operating experience to have a low susceptibility to PWSCC and is not susceptible to any other forms of corrosive degradation in the PWR environment. Thus, corrosion of these two alloys is not expected to be a concern for the applicable period.

[

] guide is not expected to be a concern for the applicable period based on the lack of an [

]

Execution of either contingency will not affect the conclusions of this document.

Controlled Document

Document No.: 51-9384465-001 Corrosion Evaluation of ANO-2 RVCH CEDM IDTB Weld Nozzle Penetration Repair Page 22

9.0 REFERENCES

References identified with an (*) are maintained within Entergys Records System and are not retrievable from Framatome Records Management. These are acceptable references per Framatome Administrative Procedure 0402-01, Attachment 7. See page [2] for Project Manager Approval of customer references.

1.

[

]

2.

[

]

3.

[

]

4.

[

]

5.

• Pressurized Water Reactor Primary Water Chemistry Guidelines: Revision 7, Volumes 1 and 2, EPRI, Palo Alto, CA: 2014. 3002000505.

6.

U.S. Nuclear Regulatory Commission, NUREG/CR-6923, Expert Panel Report on Proactive Materials Degradation Assessment, February 2007, NRC Accession Number ML070710257.

7.

• Boric Acid Corrosion Guidebook, Revision 2: Managing Boric Acid Corrosion Issues at PWR Power Stations (MRP-058, Rev 2), 1025145, Electric Power Research Institute, Palo Alto, California, July 2012.

8.

[

]

9.

[

]

10.

McCracken, S., and Patel, A., Elimination of the 48-Hour Hold for Ambient Temperature Temper Bead Welding with Austenitic Weld Metal, PVP2023-107489, Proceedings of the ASME 2023 Pressure Vessels & Piping Conference, Atlanta, Georgia, July 2023.

11.

Unites States Nuclear Regulatory Commission, Oconee Nuclear Station, Unit 1 - Review of Steam Generator Inservice Inspection Report for Unit 1 End of Cycle 30 Refueling Outage (EPID L-2019-LRO-0004), August 26, 2019, NRC Accession Number ML19233A171.

12.

Duke Energy Carolinas, LLC, Duke Energy Carolinas, LLC (Duke Energy), Catawba Nuclear Station (CNS), Unit 2, Facility Operating License Number NPF-52, Docket Number 50-414, End of cycle 21 Refueling Outage Inservice Inspection Report and Steam Generator Inservice Inspection Summary Report, Response to NRC Requests for Additional Information (RAIs), May 24, 2017, NRC Accession Number ML17146A907.

13.

Whitman, G.D., Robinson, G.C., and Savolainen, A.W., A Review of Current Practice in Design, Analysis, Materials, Fabrication, Inspection, and Test, ORNL-NSIC-21, ORNL, December 1967.

Controlled Document

Document No.: 51-9384465-001 Corrosion Evaluation of ANO-2 RVCH CEDM IDTB Weld Nozzle Penetration Repair Page 23

14.

Vreeland, D.C., Gaul, G.G., and Pearl, W.L., Corrosion of Carbon and Low-Alloy Steels in Out-of-Pile Boiling Water Reactor Environment, Corrosion, Vol 17(6), June 1961, p. 269.

15.

Vreeland, D.C., Gaul, G.G., and Pearl, W.L., Corrosion of Carbon and Other Steels in Simulated Boiling Water Reactor Environment: Phase II, Corrosion, Vol 19(10), October 1962, p. 368.

16.

Uhlig, H. H., and Revie, R. W., Corrosion and Corrosion Control, John Wiley & Sons, New York, 1985.

17.

Copson, H.R., Effects of Velocity on Corrosion by Water, Industrial Engineering Chemistry, Vol 44, p.1745, 1952.

18.

Vreeland, D.C., Corrosion of Carbon Steel and Low Alloy Steels in Primary Systems of Water-Cooled Nuclear Reactors, Presented at Netherlands-Norwegian Reactor School, Kjeller, Norway, August 1963.

19.

Pearl, W.C., and G.P. Wozadlo, Corrosion of Carbon Steel in Simulated Boiler Water and Superheated Reactor Environments, Corrosion, Vol 21(8), August 1965, p. 260.

20.

Tackett, D.E., Brown, P.E., and Esper, R.T., Review of Carbon Steel Corrosion Data in High Temperature, High Purity Water in Dynamic Systems, USAEC Report, WAPD-LSR (C)-134, Westinghouse Electric Corporation, October 1955.

21.

DePaul, E.J., ed., Corrosion and Wear Handbook for Water Cooled Reactors, USAEC Report, TID-7006, 1957.

22.

Ruther, W.E., and Hart, R.K., Influence of Oxygen on High Temperature Aqueous Corrosion of Iron, Corrosion, Vol 19(4), April 1963, p. 127t.

23.

[

]

24.

Evaluation of Yankee Vessel Cladding Penetrations, Yankee Atomic Electric Company to the U.S.

Atomic Energy Commission, WCAP-2855, License No. DPR-3, Docket No. 50-29, October 15, 1965.

25.

Hall, J.F., Frisk, R.S., ONeill, A.S., Pathania, R.S., and Neff, W.B., Boric Acid Corrosion of Carbon and Low Alloy Steels, Fourth International Symposium on Environmental Degradation of Materials in Nuclear Power Systems - Water Reactors, p.9-38, 1989.

26.

Pastina, B., Isabey, J., and Hickel, B., The Influence of Water Chemistry on the Radiolysis of the Primary Coolant Water in Pressurized Water Reactors, Journal of Nuclear Materials, 264, 1999, pp.

309-318.

27.

Scott, P., A Review of Irradiation Assisted Stress Corrosion Cracking, Journal of Nuclear Materials, 211, 1994, pp. 101-122.

28.

I. E. Information Notice No.86-108, Degradation of Reactor Coolant System Pressure Boundary Resulting from Boric Acid Corrosion, U. S. Nuclear Regulatory Commission, December 29, 1986.

29.

[

]

30.

[

]

31.

[

]

32.

Corrosion Handbook, 9th Ed., Vol. 13, ASM International, 1987.

Controlled Document

Document No.: 51-9384465-001 Corrosion Evaluation of ANO-2 RVCH CEDM IDTB Weld Nozzle Penetration Repair Page 24 33.

U.S. NRC publication NUREG-1823, U.S. Plant Experience with Alloy 600 Cracking and Boric Acid Corrosion of Light-Water Reactor Pressure Vessel Materials, NRC Accession No. ML051390139.

34.

Scott, P.M, and Tice, D.R., Stress Corrosion in Low Alloy Steels, Nuclear Engineering and Design, Vol 119, 1990.

35.

Hall, J.F., Low-Alloy Steel Component Corrosion Analysis Supporting Small-Diameter Alloy 600/690 Nozzle Repair/Replacement Programs, CE NPSD-1198-NP, Revision 00, February 2001. NRC Accession No. ML010540212.

36.

Cracking in Charging Pump Casing Cladding, IE Information Notice No. 80-38, Nuclear Regulatory Commission, October 1980.

37.

Absorption of Corrosion Hydrogen by A302B Steel at 70F to 500F, WCAP-7099, Westinghouse Electric Corporation, Pittsburgh, Pennsylvania, December 1967.

38.

Anzai, H., Kuniya, J., Kikuchi, E., and Ohnaka, N., Evaluation of Hydrogen Behavior in Low Alloy Steel Under High Temperature Conditions, Fourth International Symposium on Environmental Degradation of Materials in Nuclear Power Systems - Water Reactors, 1989.

39.

Wang, Y., Song, S., Wang, J., Behnamian, Y., Xu, L., Fan, H., and Xia, D.H., Correlation between Passivity Breakdown and Composition of Passive Film Formed on Alloy 690 Studied by Sputtering XPS and FIB-HRTEM, J. Electrochem. Soc., Vol. 166, 2019.

40.

Crum, J.R., and Nagashima, T., Review of Alloy 690 Steam Generator Studies, Eighth International Symposium on Environmental Degradation of Materials in Nuclear Power Systems - Water Reactors, August 1997, Amelia Island, Florida, ANS.

41.

Saito, N., Crevice Corrosion of Austenitic Alloys in High-Temperature Water, Corrosion, Vol 54(9), p.

700, September 1998.

42.

Demma, A., McIlree, A., and Herrera, M., Low Temperature Crack Propagation Evaluation in Pressurized Water Reactor Service, 12th International Conference on Environmental Degradation of Materials in Nuclear Power Systems - Water Reactors, 2005.

43.

Materials Reliability Program: Resistance to Primary Water Stress Corrosion Cracking of Alloy 690 in Pressurized Water Reactors (MRP-258). EPRI, Palo Alto, CA: 2009. 1019086.

44.

Sedriks, A.J., Schultz, J.W., and Cordovi, M.A., Inconel Alloy 690 - A New Corrosion Resistant Material, Boshoku Gijutsu, Japan Society of Corrosion Engineering, Vol 28(2), 1979.

45.

Jacko, R.J., Gold, R.E., and Kroes, A., Accelerated Corrosion Testing of Alloy 52M and Alloy 182 Weldments, 11th International Conference on Environmental Degradation of Materials in Nuclear Power Systems - Water Reactors, August 2003, ANS.

46.

Materials Reliability Program: Recommended Factors of Improvement for Evaluating Primary Water Stress Corrosion Cracking (PWSCC) Growth Rates of Thick-Wall Alloy 690 Materials and Alloy 52, 152, and Variants Welds (MRP-386). EPRI, Palo Alto, CA: 2017. 3002010756.

47.

Standard Specification for Nickel-Chromium-Aluminum Alloys (UNS N06699), Nickel-Chromium-Iron Alloys (UNS N06600, N06601, N06603, N06690, N06693, N06025, N06045, and N06696), Nickel-Chromium-Cobalt-Molybdenum Alloy (UNS N06617), Nickel-Iron-Chromium-Tungsten Alloy (UNS N06674), and Nickel-Chromium-Molybdenum-Copper Alloy (UNS N06235) Plate, Sheet, and Strip, (B168-19). ASTM International, May 2019.

48.

ASME B&PV Code,Section II, Part C, Specifications for Welding Rods, Electrodes, and Filler Metals, 2023 Edition.

Controlled Document

Document No.: 51-9384465-001 Corrosion Evaluation of ANO-2 RVCH CEDM IDTB Weld Nozzle Penetration Repair Page 25

49.

Materials Reliability Program: Stress Corrosion Cracking of Stainless Steel Components in Primary Water Circuit Environments of Pressurized Water Reactors, MRP-236, Revision 1, Electric Power Research Institute, April 2017.

50.

ASM Handbook, Vol. 6: Welding, Brazing and Soldering, ASM International, 1993.

51.

[

]

52.

[

]

Controlled Document

Document No.: 51-9384465-001 Corrosion Evaluation of ANO-2 RVCH CEDM IDTB Weld Nozzle Penetration Repair Page A-1 APPENDIX A: [

]

Controlled Document

Document No.: 51-9384465-001 Corrosion Evaluation of ANO-2 RVCH CEDM IDTB Weld Nozzle Penetration Repair Page A-2 Controlled Document 2 to 2CAN112403 PWSCC Evaluation for Alloy 600 in ANO-2 CEDM Penetration No. 71 IDTB Weld Repair Document Number 51-9384386-001 NON-PROPRIETARY (30 pages)

20004-028 (03/26/2024)

Page 1 of 30 Framatome Inc.

Engineering Information Record Document No.:

51 9384386 -

001 PWSCC Evaluation for Alloy 600 in ANO-2 CEDM Penetration No. 71 IDTB Weld Repair (NP)

EXPORT CONTROLLED INFORMATION Contains technology subject to U.S. export controls governed by the Export Administration Regulations (15 CFR Part 730 et seq.) and/or the Department of Energy Regulations (10 CFR Part 810). Diversion contrary to U.S. law is prohibited.

Export Classification US EC: N Part 810 EAR ECCN: N/A Controlled Document

20004-028 (03/26/2024)

Document No.: 51-9384386-001 PWSCC Evaluation for Alloy 600 in ANO-2 CEDM Penetration No. 71 IDTB Weld Repair (NP)

Page 2 Safety Related? YES NO Does this document establish design or technical requirements? YES NO Does this document contain assumptions requiring verification? YES NO Does this document contain Customer Required Format?

YES NO Signature Block Name and Title Signature and Date Role Scope/Comments Trevor Eggleston Engineer I P

All Sarah Davidsaver Advisory Engineer LR All except Section 5.0 Tomas Straka Advisory Engineer R

Section 5.0 Craig Wicker Materials and Fracture Mechanics Supervisor A

All Mike Epling Project Manager PM Approval of Customer References Role Definitions:

P/R/A designates Preparer (P), Reviewer (R), Approver (A);

LP/LR designates Lead Preparer (LP), Lead Reviewer (LR);

M designates Mentor (M);

PM designates Project Manager (PM)

 






 











 

 





 


 



Controlled Document

20004-028 (03/26/2024)

Document No.: 51-9384386-001 PWSCC Evaluation for Alloy 600 in ANO-2 CEDM Penetration No. 71 IDTB Weld Repair (NP)

Page 3 Record of Revision Revision No.

Pages/Sections/

Paragraphs Changed Brief Description / Change Authorization 000 N/A Original issue of document. Proprietary information is marked by bold brackets. The corresponding proprietary document is 51-9384385-000.

001 Section 1.0 Added purpose of revision. The corresponding proprietary document is 51-9384385-001.

Section 4.0 Added sentence establishing that the evaluation conducted in this section is superseded by the analysis summarized in Appendix B, and that the section is for information only.

Section 6.0 Added conclusions of analysis that supersedes the results of Section 4.0 and removed conclusions from the analysis in Section 4.0.

Section 7.0 Added reference for analysis that supersedes the results of Section 4.0.

Appendix B Added Appendix B supporting results of analysis that supersedes Section 4.0.

Controlled Document

Document No.: 51-9384386-001 PWSCC Evaluation for Alloy 600 in ANO-2 CEDM Penetration No. 71 IDTB Weld Repair (NP)

Page 4 Table of Contents Page SIGNATURE BLOCK................................................................................................................................2 RECORD OF REVISION..........................................................................................................................3 LIST OF TABLES.....................................................................................................................................5 LIST OF FIGURES...................................................................................................................................6 1.0 PURPOSE.....................................................................................................................................7

2.0 BACKGROUND

............................................................................................................................7 3.0 ASSUMPTIONS............................................................................................................................9 3.1 Justified Assumptions........................................................................................................9 3.2 Assumptions Requiring Verification.................................................................................11 4.0 EVALUATION.............................................................................................................................11 4.1 Evaluation of Alloy 600 PWSCC Susceptibility with No Surface Stress Remediation....................................................................................................................12 4.1.1 CEDM Nozzle Repair Modified Wall Thickness................................................12 4.1.2 Estimate of Nozzle Repair Service Life with No Surface Remediation.............13 5.0 JUSTIFICATION FOR EXTENT OF UT INSPECTION...............................................................13

6.0 CONCLUSION

............................................................................................................................16

7.0 REFERENCES

............................................................................................................................17 APPENDIX A :

CORRESPONDENCE WITH ENTERGY OPERATIONS INC. VERIFYING USE OF REVISION 7 OF EPRI PWR PRIMARY WATER CHEMISTRY GUIDELINES........................................................................................................... A-1 APPENDIX B :

SUMMARY

OF ANO-2 CEDM NOZZLE 71 IDTB REPAIR PWSCC FLAW GROWTH EVALUATION........................................................................................ B-1 Controlled Document

Document No.: 51-9384386-001 PWSCC Evaluation for Alloy 600 in ANO-2 CEDM Penetration No. 71 IDTB Weld Repair (NP)

Page 5 List of Tables Page Table B-1: Path Lines Geometry.......................................................................................................... B-4 Table B-2: Maximum Weld Residual + Normal Operating Through-Wall Hoop Stresses Profile in Alloy 600 CEDM Nozzle Near the Alloy 690 IDTB Weld..................................................... B-6 Table B-3: PWSCC Crack Growth Analysis Summary........................................................................ B-7 Table B-4: Detailed PWSCC Crack Growth Analysis.......................................................................... B-8 Controlled Document

Document No.: 51-9384386-001 PWSCC Evaluation for Alloy 600 in ANO-2 CEDM Penetration No. 71 IDTB Weld Repair (NP)

Page 6 List of Figures Page Figure 2-1: CEDM Nozzle Existing (Left) and As-Planned Repair (Right) Configurations (Adapted from [4])................................................................................................................... 8 Figure 2-2: CEDM Nozzle Shallow Cut (Left) and Overbore (Right) Contingency Repair Configurations (Adapted from [4], No Replacement Guide Shown)........................................ 9 Figure 4-1: Alloy 600 SCC CGR as a Function of Stress Intensity Factor (Adapted from [15]).............12 Figure 5-1: [

]......................................16 Figure B-1: Inside Surface-Connected, Partial Through-Wall, Semi-Elliptical Axial Flaw [1]............... B-2 Figure B-2: Path Line Locations [1]..................................................................................................... B-5 Figure B-3: Maximum Weld Residual + Normal Operating Through-Wall Hoop Stresses Profile in Alloy 600 CEDM Nozzle Near the Alloy 690 IDTB Weld [1]............................................ B-6 Controlled Document

Document No.: 51-9384386-001 PWSCC Evaluation for Alloy 600 in ANO-2 CEDM Penetration No. 71 IDTB Weld Repair (NP)

Page 7 1.0 PURPOSE The purpose of this document is to evaluate primary water stress corrosion cracking (PWSCC) for the life of the repair (defined in Reference [1] as one additional 18-month operating cycle) of the original ASME SB-166 (hereafter referred to as Alloy 600) nozzle materials that will remain following the inner diameter temper bead (IDTB) repair of the Arkansas Nuclear One Unit 2 (ANO-2) control element drive mechanism (CEDM)

Penetration No. 71 nozzle. The scope of this evaluation is limited to the Alloy 600 material affected by the repair, as required in Section 4.7.3 of Reference [1], and considers the degradation of the repaired CEDM nozzle without the use of surface stress remediation. The Alloy 600 material affected by the repair is defined as the portion of the original Alloy 600 nozzle remaining following the repair [

]

Additionally, Section 5.0 of this document satisfies a portion of Section 4.7.2 of Reference [1] by justifying that the extent of [

] is sufficient to meet the pre-service volumetric inspection requirements prescribed by ASME Section XI, Division 1, Code Case N-729-6 [2].

The purpose of this revision is to incorporate the results of Reference [3], which evaluates PWSCC flaw growth for the ANO-2 CEDM nozzle No. 71 using the crack growth rate model presented in MRP-420, Revision 1 [15].

The results of Reference [3] supersede the results of Section 4.0.

2.0 BACKGROUND

Past operating experience has shown that Alloy 600 in a pressurized water reactor (PWR) reactor coolant system (RCS) operating environment is susceptible to PWSCC. Starting around 2000, several reactor vessel closure head (RVCH) nozzles at United States (U.S.) PWRs have reported indications which have been attributed to PWSCC.

In response, Framatome developed an automated modification process for repairing indications of PWSCC in PWR RVCH penetrations.

During the Fall 2024 outage (2R30), as part of ultrasonic testing (UT) for the in-service inspection at ANO-2, an axial indication was discovered in the outer portion of the nozzle of CEDM Penetration No. 71 on the RVCH.

