Text

Baffle-Former Bolt (Bfb) Subsequent Inspection Interval Evaluation
	ML23349A052
Person / Time
Site:	Robinson
Issue date:	12/14/2023
From:	Ellis K; Duke Energy Progress
To:	; Office of Nuclear Reactor Regulation, Document Control Desk
Shared Package
ML23349A051	List: RA-23-0313, Baffle-Former Bolt (Bfb) Subsequent Inspection Interval Evaluation;
References
	RA-23-0313
	Download: ML23349A052 (1)
	v • d • e

Kevin M. Ellis General Manager Nuclear Regulatory Affairs, Policy &

Emergency Preparedness Duke Energy 13225 Hagers Ferry Rd., MG011E Huntersville, NC 28078 843-951-1329 Kevin.Ellis@duke-energy.com PROPRIETARY INFORMATION - WITHHOLD UNDER 10 CFR 2.390 UPON REMOVAL OF ENCLOSURE 3 THIS LETTER IS UNCONTROLLED PROPRIETARY INFORMATION - WITHHOLD UNDER 10 CFR 2.390 UPON REMOVAL OF ENCLOSURE 3 THIS LETTER IS UNCONTROLLED Serial: RA-23-0313 December 14, 2023 U.S. Nuclear Regulatory Commission ATTN: Document Control Desk Washington, DC 20555-0001 H. B. ROBINSON STEAM ELECTRIC PLANT, UNIT NO. 2 DOCKET NO. 50-261 / RENEWED LICENSE NO. DPR-23

SUBJECT:

Baffle-Former Bolt (BFB) Subsequent Inspection Interval Evaluation

REFERENCES:

1. Electric Power Research Institute (EPRI) Technical Report, MRP-227, Revision 1-A, Materials Reliability Program: Pressurized Water Reactor Internals Inspection and Evaluation Guidelines (ADAMS Accession No. ML19339G350)

Ladies and Gentlemen:

In accordance with MRP-227, Revision 1-A (Reference 1), safety evaluation Applicant/Licensee Action Item 1, Duke Energy Progress (Duke Energy) hereby submits, for information only, an evaluation supporting a ten year BFB subsequent inspection interval for H. B. Robinson Steam Electric Plant, Unit No. 2. The evaluation is provided in Enclosure 3, which contains information proprietary to Westinghouse Electric Company LLC (Westinghouse). A redacted version of the evaluation is provided in Enclosure 2. In accordance with 10 CFR 2.390, it is requested that be withheld from public disclosure. An Affidavit signed by Westinghouse (the owner of the information) attesting to the proprietary nature of the information is provided in. Correspondence with respect to the copyright or proprietary aspects or the supporting Westinghouse Affidavit should reference CAW-23-044 and should be addressed to:

Camille T. Zozula Interim Director Management Systems and Regulatory Compliance Westinghouse Electric Company 1000 Westinghouse Drive, Building 1 Cranberry Township, PA 16066 Email: zozulact@westinghouse.com

PROPRIETARY INFORMATION - WITHHOLD UNDER 10 CFR 2.390 UPON REMOVAL OF ENCLOSURE 3 THIS LETTER IS UNCONTROLLED U.S. Nuclear Regulatory Commission RA-23-0313 Page 2 No new regulatory commitments have been made in this submittal. If you have additional questions, please contact Ryan Treadway, Director - Nuclear Fleet Licensing, at 980-373-5873.

~

erely,,\\_~---.

Kevin M.

lis General Manager - Nuclear Regulatory Affairs, Policy & Emergency Preparedness

Enclosures:

cc:

1. Affidavit of Westinghouse Electric Company LLC

2. CPL-RV010-TM-CA-000014, Rev. 0, "H.B. Robinson Unit 2 Baffle Former Bolt Predictive Evaluation" (Redacted)

3. CPL-RV010-TM-CA-000013, Rev. 0, "H.B. Robinson Unit 2 Baffle Former Bolt Predictive Evaluation" (Proprietary)

L. Dudes, Regional Administrator USNRC Region II J. Zeiler, NRC Senior Resident Inspector L. Haeg, NRC Project Manager, NRR PROPRIETARY INFORMATION -WITHHOLD UNDER 10 CFR 2.390 UPON REMOVAL OF ENCLOSURE 3 THIS LETTER IS UNCONTROLLED

PROPRIETARY INFORMATION - WITHHOLD UNDER 10 CFR 2.390 UPON REMOVAL OF ENCLOSURE 3 THIS LETTER IS UNCONTROLLED U.S. Nuclear Regulatory Commission RA-23-0313 Page 3 PROPRIETARY INFORMATION - WITHHOLD UNDER 10 CFR 2.390 UPON REMOVAL OF ENCLOSURE 3 THIS LETTER IS UNCONTROLLED bcc:

Kevin Ellis Ryan Treadway Mark Pyne Rachel Doss Tracey LeRoy David Cummings File: (Corporate)

Electronic Licensing Library (ELL)

Laura Basta Phillip Mason Mark Hubbard RA-23-0313 Affidavit of Westinghouse Electric Company LLC

- - This record was final approved on 11/17/2023 13:14:10. (This statement was added by the PRIME system upon its validation)

Westinghouse Non-Proprietary Class 3 AFFIDAVIT CAW-23-044 Page 1 of 3 Commonwealth of Pennsylvania:

County of Butler:

(1)

I, Zachary Harper, Senior Manager, Licensing Engineering, have been specifically delegated and authorized to apply for withholding and execute this Affidavit on behalf of Westinghouse Electric Company LLC (Westinghouse).

(2)

I am requesting the proprietary portions of CPL-RV010-TM-CA-000013, Revision 0 be withheld from public disclosure under 10 CFR 2.390.

(3)

I have personal knowledge of the criteria and procedures utilized by Westinghouse in designating information as a trade secret, privileged, or as confidential commercial or financial information.

(4)

Pursuant to 10 CFR 2.390, the following is furnished for consideration by the Commission in determining whether the information sought to be withheld from public disclosure should be withheld.

(i)

The information sought to be withheld from public disclosure is owned and has been held in confidence by Westinghouse and is not customarily disclosed to the public.

(ii)

The information sought to be withheld is being transmitted to the Commission in confidence and, to Westinghouses knowledge, is not available in public sources.

(iii)

Westinghouse notes that a showing of substantial harm is no longer an applicable criterion for analyzing whether a document should be withheld from public disclosure. Nevertheless, public disclosure of this proprietary information is likely to cause substantial harm to the competitive position of Westinghouse because it would enhance the ability of competitors to provide similar technical evaluation justifications and licensing defense services for commercial power reactors without commensurate expenses. Also, public disclosure of the information would enable others to use the information to meet NRC requirements for licensing documentation without purchasing the right to use the information.

- - This record was final approved on 11/17/2023 13:14:10. (This statement was added by the PRIME system upon its validation)

Westinghouse Non-Proprietary Class 3 AFFIDAVIT CAW-23-044 Page 2 of 3 (5)

Westinghouse has policies in place to identify proprietary information. Under that system, information is held in confidence if it falls in one or more of several types, the release of which might result in the loss of an existing or potential competitive advantage, as follows:

(a)

The information reveals the distinguishing aspects of a process (or component, structure, tool, method, etc.) where prevention of its use by any of Westinghouse's competitors without license from Westinghouse constitutes a competitive economic advantage over other companies.

(b)

It consists of supporting data, including test data, relative to a process (or component, structure, tool, method, etc.), the application of which data secures a competitive economic advantage (e.g., by optimization or improved marketability).

(c)

Its use by a competitor would reduce his expenditure of resources or improve his competitive position in the design, manufacture, shipment, installation, assurance of quality, or licensing a similar product.

(d)

It reveals cost or price information, production capacities, budget levels, or commercial strategies of Westinghouse, its customers or suppliers.

(e)

It reveals aspects of past, present, or future Westinghouse or customer funded development plans and programs of potential commercial value to Westinghouse.

(f)

It contains patentable ideas, for which patent protection may be desirable.

(6)

The attached documents are bracketed and marked to indicate the bases for withholding. The justification for withholding is indicated in both versions by means of lower-case letters (a) through (f) located as a superscript immediately following the brackets enclosing each item of information being identified as proprietary or in the margin opposite such information. These lower-case letters refer to the types of information Westinghouse customarily holds in confidence identified in Sections (5)(a) through (f) of this Affidavit.

- - This record was final approved on 11/17/2023 13:14:10. (This statement was added by the PRIME system upon its validation)

Westinghouse Non-Proprietary Class 3 AFFIDAVIT CAW-23-044 Page 3 of 3 I declare that the averments of fact set forth in this Affidavit 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: 11/17/2023 Signed electronically by Zachary Harper

- - This record was final approved on 11/17/2023 13:14:10. (This statement was added by the PRIME system upon its validation)

CAW-23-044 Revision 0 Non-Proprietary Class 3

- This page was added to the quality record by the PRIME system upon its validation and shall not be considered in the page numbering of this document.**

Approval Information Manager Approval Harper Zachary S Nov-17-2023 13:14:10 Files approved on Nov-17-2023 RA-23-0313 CPL-RV010-TM-CA-000014, Rev. 0, H. B. Robinson Unit 2 Baffle Former Bolt Predictive Evaluation (Redacted)

- - This record was final approved on 11/16/2023 14:17:57. (This statement was added by the PRIME system upon its validation)

FORM NUMBER - F-GES-CMPP-PR-DD-000002-1 Rev. 1

Electronically approved records are authenticated in the electronic document management system.

FORM NUMBER F-GES-CMPP-PR-DD-000002-1 Rev. 0 Effective Date: 9/29/2021 DOCUMENT COVER SHEET DOCUMENT NO.

REVISION PAGE 1 of 26 CPL-RV010-TM-CA-000014 0

PE SEAL (If required)

ALTERNATE DOCUMENT NUMBER:

TITLE:

H. B. Robinson Unit 2 Baffle Former Bolt Predictive Evaluation ATTACHMENTS:

© 2023 WESTINGHOUSE ELECTRIC COMPANY LLC, ALL RIGHTS RESERVED - WESTINGHOUSE PROPRIETARY CLASS 2 Information included in this material is proprietary and confidential and cannot be disclosed or used for any reason beyond the intended purpose without the prior written consent of Westinghouse Electric Company LLC.

NOTE: This selection is only to be used for Westinghouse generated documents.

© 2023 WESTINGHOUSE ELECTRIC COMPANY LLC, ALL RIGHTS RESERVED and/or © 2023 WESTINGHOUSE BUSINESS PARTNER, ALL RIGHTS RESERVED WESTINGHOUSE PROPRIETARY CLASS 2 and/or WESTINGHOUSE BUSINESS PARTNER PROPRIETARY (SEE ATTACHED DOCUMENT)

Information included in this material is proprietary and confidential and cannot be disclosed or used for any reason beyond the intended purpose without the prior written consent of Westinghouse Electric Company LLC.

SUPPLIER OR THIRD PARTY PROVIDED INFORMATION - File And Protect Using Policies For Westinghouse Proprietary Class 2 Information Information included in this material is proprietary and confidential and cannot be disclosed or used for any reason beyond the intended purpose without the prior written consent of the Supplier/Third Party.

Signature Responsibility Name SIGNATURE / DATE(If processing electronic approval select option)

Originator Louis W. Turicik Electronically Approved***

Verifier Stephen J. Speicher Electronically Approved***

Responsible Manager Kaitlyn M. Musser Electronically Approved***

Approval signifies that the document and all required reviews are complete, the appropriate proprietary class has been assigned, electronic file has been provided to PRIME, and the document is released for use.

This document may contain technical data subject to the export control laws of the United States. In the event that this document does contain such information, the Recipients acceptance of this document constitutes agreement that this information in document form (or any other medium), including any attachments and exhibits hereto, shall not be exported, released or disclosed to foreign persons whether in the United States or abroad by recipient except in compliance with all U.S. export control regulations. Recipient shall include this notice with any reproduced or excerpted portion of this document or any document derived from, based on, incorporating, using or relying on the information contained in this document.

- - This record was final approved on 11/16/2023 14:17:57. (This statement was added by the PRIME system upon its validation)

Westinghouse Non-Proprietary Class 3 Page 2 of 26 This document may contain technical data subject to the export control laws of the United States. In the event that this document does contain such information, the Recipients acceptance of this document constitutes agreement that this information in document form (or any other medium), including any attachments and exhibits hereto, shall not be exported, released or disclosed to foreign persons whether in the United States or abroad by recipient except in compliance with all U.S. export control regulations. Recipient shall include this notice with any reproduced or excerpted portion of this document or any document derived from, based on, incorporating, using or relying on the information contained in this document.

November 16, 2023 From: Louis Turicik Materials & Aging Management Your ref: N/A E-mail: turicilw@westinghouse.com Our ref: CPL-RV010-TM-CA-000014, Rev. 0

Subject:

H. B. Robinson Unit 2 Baffle Former Bolt Predictive Evaluation Duke Energy completed ultrasonic testing (UT) examinations of the baffle-former bolts (BFBs) at H. B.

Robinson Unit 2 (Robinson) during the fall 2022 refueling outage. Approximately 3.0% of the 1088 (33 bolts) H. B. Robinson Unit 2 BFBs were found to have a UT indication of degradation. Five additional BFBs were unable to be inspected. No immediate replacement activity was conducted by Duke after the inspections.

This letter summarizes application of the Westinghouse BFB predictive analysis to support justification of the future BFB inspection interval based on the requirements of MRP 2017-009 [4] as supplemented by WCAP-17096-NP-A, Revision 3 [6]. The plant-specific predictive analysis for H. B. Robinson Unit 2 is documented in CPL-RV010-CN-CA-000002 [7]. Contents of this letter contained in brackets [ ]a,c are considered proprietary per Westinghouse procedure W2-8.3-108.J01 and are redacted in the non-proprietary copy of this letter.

- - This record was final approved on 11/16/2023 14:17:57. (This statement was added by the PRIME system upon its validation)

Westinghouse Non-Proprietary Class 3 Page 3 of 26 Our Ref: CPL-RV010-TM-CA-000014, Rev. 0

1.0 Background

Duke Energy performed an initial UT examination of the BFBs at Robinson during the fall 2013 refueling outage. The inspection reported 9 BFBs with relevant indications, and 12 BFBs that were non-inspectable.