Subsequently, an outside diameter (OD) surface dye penetrant test (PT) in the area of the UT indication confirmed a surface breaking indication on the J-groove weld [1]. Due to the aforementioned conditions, Entergy Nuclear Corporation (owner) contracted Framatome to adapt the IDTB modification for ANO-2 CEDM Penetration No.

71. Framatome Inc. has previously performed a similar repair on ANO-2 CEDM Penetration No. 46 during the Fall 2021 outage (2R28).

[

]

Controlled Document

Document No.: 51-9384386-001 PWSCC Evaluation for Alloy 600 in ANO-2 CEDM Penetration No. 71 IDTB Weld Repair (NP)

Page 8 Figure 2-1, adapted from Reference [4], shows the CEDM nozzle existing and as-planned repair configurations.

The as-planned repair configuration figure highlights the remaining Alloy 600 nozzle materials affected by the repair. Figure 2-2, also adapted from Reference [4], shows the CEDM nozzle repair configuration following final machining and NDE in the event that a shallow cut or overbore contingency is performed.

Figure 2-1: CEDM Nozzle Existing (Left) and As-Planned Repair (Right) Configurations (Adapted from [4])

Controlled Document

Document No.: 51-9384386-001 PWSCC Evaluation for Alloy 600 in ANO-2 CEDM Penetration No. 71 IDTB Weld Repair (NP)

Page 9 Figure 2-2: CEDM Nozzle Shallow Cut (Left) and Overbore (Right) Contingency Repair Configurations (Adapted from [4], No Replacement Guide Shown) 3.0 ASSUMPTIONS 3.1 Justified Assumptions 1.

Upon completion of the repair, it is unlikely that PWSCC flaws will be present in the portion of the Alloy 600 CEDM nozzle affected by the repair. [

] The assumption that it is unlikely that PWSCC flaws are present in the remaining Alloy 600 CEDM nozzle affected by the repair is justified for the following reasons: a) it is unlikely that PWSCC flaws were present at these locations prior to this repair, b) if pre-existing PWSCC flaws were present, then non-destructive examinations (NDE) performed over the course of the repair would observe the flaws, and c) if pre-existing PWSCC flaws were present, then such flaws would be removed during the repair process.

a.

It is unlikely that PWSCC flaws were present at these locations prior to the repair because there is no evidence that the factors that have historically caused PWSCC (elevated tensile stress (i) and/or off-chemistry conditions (ii)) were present.

Document

Document No.: 51-9384386-001 PWSCC Evaluation for Alloy 600 in ANO-2 CEDM Penetration No. 71 IDTB Weld Repair (NP)

Page 10 i.

The primary cause of elevated tensile stress in RVCH penetration nozzles is residual stresses from the original J-groove welding process, which only affects the base metal directly adjacent to the weld (see Figure 2-1). [

]

ii.

Off-chemistry conditions have caused PWSCC flaws in RVCH penetration nozzles in relatively low stress locations at one international site where resin ingress caused prolonged periods of high sulfate levels [6]. In response, the Nuclear Regulatory Commission (NRC) requested in Generic Letter (GL) 97-01 [7] that all U.S. PWRs report whether any resin intrusions exceeded the Electric Power Research Institute (EPRI) PWR Water Chemistry Guidelines. Entergy responded to GL 97-01 and the NRC was satisfied with the response [8]. Furthermore, since the ANO-2 Water Chemistry Program follows the EPRI PWR Primary Water Chemistry Guidelines (Revision 7) [9] (see Appendix A for correspondence with Entergy Operations Inc.), in the unlikely event of significant resin intrusion, it would be identified and addressed prior to becoming a concern.

b. [

]

A lack of PT indications is commonly accepted as indicative of a flaw-free surface. While PT has missed reasonably deep cracks in RVCH penetration nozzle welds, it is acknowledged that a higher quality inspection surface may help improve the reliability of the PT exams [10]. [

]

c. [

]

2. [

]

Controlled Document

Document No.: 51-9384386-001 PWSCC Evaluation for Alloy 600 in ANO-2 CEDM Penetration No. 71 IDTB Weld Repair (NP)

Page 11

3. [

]

3.2 Assumptions Requiring Verification No Assumptions Requiring Verification are identified.

4.0 EVALUATION In Revision 001 of this document, the evaluation in this section was superseded by the evaluation performed in Reference [3], which is summarized in Appendix B. This section is included for information only and for historical reference.

Stress corrosion cracking (SCC) requires three synergistic elements to occur: 1) susceptible material, 2) aggressive environment, and 3) sustained tensile stress. Based on laboratory testing and operating experience, Alloy 600 is susceptible to SCC in PWR primary water (i.e., PWSCC) when sufficient tensile stresses are present (typically due to weld residual stresses) [11]. [

] This evaluation solely considers the regions of the remnant Alloy 600 nozzle material affected by the repair that are [

] Additionally, the wall thickness of the Alloy 600 nozzle will be [

] [4]. Therefore, these locations are limiting for failure of the maximum acceptable PWSCC flaw size criteria.

[

] In 2003, the NRC published updated flaw acceptance criteria for PWR RVCH penetration nozzle materials both comprising and below the pressure boundary [12]. These flaw acceptance criteria are applicable to all upper head (i.e., RVCH) penetrations with a nominal OD of eight inches or less, which is true of the nozzle examined herein. As now specified in IWB-3660 of ASME Code Section XI, Division 1 [13], the maximum allowable flaw size is 75% of the original nozzle wall thickness for pressure boundary materials.

In French PWRs, RVCH vessel head penetration (VHP) cracking has been extensively characterized. In 1994, 103 cracks in 20 VHPs on 10 RVCHs were characterized via UT. These cracks were re-inspected after one cycle and their crack growth rates (CGRs) were calculated. The CGRs ranged from 0.000 inch/year (ipy) to 0.159 ipy, with an average of 0.052 ipy [11]. Therefore, the PWSCC flaw growth will conservatively be modeled at a rate of

[

] which bounds most of the crack growth data in Reference [14] and Reference [15], regardless of K value. This CGR is independent of the crack tip stress intensity factor, K. Use of a K-independent CGR to model crack growth for the entire life of the flaw is conservative; a K-independent CGR assumes constant and relatively fast crack growth from the instant a crack initiates, while a K-dependent CGR would suggest slower crack propagation in the early stages of crack growth where K is low. This is illustrated below in Figure 4-1.

Controlled Document

Document No.: 51-9384386-001 PWSCC Evaluation for Alloy 600 in ANO-2 CEDM Penetration No. 71 IDTB Weld Repair (NP)

Page 12 Figure 4-1: Alloy 600 SCC CGR as a Function of Stress Intensity Factor (Adapted from [15])

This evaluation will estimate the service life with respect to PWSCC of the remnant Alloy 600 RVCH penetration material affected by the repair. [

]

4.1 Evaluation of Alloy 600 PWSCC Susceptibility with No Surface Stress Remediation This section estimates the service life of the Alloy 600 material affected by the repair with no surface stress remediation for the as-planned repair and both contingency cases.

4.1.1 CEDM Nozzle Repair Modified Wall Thickness The original Alloy 600 CEDM nozzle has a nominal OD of 4.050 inches and a nominal ID of 2.719 inches [4].

Based on these dimensions, the original wall thicknesses of the CEDM nozzles is:

= 4.050 2.719 2

= 0.666 Controlled Document

Document No.: 51-9384386-001 PWSCC Evaluation for Alloy 600 in ANO-2 CEDM Penetration No. 71 IDTB Weld Repair (NP)

Page 13 As-Planned Repair Shallow Cut and Overbore Contingency Repairs 4.1.2 Estimate of Nozzle Repair Service Life with No Surface Remediation Using Equation 1, the service life with respect to PWSCC of the remnant Alloy 600 CEDM nozzle is estimated below for the as-planned repair as well as the shallow cut and overbore contingency repair cases.

As-Planned Repair:

Shallow Cut and Overbore Contingency Repairs:

5.0 JUSTIFICATION FOR EXTENT OF UT INSPECTION The purpose of this section is to establish the minimum UT inspection extent required to ensure all regions with hoop and axial stresses >20 ksi tensile are volumetrically inspected, as is required by ASME B&PV Code Case N-729-6 [2].

Controlled Document

Document No.: 51-9384386-001 PWSCC Evaluation for Alloy 600 in ANO-2 CEDM Penetration No. 71 IDTB Weld Repair (NP)

Page 14 Controlled Document

Document No.: 51-9384386-001 PWSCC Evaluation for Alloy 600 in ANO-2 CEDM Penetration No. 71 IDTB Weld Repair (NP)

Page 15 Controlled Document

Document No.: 51-9384386-001 PWSCC Evaluation for Alloy 600 in ANO-2 CEDM Penetration No. 71 IDTB Weld Repair (NP)

Page 16 Figure 5-1: [

]

6.0 CONCLUSION

An evaluation of PWSCC initiation and growth was performed for the ANO-2 CEDM nozzle Penetration No. 71 IDTB weld repair process where no surface remediation is performed. Appropriate assumptions were made for the flaw initiation time and crack growth rate. The 75% through-wall flaw acceptance criterion was used.

The results of the evaluation in Appendix B indicate that the remnant Alloy 600 material affected by the repair could exhibit an axial PWSCC flaw through 75% of the original wall thickness relatively quickly. In the as-planned repair configuration, a PWSCC flaw in the remnant Alloy 600 CEDM nozzle is estimated to exceed the through-wall flaw size acceptance criteria at [

] following restart. It is noted that the calculated [

] exceeds the minimum 1.5 EFPY (i.e., one 18-month refueling cycle) service life needed to justify one cycle of operation with the CEDM Penetration No. 71 repaired by the IDTB welding without the use of surface stress remediation.

The required minimum UT inspection extent to ensure all regions with steady state operating stresses (after roll expansion and shakedown) greater than 20 ksi are volumetrically inspected is [

] This length is based on [

] The actual UT inspection extent [

]

Controlled Document

Document No.: 51-9384386-001 PWSCC Evaluation for Alloy 600 in ANO-2 CEDM Penetration No. 71 IDTB Weld Repair (NP)

Page 17

7.0 REFERENCES

References identified with an (*) are retrievable by Arkansas Nuclear One and are not retrievable from Framatome Records Management. These are acceptable references per Framatome Administrative Procedure 0402-01, Attachment 7. See page 2 for Project Manager Approval of customer references.

1.

[

]

2.

ASME B&PV Code, Code Cases, Nuclear Components, Code Case N-729-6, Alternative Examination Requirements for PWR Reactor Vessel Upper Heads with Nozzles Having Pressure-Retaining Partial-Penetration Welds, March 2016, as modified by NRC 10 CFR 50.55a.

3.

[

]

4.

[

]

5.

[

]

6.

NRC Information Notice 96-11, Ingress of Demineralizer Resins Increases Potential for Stress Corrosion Cracking of Control Rod Drive Mechanism Penetrations, February 1996.

7.

NRC Generic Letter 97-01, Degradation of Control Rod Drive Mechanisms Nozzle and other Vessel Closure Head Penetrations, April 1997.

8.

Letter from Thomas W. Alexion, NRC, to Mr. Craig G. Anderson, Entergy Operations, Arkansas Nuclear One Unit 2 RE: Generic Letter 97-01 Degradation of CRDM/CEDM Nozzle and Other Vessel Closure Head Penetrations (TAC No. M98544), ADAMS Accession Number ML003695160, March 23, 2000.

9.

• Pressurized Water Reactor Primary Water Chemistry Guidelines: Revision 7, Volumes 1 and 2, EPRI, Palo Alto, CA: 2014. 3002000505.

10.

NRC Report NUREG/CR-6996 (PNNL-18372), Nondestructive and Destructive Examination Studies on Removed-from-Service Control Rod Drive Mechanism Penetrations, ADAMS Accession Number ML092170313 and ML092170314, July 2009.

11.

Pichon, C., Buisine, D., Faidy, C., Gelpi, A., and Vaindirlis, M., Phenomenon Analysis of Stress Corrosion Cracking in Vessel Head Penetrations of French PWRs, Seventh International Symposium on Environmental Degradation of Materials in Nuclear Power Systems - Water Reactors, August 1995.

12.

Letter from R. Barret to A. Marion, Flaw Evaluation Guidelines, April 11, 2003. ADAMS Accession

1. ML030980322.

13.

ASME B&PV Code,Section XI, Division 1, Rules for Inspection and Testing of Components of Light-Water-Cooled Plants, 2023 Edition.

Controlled Document

Document No.: 51-9384386-001 PWSCC Evaluation for Alloy 600 in ANO-2 CEDM Penetration No. 71 IDTB Weld Repair (NP)

Page 18

14.

Materials Reliability Program: Crack Growth Rates for Evaluation Primary Water Stress Corrosion Cracking (PWSCC) of Thick-Wall Alloy 600 Materials (MRP-55) Revision 1, Electric Power Research Institute, Palo Alto, CA, 2002. 1006695.

15.

Materials Reliability Program: Crack Growth Rates for Evaluation Primary Water Stress Corrosion Cracking (PWSCC) of Thick-Wall Alloy 600 Materials and Alloy 82, 182, and 132 Welds (MRP-420, Revision 1), Electric Power Research Institute, Palo Alto, CA, 2018. 3002014244.

16.

[

]

17.

[

]

18.

[

]

Note that additional references are provided on page B-10 to support the analysis summarized in Appendix B.

Controlled Document

Document No.: 51-9384386-001 PWSCC Evaluation for Alloy 600 in ANO-2 CEDM Penetration No. 71 IDTB Weld Repair (NP)

Page A-1 APPENDIX A:

CORRESPONDENCE WITH ENTERGY OPERATIONS INC. VERIFYING USE OF REVISION 7 OF EPRI PWR PRIMARY WATER CHEMISTRY GUIDELINES Controlled Document

Document No.: 51-9384386-001 PWSCC Evaluation for Alloy 600 in ANO-2 CEDM Penetration No. 71 IDTB Weld Repair (NP)

Page A-2 Controlled Document

Document No.: 51-9384386-001 PWSCC Evaluation for Alloy 600 in ANO-2 CEDM Penetration No. 71 IDTB Weld Repair (NP)

Page B-1 APPENDIX B:

SUMMARY

OF ANO-2 CEDM NOZZLE 71 IDTB REPAIR PWSCC FLAW GROWTH EVALUATION B.1 Purpose References in this appendix are found in Section B.7. The information contained in this appendix is sourced from Reference [1].

This appendix evaluates the PWSCC flaw growth analysis for the IDTB repair of the CEDM nozzle penetration

1. 71 without surface mitigation using the most recent Alloy 600 PWSCC crack growth revised disposition equation presented in Section 6.1.2 of MRP-420, Revision 1 (Reference [4]). The use of MRP-420, Revision 1 is considered appropriate since Alloy 600 PWSCC crack growth rate from MRP-55, Reference [12] predicts a slower growth rate.

The acceptable period of operation is determined based on the predicted crack growth calculated and the acceptance criteria established by ASME Section XI IWB-3663, Reference [2]. This analysis supports the ANO-2 Relief Request for the half-nozzle repair of RVCH penetration #71 (Reference [3]).

B.2 Analytical Methodology This section presents several aspects of the fracture mechanics analysis that form the basis of the present flaw evaluation.

B.2.1 Postulated Flaw Per Reference [6], [

]

[

] This common assumption reasonably bounds plant experience and is conservative based on the limited axial extent of Alloy 600 material having elevated tensile stresses characterized by the stress profile of Figure B-3.

The flaw growth analysis contained herein addresses the growth of the postulated flaw by PWSCC, weld residual stresses, and sustained loads.

Controlled Document

Document No.: 51-9384386-001 PWSCC Evaluation for Alloy 600 in ANO-2 CEDM Penetration No. 71 IDTB Weld Repair (NP)

Page B-2 Figure B-1: Inside Surface-Connected, Partial Through-Wall, Semi-Elliptical Axial Flaw [1]

B.2.2 Stress Intensity Factor (SIF) Solutions For highly nonlinear stress fields such as those due to weld residual stresses, standard stress intensity factor (K) formulas based on third order polynomials are usually not adequate in representing the stresses. This deficiency can be overcome by using the weight function method, which accounts for highly nonlinear stress distributions.

This is a well-established fracture mechanics methodology [

] The technical basis for this implementation is given in Reference [8]. [

] for the postulated flaw and nozzle geometries considered in this analysis, which have been described in Sections B.2.1 and B.4.1.

The stress intensity factors are calculated for both the flaw depth and surface locations (Points 1 and 2 from Figure B-1) according with the methodology [

]

B.2.3 PWSCC Crack Growth Mechanism For the Alloy 600 material, the PWSCC crack growth rate from equation 6-2 of MRP-420, Rev. 1, Reference [4],

is utilized. The Alloy 600 revised disposition equation provided in Section 6.1.2 of Reference [4] was developed from guidance of the full Expert Panel whose approach is documented in Section 2 of Reference [4] and accounts for cold work levels of up to 12% (Section 7 of Reference [4]). Per Section 7.4 of Reference [11], [

]

Controlled Document

Document No.: 51-9384386-001 PWSCC Evaluation for Alloy 600 in ANO-2 CEDM Penetration No. 71 IDTB Weld Repair (NP)

Page B-3 The PWSCC crack growth rate equation for Alloy 600 to be used is given by:

=

1

1

Where:

= crack growth constant at 325°C and 30 cc/kg H2 = 1.19 x 10-13 for da/dt in terms of m/s K

= stress intensity factor in terms of MPa¥m T

= metal temperature (at crack location) in units of Kelvin,

= [

]

Tref

= absolute reference temperature used to normalize data = 598.15 K (325)

= stress intensity factor exponent = 2.0 Q

= thermal activation energy for crack growth = 120 kJ/mol R

= universal gas constant = 0.008314 kJ/mol-K The values of the dissolved hydrogen term fH2 / fH2ref at various temperature and hydrogen concentration [H2]

combinations for Alloy 600 are provided in Table 6-1 of Reference [4]. Values at intermediate temperatures and/or hydrogen concentrations are linearly interpolated.

Per Reference [5], [

]

B.2.4 Methodology for Flaw Growth Analysis For the PWSCC crack growth analysis, the applied stress intensity factor of the postulated axial flaw is [

] The relevant sources of stresses are summarized below and further described in Section B.4.2 of this document.

The PWSCC crack growth of the [

]

The PWSCC crack growth calculations in the Alloy 600 CEDM nozzle are estimated using EXCEL spreadsheet.

[

]

Controlled Document

Document No.: 51-9384386-001 PWSCC Evaluation for Alloy 600 in ANO-2 CEDM Penetration No. 71 IDTB Weld Repair (NP)

Page B-4 B.2.5 Acceptance Criteria The objective of the flaw growth analysis is to establish an acceptable period of operation based on the predicted crack growth calculated and the acceptance criteria defined by ASME Section XI, Reference [2]. Per ASME Section XI IWB-3663, the service life time is determined when the crack grows through 75% of the unmachined original nozzle thickness of 0.666 inch, Reference [10], resulting in an OD nozzle ligament thickness of 0.167 inch when the flaw reaches the acceptance limit. [

]

B.3 Assumptions B.3.1 Unverified Assumptions There are no unverified assumptions in this document.

B.3.2 Justified Assumptions and Modeling Simplifications B.4 Design Inputs B.4.1 Geometry Crack growth analysis is performed along path lines in the Alloy 600 nozzle [

] The basic dimensions for the selected path lines are taken from Reference [10]. Table B-1 lists the selected path lines geometry employed for the flaw growth analysis.

Table B-1: Path Lines Geometry Controlled Document

Document No.: 51-9384386-001 PWSCC Evaluation for Alloy 600 in ANO-2 CEDM Penetration No. 71 IDTB Weld Repair (NP)

Page B-5 B.4.2 Applied Stress

[

]

Per Section C.4 of Reference [6], the effects of [

] on the residual hoop stresses were not included in the results from Figure B-3 and Table B-2 [

] However, based on a comparative evaluation in Reference [6], it was determined that the bounding location for calculating the limiting flaw growth is [

]

Figure B-2: Path Line Locations [1]

Controlled Document

Document No.: 51-9384386-001 PWSCC Evaluation for Alloy 600 in ANO-2 CEDM Penetration No. 71 IDTB Weld Repair (NP)

Page B-6 Figure B-3: Maximum Weld Residual + Normal Operating Through-Wall Hoop Stresses Profile in Alloy 600 CEDM Nozzle Near the Alloy 690 IDTB Weld [1]

Table B-2: Maximum Weld Residual + Normal Operating Through-Wall Hoop Stresses Profile in Alloy 600 CEDM Nozzle Near the Alloy 690 IDTB Weld Controlled Document

Document No.: 51-9384386-001 PWSCC Evaluation for Alloy 600 in ANO-2 CEDM Penetration No. 71 IDTB Weld Repair (NP)

Page B-7 B.5 Calculations and Results Table B-3 summarizes the flaw growth analysis results for the [

] located on the CEDM nozzle #71 and Table B-4 shows the detailed PWSCC crack growth results.

Table B-3: PWSCC Crack Growth Analysis Summary Document

Document No.: 51-9384386-001 PWSCC Evaluation for Alloy 600 in ANO-2 CEDM Penetration No. 71 IDTB Weld Repair (NP)

Page B-8 Table B-4: Detailed PWSCC Crack Growth Analysis Controlled Document

Document No.: 51-9384386-001 PWSCC Evaluation for Alloy 600 in ANO-2 CEDM Penetration No. 71 IDTB Weld Repair (NP)

Page B-9 Controlled Document

Document No.: 51-9384386-001 PWSCC Evaluation for Alloy 600 in ANO-2 CEDM Penetration No. 71 IDTB Weld Repair (NP)

Page B-10 B.6 Conclusions The results of the flaw growth analysis performed to establish an acceptable period of operation based on the predicted crack growth calculated and the acceptance criteria defined by ASME Section XI IWB-3663, Reference

[2], shows that the [

] grows to 75% of the unmachined original nozzle thickness in [

] for the CEDM nozzle #71 without surface mitigation.

B.7 References References identified with an (*) are maintained within ANO-2 Records System and are not retrievable from Framatome Records Management. These are acceptable references per Framatome Administrative Procedure 0402-01, Attachment 7. See page 2 for Project Manager Approval of customer references.

1. [

]

2.

ASME Boiler and Pressure Vessel Code,Section XI, Rules for Inservice Inspection of Nuclear Power Plant Components, 2007 Edition with 2008 Addenda.

3. [

]

4.

Materials Reliability Program: Crack Growth Rates for Evaluating Primary Water Stress Corrosion Cracking (PWSCC) of Thick-Wall Alloy 600 Materials and Alloy 82, 182, and 132 Welds (MRP-420, Revision 1), EPRI Document Number 3002014244, July 2018.

5.

• Entergy Document No. 1000.106, Change No. 017, Primary Chemistry Monitoring Program.

6. [

]

7. [

]

8. [

]

9. [

]

10. [

]

11. [

]

12. Materials Reliability Program: Crack Growth Rates for Evaluating Primary Water Stress Corrosion Cracking (PWSCC) of Thick-Wall Alloy 600 Materials (MRP-55), Revision 1, EPRI Document Number 1006695, November 2002.

Controlled Document 3 to 2CAN112403 ANO-2 CEDM Number 71 IDTB Weld Repair One-Cycle Justification Document Number 32-9384470-000 NON-PROPRIETARY (38 pages)

Page 1 of 38 0402-01-F01 (Rev. 023, 06/20/2024)

PROPRIETARY CALCULATION

SUMMARY

SHEET (CSS)

Document No.

32 9384470 000 Safety Related: Yes No Title ANO-2 CEDM Number 71 IDTB Weld Repair One-Cycle Justification (Non-Proprietary)

PURPOSE AND

SUMMARY

OF RESULTS:

Purpose:

The purpose of this calculation is to qualify Arkansas Nuclear One Unit 2 with a repaired control element drive mechanism (CEDM) inner diameter temper bead (IDTB) weld based on requirements specified in the Design Specification (Reference 1) for justifying one operating cycle.

Results:

The IDTB weld repair satisfies the applicable ASME Code requirements for one operating cycle.

FRAMATOME INC. PROPRIETARY This document and any information contained herein is the property of Framatome Inc. (Framatome) and is to be considered proprietary and may not be reproduced or copied in whole or in part. This document shall not be furnished to others without the express written consent of Framatome and is not to be used in any way which is or may be detrimental to Framatome. This document and any copies that may have been made must be returned to Framatome upon request.

EXPORT CONTROLLED INFORMATION Contains technology subject to U.S. export controls governed by the Export Administration Regulations (15 CFR Part 730 et seq.) and/or the Department of Energy Regulations (10 CFR Part 810). Diversion contrary to U.S. law is prohibited.

Export Classification US EC: N Part 810 EAR ECCN: N/A If the computer software used herein is not the latest version per the EASI list, AP 0402-01 requires that justification be provided.

THE DOCUMENT CONTAINS ASSUMPTIONS THAT SHALL BE VERIFIED PRIOR TO USE THE FOLLOWING COMPUTER CODES HAVE BEEN USED IN THIS DOCUMENT:

CODE/VERSION/REV CODE/VERSION/REV Yes No None Controlled Document

Document No. 32-9384470-000 0402-01-F01 (Rev. 023, 06/20/2024)

PROPRIETARY ANO-2 CEDM Number 71 IDTB Weld Repair One-Cycle Justification (Non-Proprietary)

Page 2 Review Method: Design Review (Detailed Check)

Alternate Calculation Does this document establish design or technical requirements? YES NO Does this document contain Customer Required Format?

YES NO Signature Block Name and Title Signature and Date Role Scope / Comments Austin Benny Engineer II LP Tomas Straka Advisory Engineer LR Rhimou Sulldi Supervisor A

Tim Wiger Advisory Engineer M

Mike Epling Project Manager PM Role Definitions:

P/R/A designates Preparer (P), Reviewer (R), Approver (A);

LP/LR designates Lead Preparer (LP), Lead Reviewer (LR);

M designates Mentor (M);

PM designates Project Manager (PM)











 

 














 



  







 

Controlled Document

Document No. 32-9384470-000 0402-01-F01 (Rev. 023, 06/20/2024)

PROPRIETARY ANO-2 CEDM Number 71 IDTB Weld Repair One-Cycle Justification (Non-Proprietary)

Page 3 Record of Revision Revision No.

Pages / Sections /

Paragraphs Changed Brief Description / Change Authorization 000 All Initial release. The corresponding proprietary document is 32-9384450-000.

Controlled Document

Document No. 32-9384470-000 PROPRIETARY ANO-2 CEDM Number 71 IDTB Weld Repair One-Cycle Justification (Non-Proprietary)

Page 4 Table of Contents Page SIGNATURE BLOCK................................................................................................................................2 RECORD OF REVISION..........................................................................................................................3 LIST OF TABLES.....................................................................................................................................5 LIST OF FIGURES...................................................................................................................................6

1.0 INTRODUCTION

...........................................................................................................................7 2.0 PURPOSE AND SCOPE...............................................................................................................7 3.0 ANALYTICAL METHODOLOGY...................................................................................................7 4.0 ASSUMPTIONS............................................................................................................................7 4.1 Unverified Assumptions.....................................................................................................7 4.2 Justified Assumptions........................................................................................................7 4.3 Modeling Simplifications....................................................................................................7 5.0 DESIGN INPUTS..........................................................................................................................8 5.1 Geometry...........................................................................................................................8 5.2 Materials..........................................................................................................................11 5.2.1 Replacement Guide Material Justification...........................................................11 6.0 CALCULATIONS.........................................................................................................................11 6.1 Primary Stress Evaluation................................................................................................12 6.1.1 ASME Code Allowable Stresses.........................................................................12 6.1.2 Loading...............................................................................................................13 6.1.3 Primary Stress Intensity and Pure Shear Stress Calculation..............................15 6.1.4 Triaxial Stress Calculation..................................................................................17 6.2 Weld Size Requirements.................................................................................................17 6.3 Tentative Thickness Calculation......................................................................................19 6.3.1 RVCH..................................................................................................................20 6.3.2 CEDM Nozzle.....................................................................................................20 6.4 Reinforcement Requirements..........................................................................................20 6.4.1 Removed Area....................................................................................................21 6.4.2 Limits of Reinforcement......................................................................................22 6.4.3 Available Reinforcement Area............................................................................23 6.5 Stress and Fatigue Usage Criteria...................................................................................25 7.0 RESULTS

SUMMARY

AND CONCLUSION...............................................................................25

8.0 REFERENCES

............................................................................................................................26 APPENDIX A : SHALLOW CUT REPAIR CONTINGENCY..................................................................27 APPENDIX B : OVERBORE REPAIR CONTINGENCY.........................................................................33 Controlled Document

Document No. 32-9384470-000 PROPRIETARY ANO-2 CEDM Number 71 IDTB Weld Repair One-Cycle Justification (Non-Proprietary)

Page 5 List of Tables Page Table 5-1: Design Inputs..........................................................................................................................8 Table 5-2: Material Properties................................................................................................................11 Table 6-1: ASME Code Allowable Stresses for Design Conditions (Level A and B).............................13 Table 6-2: ASME Code Allowable Stresses for Emergency Conditions (Level C).................................13 Table 6-3: ASME Code Allowable Stresses for Faulted Conditions (Level D).......................................13 Table 6-4: CEDM Loads (Reference 2).................................................................................................14 Table 6-5: Local Piping Loads Under Service Levels............................................................................15 Table 6-6: Primary Stress Intensities at IDTB Weld...............................................................................16 Table 6-7: Pure Shear Stresses at IDTB Weld......................................................................................16 Table 6-8: Primary Stress Intensities at CEDM Nozzle.........................................................................17 Table 6-9: IDTB Weld Size Results.......................................................................................................18 Table A-1: Primary Stress Intensities at IDTB Weld..............................................................................29 Table A-2: Pure Shear Stresses at IDTB Weld......................................................................................29 Table A-3: Primary Stress Intensities at CEDM Nozzle.........................................................................30 Table A-4: IDTB Weld Size Results.......................................................................................................31 Table B-1: Primary Stress Intensities at IDTB Weld..............................................................................34 Table B-2: Pure Shear Stresses at IDTB Weld......................................................................................34 Table B-3: Primary Stress Intensities at CEDM Nozzle.........................................................................35 Table B-4: IDTB Weld Size Results.......................................................................................................36 Controlled Document

Document No. 32-9384470-000 PROPRIETARY ANO-2 CEDM Number 71 IDTB Weld Repair One-Cycle Justification (Non-Proprietary)

Page 6 List of Figures Page Figure 5-1: CEDM IDTB Weld Repair....................................................................................................10 Figure 6-1: Analysis Locations...............................................................................................................12 Figure 6-2: Location of External Loads..................................................................................................14 Figure 6-3: NB-4244(d)-1(c)...................................................................................................................18 Figure 6-4: Weld Size Location..............................................................................................................19 Figure 6-5: Reinforcement Area Calculation..........................................................................................21 Figure 6-6: Reinforcement Area of CEDM Nozzle Numbers 71 and 46................................................24 Figure A-1: Replacement CEDM Nozzle Thickness..............................................................................28 Controlled Document

Document No. 32-9384470-000 PROPRIETARY ANO-2 CEDM Number 71 IDTB Weld Repair One-Cycle Justification (Non-Proprietary)

Page 7

1.0 INTRODUCTION

During the Fall 2024 outage (2R30), as part of the ultrasonic examination (UT) for the in-service inspection at Arkansas Nuclear One Unit 2 (ANO 2), an axial indication was discovered on the J-groove attachment weld of Control Element Drive Mechanism (CEDM) Penetration #71 on the reactor vessel closure head. Due to the aforementioned condition, Entergy Nuclear Corporation contracted Framatome to perform an Inner Diameter Temper Bead (IDTB) weld repair per Reference 1. The primary source of plant input is Reference 2. The analysis herein is the One Cycle Justification (OCJ) stress analysis that is required per Reference 1, Section 4.7.1.

The original nozzle is connected to the RV head with a partial penetration J-groove weld made on the inside of the RV head. The modification consists of removal and replacement of the lower portion of the existing CEDM nozzle (including nozzle guide) at CEDM penetration #71. The upper portion of the nozzle will remain in place.

The modification removes an existing portion of the pressure boundary partial penetration J-groove weld on the inside of the RVCH. The new pressure boundary weld is established in the RVCH penetration bore above the original weld. It should also be noted that Framatome has previously performed this IDTB modification on Nozzle #46 in ANO-2 (see Reference 3).

2.0 PURPOSE AND SCOPE This calculation justifies plant operation of one cycle with the repaired penetration based on Section III of the ASME Boiler & Pressure Vessel Code (Reference 4). The scope of this analysis includes analyzing the effects of the IDTB repair on CEDM nozzle #71 and the closest penetrations to it - specifically CEDM nozzle #46 and Incore Instrumentation (ICI) nozzle #82.

3.0 ANALYTICAL METHODOLOGY Compliant with the ASME Boiler & Pressure Vessel Code (Reference 4), the following steps will be performed to demonstrate acceptability of the IDTB weld repair:

x Primary stress criteria will be evaluated at the new IDTB weld and existing CEDM nozzle.

x Reinforcement requirements will be evaluated due to the removal of area within the RVCH and encroachment of existing reinforcement areas.

x Acceptability of the new IDTB weld configuration with respect to the ASME Code dimensional requirements will be determined.

x A qualitative assessment of the primary + secondary stress (P+Q), as well as fatigue, will be made regarding a single cycle of operation (18 months).

4.0 ASSUMPTIONS 4.1 Unverified Assumptions There are no unverified assumptions used in this calculation.

4.2 Justified Assumptions There are no justified assumptions used in this calculation.

4.3 Modeling Simplifications Minor modeling simplifications (or idealizations) that make the analysis more conservative are stated throughout the calculation when used.

Controlled Document

Document No. 32-9384470-000 PROPRIETARY ANO-2 CEDM Number 71 IDTB Weld Repair One-Cycle Justification (Non-Proprietary)

Page 8 5.0 DESIGN INPUTS 5.1 Geometry The repair is illustrated in Figure 5-1. Key nominal dimensions are listed below in inches.

Table 5-1: Design Inputs Name Reference RV head inside radius to base metal Reference 2, Pg. 3, Dimension K RV head thickness at penetration #71 Reference 2, Pg. 3, Dimension G RV head cladding thickness Reference 2, Pg. 3, Dimension F Original CEDM nozzle OD Reference 2, Pg. 4, Dimension P Original CEDM nozzle ID Reference 2, Pg. 3, Dimension C Location (x, y) of CEDM Nozzle #71 Reference 2, Pg. 3, Dimension D1 IDTB Weld Length Reference 5, Step 3 IDTB Weld OD Reference 5, Step 2 IDTB Weld ID Reference 5, Step 4 Corrosion Rate Reference 6, Section 8.0 Corrosion Time Reference 3, Section 6.1 Design Temperature Reference 1, Section 4.5 Design Pressure Reference 1, Section 4.4 Replacement Nozzle ID of the Thick Portion Reference 5, Step 4 Replacement Nozzle OD Reference 5, Step 2 Replacement Maximum Bore Diameter Reference 5, Step 2 Distance from CEDM nozzle #71 to #46 Calculated from Reference 2, Pg. 3, Dimension D1 Location of ICI Nozzle

1. 82 Reference 2, Pg. 14 Location of ICI Nozzle

1. 83 Reference 2, Pg. 14 ICI Nozzle #82 Bore Diameter Reference 2, Pg. 14 Controlled Document

Document No. 32-9384470-000 PROPRIETARY ANO-2 CEDM Number 71 IDTB Weld Repair One-Cycle Justification (Non-Proprietary)

Page 9 Name Reference J-groove Depth in ICI Nozzle for uphill and downhill side Reference 2, Pg. 14 J-groove Buttering Thickness for ICI Nozzle Reference 2, Pg. 14 J-groove Depth in CEDM Nozzle for Uphill and Downhill Side Reference 2, Pg. 4 J-groove Weld Buttering Thickness for CEDM Nozzle Reference 2, Pg. 4 Controlled Document

Document No. 32-9384470-000 PROPRIETARY ANO-2 CEDM Number 71 IDTB Weld Repair One-Cycle Justification (Non-Proprietary)

Page 10 Figure 5-1: CEDM IDTB Weld Repair Controlled Document

Document No. 32-9384470-000 PROPRIETARY ANO-2 CEDM Number 71 IDTB Weld Repair One-Cycle Justification (Non-Proprietary)

Page 11 5.2 Materials The materials designations of the sub-components are:

RV head =

(Reference 1, 5.1.1)

Original CEDM housing nozzle =

(Reference 1, 5.1.2)

Cladding =

(Reference 1, 5.1.5)

IDTB Repair weld (1) =

(Reference 1, 5.2.3)

Replacement lower portion of CEDM =

(Reference 1, 5.2.1)

J-groove weld =

(Reference 1, 5.1.4)

Replacement guide (2) =

(Reference 1, 5.2.2)

Original CEDM guide =

(Reference 1, 5.1.3)

Notes:

(1) The allowable stress value used for the IDTB weld are taken to be [

]

(2) The replacement guide material differs from the replacement CEDM material. See Section 5.2.1 for further explanation.

Table 5-2 lists the material properties for the materials used in the analysis at the design temperature. Stress Intensity or Sm values come from Reference 8. Yield Strength or Sy and Ultimate Strength or Su values come from Reference 9. Note that both materials share the same Sm and Su values.

Table 5-2: Material Properties Material Sm (psi)

Sy (psi)

Su (psi)

SB-166 23,300 35,000 80,000 SB-167 23,300 30,000 80,000 SA-533 Gr. B Cl. 1 26,700 Not used Not used 5.2.1 Replacement Guide Material Justification The purpose of this section is to ensure the threaded connection between the replacement CEDM nozzle and replacement guide are not compromised due to the material differences. From Reference 9, the thermal expansion of the guide material (18Cr-8Ni) at the design temperature is 9.9E-6 in/in/F from Table TE-1, whereas the thermal expansion of the CEDM Nozzle material (58Ni-29Cr-9Fe) at the design temperature is 8.3E-6 in/in/F from Table TE-4. The two components have different thermal expansion coefficients, therefore, during thermal expansion they expand at different rates. Using Figure 5-1, the replacement guide will expand faster than the replacement nozzle, making the threaded connection tighter. In addition, per Reference 5, Step 5, once the guide is fully seated on the end of the nozzle, they are welded together to ensure the guide does not become unthreaded during operation.

6.0 CALCULATIONS The calculation approach taken in this document is to abide by Method 2 in Section 4.1.7 of Reference 7. All calculations were completed in excel file ocj-idbt-ano-2-cedm-71.xlsx. This file can be found in Framatome Inc ColdStor system in folder /cold/General-Access/32/32-9000000/32-9384450-000/official.