These inspection results are shown in Figure 1, and documented in [1]. Green cells (marked G) identify intact BFBs without UT indications. Red cells (marked X) identify bolts with UT indications. Yellow cells (marked NI) are locations where BFBs were non-inspectable. For conservatism in this evaluation, non-inspectable BFBs are considered to be failed. This results in 21 failures, approximately 2% of the 1088 total population. BFB aging management guidance at the time of inspection specified a reinspection interval of ten calendar years.

Figure 1: Robinson Unit 2 BFB Inspection Results - 2013 [1]

1 2

3 4

5 6

7 8

9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 Top 8 or H

G G

7 or G

G G

6 or F

G G

5 or E

G G

Formers 4 or D

G G

G NI G

G G

G 3 or C

G G

G NI G

G G

G 2 or B

G G

Bottom 1 or A

G G

6 7

8 9

10 11 7

8 9

10 1R 1-2 A.

2 3

4 5

6 1R Bolt 11 12L 2

3 4

5 11-12 A.

12L Baffle Plate Octant 1 Octant 2 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 Top 8 or H

G G

G NI G

G G

G 7 or G

G G

G NI G

G G

G 6 or F

G G

G X

G G

5 or E

G G

X G

G G

Formers 4 or D

G G

3 or C

G G

G NI G

X G

G G

G 2 or B

G G

G NI G

G G

G Bottom 1 or A

G G

G NI G

G G

G 16 17 18 19 20 21 18 19 20 21 Bolt 22 23L 12R 13 14 15 22 22-23 A.

23L 15 16 17 Baffle Plate 12R 12-13 A.

13 14 Octant 3 Octant 4 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 Top 8 or H

G G

G NI G

G G

G 7 or G

G G

6 or F

G G

5 or E

G G

G X

G G

Formers 4 or D

G G

3 or C

G G

2 or B

G G

Bottom 1 or A

G G

27 28 29 30 31 32 29 30 31 32 Bolt 33 34L 23R 24 25 26 33 33-34 A.

34L 26 27 28 Baffle Plate 23R 23-24 A.

24 25 Octant 5 Octant 6 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 Top 8 or H

G G

7 or G

G G

G X

6 or F

G G

5 or E

G G

G X

G G

G X

G G

Formers 4 or D

G G

NI G

G G

3 or C

G G

G NI G

G G

X G

G G

G 2 or B

G G

NI G

G G

Bottom 1 or A

G G

G NI G

G G

X G

G 38 39 40 41 42 43 40 41 42 43 Bolt 44 1L 34R 35 36 37 44 44-1 A.

1L 37 38 39 Baffle Plate 34R 34-35 A.

35 36 Octant 7 Octant 8

- - This record was final approved on 11/16/2023 14:17:57. (This statement was added by the PRIME system upon its validation)

Westinghouse Non-Proprietary Class 3 Page 4 of 26 Our Ref: CPL-RV010-TM-CA-000014, Rev. 0 The subsequent BFB inspection was performed at Robinson during the fall 2022 refueling outage. The inspection reported 33 BFBs with relevant indications (approximately 3.0% of 1088 total bolts), and 5 BFBs that were non-inspectable. These inspection results are shown in Figure 2 and documented in [2]. Green cells (marked G) identify intact BFBs without UT indications. Red cells (marked X) identify bolts with UT indications. Yellow cells (marked NI) are locations where BFBs were non-inspectable. The two inspections performed at Robinson are not 100% congruent, with six of the nine BFB locations with indications in 2013 having been inspected as intact in 2022. This inconsistency is addressed by conservative assumptions applied to the inspection data that are detailed in Section 2.0.

MRP-227 Rev. 1-A [5] addresses the re-inspection interval for the BFBs, which includes interim guidance provided in MRP 2017-009 [4]. MRP 2017-009 states that for downflow plants that exhibit 3%

indications or clustering, the re-examination period is not to exceed 6 years, however a longer reinspection interval, not to exceed 10-years, may be justified by plant-specific evaluation based on plant-specific exam findings.

For conservatism in this evaluation, all non-inspectable BFBs are considered to be failed. This results in 38 failures, approximately 3.5% of the total population. No BFB replacement activity has occurred at Robinson.

Figure 2: Robinson Unit 2 BFB Inspection Results - 2022 [2]

1 2

3 4

5 6

7 8

9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 Top 8 or H

G G

X G

G G

7 or G

G G

6 or F

G G

X G

G G

5 or E

G G

Formers 4 or D

G G

G X

G G

G X

G G

3 or C

G G

G NI G

G G

G 2 or B

G G

G X

G G

Bottom 1 or A

G G

G X

G G

6 7

8 9

10 11 7

8 9

10 1R 1-2 A.

2 3

4 5

6 1R Bolt 11 12L 2

3 4

5 11-12 A.

12L Baffle Plate Octant 1 Octant 2 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 Top 8 or H

G G

7 or G

G G

NI X

X G

G G

X G

G G

6 or F

G G

X G

G G

5 or E

G G

X G

G G

Formers 4 or D

G G

X G

G G

3 or C

G G

2 or B

G G

X G

G G

G NI G

G G

G Bottom 1 or A

G G

X G

G G

16 17 18 19 20 21 18 19 20 21 Bolt 22 23L 12R 13 14 15 22 22-23 A.

23L 15 16 17 Baffle Plate 12R 12-13 A.

13 14 Octant 3 Octant 4 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 Top 8 or H

G G

G X

G G

G NI G

G G

G 7 or G

G G

G X

G G

X G

G G

6 or F

G G

X G

G G

X G

5 or E

G G

G X

G G

G X

G G

Formers 4 or D

G G

3 or C

G G

2 or B

G G

G X

G G

X G

G G

Bottom 1 or A

G G

X G

27 28 29 30 31 32 29 30 31 32 Bolt 33 34L 23R 24 25 26 33 33-34 A.

34L 26 27 28 Baffle Plate 23R 23-24 A.

24 25 Octant 5 Octant 6 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 Top 8 or H

G G

7 or G

G G

G X

G G

G X

X G

G G

G X

6 or F

G G

5 or E

G G

Formers 4 or D

G G

3 or C

G G

G X

X G

G G

2 or B

G G

NI G

G G

X G

G G

G X

G G

G X

G G

Bottom 1 or A

G G

38 39 40 41 42 43 40 41 42 43 Bolt 44 1L 34R 35 36 37 44 44-1 A.

1L 37 38 39 Baffle Plate 34R 34-35 A.

35 36 Octant 7 Octant 8

- - This record was final approved on 11/16/2023 14:17:57. (This statement was added by the PRIME system upon its validation)

Westinghouse Non-Proprietary Class 3 Page 5 of 26 Our Ref: CPL-RV010-TM-CA-000014, Rev. 0 BFB degradation is a known occurrence in PWR operating experience and believed to be initiated by irradiation-assisted stress corrosion cracking (IASCC). The observed degradation of BFBs led to development of the acceptable bolting pattern analysis (ABPA) methodology [14], which has since been applied to many operating plants. An ABPA can be used to assess whether a baffle former assembly with degraded BFBs is acceptable for continued safe operation. However, the ABPA does not directly consider future degradation rates of bolts or the locations where degradation may occur.