Controlled Document

Document No. 32-9384470-000 PROPRIETARY ANO-2 CEDM Number 71 IDTB Weld Repair One-Cycle Justification (Non-Proprietary)

Page 12 Note that all dimensions in the following sections will use the worst-case dimension, accounting for tolerances stated on the design drawings, unless otherwise stated. If no tolerance is listed, the nominal value is used.

In addition, similar analyses of RVCH IDTB repairs performed for other plants have successfully met all ASME Section III criteria in the required follow-on analysis for the life of repair. Specifically, Reference 3 is an OCJ of performing the IDTB weld in CEDM nozzle #46 at the same plant in the Fall 2021 (2R28) outage. The calculation herein heavily borrows the methodology and structure from that of Reference 3.

6.1 Primary Stress Evaluation Per Reference 1, a primary stress intensity evaluation is required using the criteria of Reference 4. The evaluation checks stresses on the IDTB weld and the CEDM nozzle due to internal pressure and external loads. Stresses at each service level are evaluated. Figure 6-1 describes the locations analyzed. Conservatively, the nozzle analysis location uses the same moment arm and ID as the weld analysis.

Figure 6-1: Analysis Locations Based on the slow corrosion rate referenced in Table 5-1, it is concluded that corrosion has an insignificant impact on the CEDM nozzle and the weld. However, the effects of corrosion are considered in the reinforcement requirements only for the RVCH, as it is made of low alloy steel. The length of time used in the calculations considering corrosion is also found in Table 5-1.

6.1.1 ASME Code Allowable Stresses Allowable stresses are calculated at the design temperature (see Table 5-1) using Reference 8.

Controlled Document

Document No. 32-9384470-000 PROPRIETARY ANO-2 CEDM Number 71 IDTB Weld Repair One-Cycle Justification (Non-Proprietary)

Page 13 Table 6-1: ASME Code Allowable Stresses for Design Conditions (Level A and B)

Location Membrane (ksi)

Membrane + Bending (ksi)

Pure Shear (ksi)

Sm 1.5Sm 0.6Sm IDTB Weld and CEDM 23.30 34.95 13.98 The allowable stresses for Normal (Level A) and Upset (Level B) Conditions are per NB-3222 and NB-3223, respectively, Reference 4. Level A and B stresses are bounded by the design conditions. Note that Reference 4 states that Level B allowable stress intensity values shall be increased to 110% of the values given on Figure NB-3221-1. Conservatively, this is not considered. The allowable stresses for pure shear are per NB-3227.2.

Table 6-2: ASME Code Allowable Stresses for Emergency Conditions (Level C)

Location Membrane (ksi)

Membrane + Bending (ksi)

Pure Shear (ksi) 1.2Sm 1.8Sm 1.2(0.6Sm)

IDTB Weld and CEDM 27.96 41.94 16.78 The allowable stresses for emergency (Level C) Conditions are per NB-3224, Reference 4.

Table 6-3: ASME Code Allowable Stresses for Faulted Conditions (Level D)

Location Membrane (ksi)

Membrane + Bending (ksi)

Pure Shear (ksi) 2.4Sm 1.5(2.4Sm) 0.42Su (1)

IDTB Weld and CEDM 55.92 83.88 33.60 (1) Su value is from Table I, Reference 9.

The allowable stresses for Faulted (Level D) Conditions are per NB-3225 and Appendix F, Reference 4. Note that the primary side hydrostatic test condition is not checked since it is not expected to be performed anymore.

6.1.2 Loading The external mechanical loadings are specified in Reference 2. The internal pressure used in the analysis is the same as the design pressure found in Table 5-1. Based on Reference 2, the external loads are applied at the RVCH outer surface and CEDM nozzle junction. Conservatively, the uphill side of the CEDM nozzle and RVCH outer surface location is used as the point the external loads act on. Figure 6-2 shows the location the external loads act on.

Controlled Document

Document No. 32-9384470-000 PROPRIETARY ANO-2 CEDM Number 71 IDTB Weld Repair One-Cycle Justification (Non-Proprietary)

Page 14 Figure 6-2: Location of External Loads The uphill side location was calculated to be [

] away from the weld; this is the value used as the moment arm - the vertical distance from the loads to the weld analysis location in Figure 6-1. Applicable loads from Reference 2 are collected in Table 6-4 where direction A is the nozzle axial positive upwards, B is horizontal positive outwards, and C is determined by the right-hand rule.

Table 6-4: CEDM Loads (Reference 2)

Controlled Document

Document No. 32-9384470-000 PROPRIETARY ANO-2 CEDM Number 71 IDTB Weld Repair One-Cycle Justification (Non-Proprietary)

Page 15 The load combinations are specified in Reference 2. For primary stress evaluation, the load combinations are listed as follows:

Table 6-5 calculates the services loads based on the loading combinations, where x, y, and z are the directions A, B, and C in Table 6-4, respectively. Cap axial force due to pressure is included in service loads. Conservatively, deadweight is considered to act in the same direction as pressure and seismic loads.

Table 6-5: Local Piping Loads Under Service Levels 6.1.3 Primary Stress Intensity and Pure Shear Stress Calculation The primary stress intensities are calculated in the excel file (in sheet Primary Stresses IDTB Weld and Primary Stresses Nozzle for the weld and nozzle, respectively) at the inner radius, mean radius, and outer radius, not including corrosion. The pure shear stresses are calculated in the excel file only at the outer radius of the IDTB weld; this calculation includes the effects of corrosion. The corrosion reduces the length of the weld along the head, ultimately reducing the area. All values are listed below, including the stress ratio, which is calculated as shown below.

=

Below are the general equations used to calculate the stresses:

Axial stress:

=

+

()

+

Hoop stress:

=

(

+ 1)

Radial stress:

=

(

1)

Shear stresses:

=

+

, = = 0 All calculated stresses conservatively do not consider the support of the RVCH. The original CEDM nozzle is roll expanded, therefore the IDTB weld and nozzle only see a fraction of the stresses listed in Table 6-6, Table 6-7, and Table 6-8. It should be noted again that the primary stress analysis for the CEDM nozzle (Table 6-8) uses the original OD of the nozzle but the appropriate ID of the weld to be more conservative - less cross-sectional area, more stress. Also, Service Level C is considered in this calculation - the loading for Service Level C is that of internal pressure only and no external loads are defined.

Controlled Document

Document No. 32-9384470-000 PROPRIETARY ANO-2 CEDM Number 71 IDTB Weld Repair One-Cycle Justification (Non-Proprietary)

Page 16 Note membrane stresses are typically listed as average values. Since membrane stresses are listed at all three locations; they only need to meet criteria at the mean radius location.

Table 6-6: Primary Stress Intensities at IDTB Weld Table 6-7: Pure Shear Stresses at IDTB Weld Service Level Location Level A Weld OD Level B Weld OD Level C Weld OD Level D Weld OD Controlled Document

Document No. 32-9384470-000 PROPRIETARY ANO-2 CEDM Number 71 IDTB Weld Repair One-Cycle Justification (Non-Proprietary)

Page 17 Table 6-8: Primary Stress Intensities at CEDM Nozzle Service Level Location Level A Inside Outside Mean Level B Inside Outside Mean Level C Inside Outside Mean Level D Inside Outside Mean Both the IDTB weld and the CEDM nozzle met the primary stress intensity requirements at all locations and all service levels. In addition, the IDTB weld meets the pure shear requirements at all service levels.

6.1.4 Triaxial Stress Calculation To meet the triaxial stress requirement, Reference 4 states that the algebraic sum of the three primary stresses shall not exceed 4Sm, excect for service level D.

4= 4(23,300 ) = 93,200 The three primary stresses that bound the IDTB weld and CEDM nozzle are:

[

] from the outside location of the CEDM Nozzle at Service Level B. The algebraic sum of the three primary stresses is [

] Since [

] the triaxial stress requirement is met.

6.2 Weld Size Requirements Weld Size (NB-3352.4, Reference 4)

This weld needs to satisfy the minimum dimension requirements of NB-3352.4(d)(2) or FIG. NB-4244(d)-1(c) per Reference 4. FIG. NB-4244(d)-1(c) is shown in Figure 6-3. From Table 5-1, with the CEDM nozzle OD and IDTB weld ID, the nominal thickness (tn) is [

] With the nominal thickness, the weld size requirements can be determined. Table 6-9 lists the IDTB weld size requirements and results. Figure 6-4 shows how the weld size results are applicable to the requirements of NB-4244(d)-1(c).

Controlled Document

Document No. 32-9384470-000 PROPRIETARY ANO-2 CEDM Number 71 IDTB Weld Repair One-Cycle Justification (Non-Proprietary)

Page 18 Figure 6-3: NB-4244(d)-1(c)

Table 6-9: IDTB Weld Size Results Criteria met?

Yes Yes Yes Controlled Document

Document No. 32-9384470-000 PROPRIETARY ANO-2 CEDM Number 71 IDTB Weld Repair One-Cycle Justification (Non-Proprietary)

Page 19 Figure 6-4: Weld Size Location Nozzle Diametric Clearance (NB-3337.3(a), Reference 4)

For a nozzle OD greater than 4, the maximum diametric clearance is 0.030 per NB-3337.3(a). Per Table 5-1, using the replacement nozzle OD and the bore diameter, the nozzle diametric clearance is:

=

= 0.000 Considering, The diametric clearance of the original nozzle (that is part of the pressure boundary) is also checked. From Reference 4, Step 0, there is no clearance between the original nozzle and the original bore. In addition, the original nozzle is roll expanded before the IDTB weld. Therefore, the nozzle diametric requirement is met.

6.3 Tentative Thickness Calculation Tentative Thickness Calculation (NB-3324.1)

The tentative thickness calculation of the RVCH is determined by the methodology specified in NB-3324 of the ASME boiler and Pressure Vessel Code (Reference 4). As stated in the article, except in local areas, the wall thickness of a vessel shall never be less than that obtained from the formula in NB-3324.1 for cylindrical shells and NB-3324.2 for spherical shells.

NB-3324.1 (Cylindrical Shells):

=

NB-3324.2 (Spherical Shells):

=

Controlled Document

Document No. 32-9384470-000 PROPRIETARY ANO-2 CEDM Number 71 IDTB Weld Repair One-Cycle Justification (Non-Proprietary)

Page 20 Where:

t = Tentative thickness, in.

P = Design pressure, psi R = Inside radius, in.

Sm = Design stress intensity value, psi 6.3.1 RVCH From Table 5-1, the original RVCH inner radius is [

] (including maximum tolerance) and the RVCH thickness is [

] Using the spherical shell formula with P ( [

] ) and Sm ( [

] ), the tentative pressure thickness is:

Comparing the design thickness to the tentative thickness.

Therefore, the tentative thickness requirement is met.

6.3.2 CEDM Nozzle From Table 5-1, the original nozzle OD is [

] and the ID of the weld including maximum tolerance is

[

] The ID of the weld instead of the ID of the nozzle is used to make the resulting solution more conservative. Using the cylindrical shell formula with P ( [

] ), R ( [

] ), and Sm

( [

] ), the tentative pressure thickness is:

The nozzle wall thickness considering the nominal dimensions is:

Therefore, the tentative thickness requirement is met.

6.4 Reinforcement Requirements Due to the area removal in the RVCH to accommodate the IDTB weld repair, an evaluation is required to determine the reinforcement requirements are met. For some amount of area removed, an appropriate amount of area around the nozzle must exist to reinforce the opening against primary stresses. A comparison of the area removed against the reinforcement area is performed to determine if the area removed by the IDTB modification is acceptable. The calculation for the minimum required area of reinforcement is based on the methodology in NB-3330 Reference 4. Figure 6-5 describes the dimensions and areas being analyzed.

Controlled Document

Document No. 32-9384470-000 PROPRIETARY ANO-2 CEDM Number 71 IDTB Weld Repair One-Cycle Justification (Non-Proprietary)

Page 21 Figure 6-5: Reinforcement Area Calculation 6.4.1 Removed Area The maximum penetration diameter using the replacement maximum bore diameter with the maximum dimensioning tolerances, including the effects of corrosion over the full remaining life of the plant (see Table 5-1) is:

do

[

]

As stated earlier, refer to the excel spreadsheet to see the detailed calculations - the reinforcement calculations can be found in sheet Reinforcement.

The plane distance to the center of penetration No. 71 (C) can be calculated by the x and y coordinates in Reference 2 to be:

C

[

]

Using the Tentative Thickness (tt) of the head that was previously determined in Section 6.3.1, and the inner radius of the head with maximum tolerance (Ri), the tentative outer radius of the head (Rt) is:

Rt

= Ri + tt

[

]

Controlled Document

Document No. 32-9384470-000 PROPRIETARY ANO-2 CEDM Number 71 IDTB Weld Repair One-Cycle Justification (Non-Proprietary)

Page 22 The vertical distance from center of head-to-head inside radius (Hi) is:

Hi

= (Ri2 - C2)0.5

[

]

The vertical distance from center of head to the outside radius of the required head thickness (Ht) is:

Ht

= (Rt2 - C2)0.5

[

]

Removed area due to opening (Arem) is:

Arem

= (Ht - Hi)*do

[

]

The value above represents the area removed by the IDTB modification. For the IDTB modification to be acceptable, there shall be an amount of reinforcement area greater than this value of the area removed.

6.4.2 Limits of Reinforcement Reference 4 establishes the limits of the reinforcement area along and normal to the vessel surface. The limits of reinforcement, denoted by Lr, is a measure of how much area around the nozzle can be declared as area for reinforcement. A larger value of Lr implies that the opening is more isolated, and therefore, has more area that can be declared as reinforcement area.

From Table 5-1, the inside radius of the head (Ri) with the maximum tolerance and the thickness of the head (t) can be used to calculate the mean radius of the head:

R

= Ri + t/2

[

]

The limits of reinforcement, measured along the mid surface of the nominal wall thickness, shall meet the following:

A. One hundred percent of the required reinforcement shall be within a distance on each side of the axis of the opening equal to the greater of the following:

a.

NB-3334.1(a)(1), Diameter of finished opening, do [

]

b.

NB-3334.1(a)(2), Sum of radius of finished opening, thickness of nozzle (conservatively equal to zero), and vessel wall which equals [

]

B. Two thirds of the required reinforcement shall be within a distance on each side of the axis of the opening equal to the greater of the following:

a.

NB-3334.1(b)(1): r+0.5 (Rt)0.5 Where R is the mean radius of head, t is the nominal vessel wall thickness, and r is the radius of the finished opening in the corroded condition:

r+0.5 (Rt)0.5 [

]

b.

NB-3334.1(b)(2): r+2(t + tn)/3 Where r is the radius of the finished opening in the corroded condition, tn is the nozzle thickness (conservatively equal to zero), and t is the nominal vessel wall thickness:

Controlled Document

Document No. 32-9384470-000 PROPRIETARY ANO-2 CEDM Number 71 IDTB Weld Repair One-Cycle Justification (Non-Proprietary)

Page 23 r+2(t+ tn)/3 [

]

Furthermore, the ASME code in Section NB-3335(f) prohibits the same reinforcing material from being applied to more than one opening. Since the CEDM penetrations in the head are in a grid-like pattern with a fixed longitudinal and latitudinal interval, half of the reinforcing material in any one nozzle should lie on each side of the nozzle. Therefore, the reinforcement limit is restricted to one-half of the distance between similar adjacent penetrations. Table 5-1 shows shortest distance to another opening (CEDM penetration #46) from penetration No.

71. Accordingly, the limit of reinforcement Lr is [

]

6.4.3 Available Reinforcement Area The available area of reinforcement is shown in Figure 6-5 and is calculated as follows:

The outside radius of the RVCH (Ro) is:

Ro

= Ri + t

[

]

The vertical distance from center of head to outside radius of the head (Ho) is:

Ho

= (Ro2 - C2)0.5

[

]

The thickness of the RVCH (tr) that was not removed is:

tr

= Ho - Ht

[

]

The area of the original flawed J-groove weld needs to be account for as area removed. It is conservatively estimated to be 3 in2. Conservatively, the IDTB weld is not being credited for area of reinforcement.

Ajgw

[

]

Total area removed is:

Aremoved = Arem + Ajgw

[

]

The total area of reinforcement is:

Arein

= 2*tr*(Lr - (do/2))

[

]

Since the total reinforced area is greater than the total area removed, the reinforcement requirements for CEDM nozzle #71 with respect to other adjacent CEDM nozzles are met.

It should be noted that the IDTB weld modification was also performed for nozzle #46 (see Reference 3). But the reinforcement area determined in Reference 3 does not impact the reinforcement area determined herein. In Reference 3, Section 6.4.2, the limits of reinforcement (Lr) is also defined as half the distance to an adjacent CEDM nozzle, which was 51. But since the ANO-2 CEDM penetrations are spaced in a grid with the same fixed latitudinal and longitudinal interval, the distance from nozzle #46 to #51 is the same as the distance from nozzle

1. 46 to #71. Since the same logic, Lr is half the distance to an adjacent CEDM nozzle, is used to determine the limits of reinforcement herein, the reinforcement area of neither #46 nor #71 encroach each others boundaries.

This is illustrated in Figure 6-6.

Controlled Document

Document No. 32-9384470-000 PROPRIETARY ANO-2 CEDM Number 71 IDTB Weld Repair One-Cycle Justification (Non-Proprietary)

Page 24 Figure 6-6: Reinforcement Area of CEDM Nozzle Numbers 71 and 46 From Reference 2, Figure 4, CEDM nozzle #71 is adjacent to other CEDM nozzles as well as In-core Instrumentation (ICI) nozzles. Since a new reinforcement area is declared because metal was removed to perform the IDTB weld, and nozzle #71 is adjacent to ICI nozzles, the amount of area removed in the ICI nozzle is compared against the available reinforcement area of the ICI nozzle to ensure enough metal exists between the ICI nozzle and CEDM nozzle #71. The primary concern is that there is an inadequate amount of reinforcement metal for the ICI nozzle closest to CEDM nozzle #71.

The locations for the closest ICI nozzles to CEDM nozzle #71 are shown in Table 5-1. Since the distance from CEDM nozzle #71 to either ICI nozzle #83 or #82 is the same, or LICI = [

] the reinforcement calculation is performed for ICI nozzle #82. The general process is to first calculate the area removed by the ICI nozzle, determine the limits of reinforcement of the ICI nozzle, determine the corresponding area of reinforcement, and finally check the area removed against the area of reinforcement available to the ICI nozzle.

The same process done to determine the area removed for CEDM nozzle #71 in Section 6.4.1 is performed for ICI nozzle #82. Table 5-1 lists a maximum bore diameter and the ICI nozzle x-y location for the ICI nozzle. The corrosion rate is not expected to have a noticeable impact on the analysis, so using the same corrosion rate and time listed in Table 5-1, the area removed (Arem) from the ICI nozzles is [

] From Table 5-1, the depth of the J-groove weld for the ICI nozzle is smaller than the depth of the J-groove weld on the CEDM nozzle.

However, the same area used for the J-groove weld in the CEDM nozzle is conservatively used for the J-groove weld in the ICI nozzle. The total area removed when the area of the J-groove weld is included to Arem is Aremoved =

[

] Refer to the excel file and the sheet Reinforcement ICI for the full calculation.

Controlled Document

Document No. 32-9384470-000 PROPRIETARY ANO-2 CEDM Number 71 IDTB Weld Repair One-Cycle Justification (Non-Proprietary)

Page 25 Since the CEDM nozzle for which the IDTB weld modification is being performed is adjacent to ICI nozzle #82, the limits of reinforcement for the ICI nozzle should be determined. Following the same methodology in Section 6.4.2, to accommodate 100% of the reinforcement area per NB-3334.1(a), the limits of reinforcement must be within LrICI = [

] Note that, unlike Section 6.4.2, the LrICI produced using the methodology outlined in NB-3334.1(a) is obeyed, as opposed to selecting LrICI to be one half the distance to CEDM Nozzle #71. It should also be noted that using the LrICI value results in limits of reinforcement for the ICI nozzle that does not encroach on the limits of reinforcement for the CEDM nozzle (or Lr = [

]). Since the scope of this analysis (see Section 2.0) is a repair to CEDM nozzle #71, the limits of reinforcement of ICI nozzle #82 with respect to any other CEDM nozzle is unaffected. Therefore, the definition of LrICI is valid because it only includes the limits of reinforcement of ICI nozzle #82 with respect to the CEDM nozzle in the scope of this analysis - the CEDM nozzle undergoing repair.

Using the same process for the CEDM penetrations, the corresponding area of reinforcement (Arein) for ICI nozzle

1. 82 is [

] Since, (1) the area removed from ICI nozzle #82 is less than the reinforcement area of the ICI nozzle, and (2) the reinforcement area of the ICI nozzle does not encroach on the reinforcement area of CEDM nozzle #71, the reinforcement requirements for CEDM nozzle #71 with respect to the ICI nozzles are met.

6.5 Stress and Fatigue Usage Criteria The ASME Code places a limit on the primary plus secondary stress intensity to prevent failure by excessive distortion caused by the repeated application of loads. The Code also limits total stresses, through the cumulative fatigue usage factor, to prevent failure by fatigue. Primary plus secondary stress intensity and fatigue for one cycle are qualitatively assessed. In addition, the presence of differential thermal expansion is discussed in Section 5.2.1.

[

]

7.0 RESULTS

SUMMARY

AND CONCLUSION The repair of CEDM nozzle #71 is acceptable for one cycle of operation.

Document

Document No. 32-9384470-000 PROPRIETARY ANO-2 CEDM Number 71 IDTB Weld Repair One-Cycle Justification (Non-Proprietary)

Page 26

8.0 REFERENCES

Note: The references in this section are at the appropriate revision level for the main body results. There are additional references in Appendix A and Appendix B. The references in the appendices are updated to the current revision level and are at the appropriate revision level for the appendix results.

1.

Framatome Document 08-9384265-003, ANO-2 CEDM Penetration No. 71 Modification.

2.

Framatome Document 38-2201986-002, Design Input for Framatome IDTB Weld Repair at ANO-2 Penetration 71.

3.

Framatome Document 32-9338944-001, ANO-2 CEDM IDTB Weld Repair One-Cycle Justification.

4.

ASME Boiler and Pressure Vessel Code,Section III, Rules for Construction of Nuclear Facility Components, Division I, 1992 with no Addenda.

5.

Framatome Drawing 02-8145101-E-001, ANO-2 CEDM Nozzle IDTB Weld Repair.

6.

Framatome Document 51-9384397-000, Corrosion Evaluation of ANO-2 RVCH CEDM IDTB Weld Nozzle Penetration Repair.

7.

Framatome Document 0402-01 Revision 57, Calculations.

8.

ASME Boiler and Pressure Vessel Code,Section III, Rules for Construction of Nuclear Vessels, Division 1, 1968 Edition with Addenda through Summer 1970.

9.

ASME Boiler and Pressure Vessel Code,Section II, Material Specifications Part B - Nonferrous, 1968 Edition with Addenda through Summer 1970.

Controlled Document

Document No. 32-9384470-000 PROPRIETARY ANO-2 CEDM Number 71 IDTB Weld Repair One-Cycle Justification (Non-Proprietary)

Page 27 APPENDIX A:

SHALLOW CUT REPAIR CONTINGENCY A.1 Introduction Per Reference A3, Section 8.2, a shallow cut contingency at CEDM penetration #71 at ANO-2 must be performed.

A.2 Purpose The purpose of this calculation is to evaluate the ASME code requirements per Reference A1 based on the updated shallow cut contingency dimensions in step 4A per Reference A2.

A.3 Methodology The methodology is the same as the original analysis contained in the main body of the document, herein referred to as the original analysis.

A.4 Assumptions The assumptions are the same as the original analysis.

A.5 Design Inputs A.5.1 Geometry Most of the geometry is the same as the original analysis. The geometry that is not the same is listed below.

IDTB Weld ID:

[

]

(Reference A2, Step 4A.3)

It is worth noting that the shallow cut repair does not cut into the replacement CEDM nozzle ID. Also, from Reference A2, Step 4A.3, by inspection, the cut area is not the thinnest part of the replacement CEDM nozzle -

see Figure A-1.

Controlled Document

Document No. 32-9384470-000 PROPRIETARY ANO-2 CEDM Number 71 IDTB Weld Repair One-Cycle Justification (Non-Proprietary)

Page 28 Figure A-1: Replacement CEDM Nozzle Thickness A.5.2 Materials The materials are the same as the original analysis.

A.6 Calculations All calculations were completed in excel file shallow-cut-ocj-idtb-ano-2-cedm-71.xlsx. This file can be found in Framatome Inc ColdStor system in folder /cold/General-Access/32/32-9000000/32-9384450-000/official.

Note that all dimensions in the following sections will use the worst-case dimension, accounting for tolerances stated on the design drawings, unless otherwise stated. If no tolerance is listed, the nominal value is used.

A.6.1 Primary Stress Evaluation The primary stress evaluation uses the same methodology as the original analysis.

A.6.1.1 ASME Code Allowable Stresses All the information in the ASME code allowable stresses section in the original analysis is applicable to this analysis.

Controlled Document

Document No. 32-9384470-000 PROPRIETARY ANO-2 CEDM Number 71 IDTB Weld Repair One-Cycle Justification (Non-Proprietary)

Page 29 A.6.1.2 Loading All the information in the loading section in the original analysis is applicable to this analysis.

A.6.1.3 Primary Stress Intensities and Pure Shear Calculation The same process used in Section 6.1.3 is used to calculate the stresses herein. The calculated values are tabulated in Table A-1, Table A-2, and Table A-3.

Note membrane stresses are typically listed as average values. Since membrane stresses are listed at all three locations, they only need to meet criteria at the mean radius location.

Table A-1: Primary Stress Intensities at IDTB Weld Service Level Location Level A Inside Outside Mean Level B Inside Outside Mean Level C Inside Outside Mean Level D Inside Outside Mean Table A-2: Pure Shear Stresses at IDTB Weld Service Level Location Level A Weld OD Level B Weld OD Level C Weld OD Level D Weld OD Controlled Document

Document No. 32-9384470-000 PROPRIETARY ANO-2 CEDM Number 71 IDTB Weld Repair One-Cycle Justification (Non-Proprietary)

Page 30 Table A-3: Primary Stress Intensities at CEDM Nozzle Service Level Location Level A Inside Outside Mean Level B Inside Outside Mean Level C Inside Outside Mean Level D Inside Outside Mean Both the IDTB weld and the CEDM nozzle met the primary stress intensity requirements at all locations and all service levels. In addition, the IDTB weld meets the pure shear requirements at all service levels.

A.6.1.4 Triaxial Stress Calculation To meet the requirement, Reference A1 states that the algebraic sum of the three primary stresses shall not exceed 4Sm, excect for service level D.

4= 4(23,300 ) = 93,200 The three primary stresses that bound the IDTB weld and CEDM nozzle are: [

] from the outside location of the CEDM Nozzle at Service Level B. The algebraic sum of the three primary stresses is [

] Since [

] the triaxial stress requirement is met.

A.6.2 Weld Size Requirements This weld needs to satisfy the minimum dimension requirements of FIG. NB-4244(d)-1(c) per Reference A1.

Using the value of the original CEDM nozzle OD in Table 5-1, and the shallow-cut IDTB weld ID of [

] (with the most conservative tolerance), the nominal thickness is [

] With the nominal thickness, the weld size requirements can be determined. Table A-4 lists the IDTB weld size requirements and results.

Controlled Document

Document No. 32-9384470-000 PROPRIETARY ANO-2 CEDM Number 71 IDTB Weld Repair One-Cycle Justification (Non-Proprietary)

Page 31 Table A-4: IDTB Weld Size Results Criteria met?

Yes Yes Yes Nozzle Diametric Clearance (NB-3337.3(a), Reference A1)

No change from the analogous subsection in Section 6.2. The nozzle diametric requirement is met.

A.6.3 Tentative Thickness Calculation Tentative Thickness Calculation (NB-3324.1)

A.6.3.1 RVCH The RVCH tentative thickness requirement is the same as the original analysis contained in the main body of this document.

A.6.3.2 CEDM Nozzle From Table 5-1, the original CEDM nozzle OD is [

] and, from Reference A2, the ID of the IDTB weld is [

] with the maximum tolerance. Using the cylindrical shell formula with P ( [

] ), R

( [

] ), and Sm ( [

] ), the tentative pressure thickness is:

The nozzle wall thickness considering the nominal dimensions is:

Therefore, the tentative thickness requirement is met.

A.6.4 Reinforcement Requirements The reinforcement requirements are the same as the original analysis contained in the main body of this document.

A.6.5 Stress and Fatigue Usage Criteria The stress and fatigue usage criteria are the same as the original analysis contained in the main body of this document.

A.7 Results Summary and Conclusion The repair of CEDM nozzle #71 is acceptable for one cycle of operation.

Controlled Document

Document No. 32-9384470-000 PROPRIETARY ANO-2 CEDM Number 71 IDTB Weld Repair One-Cycle Justification (Non-Proprietary)

Page 32 A.8 References A1.

ASME Boiler and Pressure Vessel Code,Section III, Rules for Construction of Nuclear Facility Components, Division I, 1992 with no Addenda.

A2.

Framatome Drawing 02-8145101-E-001, ANO-2 CEDM Nozzle IDTB Weld Repair.

A3.

Framatome Document 08-9384265-003, ANO-2 CEDM Penetration No. 71 Modification.

Controlled Document

Document No. 32-9384470-000 PROPRIETARY ANO-2 CEDM Number 71 IDTB Weld Repair One-Cycle Justification (Non-Proprietary)

Page 33 APPENDIX B: OVERBORE REPAIR CONTINGENCY B.1 Introduction Per Reference B3, Section 8.3, an overbore contingency at CEDM penetration #71 at ANO-2 must be performed.

B.2 Purpose The purpose of this calculation is to re-evaluate the ASME code requirements per Reference B1 based on the updated overbore contingency dimensions in step 4B in Reference B2.

B.3 Methodology The methodology is the same as the original analysis contained in the main body of this document, herein referred to as the original analysis.

B.4 Assumptions The assumptions are the same as the original analysis.

B.5 Design Inputs B.5.1 Geometry Most of the geometry is the same as the original analysis. The geometry that is not the same is listed below.

IDTB Weld OD:

[

]

(Reference B2, Step 4B.1)

IDTB Weld ID:

[

]

(Reference B2, Step 4B.2)

B.5.2 Materials The materials are the same as the original analysis.

B.6 Calculations All calculations were completed in excel file overbore-ocj-idtb-ano-2-cedm-71.xlsx. This file can be found in Framatome Inc ColdStor system in folder /cold/General-Access/32/32-9000000/32-9384450-000/official.

Note that all dimensions in the following sections will use the worst-case dimension, accounting for tolerances stated on the design drawings, unless otherwise stated. If no tolerance is listed, the nominal value is used.

In addition, similar analyses of RVCH IDTB repairs performed for other plants have successfully met all ASME Section III criteria in the required follow-on analysis for the life of repair.

B.6.1 Primary Stress Evaluation The primary stress evaluation uses the same methodology as the original analysis.

B.6.1.1 ASME Code Allowable Stresses All information in the ASME code allowable stresses section in the original analysis is applicable to this analysis.

B.6.1.2 Loading All information in the loading section in the original analysis is applicable to this analysis.

Controlled Document

Document No. 32-9384470-000 PROPRIETARY ANO-2 CEDM Number 71 IDTB Weld Repair One-Cycle Justification (Non-Proprietary)

Page 34 B.6.1.3 Primary Stress Intensities and Pure Shear Calculation The same process used in Section 6.1.3 is used to calculate the stresses herein. The calculated values are tabulated in Table B-1, Table B-2, and Table B-3.

Note membrane stresses are typically listed as average values. Since membrane stresses are listed at all three locations, they only need to meet criteria at the mean radius location.

Table B-1: Primary Stress Intensities at IDTB Weld Service Level Location Level A Inside Outside Mean Level B Inside Outside Mean Level C Inside Outside Mean Level D Inside Outside Mean Table B-2: Pure Shear Stresses at IDTB Weld Service Level Location Level A Weld OD Level B Weld OD Level C Weld OD Level D Weld OD Controlled Document

Document No. 32-9384470-000 PROPRIETARY ANO-2 CEDM Number 71 IDTB Weld Repair One-Cycle Justification (Non-Proprietary)

Page 35 Table B-3: Primary Stress Intensities at CEDM Nozzle Service Level Location Level A Inside Outside Mean Level B Inside Outside Mean Level C Inside Outside Mean Level D Inside Outside Mean Both the IDTB weld and the CEDM nozzle met the primary stress intensity requirements at all locations and all service levels. In addition, the IDTB weld meets the pure shear requirements at all service levels.

B.6.1.4 Triaxial Stress Calculation To meet the requirement, Reference B1 states that the algebraic sum of the three primary stresses shall not exceed 4Sm, excect for service level D.

4= 4(23,300 ) = 93,200 The three primary stresses that bound the IDTB weld and CEDM nozzle are (from the nozzle): [

] from the outside location of the CEDM Nozzle at Service Level B.

The algebraic sum of the three primary stresses is [

] Since [

] the triaxial stress requirement is met.

B.6.2 Weld Size Requirements This weld needs to satisfy the minimum dimension requirements of FIG. NB-4244(d)-1(c) per Reference B1.

Using the value of the original CEDM nozzle OD in Table 5-1 of [

] and the IDTB weld ID (with the most conservative tolerance) of [

] the nominal thickness is [

] With the nominal thickness, the weld size requirements can be determined. Table B-4 lists the IDTB weld size requirements and results.

Controlled Document

Document No. 32-9384470-000 PROPRIETARY ANO-2 CEDM Number 71 IDTB Weld Repair One-Cycle Justification (Non-Proprietary)

Page 36 Table B-4: IDTB Weld Size Results Criteria met?

Yes Yes Yes Nozzle Diametric Clearance (NB-3337.3(a), Reference B1)

For a nozzle OD greater than 4, the maximum diametric clearance is 0.030, per NB-3337.3(a). Per Reference B2, the replacement nozzle OD is [

] and the bore ID is [

] The equation below solves for the nozzle diametric clearance.

[

]

Considering,

[

]

The diametric clearance of the original nozzle (that is part of the pressure boundary) is also checked. From Reference 4, Step 0, there is no clearance between the original nozzle and the original bore. In addition, the original nozzle is roll expanded before the IDTB weld. Therefore, the nozzle diametric requirement is met.

B.6.3 Tentative Thickness Calculation Tentative Thickness Calculation (NB-3324.1)

The tentative thickness calculation of the RVCH is determined by the methodology specified in NB-3324 of the ASME Boiler and Pressure Vessel Code (Reference B1). As stated in the article, except in local areas, the wall thickness of a vessel shall never be less than that obtained from the formula in NB-3324.1 for cylindrical shells and NB-3324.2 for spherical shells.

NB-3324.1 (Cylindrical Shells):

=

NB-3324.2 (Spherical Shells):

=

Where:

t = Tentative thickness, in.

P = Design pressure, psi R = Inside radius, in.

Sm = Design stress intensity value, psi B.6.3.1 RVCH The RVCH tentative thickness requirement is the same as the original analysis.

Document

Document No. 32-9384470-000 PROPRIETARY ANO-2 CEDM Number 71 IDTB Weld Repair One-Cycle Justification (Non-Proprietary)

Page 37 B.6.3.2 CEDM Nozzle From Table 5-1, the original nozzle OD is [

] and the ID of the over bored weld including maximum tolerance is [

] The ID of the weld instead of the ID of the nozzle is used to ensure the resulting solution is more conservative. Using the cylindrical shell formula with P ( [

] ), R ( [

] ), and Sm ( [

] ), the tentative pressure thickness is:

The nozzle wall thickness considering the nominal dimensions is:

Therefore, the tentative thickness requirement is met.

B.6.4 Reinforcement Requirements Reinforcement calculations have been updated to reflect the diameter expansion from the reboring process.

B.6.4.1 Removed Area The removed area calculation is almost identical to the one used in the original analysis. The only change is the maximum penetration diameter, including the effects of corrosion and dimensioning tolerances, is:

do

[

]

Following the methodology used in Section 6.4.1, using the same parameters, the removed area due to opening (Arem) is:

Arem

[

]

B.6.4.2 Limits of Reinforcement The same process used in Section 6.4.2 is used herein, the limits of reinforcement or Lr is [

]

B.6.4.3 Available Reinforcement Area The available reinforcement area calculation is almost identical to the one used in the original analysis. The only change is the maximum penetration diameter, including the effects of corrosion and dimensioning tolerances.

Following the methodology used in Section 6.4.3, using the same parameters, the total area of reinforcement (Arein) is:

Arein

[

]

Since the total reinforced area is greater than the total area removed, the reinforcement requirements are met.

Since Lr is the same for the over bored condition, Section 6.4.3 can be used to state that the reinforcement requirements for the ICI nozzles are also met.

B.6.5 Stress and Fatigue Usage Criteria The stress and fatigue usage criteria are the same as the original analysis.

B.7 Results Summary and Conclusion The repair of CEDM nozzle #71 is acceptable for one cycle of operation.

Controlled Document

Document No. 32-9384470-000 PROPRIETARY ANO-2 CEDM Number 71 IDTB Weld Repair One-Cycle Justification (Non-Proprietary)

Page 38 B.8 References B1.

ASME Boiler and Pressure Vessel Code,Section III, Rules for Construction of Nuclear Facility Components, Division I, 1992 with no Addenda.

B2.

Framatome Drawing 02-8145101-E-001, ANO-2 CEDM Nozzle IDTB Weld Repair.

B3.

Framatome Document 08-9384265-003, ANO-2 CEDM Penetration No. 71 Modification.

Controlled Document 4 to 2CAN112403 ANO-2 CEDM Penetration 71 Modification As-Left J-Groove Weld One Cycle Justification Document Number 32-9384463-000 NON-PROPRIETARY (21 pages)

Page 1 of 21 0402-01-F01 (Rev. 023, 06/20/2024)

PROPRIETARY CALCULATION

SUMMARY

SHEET (CSS)

Document No.