In 2016, UT inspections were conducted at Indian Point Unit 2, Salem Unit 1, and D. C. Cook Unit 2.

Extensive BFB degradation was detected in these 4-loop units. A nuclear safety advisory letter NSAL 1, Rev. 1 [3] was published in response to these inspection results, classifying plants into categories based on internals design and BFB degradation risk. Robinson is classified in NSAL-16-1, Rev. 1 [3] as Tier 2b, a 3-loop downflow plant with Type 347 BFBs, which are susceptible to IASCC [10], [11], [12], [13].

The recommendations of [3] were used to create interim guidance MRP 2017-009 [4] for MRP-227, Rev.

1-A [5] and were incorporated into NEI-03-08 Needed Requirements. Additionally, the safety evaluation for [5] contains Applicant/Licensee Action Item (A/LAI) 1 which states that if the table in MRP 2017-009 indicates that the subsequent inspection interval is not to exceed 6 years (e.g., downflow plants with 3 percent BFBs with indications or clustering), the plant-specific evaluation to determine a subsequent inspection interval shall be submitted to the NRC for information within one year following the outage in which the degradation was found. Any evaluation to lengthen the determined inspection interval or to exceed the maximum inspection interval recommended in MRP-2017-009 shall be submitted to the NRC for information at least one year prior to the end of the current applicable interval for BFB subsequent examination.

The needed guidance in MRP 2017-009 applies additional constraints to the Examination Method/Frequency in MRP-227 Rev. 1-A. The modified requirement, states that Subsequent volumetric (UT) examinations shall be performed on an interval established by plant-specific evaluation per MRP-227 Needed Requirement 7.5 A reduced reinspection interval has been determined to be an appropriate response to atypical or aggressive BFB degradation It then defines a category of degradation for plants that either observe 3% or greater indications in their baffle-former bolts (BFB), or observe clustering.

While unnamed in MRP 2017-009, bolt degradation that fits this category was later named accelerated in WCAP-17096-NP-A Rev. 3 [6].

The 2022 results from H. B. Robinson meet the criteria described in the A/LAI from [5] and the interim guidance from [4]: 33 indications out of 1088 bolts constitutes 3.03% of the total population, and octant 4 contains a cluster of three adjacent bolts with indications on the same baffle plate. MRP 2017-009 [4] states that plants with accelerated degradation must impose a reduced re-inspection interval, which is not to exceed 6 years. MRP 2017-009 [4] also states that a longer reinspection interval, not to exceed 10-years, may be justified by plant-specific evaluation based on plant-specific exam findings WCAP-17096-NP-A Rev. 3 [6] incorporates the accelerated degradation terminology from [4] and states that plants with accelerated degradation must apply a probabilistic model in order to demonstrate sufficient margin exists to account for potential bolt degradation throughout the next re-inspection interval.

It then outlines the required process steps for the implementation of the probabilistic model, which include the development of an empirical and/or mechanistic bolt degradation model, determination of patterns of predicted failed bolts at the end of the re-inspection interval based upon the likelihood of failure, and the implementation of a probabilistic reliability analysis to demonstrate reasonable assurance that the pattern

- - This record was final approved on 11/16/2023 14:17:57. (This statement was added by the PRIME system upon its validation)

Westinghouse Non-Proprietary Class 3 Page 6 of 26 Our Ref: CPL-RV010-TM-CA-000014, Rev. 0 of failed bolts will be acceptable at the end of the re-inspection interval. Additional detail is provided in condition 2 (C-02) of the WCAP-17096-NP Rev. 3 safety evaluation (SE), which states:

For bolted assembly analysis methods that use predictive, probabilistic ABPA models, the models and methods should appropriately account for limits on the number of allowable bolts with presumed failed conditions, geometric bolt failure considerations (i.e., bolt clustering considerations), and bolting analysis reliability considerations (i.e., addressing 95% reliability confidence limits.) These models and methods should be appropriately documented and justified in a site-specific or owner-defined record.

The Westinghouse Baffle-Former Bolt predictive reliability analysis [7] meets the requirements of C-02 in the following manner.

Bolting analysis reliability considerations (see Appendix G of [6]): The Westinghouse BFB predictive model includes conservatism which bounds the uncertainties applied to the various inputs and calculations of the model. Uncertainty is added to the inputs, including the neutron dose, bolt stress, and bolt geometry and is added to the model parameters, including model scale and shape parameters, dose threshold, and stress relaxation. These uncertainties are aggregated in the model calculations and provide a large spread in the predicted degradation patterns, including degradation significantly more severe than could be expected. A simplified risk assessment of BFB degradation is presented in Appendix G, RAI 13, Part D of [6] and concludes that the BFB predictive methodology and ABPA methodology on which it is based both have inherent conservatisms, and the low likelihood of developing an unacceptable bolting pattern does not directly translate to an accident scenario but represents an entry condition to increased risk. The 95% reliability criterion provides an additional layer of conservatism to a scenario that is already judged to have low risk significance.

The Westinghouse BFB Predictive methodology has been in use since 2016 for reinspection interval justification and BFB replacement planning. In 2019, during an NRC closed meeting, Westinghouse presented to NRC staff the Westinghouse Baffle-Former Bolt Predictive Methodology. The presentation provided an overview of the proprietary methodology for probabilistic predictive evaluations of BFB degradation as stated in the basic framework of WCAP-17096-NP, Revision 3. A safety evaluation was not pursued, however several NRC RAIs were issued and addressed ([6], Appendix G, RAI 13). As a result, a,c

- - This record was final approved on 11/16/2023 14:17:57. (This statement was added by the PRIME system upon its validation)

Westinghouse Non-Proprietary Class 3 Page 7 of 26 Our Ref: CPL-RV010-TM-CA-000014, Rev. 0 the NRC staff finds that the predictive bolting pattern model is an acceptable method for establishing the reinspection interval for a specified BFB because the NRC staff has confirmed that the ABPA model is capable of generating a conservative, predictive set of future bolting pattern outputs starting from an initial degraded bolting pattern. This review of methodology with the NRC provides compliance with the BWRVIP 2019-016 [17] and WCAP-17096-NP-A, Rev. 3 [6] requirement that the submitter should have a plan for making the proprietary supporting materials available if needed for NRC review of the submittal.

The BFB predictive evaluation summarized herein is used to justify a longer reinspection interval than 6 years by demonstrating a high likelihood of future BFB degradation being acceptable for an ABPA at the end of the planned reinspection interval, and also satisfies the above requirements set forth in WCAP-17096-NP-A Rev. 3 [6].

- - This record was final approved on 11/16/2023 14:17:57. (This statement was added by the PRIME system upon its validation)

Westinghouse Non-Proprietary Class 3 Page 8 of 26 Our Ref: CPL-RV010-TM-CA-000014, Rev. 0 2.0 BFB Predictive Evaluation Overview Westinghouse developed a predictive methodology for simulating the degradation of BFBs due to IASCC.

The evaluation characterizes the evolution of stress in a reactor environment, as well as the redistribution of stress amidst neighboring bolt failures. Empirically-validated Weibull parameters are utilized in a stochastic framework. The bolt degradation model within the evaluation is exercised as a Monte Carlo simulation to evaluate a range of plausible scenarios from which trends of bolt failure rates and patterns can be determined. The predictive evaluation was developed from industry operating experience, laboratory testing, and a plant-specific finite element analysis that quantifies stress at each bolt location throughout the reactor operating history. Degradation rate is generated via Weibull reliability analysis, and is an aggregation of the Weibull shape parameter, Weibull scale factor, and plant inspection data.