32 9384463 000 Safety Related: Yes No Title ANO-2 CEDM Penetration 71 Modification As-Left J-Groove Weld One Cycle Justification (Non-Proprietary)

PURPOSE AND

SUMMARY

OF RESULTS:

PURPOSE: During the Fall 2024 outage (2R30), an axial indication was discovered on the downhill side of the J-Groove weld (JGW) of Control Element Drive Mechanism (CEDM) Penetration No. 71 on the reactor vessel closure head (RVCH) at Arkansas Nuclear One Unit 2 (ANO-2). Therefore, a half nozzle repair is performed. The repair moves the pressure boundary from the existing JGW to the new pressure boundary weld located in the RVCH penetration bore above the original JGW. The purpose of this evaluation is to perform a one cycle justification (OCJ) to assess the suitability of leaving a degraded, as-left J-Groove weld (ALJGW) in the RVCH following the CEDM nozzle repair. Appendix A provides additional discussion on the effects of the weld residual stress (WRS) plus

[

] on the stress intensity factors (SIFs). Appendix B provides justification for the Contingency Shallow Cut and Contingency Overbore repair methods.

SUMMARY

OF RESULTS: As summarized in Section 6.0, it is demonstrated by comparative analysis that, based on evaluation of fatigue crack growth of the ALJGW flaw into the low alloy steel RVCH, the ASME Code,Section XI, IWB-3612 requirements for fracture toughness are met for at least one fuel cycle (18 months) based on the transient input provided in Reference [3]. In addition, the primary stress limits considering reinforcement requirements of NB-3330 are met, considering a local area reduction of the pressure retaining membrane of the nozzle opening that includes the area of the JGW and a conservatively bounding flaw size for the 18-month fuel cycle.

FRAMATOME INC. PROPRIETARY This document and any information contained herein is the property of Framatome Inc. (Framatome) and is to be considered proprietary and may not be reproduced or copied in whole or in part. This document shall not be furnished to others without the express written consent of Framatome and is not to be used in any way which is or may be detrimental to Framatome. This document and any copies that may have been made must be returned to Framatome upon request.

EXPORT CONTROLLED INFORMATION Contains technology subject to U.S. export controls governed by the Export Administration Regulations (15 CFR Part 730 et seq.) and/or the Department of Energy Regulations (10 CFR Part 810). Diversion contrary to U.S. law is prohibited.

Export Classification US EC: N Part 810 EAR ECCN: N/A If the computer software used herein is not the latest version per the EASI list, AP 0402-01 requires that justification be provided.

THE DOCUMENT CONTAINS ASSUMPTIONS THAT SHALL BE VERIFIED PRIOR TO USE THE FOLLOWING COMPUTER CODES HAVE BEEN USED IN THIS DOCUMENT:

CODE/VERSION/REV CODE/VERSION/REV Yes No NONE Controlled Document

Document No. 32-9384463-000 0402-01-F01 (Rev. 023, 06/20/2024)

PROPRIETARY ANO-2 CEDM Penetration 71 Modification As-Left J-Groove Weld One Cycle Justification (Non-Proprietary)

Page 2 Review Method: Design Review (Detailed Check)

Alternate Calculation Does this document establish design or technical requirements? YES NO Does this document contain Customer Required Format?

YES NO Signature Block Name and Title Signature and Date Role Scope / Comments Martin Kolar, Principal Engineer LP All Luziana Matte, Advisory Engineer LR All Craig Wicker Supervisory Engineer A

All Mike Epling Project Manager PM Approval of customer references.

Role Definitions:

P/R/A designates Preparer (P), Reviewer (R), Approver (A);

LP/LR designates Lead Preparer (LP), Lead Reviewer (LR);

M designates Mentor (M);

PM designates Project Manager (PM)







 

 





 

 



  

 


 



Controlled Document

Document No. 32-9384463-000 0402-01-F01 (Rev. 023, 06/20/2024)

PROPRIETARY ANO-2 CEDM Penetration 71 Modification As-Left J-Groove Weld One Cycle Justification (Non-Proprietary)

Page 3 Record of Revision Revision No.

Pages / Sections /

Paragraphs Changed Brief Description / Change Authorization 000 All Initial Issue. The corresponding proprietary document is 32-9384449-000. Proprietary information in this document is indicated by bold brackets ([ ]).

Controlled Document

Document No. 32-9384463-000 PROPRIETARY ANO-2 CEDM Penetration 71 Modification As-Left J-Groove Weld One Cycle Justification (Non-Proprietary)

Page 4 Table of Contents Page SIGNATURE BLOCK................................................................................................................................ 2 RECORD OF REVISION.......................................................................................................................... 3 LIST OF TABLES..................................................................................................................................... 5 LIST OF FIGURES................................................................................................................................... 6 1.0 PURPOSE..................................................................................................................................... 7 2.0 ANALYTICAL METHODOLOGY................................................................................................... 7 2.1 Applied Stress Intensity Factor Acceptance Criteria (IWB-3612)...................................... 7 2.2 Primary Stress Limits (NB-3000)....................................................................................... 8 3.0 ASSUMPTIONS............................................................................................................................ 8 3.1 Unverified Assumptions..................................................................................................... 8 3.2 Justified Assumptions........................................................................................................ 9 4.0 COMPUTER USAGE.................................................................................................................... 9 5.0 CALCULATIONS........................................................................................................................... 9 5.1 Applied Stress Intensity Factor Acceptance Criteria (IWB-3612) Evaluation

[

]................................................................................................................... 9 5.1.1 Geometry.............................................................................................................. 9 5.1.2 Material...............................................................................................................12 5.1.3 Weld Residual Stresses......................................................................................12 5.1.4 Transient Loading Conditions.............................................................................13 5.1.5 Review of ASME Section XI Criteria...................................................................14 5.2 Primary Stress Limit Evaluation (NB-3000).....................................................................15 6.0 RESULTS....................................................................................................................................18

7.0 REFERENCES

............................................................................................................................19 APPENDIX A : EFFECTS OF WRS + [

] ON SIF..................... A-1 APPENDIX B : JUSTIFICATION FOR CONTINGENCY REPAIRS.................................................... B-1 Controlled Document

Document No. 32-9384463-000 PROPRIETARY ANO-2 CEDM Penetration 71 Modification As-Left J-Groove Weld One Cycle Justification (Non-Proprietary)

Page 5 List of Tables Page Table 5-1: Geometry [

].....................................................................................................11 Table 5-2: Material [

]........................................................................................................12 Table 5-3: Transient Cycles...................................................................................................................14 Table 5-4: Primary Stress Limit Reinforcement Evaluation...................................................................15 Controlled Document

Document No. 32-9384463-000 PROPRIETARY ANO-2 CEDM Penetration 71 Modification As-Left J-Groove Weld One Cycle Justification (Non-Proprietary)

Page 6 List of Figures Page Figure 5-1: Reinforcement Area Diagram..............................................................................................17 Figure 5-2: J-Groove Weld plus Flaw Area Removed...........................................................................17 Controlled Document

Document No. 32-9384463-000 PROPRIETARY ANO-2 CEDM Penetration 71 Modification As-Left J-Groove Weld One Cycle Justification (Non-Proprietary)

Page 7 1.0 PURPOSE During the Fall 2024 outage (2R30), as a part of the ultrasonic examination (UT) for the inservice inspection at Arkansas Nuclear One Unit 2 (ANO-2), an axial indication was discovered on the downhill side of the J-Groove (JGW) attachment weld of Control Element Drive Mechanism (CEDM) Penetration No. 71 on the reactor vessel closure head (RVCH). Therefore, a half nozzle repair is performed, which removes and replaces the lower portion of the CEDM nozzle, using the inside diameter tempered bead (IDTB) weld process to attach the replacement nozzle to the RVCH and the remaining upper portion of the CEDM nozzle. The repair moves the pressure boundary from the existing JGW to the new pressure boundary weld located in the RVCH penetration bore above the original JGW. The purpose of this evaluation is to perform a one cycle justification (OCJ) to assess the suitability of leaving a degraded, as-left J-Groove weld (ALJGW) in the RVCH following the CEDM nozzle repair.

Appendix A provides additional discussion on the effects of the weld residual stress (WRS) plus [

] on the stress intensity factors (SIFs).

Appendix B provides justification for the Contingency Shallow Cut and Contingency Overbore repair methods.

2.0 ANALYTICAL METHODOLOGY Reference [1] and Reference [2] contain the design input relevant to the RVCH CEDM penetration No. 71 repair and evaluation. Per Reference [2], the design transients provided in CARK2-RV030-TM-PA-000001 (Reference

[3]) remain applicable. Reference [4] is the design specification for this repair and evaluation. The requirements of Reference [5] and Reference [6] are used in this evaluation. Material properties are obtained from Reference

[7].

Per ASME Section XI, IWB-3610(d), a component containing a flaw is acceptable for continued service during the evaluated time period if the following criteria are satisfied:

1)

The criteria of IWB-3611 or IWB-3612 (Reference [5]).

2)

The primary stress limits of NB-3000 (Reference [6]), assuming a local area reduction of the pressure retaining membrane that is equal to the area of the detected flaw(s) as determined by the flaw characterization rules of IWA-3000.

The evaluation time period for this calculation is one fuel cycle (18 months).

This calculation follows a similar methodology as used in the OCJ evaluation for ANO-2 RVCH CEDM penetration No. 46, Reference [8]. Therefore, a comparative analysis is made between ANO-2 RVCH CEDM penetration No. 71 and the life of repair (LOR) analysis (Reference [9]) for a similar plant (will be referred to as Plant A in this document), since the Plant A evaluation is done for the outermost CEDM location, consistent with the ANO-2 CEDM 71 location. It is also noted that the LOR ALJGW evaluation for ANO-2 nozzle penetration No. 46 is documented in Reference [10]. It is expected that the ANO-2 CEDM penetration No. 71 ALJGW evaluation results will be similar to the LOR analysis results for CEDM penetration No. 46, since these openings have similar JGW geometry, and there are no appreciable differences in material or loads given the relatively close location of nozzles. However, as noted above, since the ANO-2 CEDM penetration No. 71 is located at an outmost penetration, the comparison in this OCJ is done for Plant A, which also considers the outermost location.

2.1 Applied Stress Intensity Factor Acceptance Criteria (IWB-3612)

Per Section 4.7.4 of Reference [4], a comparative ALJGW flaw evaluation shall be performed considering, geometry, materials, and transient loading conditions appropriate to the ANO-2 nozzle penetration No. 71 repair Controlled Document

Document No. 32-9384463-000 PROPRIETARY ANO-2 CEDM Penetration 71 Modification As-Left J-Groove Weld One Cycle Justification (Non-Proprietary)

Page 8 configuration to demonstrate acceptability for one-fuel cycle (18 months). The existing ALJGW flaw evaluation performed for Plant A, which is used for this comparative analysis, is documented in Reference [9]. The general methodology of the analysis used in Reference [9] is summarized below:

Since a potential flaw in the JGW cannot be sized by currently available non-destructive examination techniques, it is assumed that the as-left condition of the remaining JGW includes degraded or cracked weld material extending through the entire JGW and Alloy 182 butter material. The purpose of this analysis is to determine from a fracture mechanics viewpoint the suitability of leaving degraded JGW material in the RVCH following repair of the nozzle. [

]

The fracture mechanics analysis is performed wherein stress intensity factors are calculated at increments of fatigue crack growth for comparison with the fracture toughness requirements of Section XI. Article IWB-UHTXLUHVDVDIHW\\IDFWRURI¥IRUQormal conditions to be used when comparing the applied stress intensity factor to the material fracture toughness. Calculations are performed for a postulated radial corner crack on the [

] side ([

]) of the CEDM nozzle.

Therefore, comparison of the ANO-2 specific design inputs to the existing Plant A ALJGW evaluation is done to demonstrate that the component containing the postulated flaw satisfies the acceptance criteria of IWB-3612 (Reference [5]) per IWB-3610(d)(1), and thus it is acceptable for continued service during the evaluation time period (one fuel cycle).

This evaluation explicitly considers IWB-3612 (a) criteria for normal conditions only. IWB-3612 (b) criteria for emergency and faulted conditions are inferred to be met based on the discussion in Section 5.1.4, Item 3.

2.2 Primary Stress Limits (NB-3000)

Per IWB-3610(d)(2), primary stress limits of NB-3000 (Reference [6]), assuming a local area reduction of the pressure retaining membrane that is equal to the area of the flaw, shall be satisfied. To evaluate this criterion, the reinforcement requirements of NB-3330 are evaluated, which compares the available reinforcement area at the location of the repaired nozzle with the area removed, including conservatively considering the entire area of the JGW and a bounding flaw growth associated with the life of the Plant A repair analysis and applying it to a one fuel cycle repair for ANO-2 Penetration No. 71 repair configuration.

3.0 ASSUMPTIONS 3.1 Unverified Assumptions None.

Document

Document No. 32-9384463-000 PROPRIETARY ANO-2 CEDM Penetration 71 Modification As-Left J-Groove Weld One Cycle Justification (Non-Proprietary)

Page 9 3.2 Justified Assumptions The following justified assumptions are used in this evaluation:

4.0 COMPUTER USAGE No engineering software was used in this calculation.

5.0 CALCULATIONS 5.1 Applied Stress Intensity Factor Acceptance Criteria (IWB-3612) Evaluation

[

]

As stated in Section 2.1, comparison of the ANO-2 nozzle Penetration No. 71 repair configuration design inputs to the design inputs used in the Plant A ALJGW evaluation (Reference [9]) is done to demonstrate the ANO-2 component containing the flaw satisfies the acceptance criteria of IWB-3612 (Reference [5]). Thus, it is acceptable for continued service for one fuel cycle (18 months).

5.1.1 Geometry The geometry of the ANO-2 CEDM nozzle Penetration No. 71 modification is compared to the geometry evaluated in a Plant A ALJGW analysis (Reference [9]), which is summarized in Table 5-1. The following conclusions are made regarding the geometry of the analyzed configuration compared to the ANO-2 specific penetration:

Controlled Document

Document No. 32-9384463-000 PROPRIETARY ANO-2 CEDM Penetration 71 Modification As-Left J-Groove Weld One Cycle Justification (Non-Proprietary)

Page 10

1. [

] Therefore, it is concluded that the ANO-2 penetration is bounded by the Plant A penetration, in terms of the impact of geometry on [

]

2. [

] Therefore, in terms of [

] the ANO-2 configuration is bounded by Plant A.

Controlled Document

Document No. 32-9384463-000 PROPRIETARY ANO-2 CEDM Penetration 71 Modification As-Left J-Groove Weld One Cycle Justification (Non-Proprietary)

Page 11 Table 5-1: Geometry [ Comparison ]

Description Equation Total Horizontal Distance to Penetration D=¥(D12+D22)

Nozzle Angle (Hillside)

=sin-1(D/(R-tc))

Head Thickness at Penetration t

Radius to Base Metal R

R/t Ratio R/t Cladding Thickness tc CEDM Nozzle OD ODn Counterbore Db JGW Butter Layer Thickness tb Uphill, JGW Height, Chamfer to Butter-RVCH Interface (Plant A)

H1U Downhill, JGW Height, Chamfer to Butter-RVCH Interface (Plant A)

H1D Uphill, JGW Height, Clad to Chamfer (Plant A)

H2U Downhill, JGW Height, Clad to Chamfer (Plant A)

H2D Uphill, JGW Height, Clad to JGW-Butter Interface (ANO2)

H Downhill, JGW Height, Clad to JGW-Butter Interface (ANO2)

J Uphill, Equivalent Weld Height, Clad to Butter-RVCH Interface HWUH = H+tb (ANO2)

HWUH = H1U+H2U (Plant A)

Downhill, Equivalent Weld Height, Clad to Butter-RVCH Interface HWDH = J+tb (ANO2)

HWDH = H1D+H2D (Plant A)

Controlled Document

Document No. 32-9384463-000 PROPRIETARY ANO-2 CEDM Penetration 71 Modification As-Left J-Groove Weld One Cycle Justification (Non-Proprietary)

Page 12 5.1.2 Material The material aspects of the ANO-2 configuration are compared to the materials evaluated in the existing Plant A ALJGW analysis (Reference [9]), which are summarized in Table 5-2. The following conclusions are made regarding the materials of the analyzed configuration compared to the ANO-2 specific penetration:

1. [

]

Therefore, it is concluded that the ANO-2 penetration is equivalent to the Plant A penetration in terms of the impact of [

]

2. [

] It is concluded that the yield strength is equivalent for SA-533 Gr. B CL. 1 material, applicable for both ANO-2 and Plant A.

3. [

] Since the ANO-2 RTNDT is less than the RTNDT value used for Plant A, the fracture toughness of the ANO-2 RVCH is bounded by the Plant A fracture toughness evaluation.

Table 5-2: Material [

]

Item RVCH Material Cladding Material Existing Weld Material RVCH Yield Strength at 600°F RVCH RTNDT 5.1.3 Weld Residual Stresses Consideration of WRS for the Plant A evaluation is discussed in Section 5.0 of Reference [9]. [

]

Controlled Document

Document No. 32-9384463-000 PROPRIETARY ANO-2 CEDM Penetration 71 Modification As-Left J-Groove Weld One Cycle Justification (Non-Proprietary)

Page 13 Comparing the repair drawings for ANO-2 (Reference [14]) and Plant A (Reference [15]), the original weld size for the ANO-2 JGW and butter is smaller than the Plant A weld. Therefore, the WRS conclusions made for the Plant A evaluation would bound the ANO-2 configuration [

]

Effects of WRS plus [

] on the stress intensity factors are discussed in Appendix A.

5.1.4 Transient Loading Conditions

[

] stresses due to transient loading conditions and cycles are considered in the flaw growth evaluation.

The transient loading conditions applicable to ANO-2 and Plant A are defined in the following references.

ANO-2: Per Section 4.2 of Reference [4], the applicable transients, cycles, temperature, and pressures for ANO-2 are specified in Reference [3] (CARK2-RV030-TM-PA-000001).

Plant A: Per Section 5.0 of Reference [9], transient stresses are obtained from the IDTB repair analysis (Reference [13]). The transients used for this evaluation are listed in Table 5-1 of Reference [13], with pressure and temperature values for each transient defined in Table 5-2 through Table 5-6 of Reference [13],

with timepoints selected for the Section III structural evaluation listed in Table 6-1 through Table 6-5 of Reference [13].

Reviewing the above inputs, the following conclusions are made regarding the transient loading conditions of the analyzed configuration compared to the ANO-2 specific penetration:

1. [

] Thus, it is concluded that the ANO-2 penetration is bounded by the Plant A penetration in terms of the transient impact on the applied stresses.

2. [

] For all transients evaluated in Reference [9], the number of cycles evaluated for Plant A bound the cycles for ANO-2 for 1 fuel cycle (1.5 years).

Controlled Document

Document No. 32-9384463-000 PROPRIETARY ANO-2 CEDM Penetration 71 Modification As-Left J-Groove Weld One Cycle Justification (Non-Proprietary)

Page 14

[

]

3.

It is noted that Level C/D (Emergency/Faulted) requirements are not explicitly evaluated in Reference [9].

However, the IWB-3612 safety factor for Normal/Upset conditions is ¥10 = 3.16, versus ¥2 = 1.414 for Emergency/Faulted conditions. Per Reference [3], the maximum Level C/D pressure is [

]

which is lower than the maximum pressure evaluated in Reference [9] of [

] Therefore, it can be inferred that Level C/D criteria are met.

Table 5-3: Transient Cycles 5.1.5 Review of ASME Section XI Criteria Reviewing the equations used in Reference [9], the following conclusions are made regarding the differences in Reference [9] compared to the equations applicable to ANO-2 using ASME Code,Section XI, Reference [5].

Controlled Document

Document No. 32-9384463-000 PROPRIETARY ANO-2 CEDM Penetration 71 Modification As-Left J-Groove Weld One Cycle Justification (Non-Proprietary)

Page 15

1. [

] Therefore, the evaluation contained in Reference [9] is conservative in this respect, per the requirements of Reference [5].

5.2 Primary Stress Limit Evaluation (NB-3000)

Per IWB-3610(d)(2), primary stress limits of NB-3000 (Reference [6]), assuming a local area reduction of the pressure retaining membrane that is equal to the area of the flaw, shall be satisfied. To evaluate this criterion, the reinforcement requirements of NB-3330 are evaluated, which compares the available reinforcement area at the location of the repaired nozzle with the area removed, including the entire area of the JGW and bounding flaw growth obtained from the existing Plant A analysis, and making it applicable for one fuel cycle for ANO-2.

Table 5-4 calculates the available reinforcement area (Ah), as depicted in Figure 5-1, and the area removed (Arem) by the penetration bore and JGW plus flaw, as depicted in Figure 5-1 and Figure 5-2. Since the available reinforcement area is larger than the area removed, the reinforcement requirements of NB-3330 are met.

Table 5-4: Primary Stress Limit Reinforcement Evaluation Calculation Parameter Tentative Pressure Thickness Design Pressure Inside radius of head Design stress intensity Tentative pressure thickness (NB-3324.2)

Removed Area due to Nozzle Bore Bore Diameter (Max)(1)

Plane distance of center of nozzle Tentative outside radius of head Vertical distance to inside radius Vertical distance to outer tentative thickness Depth of opening Opening area removed Removed Area due to JGW plus Crack Growth Maximum JGW Height Maximum Crack Growth + Compressive Zone Total height of flaw into RVCH Width of JGW from RVCH bore (at top of JGW)(2)

Document

Document No. 32-9384463-000 PROPRIETARY ANO-2 CEDM Penetration 71 Modification As-Left J-Groove Weld One Cycle Justification (Non-Proprietary)

Page 16 Calculation Parameter Total width of JGW + flaw into RVCH (at top)

JGW Angle Width of JGW angle area Nozzle Angle (Hillside)

Downhill area removed Total JGW + flaw removed area Removed Area Total removed area Limits of Reinforcement Radius RVCH thickness Nozzle thickness (no credit taken)

Mean radius of RVCH NB-3334.1(a)(1) Lw1 NB-3334.1(a)(2) Lw2 Distance to accommodate 100%

reinforcement NB-3334.1(b)(1)

NB-3334.1(b)(2)

Distance to accommodate 2/3 reinforcement Length available for Reinforcement (Half distance to nearest opening)

Reinforcement Area Outer RVCH radius Vertical distance to outer RVCH Depth of reinforcement RVCH reinforcement area available Verify Reinforcement Area is greater than Removed Area Controlled Document

Document No. 32-9384463-000 PROPRIETARY ANO-2 CEDM Penetration 71 Modification As-Left J-Groove Weld One Cycle Justification (Non-Proprietary)

Page 17 Figure 5-1: Reinforcement Area Diagram Figure 5-2: J-Groove Weld plus Flaw Area Removed Controlled Document

Document No. 32-9384463-000 PROPRIETARY ANO-2 CEDM Penetration 71 Modification As-Left J-Groove Weld One Cycle Justification (Non-Proprietary)

Page 18 6.0 RESULTS Per Section 5.1, it is demonstrated by comparative analysis that based on the evaluation of fatigue crack growth of the ALJGW flaw into the low alloy steel RVCH, the ASME Code,Section XI, IWB-3612 requirements for fracture toughness are met for at least one fuel cycle (18 months) for the key transient inputs provided in Reference [3] for the evaluation. In addition, per Section 5.2, the primary stress limits considering reinforcement requirements of NB-3330 are met, considering a local area reduction in the pressure retaining membrane of the nozzle opening which includes the JGW and a conservatively bounding flaw size for the 18-month fuel cycle.

Based on the comparative analysis between ANO-2 and the existing Plant A ALJGW evaluation, the following conservatisms are noted for the ANO-2 configuration:

x The Plant A evaluation is based on the final flaw size at the predicted end life of the repair, which is

[

] The ANO-2 OCJ requires evaluation for only 1.5 years (18 months). Table 5-3 summarizes the transient cycles for each plant for the applicable number of years, which demonstrates the cycles considered for Plant A are conservative. See Section 5.1.4.

x The Plant A RVCH radius is about [

] than the ANO-2 RVCH radius, while the RVCH thickness is [

] which results in conservative primary stresses for ANO-2. In addition, the initial flaw depth for Plant A is [

] than the flaw depth for ANO-2. See Section 5.1.1.

x The Plant A evaluation used the crack arrest fracture toughness, KIa, instead of the crack initiation fracture toughness, KIc. In addition, the Plant A evaluation considers a RTNDT of [

] while a RTNDT of

[

] is applicable to ANO-2. Both factors result in a conservative calculation of the structural margins per the ASME code requirement per Reference [5] for ANO-2. See Sections 5.1.2 and 5.1.5.

x The reinforcement requirements of ASME NB-3330 consider the reduction in the nozzle opening area including the JGW and flaw growth area based on the flaw growth at the end life for Plant A repair (See Section 5.2), which as summarized above is very conservative for ANO-2.

All other items considered are comparable between ANO-2 and Plant A.

Controlled Document

Document No. 32-9384463-000 PROPRIETARY ANO-2 CEDM Penetration 71 Modification As-Left J-Groove Weld One Cycle Justification (Non-Proprietary)

Page 19

7.0 REFERENCES

References identified with an (*) are maintained within ANO-2 Records System and are not retrievable from Framatome Records Management. These are acceptable references per Framatome Administrative Procedure 0402-01, Attachment 7. See page 2 for Project Manager Approval of customer references.

1.

[

]

2.

[

]

3.

[

]

4.

[

]

5.

ASME Boiler and Pressure Vessel Code,Section XI, Rules for Inservice Inspection of Nuclear Power Plant Components, Division 1, 2007 Edition with 2008 Addenda.

6.

ASME Boiler and Pressure Vessel Code,Section III, Rules for Construction of Nuclear Facility Components, Division 1, 1992 Edition with no Addenda.

7.

ASME Boiler and Pressure Vessel Code,Section II, Part D, 1992 Edition with no Addenda.

8.

[

]

9.

[

]

10.

[

]

11.

[

]

12.

• Arkansas Nuclear One - Unit 2, Safety Analysis Report, Facility Operating License Number NPF-6, Docket Number 50-368, updated through Amendment 32.

13.

[

]

14.

[

]

15.

[

]

16.

• ANO-2 Document M-2001-C2-26, Closure Head Penetrations, 234-761, Rev. 3.

17.

[

]

18.

[

]

Controlled Document

Document No. 32-9384463-000 PROPRIETARY ANO-2 CEDM Penetration 71 Modification As-Left J-Groove Weld One Cycle Justification (Non-Proprietary)

Page A-1 APPENDIX A: EFFECTS OF WRS + [

] ON SIF The purpose of this appendix is to provide additional discussion on the effects of the weld residual stresses (WRS) plus [

] on the stress intensity factors (SIFs).

Stress intensity factors are calculated for Plant A in Section 6.0 of Reference [9]. Table 5 of Reference [9]

contains SIF values due to effects of [

] only. As discussed in Section 5.1.3, [

]

Therefore, an additional existing ALJGW flaw evaluation performed for a similar plant in Reference [17] (referred to as Plant B in this appendix), is used for this comparative analysis.

Plant B RVCH and CRDM nozzle penetration key dimensions are listed as follows:

Spherical radius to cladding = [

]

Head thickness = [

]

Cladding thickness = [

]

Penetration bore = [

]

Horizontal Radius to Outermost Penetration = [

]

Based on the dimensions listed for ANO-2 in Table 5-1, the R/t ratio for ANO-2 is [

] than for Plant B and therefore, the hoop stresses due to pressure in the RVCH are [

] for ANO-2. In addition, Plant B RVCH and JGW filler and butter materials are [

]

With respect to JGW dimensions, Plant B has [

] JGW volume with an initial flaw depth of

[

] which is [

] than ANO-2 initial flaw size

[

]

[

] Table A-1 of Reference

[17] calculates a SIF for the initial flaw depth due WRS of [

] Table A-7 of Reference [17] calculates the SIF due to [

] The total SIF at the initial flaw depth due to WRS plus

[

] is calculated to be [

] which is below the maximum allowable SIF value of 63.2 ksiin based on a required linear elastic fracture mechanics (LEFM) safety margin of 10 per IWB-3612 (Reference [5]).

Based on the comparative analysis between ANO-2 and the existing Plant B ALJGW evaluation, it is concluded that the effects of WRS plus [

] on the initial flaw size for Plant B would bound the ANO-2 configuration.

Controlled Document

Document No. 32-9384463-000 PROPRIETARY ANO-2 CEDM Penetration 71 Modification As-Left J-Groove Weld One Cycle Justification (Non-Proprietary)

Page B-1 APPENDIX B:

JUSTIFICATION FOR CONTINGENCY REPAIRS The purpose of this appendix is to address the two contingency repairs identified in Reference [14]. Section B.1 addresses the Contingency Shallow Cut repair and Section B.2 addresses the Contingency Overbore repair.

B.1 Contingency Shallow Cut Repairs The Contingency Shallow Cut repair is identified in Steps 4A.1 through 4A.3 of Reference [14]. [

]

[

] this repair does not impact the evaluation contained in the main body of this document, with the following considerations noted:

B.2 Contingency Overbore Repair The Contingency Overbore repair is identified in Steps 4B.1 through 4B.3 of Reference [14]. [

]

[

] Therefore, the analysis detailed in Section 5.2 is still applicable and this contingency repair has no impact on the evaluation contained in the main body of this document.

[

]

Controlled Document 5 to 2CAN112403 OCJ IDTB Weld Anomaly Assessment at CEDM Nozzle No. 71 at ANO 2 Document Number 32-9384462-000 NON-PROPRIETARY (18 pages)

Page 1 of 18 0402-01-F01 (Rev. 023, 06/20/2024)

PROPRIETARY CALCULATION

SUMMARY

SHEET (CSS)

Document No.

32 9384462 000 Safety Related: Yes No Title OCJ IDTB Weld Anomaly Assessment at CEDM Nozzle No. 71 at ANO-2 (Non-Proprietary)

PURPOSE AND

SUMMARY

OF RESULTS:

Purpose:

The purpose of this evaluation is to provide a One Cycle Justification (OCJ) for acceptability of potential Inner Diameter Temper Bead (IDTB) triple point weld anomalies in the repaired Control Element Drive Mechanism (CEDM) nozzle penetration No. 71 at Arkansas Nuclear One Unit 2 (ANO-2).

Summary: This document demonstrates by comparison to an existing IDTB weld anomaly life of the repair analysis with a postulated initial flaw depth of [

] and similar geometry, material and loading conditions, that potential weld anomalies in the ANO-2 CEDM nozzle penetration No. 71 IDTB weld repair meet the following ASME acceptance criteria for normal/upset and emergency/faulted operating conditions for one cycle (18 months) of operation:

x Section XI IWB-3612: Applied stress intensity factor criteria x

Section XI IWB-3642: For a full 360° radial circumferential flaw, limit load criteria to demonstrate sufficient loading capacity x

Section III NB 3227.1: For a cylindrical flaw, shear stress criteria x

Section XI IWB-3643 that flaw depths shall not exceed 75% of the wall thickness.

Based on the comparative analysis between ANO-2 and an existing IDTB repair weld anomaly evaluation for a similar nuclear unit (Plant A), the following conservatisms are noted for the ANO-2 configuration:

x The Plant A evaluation is based on the final flaw size at the predicted end life of the repair, [

] years.

The ANO-2 OCJ requires evaluation for only 1.5 years (18 months). Table 4-3 summarizes the transient cycles for each plant for the applicable number of years, which demonstrates that the associated cycles considered in the reference analysis are conservative.

x The Plant A RVCH radius is about [

] than the ANO-2 RVCH radius, while the RVCH thickness is comparable for both plants, which results in conservative prediction of primary stresses for ANO-2.

x The Plant A evaluation considered the [

] instead of the [

] In addition, the evaluation considered an RTNDT of [

] while an RTNDT of [

]

is applicable to ANO-2. Both factors result in conservative structural margins per the ASME code requirements for ANO-2.

Note: Proprietary information in this document is indicated by bolded brackets ([ ]).

FRAMATOME INC. PROPRIETARY This document and any information contained herein is the property of Framatome Inc. (Framatome) and is to be considered proprietary and may not be reproduced or copied in whole or in part. This document shall not be furnished to others without the express written consent of Framatome and is not to be used in any way which is or may be detrimental to Framatome. This document and any copies that may have been made must be returned to Framatome upon request.

EXPORT CONTROLLED INFORMATION Contains technology subject to U.S. export controls governed by the Export Administration Regulations (15 CFR Part 730 et seq.) and/or the Department of Energy Regulations (10 CFR Part 810). Diversion contrary to U.S. law is prohibited.

Export Classification US EC: N Part 810 EAR ECCN: N/A If the computer software used herein is not the latest version per the EASI list, AP 0402-01 requires that justification be provided.

THE DOCUMENT CONTAINS ASSUMPTIONS THAT SHALL BE VERIFIED PRIOR TO USE THE FOLLOWING COMPUTER CODES HAVE BEEN USED IN THIS DOCUMENT:

CODE/VERSION/REV CODE/VERSION/REV Yes No N/A Controlled Document

Document No. 32-9384462-000 0402-01-F01 (Rev. 023, 06/20/2024)

PROPRIETARY OCJ IDTB Weld Anomaly Assessment at CEDM Nozzle No. 71 at ANO-2 (Non-Proprietary)

Page 2 Review Method: Design Review (Detailed Check)

Alternate Calculation Does this document establish design or technical requirements? YES NO Does this document contain Customer Required Format?

YES NO Signature Block Name and Title Signature and Date Role Scope / Comments Samer Mahmoud Advisory Engineer P

All Pages / All Sections Jennifer Nelson Principal Engineer R

All Pages / All Sections Craig Wicker Supervisory Engineer A

All Pages / All Sections Role Definitions:

P/R/A designates Preparer (P), Reviewer (R), Approver (A);

LP/LR designates Lead Preparer (LP), Lead Reviewer (LR);

M designates Mentor (M);

PM designates Project Manager (PM)

 

 



 

 



 


 



Controlled Document

Document No. 32-9384462-000 0402-01-F01 (Rev. 023, 06/20/2024)

PROPRIETARY OCJ IDTB Weld Anomaly Assessment at CEDM Nozzle No. 71 at ANO-2 (Non-Proprietary)

Page 3 Record of Revision Revision No.

Pages / Sections /

Paragraphs Changed Brief Description / Change Authorization 000 All Pages / All Sections Initial release of the document. The corresponding proprietary document is 32-9384443-000.

Controlled Document

Document No. 32-9384462-000 PROPRIETARY OCJ IDTB Weld Anomaly Assessment at CEDM Nozzle No. 71 at ANO-2 (Non-Proprietary)

Page 4 Table of Contents Page SIGNATURE BLOCK................................................................................................................................2 RECORD OF REVISION..........................................................................................................................3 LIST OF TABLES.....................................................................................................................................5 LIST OF FIGURES...................................................................................................................................6 1.0 PURPOSE.....................................................................................................................................7 2.0 METHODOLOGY..........................................................................................................................8 2.1 Postulated Flaws...............................................................................................................................8 2.2 Acceptance Criteria...........................................................................................................................8 3.0 ASSUMPTIONS............................................................................................................................9 3.1 Unverified Assumptions.....................................................................................................................9 3.2 Justified Assumptions........................................................................................................................9 4.0 DESIGN INPUTS........................................................................................................................10 4.1 Construction Materials.....................................................................................................................10 4.2 Geometry.........................................................................................................................................10 4.3 Transient Loading............................................................................................................................11 4.4 Weld Residual Stresses..................................................................................................................13 4.5 Proximity of Nozzle Penetration to Circumferential Seam Weld in RVCH......................................13 4.6 Comparison of Flaw Evaluations.....................................................................................................14 4.6.1 Acceptance Criteria..........................................................................................................14 4.6.2 Crack Growth Rates.........................................................................................................14 5.0 RESULTS / CONCLUSION.........................................................................................................15

6.0 REFERENCES

............................................................................................................................16 APPENDIX A : CONTINGENCY REPAIRS EVALUATION................................................................. A-1 Controlled Document

Document No. 32-9384462-000 PROPRIETARY OCJ IDTB Weld Anomaly Assessment at CEDM Nozzle No. 71 at ANO-2 (Non-Proprietary)

Page 5 List of Tables Page Table 4-1: Materials of Construction.......................................................................................................10 Table 4-2: Dimensions............................................................................................................................11 Table 4-3: List of Design Transient Cycles............................................................................................13 Document

Document No. 32-9384462-000 PROPRIETARY OCJ IDTB Weld Anomaly Assessment at CEDM Nozzle No. 71 at ANO-2 (Non-Proprietary)

Page 6 List of Figures Page Figure 1-1: IDTB Repair Geometry and Weld Anomaly Locations..........................................................7 Controlled Document

Document No. 32-9384462-000 PROPRIETARY OCJ IDTB Weld Anomaly Assessment at CEDM Nozzle No. 71 at ANO-2 (Non-Proprietary)

Page 7 1.0 PURPOSE During the Fall 2024 outage (2R30) at Arkansas Nuclear One Unit 2 (ANO-2), an axial indication was discovered on the downhill side in the J-groove attachment weld of Control Element Drive Mechanism (CEDM) Penetration No. 71 on the reactor vessel closure head (RVCH). As a mitigative measure, a half nozzle repair is being performed to remove and replace the lower portion of the CEDM nozzle. The inside diameter tempered bead (IDTB) weld procedure is used to attach the replacement nozzle to the RVCH and the remaining upper portion of the CEDM nozzle. The repair moves the pressure boundary from the existing J-Groove weld (JGW) to the new pressure boundary at the IDTB weld located in the RVCH penetration bore above the original JGW. During the welding process, weld anomalies may form at the triple point locations, where the three materials of the weld, nozzle and RVCH intersect. Two weld anomalies may potentially form at the upper and lower triple points, as depicted in Figure 1-1. The upper triple point is defined as the intersection of the RVCH low alloy steel (LAS) base material, the existing CEDM nozzle, and the [

] weld. The lower triple point is defined as the intersection of the RVCH low alloy steel base material, the [

] replacement CEDM nozzle, and the [

]

weld. The purpose of this evaluation is to provide a one cycle justification (OCJ) for the acceptability of the CEDM nozzle repair using a fracture mechanics comparative analysis to assess the triple point weld anomalies impact on the structural integrity of the repair. The evaluation of contingency repair options is included in Appendix A of this document.

This justification focuses only on weld anomalies at pressure the boundary formed by newly installed IDTB weld; the as left J-groove weld is addressed elsewhere.

Figure 1-1: IDTB Repair Geometry and Weld Anomaly Locations Controlled Document

Document No. 32-9384462-000 PROPRIETARY OCJ IDTB Weld Anomaly Assessment at CEDM Nozzle No. 71 at ANO-2 (Non-Proprietary)

Page 8 2.0 METHODOLOGY As required by Section 4.7.5 of Reference [9], a comparative weld anomaly analysis shall be performed considering geometry, material, and transient loading conditions that are appropriate to the ANO-2 nozzle penetration No. 71 repair configuration. The evaluation shall demonstrate acceptability for one-fuel cycle by demonstrating that the potential IDTB weld anomalies at the modified RVCH nozzle penetration meet the applicable acceptance criteria of the ASME Code Section XI, 2007 Edition with 2008 Addenda (Reference [2]), such as paragraph IWB-3612 for normal/upset and emergency/faulted conditions.