Weibull shape factor: Describes and characterizes the modeled degradation mechanism, IASCC. BFB failure data from lab testing and plant UT inspections were analyzed independently and compared with good agreement in degradation characterization. The shape factor does not vary in application of the BFB predictive model due to IASCC being considered the leading degradation mechanism.

Weibull scale factor: accounts for design and operational differences seen across model applications. Key inputs to scale factor include BFB normal operating loads and preload, BFB dose history, plant and BFB geometry, plant operation parameters and history. Uncertainty is applied to these inputs and as a result a range of predicted degradation scenarios is generated, both more severe and less severe than known OE.

Effects of other degradation mechanisms are addressed empirically via calibration of scale factor to plant OE, which is demonstrated as appropriate by comparison of predicted degradation versus UT indications in Figure 6 through Figure 13.

Plant inspection data: influences degradation rate by applying the failures observed in UT examination at the designated time of inspection during the plant life. This influences both the overall quantity of degradation and its spatial distribution. For example, development of clustered BFB failures can generally be expected to accelerate degradation in neighboring bolts, and BFB replacement activity can be expected to slow degradation.

Although the only degradation mechanism explicitly modeled is IASCC, the modeled degradation rates are influenced by BFB inspection operating experience, potentially resulting from other mechanisms, such as fatigue, irradiation embrittlement, void swelling, etc.

- - This record was final approved on 11/16/2023 14:17:57. (This statement was added by the PRIME system upon its validation)

Westinghouse Non-Proprietary Class 3 Page 9 of 26 Our Ref: CPL-RV010-TM-CA-000014, Rev. 0 This stochastic semi-empirical model is constructed as a probabilistic network / influence diagram, as illustrated in Figure 3.

Figure 3: Influence Diagram of BFB Predictive Reliability Model

- - This record was final approved on 11/16/2023 14:17:57. (This statement was added by the PRIME system upon its validation)

Westinghouse Non-Proprietary Class 3 Page 10 of 26 Our Ref: CPL-RV010-TM-CA-000014, Rev. 0 Figure 4: Flowchart of BFB Predictive Model Application A flowchart demonstrating general application of the BFB predictive methodology is shown in Figure 4.

The steps to complete the evaluation are as follows:

1.

Apply plant specific inputs: Geometry, operating history/parameters, inspection data, ABPA results.

2.

Input into statistical degradation model calibrated to specific plant design.

3.

Simulate approximately 60-year plant life using statistical model degradation and FEA model load redistribution. Many individual degradation scenario samples are generated.

4.

Generate acceptability criteria for post processor using ABPA results, sensitivity studies and engineering judgment. Check all predicted degradation scenarios using post processor logic.

5.

Aggregate results to determine reinspection recommendation and justification.

For this evaluation, the BFB degradation model within the generic predictive evaluation was calibrated to 3-loop downflow plant operating experience and modified to include the following Robinson 2 plant-specific inputs:

Baffle plate and BFB geometry Preload and pressure stresses at each BFB location BFB design stress concentration factor including head-to-shank fillet radius Differential pressure across the baffle plates Stress relaxation due to accumulated dose at each BFB location UT inspection results (2013 and 2022)

- - This record was final approved on 11/16/2023 14:17:57. (This statement was added by the PRIME system upon its validation)

Westinghouse Non-Proprietary Class 3 Page 11 of 26 Our Ref: CPL-RV010-TM-CA-000014, Rev. 0 The two BFB inspections at Robinson were performed by two different vendors and have results that are not 100% congruent. Six of the nine BFB locations with UT indications found in 2013 were found to be intact in the 2022 inspection. Inspection uncertainty is present in the UT inspection process but is not explicitly modeled in the predictive evaluation. Therefore, a set of conservative assumptions were applied to the inspection data to prevent any potential under-prediction of future failures resulting from inspection uncertainty. Additionally, a parallel case of the BFB predictive model was run with an increased level of conservative assumptions applied to the inspection data in order to validate the results of the first case. The goal is to generate a conservative prediction of degradation that can be used to justify an increased re-inspection interval (Case 1) that is validated by a further conservative and bounding worst case prediction (Case 2).

The level of BFB degradation present at Robinson for both the 2013 and 2022 inspections is relatively low (all quadrants have less than 5% BFBs failed as inspected, including treating non-inspectable bolts as failed), such that even a few bolts failed or non-failed can have a significant influence on the predicted degradation rate.

The cases run are as follows:

Case 1: Conservative Prediction. Robinson Unit 2 prediction given 2013 and 2022 inspection results and no BFB replacement activity. Conservative assumptions applied include:

Case 2: Worst Case Bounding. Robinson Unit 2 prediction given 2013 and 2022 inspection results and no BFB replacement activity. Case 2 includes all of the assumptions applied to Case 1 in addition to:

a,c a,c

- - This record was final approved on 11/16/2023 14:17:57. (This statement was added by the PRIME system upon its validation)

Westinghouse Non-Proprietary Class 3 Page 12 of 26 Our Ref: CPL-RV010-TM-CA-000014, Rev. 0 The data from each run are displayed in plots of the predicted overall fraction of failed bolts versus time, expressed as effective full-power years (EFPY). EFPY can be converted into calendar years using a plant capacity factor. For this analysis a standard capacity factor of 0.9 EFPY/calendar year was used. Heat maps of bolt failure probability at each location for a specific point in time (six and ten calendar years of operation following the inspection) are also provided in Section 3.0.

The determination of recommended inspection intervals for Robinson Unit 2 is based on 95th percentile projections to maintain conservatism in the recommendations. Although no replacement activity was conducted at the time of inspection, there is minimal evidence of BFB clustering, which also supports the Robinson Unit 2 recommended inspection interval discussed in Section 5.0.

- - This record was final approved on 11/16/2023 14:17:57. (This statement was added by the PRIME system upon its validation)

Westinghouse Non-Proprietary Class 3 Page 13 of 26 Our Ref: CPL-RV010-TM-CA-000014, Rev. 0 3.0 Robinson BFB Predicted Degradation Results Table 1 and Figure 6 through Figure 13 depict the predicted proportion of failed bolts for each quadrant and run case (Case 1 or Case 2), given the inspection results and conservative assumptions applied to the inspection data. For comparison purposes, the raw UT inspection data with no conservative assumptions applied (Unit AVG UT Indications for 2013 and 2022) is also shown. These figures are intended to give a general overview of the predicted degradation rate relative to the inspection results. Note that the Case 2 results are provided for information only.

The proportion failed table and plots display degradation broken out into fractiles, with the given percentage of generated degradation patterns being bounded by each fractile. For example, the 0.50 fractile represents the best estimate level of degradation with half of the generated patterns having more degradation and half having less degradation at any given point in time. The 0.95 fractile represents the worst case level of degradation, with 95% of generated patterns having less degradation at any given point in time.