To conduct the OCJ comparative assessment, the fracture analysis of the IDTB repair weld triple point anomaly performed in Reference [12] for a similar plant is used. The analyzed plant in Reference [12] is referred to as Plant A throughout this document. The justification in this document is based on the comparison of geometry, materials of construction, weld residual stresses (WRS), operating loads, transient cycles, and possible margins gained by changes in acceptance criteria. General methodology for the weld analysis assessment is summarized in Sections 2.1 and 2.2 Note that this calculation follows similar methodology as used in the OCJ evaluation for ANO-2 nozzle penetration No. 46 (Reference [18]). Therefore, the comparative analysis is made between ANO-2 nozzle penetration No. 71 and the life of repair (LOR) analysis for Plant A (Reference [12]), since the Plant A evaluation is done for the outermost CEDM location, consistent with the CEDM 71 location. It is also noted that the LOR weld anomaly evaluation for ANO-2 nozzle penetration No. 46 is documented in Reference [19]. It is expected that the ANO-2 nozzle penetration No. 71 weld anomaly evaluation results will closely follow the LOR analysis results for No. 46, since there are no appreciable differences in IDTB weld geometry, material or loads given the relatively close location of nozzles. However, as noted above, since the ANO-2 nozzle penetration No. 71 is located at an outermost penetration, the comparison in this OCJ is done for Plant A, which also considers the outermost location.

2.1 Postulated Flaws The following flaws are postulated at both the upper and lower weld anomalies (triple points) locations.

All postulated flaws are [

] deep:

1.

Radial-circumferential with respect to the CEDM nozzle axis (see Figure A-3541-1 of Reference [3], full 360° circumferential flaw). Since this flaw reduces the cross section of the nozzle, it is required to demonstrate by limit load analysis that the remaining ligament has sufficient loading capacity (IWB-3642 of Reference [2]).

2.

Radial-axial with respect to the CEDM nozzle axis (see Figure A-3560-1 of Reference [3]).

3.

Cylindrical flaw, which is a flaw concentric with the CEDM nozzle; the flaw is located at the interface between the IDTB weld and closure head penetration surface.

2.2 Acceptance Criteria According to IWB-3612 (Reference [2]), a flaw is acceptable if the applied stress intensity factor (SIF) at the final flaw size is less than the fracture toughness (at the crack tip temperature) of the material with appropriate safety factors, and it satisfies the following criteria:

1.

For Level A and Level B (Normal and Upset) service level condition:

_ (_) < _/10 2.

For Level C and Level D (Emergency and Faulted) service level conditions:

_ (_) < _/2 Where KI(af) is the maximum applied SIF at the final flaw size af, and KIc is the initiation fracture toughness of the material at the corresponding crack tip temperature and irradiation level obtained from Figure A-4200-1 of Reference [2].

Document

Document No. 32-9384462-000 PROPRIETARY OCJ IDTB Weld Anomaly Assessment at CEDM Nozzle No. 71 at ANO-2 (Non-Proprietary)

Page 9 For the radial-circumferential (full 360° circumferential) flaw, paragraph IWB-3642 requires that remaining ligament has sufficient loading capacity.

For the cylindrical flaw, the shear stress requirement of NB-3227.1 shall be met.

Any flaw is less than 75% of the wall thickness (IWB-3643).

3.0 ASSUMPTIONS 3.1 Unverified Assumptions There are no unverified assumptions.

3.2 Justified Assumptions 1.

For fatigue crack growth calculations, cycles are assumed to accumulate at a linear rate. Based on plant operating experience, it can be demonstrated that linear rates generally envelope the actual accumulation rates observed for transients.

2.

Per Reference [16] and [17] there are one million cycles of Normal Cyclic Variations (step changes) of

[

] and [

], and that is selected based on one million cycles approximating an infinite number of cycles so that the limiting stress is the endurance limit. Based on experience with flaw growth calculations, [

] of [

] and [

] do not significantly contribute to the flaw growth since the stress intensity factor range (K) produced by these variations is less than [

], as determined by reviewing the data in References [10] and [12]. Since K is the key parameter that drives fatigue crack growth, even considering [

] cycles, these variations would result in insignificant crack growth for the OCJ herein, and are therefore not considered further in this comparative evaluation.

3.

Given the purpose of this document (OCJ) and that the postulated flaw propagates in [

]

weld material or ferritic LAS, stress corrosion cracking (SCC) is considered negligible. Also, for the upper triple point anomaly that can potentially grow in the [

] nozzle, primary water stress corrosion cracking (PWSCC) is ruled out since the flaw postulated at the upper triple point will not be exposed to the reactor coolant.

4.

The design of the CEDM housing nozzle modification includes [

]

IDTB weld. According to Section 5.3 of Reference [10], mechanical loads from CEDM are transmitted to the reactor vessel (RV) head [

] The [

] design feature [

] For this reason, the IDTB weld [

] Thus, this document treats [

]

Controlled Document

Document No. 32-9384462-000 PROPRIETARY OCJ IDTB Weld Anomaly Assessment at CEDM Nozzle No. 71 at ANO-2 (Non-Proprietary)

Page 10 4.0 DESIGN INPUTS 4.1 Construction Materials The material aspects of the ANO-2 configuration are compared to the materials evaluated in the Plant A analysis (Reference [12]), which are summarized in Table 4-1. The following conclusions are made regarding the materials of the analyzed configuration compared to the repaired ANO-2 Nozzle No. 71 specific penetration.

1.

As shown in Table 4-1, the RV closure head base metal RTNDT for ANO-2 is taken from Reference [17];

the Plant A RTNDT [

] Therefore, the RTNDT of the ANO-2 closure head is bounded by the Plant A analysis. Given that operating temperature are comparable (Section 4.3) for both ANO-2 and Plant A, the fracture toughness of ANO-2 is also bounded by the fracture toughness for Plant A.

2.

The IDTB weld materials are considered identical for both ANO-2 and the Plant A analysis.

3.

Material of the CEDM nozzle is also identical for both ANO-2 and the Plant A analysis.

Table 4-1: Materials of Construction Item ANO-2 Design Reference Plant A Design Reference RV Material RV Material RTNDT CEDM Nozzle Material Replacement CEDM Nozzle Material IDTB Weld Material 4.2 Geometry The geometry comparison between the ANO-2 CEDM nozzle penetration No. 71 modification and the geometry evaluated in the Plant A analysis (Reference [12]) is shown in Table 4-2. The following conclusions are made regarding the geometry of the analyzed configuration compared to the ANO-2 Nozzle No. 71 specific penetration:

1.

The RVCH base metal radius (Ri) for ANO-2 is approximately [

] smaller than the Plant A analysis radius ( [

] ). However, the RVCH base metal thickness (tRV) is similar ( [

] ), which produces a smaller R/t ratio for ANO-2 ( [

] ). Thus, the hoop stresses due to pressure in the RVCH are smaller for ANO-2, while the thermal stresses will be of similar magnitude due to comparable thicknesses (including cladding). In addition, the bore diameter and counterbore are comparable ( [

] ). Therefore, it is concluded that the ANO-2 penetration is bounded by the Plant A analysis, in terms of the impact of geometry on the applied primary and secondary stresses.

2.

The dimensions of the IDTB weld and relevant dimensions of the repaired nozzle are nearly identical. Thus, the dimensions of the IDTB weld and the nozzle have no impact on the analysis.

Controlled Document

Document No. 32-9384462-000 PROPRIETARY OCJ IDTB Weld Anomaly Assessment at CEDM Nozzle No. 71 at ANO-2 (Non-Proprietary)

Page 11 Table 4-2: Dimensions Item Symbol ANO-2 Design Reference Plant A Design Reference Closure Head Inner Radius (base metal) [inch]

Closure Head Thickness (base metal) [inch]

Closure Head Unit Membrane Hoop Stress [psi]

Ratio of Membrane Hoop Stresses Nozzle Outer Diameter (CEDM) [inch]

Nozzle Wall Thickness (CEDM) [inch]

IDTB Weld Outer Diameter [inch]

IDTB Weld Thickness [inch]

IDTB Weld Length [inch]

4.3 Transient Loading The transient comparison between the ANO-2 CEDM nozzle penetration No. 71 and the Plant A analysis (Reference [12]) is listed below, which demonstrates that the ANO-2 CEDM nozzle penetration No. 71 transients are either comparable, or bounded by the Plant A transients and cycles.

1.

The Plant A analysis uses transient stresses developed in Reference [10] and it is recognized that like ANO-2 opening No. 71 (see Figure 4 of Reference [17]), the Plant A analysis covers [

] Therefore, the transient stresses from Plant A analysis of Reference [12] are comparable to the transient stresses applicable to ANO-2 opening No. 71.[

]. Thus, it is concluded that the ANO-2 penetration is bounded by the Plant A penetration, in terms of the transient impact on the applied stresses.

2.

Table 4-3 lists the transient cycles applicable to ANO-2 for one fuel cycle (18 months), with comparison to the number of Plant A cycles for [

] of operation, which is the evaluated number of years for the crack growth evaluation (for the LOR analysis) per Section 8 of Reference [12]. For all transients evaluated in Reference [12], the number of cycles evaluated for Plant A bound the cycles for ANO-2 for one fuel cycle (1.5 years).

3.

Per Reference [15] and [17] there are one million cycles of Normal Cyclic Variations (step changes) of

[

] and [

], and that is selected based on one million cycles approximating an infinite number of cycles so that the limiting stress is the endurance limit. Based on experience with flaw growth calculations, [

] of [

]

and [

] do not contribute to significant flaw growth since the SIF range (K) produced by these variations is less than [

],

as determined by reviewing the data in References [10] and [12]. Since K is the key parameter that drives fatigue crack growth, even considering [

] cycles, these variations would result in insignificant crack growth, for one fuel cycle, and are therefore not considered further in this comparative evaluation.

See Section 3.2, Item #2.

Controlled Document

Document No. 32-9384462-000 PROPRIETARY OCJ IDTB Weld Anomaly Assessment at CEDM Nozzle No. 71 at ANO-2 (Non-Proprietary)

Page 12 4.

It is noted that Level C/D (Emergency/Faulted) conditions are not explicitly evaluated in Reference [12].

However, the IWB-3612 safety factor for Normal/Upset conditions is ¥10 = 3.16, versus ¥2=1.414 for Emergency/Faulted conditions. Per Reference [15] and [17], the maximum Level C/D pressure is

[

]

which is less than the maximum pressure of [

]

evaluated in Reference [12].

Therefore, it is inferred that Level C/D criteria are met without specific evaluation.

Controlled Document

Document No. 32-9384462-000 PROPRIETARY OCJ IDTB Weld Anomaly Assessment at CEDM Nozzle No. 71 at ANO-2 (Non-Proprietary)

Page 13 Table 4-3: List of Design Transient Cycles 4.4 Weld Residual Stresses Consideration of WRS in the Plant A analysis is discussed in Section 5.0 of Reference [12]. [

]

Comparing the repair drawings for ANO-2 (Reference [7]) with the configuration in the Plant A analysis documented in Reference [6], shows that both weld sizes are effectively identical. [

]

are applicable to the ANO-2 comparative analysis.

4.5 Proximity of Nozzle Penetration to Circumferential Seam Weld in RVCH It is noted that the ANO-2 Nozzle at Penetration No. 71 is in the proximity of the RVCH circumferential seam weld, which was not the case for the analyzed weld anomaly for Plant A documented in Reference [12] and used as the basis for the current OCJ. In theory having the circumferential seam weld in the proximity of Penetration No. 71 may have some potential impact on crack growth rate, KIc fracture toughness, and the WRS. Each of the potential factors that may have impact on the weld proximity is discussed below:

1.

Crack Growth Rate - this can potentially impact crack growth for a postulated cylindrical vertical flaw that can propagate by fatigue at the interface between the IDTB weld and the RVCH. Crack growth for LAS ferritic material are documented in Article A-4300 of Section XI of the ASME Code [2], and it does not distinguish between the base metal and weld. However, Reference [12] did not use crack growth in the LAS ferritic material. Reference [12] only used crack growth in austenitic stainless steel multiplied by a factor of 2 which was deemed to be appropriate. [

Controlled Document

Document No. 32-9384462-000 PROPRIETARY OCJ IDTB Weld Anomaly Assessment at CEDM Nozzle No. 71 at ANO-2 (Non-Proprietary)

Page 14

]. Thus, there is no impact on the OCJ comparative analysis due to the proximity of Nozzle Penetration No. 71 to the circumferential seam weld of fatigue crack growth rate.

2.

Fracture Toughness (KIc) - KIc is indexed to the nil-ductility reference temperature (RTNDT). The RTNDT for the ANO-2 RVCH is reported for the entire RVCH. The weld seam intersects the ANO-2 No 71 penetration opening at the OD of the RVCH, away from the IDTB repair. Therefore, the appropriate RTNDT is for the base metal. Thus, there is no impact on the OCJ comparative analysis due to the proximity of Nozzle Penetration No. 71 to the circumferential seam weld.

3.

Weld residual stress - The RVCH received post weld heat treatment (PWHT), which relieves the residual stress produced by the fabrication of the circumferential seam weld. Additionally, the WRS from the IDTB will overcome any impact of the circumferential seam weld on WRS. Thus, there is no impact on the OCJ comparative analysis due to the proximity of Nozzle Penetration No. 71 to the circumferential seam weld.

To conclude, the current OCJ comparative analysis is not impacted by the proximity of Nozzle Penetration No.

71 to the RVCH circumferential seam weld.

4.6 Comparison of Flaw Evaluations 4.6.1 Acceptance Criteria Comparing the equations used in Reference [12] to the equations applicable to ANO-2 using ASME Code,Section XI, Reference [2], the following conclusion is made:

Reference [12] uses the equation for [

] per Section XI, Article A-4200 when evaluating the IWB-3612 safety margins. [

] Therefore, the evaluation contained in Reference [12] is bounding in this respect per the requirements of Reference [2].

As demonstrated in Reference [16], the shear stress criteria of NB-3227.1 are met for the IDTB weld without a flaw with substantial margin, therefore the reduction in cross section caused by a flaw of up to [

] is met [

]

4.6.2 Crack Growth Rates The IDTB weld is made of [

], Step 3 in Reference [7]). Although the 2007 edition of ASME BPV Code Section XI (Reference [2]) [

] it states in paragraph C-8430 that crack growth rates for materials not covered by crack growth rates for austenitic and ferritic steels may be obtained from other sources. The growth rate curve should represent conservative values of fatigue crack growth rates for appropriate environment, cyclic loading and R ratios.

Controlled Document

Document No. 32-9384462-000 PROPRIETARY OCJ IDTB Weld Anomaly Assessment at CEDM Nozzle No. 71 at ANO-2 (Non-Proprietary)

Page 15 The analysis of Plant A uses [

] weld material. The 2021 edition of ASME BPV Code Section XI (Reference [3]) provides

[

] Therefore, the results of fatigue crack growth in Plant A analysis are applicable.

Considering that the fatigue crack growth in Plant A is shown as relatively small and that fatigue crack growth

[

] the analysis of Plant A valid for the life of repair is bounding.

5.0 RESULTS / CONCLUSION This document demonstrates by comparison to an existing IDTB weld anomaly life of the repair analysis with a postulated initial flaw depth of [ 0.1 inch ] and comparable geometry, material and loading conditions, that potential weld anomalies in the ANO-2 CEDM nozzle penetration No. 71 IDTB weld repair meet the following ASME acceptance criteria for normal/upset and emergency/faulted operating conditions for one cycle (18 months) of operation:

x Section XI IWB-3612: Applied SIF criteria x

Section XI IWB-3642: For a full 360° radial circumferential flaw, limit load criteria to demonstrate sufficient loading capacity x

Section III NB 3227.1: For a cylindrical flaw, shear stress criteria x

Section XI IWB-3643 that flaw depths shall not exceed 75% of the wall thickness.

Based on the comparative analysis between ANO-2 and an existing IDTB repair weld anomaly evaluation for a similar nuclear unit (Plant A), the following conservatisms are noted for the ANO-2 configuration:

The Plant A evaluation is based on the final flaw size at the predicted end life of the repair, [

] years. The ANO-2 OCJ requires evaluation for only 1.5 years (18 months). Table 4-3 summarizes the transient cycles for each plant for the applicable number of years, which demonstrates that the associated cycles considered in the Plant A evaluation are conservative.

The Plant A RVCH radius is about [

] than the ANO-2 RVCH radius, while the RVCH thickness is comparable for both plants, which results in conservative primary stresses for ANO-2.

The Plant A evaluation used the [

] instead of the

[

] In addition, the Plant A evaluation considered an RTNDT of [

] while an RTNDT of [

] is applicable to ANO-2. Both factors result in conservative structural margins per the ASME code requirement for ANO-2.

Controlled Document

Document No. 32-9384462-000 PROPRIETARY OCJ IDTB Weld Anomaly Assessment at CEDM Nozzle No. 71 at ANO-2 (Non-Proprietary)

Page 16

6.0 REFERENCES

1.

Code of Federal Regulations, Title 10, Part 50.55a, Domestic Licensing of Production and Utilization Facilities, Codes and Standards, Federal Register Vol. 85, p. 65662, Oct. 16, 2020.

2.

ASME Boiler and Pressure Vessel Code,Section XI, Rules for Inservice Inspection of Nuclear Power Plant Components, Division 1, 2007 Edition with 2008 Addenda.

3.

ASME Boiler and Pressure Vessel Code,Section XI, Rules for Inservice Inspection of Nuclear Power Plant Components Division 1, 2021 Edition.

4.

5.

6.

7.

8.

9.

10.

11.

12.

13.

14.

15.

16.

17.

18.

19.

Controlled Document

Document No. 32-9384462-000 PROPRIETARY OCJ IDTB Weld Anomaly Assessment at CEDM Nozzle No. 71 at ANO-2 (Non-Proprietary)

Page A-1 APPENDIX A:

CONTINGENCY REPAIRS EVALUATION A.1 Purpose This appendix addresses the impact of the proposed contingency repairs on the OCJ pertaining to the triple point weld anomaly fracture mechanics evaluation. Contingency repairs are proposed to remove an indication detected in the IDTB weld by the post weld non-destructive examination (NDE) that is performed after the initial implementation of the half nozzle IDTB repair procedure. Two continency repairs are proposed and described in the design drawing (Reference [7])

A.1.1 Option 1: STEP 4A.1 through 4A.3-CONTINGENCY SHALLOW CUT Description Assessment Controlled Document

Document No. 32-9384462-000 PROPRIETARY OCJ IDTB Weld Anomaly Assessment at CEDM Nozzle No. 71 at ANO-2 (Non-Proprietary)

Page A-2 A.1.2 Option 2: STEPS 4B.1 through 4B.3 - CONTINGENCY OVERBORE Description Assessment A.2 Conclusion The relevant parameters to the IDTB weld anomaly FM evaluation include geometry, residual stresses, operating stresses, and acceptance criteria. As discussed in Sections A.1.1 and A.1.2, both contingency repairs have minor or no impact on these parameters. Thus, it is concluded that OCJ for the postulated weld anomalies FM evaluation in the main body of this document is valid for both contingency repairs.

Controlled Document