The data in Table 1 reports the proportion failed at the time of second inspection in 2022 (with conservative assumptions applied) and at six and ten calendar years following inspection. For example, the proportion of failed bolts for Case 1, Quadrant 1 is predicted as [*****]a,c or less at six calendar years and [*****]a,c or less at ten calendar years of operation post inspection for 95% of the predicted degradation scenarios.

The raw degradation data at these time points will be post-processed to determine acceptability for the reinspection interval.

Figure 6 through Figure 13 also include a predicted bolt failure probability heat map at the end of the six and ten calendar years of operation following the UT inspection. The heat maps display the proportion of generated degradation patterns that contain an individual failed bolt. These are intended to highlight potential future BFB regions of concern and can be used to help inform a future replacement pattern if needed.

Table 1: Baffle-Former Bolt Predicted Proportion Failed Result a,c

- - This record was final approved on 11/16/2023 14:17:57. (This statement was added by the PRIME system upon its validation)

Westinghouse Non-Proprietary Class 3 Page 14 of 26 Our Ref: CPL-RV010-TM-CA-000014, Rev. 0 Note that the quadrant location definitions seen in the inspection results and predictive model are not the same. The predictive model intent is to analyze the baffle plates with the longest span of BFBs (six BFB across) without introducing symmetry constraints. These plates are centered at 0°, 90°, 180°, and 270° locations around the baffle assembly. This requires a 45° shift in the definition of each quadrant. For example, ABPA quadrant 1 is defined in the inspection data as octants 1 and 2, while predictive analysis quadrant 1 is defined as the bolts from ABPA octants 2 and 3. Figure 5 overlays the predictive quadrants (green) onto the ABPA octants (blue).

Figure 5: Quadrant Definition for the Predictive Model Q4 Q1 Q2 Q3

- - This record was final approved on 11/16/2023 14:17:57. (This statement was added by the PRIME system upon its validation)

Westinghouse Non-Proprietary Class 3 Page 15 of 26 Our Ref: CPL-RV010-TM-CA-000014, Rev. 0 Figure 6: Robinson Unit 2, Case 1, Quadrant 1 Predicted Fraction of Failed Bolts and Bolt Failure Probability Heat Maps Following Six and Ten Calendar Years of Operation 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 Top 8 or H

7 or G

6 or F

5 or E

Formers 4 or D

3 or C

2 or B

Bottom 1 or A

12R 13 14 15 16 17 Bolt inspection + 6 years Quadrant 1 Octant 2 Octant 3 Baffle Plate 7

8 9

10 11 11-12 A.

12L 12R 12-13 A.

13 14 15 16 17 7

8 9

10 11 12L 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 Top 8 or H

7 or G

6 or F

5 or E

Formers 4 or D

3 or C

2 or B

Bottom 1 or A

17 Bolt 9

10 11 12L 12R 13 14 15 16 inspection + 10 years Quadrant 1 Octant 2 Octant 3 Baffle Plate 7

8 9

10 11 11-12 A.

12L 12R 12-13 A.

13 14 15 16 17 7

8 a,c

- - This record was final approved on 11/16/2023 14:17:57. (This statement was added by the PRIME system upon its validation)

Westinghouse Non-Proprietary Class 3 Page 16 of 26 Our Ref: CPL-RV010-TM-CA-000014, Rev. 0 Figure 7: Robinson Unit 2, Case 1, Quadrant 2 Predicted Fraction of Failed Bolts and Bolt Failure Probability Heat Maps Following Six and Ten Calendar Years of Operation 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 Top 8 or H

7 or G

6 or F

5 or E

Formers 4 or D

3 or C

2 or B

Bottom 1 or A

Bolt 24 25 26 27 28 18 19 20 21 22 23L 23R 24 25 26 27 28 18 19 20 21 22 22-23 A.

23L 23R 23-24 A.

inspection + 6 years Quadrant 2 Octant 4 Octant 5 Baffle Plate 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 Top 8 or H

7 or G

6 or F

5 or E

Formers 4 or D

3 or C

2 or B

Bottom 1 or A

26 27 28 Bolt 18 19 20 21 22 23L 23R 24 25 inspection + 10 years Quadrant 2 Octant 4 Octant 5 Baffle Plate 18 19 20 21 22 22-23 A.

23L 23R 23-24 A.

24 25 26 27 28 a,c

- - This record was final approved on 11/16/2023 14:17:57. (This statement was added by the PRIME system upon its validation)

Westinghouse Non-Proprietary Class 3 Page 17 of 26 Our Ref: CPL-RV010-TM-CA-000014, Rev. 0 Figure 8: Robinson Unit 2, Case 1, Quadrant 3 Predicted Fraction of Failed Bolts and Bolt Failure Probability Heat Maps Following Six and Ten Calendar Years of Operation 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 Top 8 or H

7 or G

6 or F

5 or E

Formers 4 or D

3 or C

2 or B

Bottom 1 or A

38 39 Bolt 30 31 32 33 34L 34R 35 36 37 inspection + 6 years Quadrant 3 Octant 6 Octant 7 Baffle Plate 29 30 31 32 33 33-34 A.

34L 34R 34-35 A.

35 36 37 38 39 29 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 Top 8 or H

7 or G

6 or F

5 or E

Formers 4 or D

3 or C

2 or B

Bottom 1 or A

37 38 39 Bolt 29 30 31 32 33 34L 34R 35 36 inspection + 10 years Quadrant 3 Octant 6 Octant 7 Baffle Plate 29 30 31 32 33 33-34 A.

34L 34R 34-35 A.

35 36 37 38 39 a,c

- - This record was final approved on 11/16/2023 14:17:57. (This statement was added by the PRIME system upon its validation)

Westinghouse Non-Proprietary Class 3 Page 18 of 26 Our Ref: CPL-RV010-TM-CA-000014, Rev. 0 Figure 9: Robinson Unit 2, Case 1, Quadrant 4 Predicted Fraction of Failed Bolts and Bolt Failure Probability Heat Maps Following Six and Ten Calendar Years of Operation 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 1

2 3

4 5

6 7

8 9

10 11 12 13 14 15 16 17 Top 8 or H

7 or G

6 or F

5 or E

Formers 4 or D

3 or C

2 or B

Bottom 1 or A

5 6

Bolt 41 42 43 44 1L 1R 2

3 4

inspection + 6 years Quadrant 4 Octant 8 Octant 1 Baffle Plate 40 41 42 43 44 44-1 A.

1L 1R 1-2 A.

2 3

4 5

6 40 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 1

2 3

4 5

6 7

8 9

10 11 12 13 14 15 16 17 Top 8 or H

7 or G

6 or F

5 or E

Formers 4 or D

3 or C

2 or B

Bottom 1 or A

4 5

6 Bolt 40 41 42 43 44 1L 1R 2

3 inspection + 10 years Quadrant 4 Octant 8 Octant 1 Baffle Plate 40 41 42 43 44 44-1 A.

1L 1R 1-2 A.

2 3

4 5

6 a,c

- - This record was final approved on 11/16/2023 14:17:57. (This statement was added by the PRIME system upon its validation)

Westinghouse Non-Proprietary Class 3 Page 19 of 26 Our Ref: CPL-RV010-TM-CA-000014, Rev. 0 Figure 10: Robinson Unit 2, Case 2, Quadrant 1 Predicted Fraction of Failed Bolts and Bolt Failure Probability Heat Maps Following Six and Ten Calendar Years of Operation 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 Top 8 or H

7 or G

6 or F

5 or E

Formers 4 or D

3 or C

2 or B

Bottom 1 or A

Bolt 7

8 9

10 11 12L 12R 13 14 15 16 17 inspection + 6 years Quadrant 1 Octant 2 Octant 3 Baffle Plate 7

8 9

10 11 11-12 A.

12L 12R 12-13 A.

13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 Top 8 or H

7 or G

6 or F

5 or E

Formers 4 or D

3 or C

2 or B

Bottom 1 or A

13 14 15 16 17 Bolt 13 14 15 16 17 7

8 9

10 11 12L 12R 7

8 9

10 11 11-12 A.

12L 12R 12-13 A.

inspection + 10 years Quadrant 1 Octant 2 Octant 3 Baffle Plate a,c

- - This record was final approved on 11/16/2023 14:17:57. (This statement was added by the PRIME system upon its validation)

Westinghouse Non-Proprietary Class 3 Page 20 of 26 Our Ref: CPL-RV010-TM-CA-000014, Rev. 0 Figure 11: Robinson Unit 2, Case 2, Quadrant 2 Predicted Fraction of Failed Bolts and Bolt Failure Probability Heat Maps Following Six and Ten Calendar Years of Operation 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 Top 8 or H

7 or G

6 or F

5 or E

Formers 4 or D

3 or C

2 or B

Bottom 1 or A

Bolt 18 19 20 21 22 23L 23R 24 25 26 27 28 23-24 A.

24 25 26 27 28 Baffle Plate 18 19 20 21 22 22-23 A.

23L 23R inspection + 6 years Quadrant 2 Octant 4 Octant 5 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 Top 8 or H

7 or G

6 or F

5 or E

Formers 4 or D

3 or C

2 or B

Bottom 1 or A

26 27 28 Bolt 26 27 28 18 19 20 21 22 23L 23R 24 25 20 21 22 22-23 A.

23L 23R 23-24 A.

24 25 Baffle Plate 18 19 inspection + 10 years Quadrant 2 Octant 4 Octant 5 a,c

- - This record was final approved on 11/16/2023 14:17:57. (This statement was added by the PRIME system upon its validation)

Westinghouse Non-Proprietary Class 3 Page 21 of 26 Our Ref: CPL-RV010-TM-CA-000014, Rev. 0 Figure 12: Robinson Unit 2, Case 2, Quadrant 3 Predicted Fraction of Failed Bolts and Bolt Failure Probability Heat Maps Following Six and Ten Calendar Years of Operation 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 Top 8 or H

7 or G

6 or F

5 or E

Formers 4 or D

3 or C

2 or B

Bottom 1 or A

Bolt 29 30 31 32 33 34L 34R 35 36 37 38 39 34-35 A.

35 36 37 38 39 Baffle Plate 29 30 31 32 33 33-34 A.

34L 34R inspection + 6 years Quadrant 3 Octant 6 Octant 7 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 Top 8 or H

7 or G

6 or F

5 or E

Formers 4 or D

3 or C

2 or B

Bottom 1 or A

37 38 39 Bolt 37 38 39 29 30 31 32 33 34L 34R 35 36 31 32 33 33-34 A.

34L 34R 34-35 A.

35 36 Baffle Plate 29 30 inspection + 10 years Quadrant 3 Octant 6 Octant 7 a,c

- - This record was final approved on 11/16/2023 14:17:57. (This statement was added by the PRIME system upon its validation)

Westinghouse Non-Proprietary Class 3 Page 22 of 26 Our Ref: CPL-RV010-TM-CA-000014, Rev. 0 Figure 13: Robinson Unit 2, Case 2, Quadrant 4 Predicted Fraction of Failed Bolts and Bolt Failure Probability Heat Maps Following Six and Ten Calendar Years of Operation 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 1

2 3

4 5

6 7

8 9

10 11 12 13 14 15 16 17 Top 8 or H

7 or G

6 or F

5 or E

Formers 4 or D

3 or C

2 or B

Bottom 1 or A

Bolt 40 41 42 43 44 1L 1R 2

3 4

5 6

1-2 A.

2 3

4 5

6 Baffle Plate 40 41 42 43 44 44-1 A.

1L 1R inspection + 6 years Quadrant 4 Octant 8 Octant 1 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 1

2 3

4 5

6 7

8 9

10 11 12 13 14 15 16 17 Top 8 or H

7 or G

6 or F

5 or E

Formers 4 or D

3 or C

2 or B

Bottom 1 or A

4 5

6 Bolt 4

5 6

40 41 42 43 44 1L 1R 2

3 42 43 44 44-1 A.

1L 1R 1-2 A.

2 3

Baffle Plate 40 41 inspection + 10 years Quadrant 4 Octant 8 Octant 1 a,c

- - This record was final approved on 11/16/2023 14:17:57. (This statement was added by the PRIME system upon its validation)

Westinghouse Non-Proprietary Class 3 Page 23 of 26 Our Ref: CPL-RV010-TM-CA-000014, Rev. 0 4.0 Evaluation of Predicted BFB Degradation The proportion of failed BFBs in each quadrant or in the full assembly is an indicator of the long-term operability of Robinson Unit 2, but it does not account for the specific patterns of failed bolts. The BFB predictive model produced hundreds of likely bolt patterns, which correspond to potential degraded states at the end of the re-inspection interval at Robinson Unit 2. All of these patterns were evaluated in terms of the likelihood of passing an ABPA. The goal is to meet the reinspection interval justification requirement from WCAP-17096, Rev. 3 [6], which states:

The projected statistically significant number of future bolting patterns (e.g. 10,000 samples) that may exist at the end of the re-inspection interval will be compared to the results of the ABPA to justify at least a 95% probability of an acceptable bolt pattern at the end of the re-inspection interval. It is anticipated that this method will be used to demonstrate a 10-year re-inspection interval.

In order to evaluate the resultant predicted patterns for acceptability, a series of prescriptive and formulaic checks are performed on each predictive pattern. Bolting pattern attributes considered include the following.

These checks are based on an understanding of the results and behavior of the acceptable bolting patterns that were recently analyzed for the updated ABPA. The Robinson Unit 2 ABPA [15] was updated for real time analysis (RTA) use in 2022, and an RTA was completed for the Fall 2022 refueling outage [16]. The ABPA considered five octant patterns of BFB failures based on postulated BFB degradation and analyzed these patterns for acceptability explicitly against six ABPA criteria (faulted bolt stress, low-cycle fatigue, high-cycle fatigue, momentum flux and core bypass) using the methodology detailed in WCAP-15029-P-A [14]. Additional analysis was performed for the Robinson fuel vendor for fuel grid impact analysis. All five patterns analyzed were acceptable. The five acceptable patterns ranged between 50% and 96% intact BFBs. Additionally, to further inform the pattern criteria checks, several of the most limiting degradation patterns generated by the Case 2 runs were analyzed using the Robinson-specific ABPA faulted and high-cycle fatigue analyses. At more advanced stages of BFB degradation, the faulted and high-cycle fatigue stresses are the most likely to limit ABPA acceptability due to redistributed loads from failed neighboring bolts.

a,c a,c

- - This record was final approved on 11/16/2023 14:17:57. (This statement was added by the PRIME system upon its validation)

Westinghouse Non-Proprietary Class 3 Page 24 of 26 Our Ref: CPL-RV010-TM-CA-000014, Rev. 0 Note that any pattern that is classified as a subset of an acceptable ABPA pattern is automatically given a ranking of Pass. The four risk ranking levels are thus assigned a specific probability of passing an ABPA, as follows:

These weighted values for each predicted degradation sample were aggregated to generate respective probabilities for each quadrant failing a future ABPA. In order to continue operation to the end of a specified time interval, the probabilistic evaluation must show acceptability for at least 95% of the predicted patterns [6]. The results of the aggregated data are shown in Table 2.

Table 2: Robinson Unit 2, Case 1 and Case 2 Degradation Prediction Aggregated Likelihood of Passing ABPA The Case 1 analysis meets the requirement of 95% or greater pattern acceptability for all quadrants at ten calendar years of operation following inspection, with margin. The favorable results of the more conservative Case 2 analysis provide additional confidence in the conclusions drawn from Case 1.

5.0 Summary and Conclusions Based on the 2022 inspection results (3% total failed BFBs, no replacement), the maximum allowable UT re-examination period is not to exceed 6 calendar years per A/LAI 1 in the NRC safety evaluation of MRP-227, Rev. 1-A, which is based on MRP 2017-009 [4] modified requirements for subsequent UT examinations. However, the plant-specific evaluation as performed in this predictive analysis shows that at least 95% of the generated degraded bolting patterns will pass an ABPA at both 6 and 10 calendar years of operation post-inspection. This analysis includes significant levels of conservatism applied to the inspection data to account for inspection uncertainty. Additionally, there is little evidence of BFB failure acceleration post-inspection. Westinghouse considers this a reasonable technical basis to support 10 calendar years of operation from the 2R33 outage prior to the next UT inspection at H. B. Robinson Unit 2 a,c a,c a,c

- - This record was final approved on 11/16/2023 14:17:57. (This statement was added by the PRIME system upon its validation)

Westinghouse Non-Proprietary Class 3 Page 25 of 26 Our Ref: CPL-RV010-TM-CA-000014, Rev. 0 6.0 References 1.

Wesdyne Report, WDI-PJF-1307566-FSR-001, Rev. 0, H.B. Robinson Unit 2 RO-28 Baffle Bolt UT Final Report, October 2013.

2.

Framatome Letter, INR-HBR-2R33-UT-001, Rev. 0, HB Robinson Unit 2 (2R33) Ultrasonic Bolt Examination In-Service Inspection, December 2, 2022.

3.

Westinghouse Nuclear Safety Advisory Letter, NSAL-16-1, Revision 1, Baffle-Former Bolts, August 1, 2016.

4.

Materials Reliability Program Letter, MRP 2017-009, Rev. 0, Transmittal of NEI-03-08 Needed Interim Guidance Regarding Baffle Former Bolt Inspections for PWR Plants as Defined in Westinghouse NSAL 16-01 Rev. 1, March 15, 2017.

5.

Materials Reliability Program: Pressurized Water Reactor Internals Inspection and Evaluation Guidelines (MRP-227, Revision 1-A). EPRI, Palo Alto, CA: 2019. 3002017168.

6.

Westinghouse Report, WCAP-17096-NP-A, Rev. 3, Reactor Internals Acceptance Criteria Methodology and Data Requirements, August 2023.

7.

Westinghouse Calculation Note, CPL-RV010-CN-CA-000002, Rev. 0, Baffle-Former Predictive Reliability Analysis for H.B. Robinson Unit 2, October 30, 2023. (Proprietary) 8.

Westinghouse Report, WCAP-13266, Rev. 1, Baffle-Former Bolt Program for the Westinghouse Owners Groups Phase 1: Plant Categorization, July 1993. (Proprietary) 9.

Westinghouse Drawing, 206C003, Rev. 2, 155.5/157-00-000-000 PWR Baffle to Former.625 External Hex Cap Screw. (Proprietary)

10. Hot Cell Testing of Baffle/Former Bolts Removed from Two Lead Plants: (PWRMRP-28), EPRI, Palo Alto, CA: 2000. 1000971.

11. Materials Reliability Program: Hot Cell Testing of Baffle/Former Bolts Removed from Two Lead PWR Plants (MRP-51), EPRI, Palo Alto, CA: 2001. 1003069.

12. McKinley, J., et al., Examination of Baffle-Former Bolts from D.C. Cook Unit 2, 16th International Conference on Environmental Degradation of Materials in Nuclear Power Systems, Asheville, North Carolina, USA, August 11-15, 2013.

13. Somville, F., et al., Ageing Management of Baffle Former Bolts in Belgian Nuclear Power Plants, Fontevraud 8, Avignon, France, September 15-18, 2014.

14. Westinghouse Report, WCAP-15029-P-A, Rev. 1, Westinghouse Methodology for Evaluating the Acceptability of Baffle-Former-Barrel Bolting Distributions Under Faulted Load Conditions, January 1999. (Proprietary)

15. Westinghouse Report, WCAP-17830-P, Rev. 1, Determination of Acceptable Baffle-Barrel Bolting for H. B. Robinson Unit 2, September 2022. (Proprietary)

16. Westinghouse Report, WCAP-17830-P, Rev. 2, Determination of Acceptable Baffle-Barrel Bolting for H. B. Robinson Unit 2, May 2023. (Proprietary)

- - This record was final approved on 11/16/2023 14:17:57. (This statement was added by the PRIME system upon its validation)

Westinghouse Non-Proprietary Class 3 Page 26 of 26 Our Ref: CPL-RV010-TM-CA-000014, Rev. 0

17. Electric Power Research Institute (EPRI) Letter No. BWRVIP 2019-016, White Paper on Suggested Content for PFM Submittals to the NRC, February 27, 2019 (ADAMS Accession No. ML19241A545).

- - This record was final approved on 11/16/2023 14:17:57. (This statement was added by the PRIME system upon its validation)

CPL-RV010-TM-CA-000014 Revision 0 Non-Proprietary Class 3

- This page was added to the quality record by the PRIME system upon its validation and shall not be considered in the page numbering of this document.**

Approval Information Author Approval Turicik Louis W Nov-16-2023 13:24:22 Verifier Approval Speicher Stephen Nov-16-2023 13:29:52 Manager Approval Musser Kaitlyn M Nov-16-2023 14:17:57 Files approved on Nov-16-2023 RA-23-0313 CPL-RV010-TM-CA-000013, Rev. 0, H. B. Robinson Unit 2 Baffle Former Bolt Predictive Evaluation (Proprietary)

v t e Letter Sequence Request
EPID:L-2019-PMP-0031, Baffle-Former Bolt (Bfb) Subsequent Inspection Interval Evaluation (Open)
Initiation Request Acceptance... Administration Withholding Request Acceptance Questions Answers Results Approval... Other:
MONTHYEAR2023-12-14 [Table View]

RA-23-0313, Baffle-Former Bolt (Bfb) Subsequent Inspection Interval Evaluation

Text

SUBJECT:

REFERENCES:

Enclosures:

Subject:

1.0 Background

Navigation menu

Search