ML23321A045

EC 639996 (Byron), Revision 1 and 640160 (Braidwood), Revision 0, Technical Evaluation for NEI 03-08 Deviation of Baffle-Former Bolts Volumetric Examinations for Byron and Braidwood

ML23321A045
Person / Time
Site:	Byron, Braidwood
Issue date:	11/17/2023
From:	Constellation Energy Generation
To:	Office of Nuclear Reactor Regulation
Shared Package
ML23321A043	List: BW230054, Attachment 2: MDMP Deviation Form ML23321A044 ML23321A045
References
BW230054
Download: ML23321A045 (1)

Text

EC 639996 (Byron), Revision 1 and 640160 (Braidwood), Revision 0 Technical Evaluation for NEI 03-08 Deviation of Baffle-Former Bolts Volumetric Examinations for Byron and Braidwood

1. Reason for Evaluation/Scope

Byron Units 1 and 2 and Braidwood Unit 2 are scheduled to perform the Reactor Vessel lnternals (RV!)

examinations in accordance with MRP-227. Revision 1-A [1] during the Spring 2026. Fall 2026, and Fall 2027 refueling outages. respectively. These examinations include the volumetric examinations of the Baffle-Former Bolts (BFBs). which are typically performed using the ultrasonic testing (UT) method.

These plants are considered Tier 4 plants per NSAL-16-1, Revision l [2].

Table 4-3 (Item W6) of MRP-227. Revision 1-A [ 1] requires that Tier 4 plants perform baseline volumetric examinations of BFBs no later than 35 effective full power years (EFPY). as stated in Note 8 of Table 4-3 [l]. Based on the schedule of the RV! examinations for Byron Units 1 and 2 and Braidwood Unit 2. these plants will exceed the EFPY requirement for performing these baseline examinations. Per the implementation requirements under Subsection 7.3 or MRP-227. Revision 1-A [ l], there is a NE! 03-08 [3] "'Needed** requirement which states. each commercial [/S PWR unit shall implemenl the requirements of Tables 4-1 through 9 and Tables 5-1 through 5-Jfor the applicah!e design [1]. Per NE!

03-08 [3]. "'Needed** requirements or guidance are to he implemented 1t"hcnevcr possible hut alternative approaches are acceptohlc. Technical justification shall be developed lo deviate from the "'Needed" requirement above because it will not he implemented 11*ithin the timeframe specified in MRP-227.

Revision 1-A [ 1 ]. As such. a deviation is required to extend the current requirement of 35 EFPY to 36 EFPY to bundle the baseline volumetric examinations of BFBs with the rest of the RV! examinations to reduce person-rem exposure and outage complexity. This evaluation serves as the technical justification for that deviation.

2. Detailed Evaluation

Byron and Braidv,ood are Westinghouse 4-loop plants with neutron panels continuously operated with the baffle-former assembly in the upflmv configuration. As such. they are considered Tier 4 plants per NSAL-16-1. Revision I r2J. Each unit has a total of832 BFBs made ofType 316 stainless steel material. The BFBs are located on the baffle plates and fasten the baffle plates to the former plates. The baffle plates are the vertical components that are next to the fuel v\\hen the core is in place. The baffle plates are supported by horizontal supports called former plates. These components compose the baffle-former assembly. The function of the baffle-former assembly is to maintain the fuel assembly structural integrity to ensure that the control rods insert. maintain a coolable core geometry. and ensure a core configuration that supports long-term reactor shutdown.

As shown in Table 4-3, MRP-227, Revision I -A [I] requires a volumetric examination of 100% of the BFBs. The initial examination for Tier 4 plants is required by 35 EFPY, and subsequent examinations are required on a l 0-year interval unless significant degradation (2' 5% or BFBs with indications or clustering as defined in NSAL-16-1 Revision 1 [2]) is observed. With the current RV! examination schedule in place for Byron Units 1 and 2 and Braidv\\OOd Unit 2, these three units are projected to exceed 35 EFPY prior to performing the required baseline volumetric examinations of their BFBs. Table I shows the RV!

examination schedule for these units and the projected cumulative EFPY at which these examinations are scheduled to be performed. EFPY projections were made by adding 1.5 EFPY per 18-month fuel cycle from the accumulated EFPY values from the last refueling outage.

Page 1 of5 EC 639996 (Byron), Revision 1 and 640160 (Braidwood), Revision 0 Technical Evaluation for NEI 03-08 Deviation of Baffle-Former Bolts Volumetric Examinations for Byron and Braidwood

Table 1 - RVI Examinations Schedule and EFPY Projections

Plant Last Outage Last Outage Examination Projected EFPY Date EFPY Outage Date at Examination Bvron Unit 1 Spring 2023 32.951 Spring 2026 35.951 Bvron Unit 2 Fall 2023 32.814 Fall 2026 35.814 Braidwood Unit 2 Spring 2023 31.275 Fall 2027 35.775

The volumetric examinations of BFBs are intended to detect the potential cracking failure of the bolts due to irradiation-assisted stress corrosion cracking (IASCC) or fatigue. Most of the BFB degradation observed in the industry, and the vvorst of the degradation. has been found in plants that operate in the downflow configuration. The elevated degradation in those plants has been linked to the higher stresses on the BFBs due to the pressure differential caused by the downtlovv configuration. Plants with upflow configuration. like Byron Units 1 and 2 and Braidwood Unit 1. have lower differential pressure which causes lower stresses on the BFBs.

The most recent UT inspection results from the original and conve11ed upflow plants that have performed their RVI examinations shm, very minimal BFB degradation (less than 1 % of BFBs \\Yith indications and no clustering). These results as sho\\\\n in Table 2.

Table 2 - Industry Results of Volumetric Examinations of BFBs for Tier 3 and 4 Plants

Plant Reactor Config. Year EFPY Total SAT RI UI Design lnsp.

Wolf 4-loop Uptlow 2021 30.15 8"'"' 831 0 1

.J~

Creek Neutron Panel vc 3-loop Converted UptlO\\\\ 2021 32.3 1088 1080 7 I Summer Neutron Panel (-2008)

Callavvay 4-loop Up Neutron Panel flow 2022 31.76 832 832 0 0 Point 2-loop Converted 2022 42.2 728 728 0 0 Beach I Thermal Shield Uptlow 202 The rest of 526 Point 2-loop Converted 2023 42.89 (out 202 0 BFBs not inspected Beach 2 Thermal Shield Uptlow of due to vendor 728) equipment issues North 3-loop Converted Annal Thermal Shield Upflow 2016 31.05 1088 1078 3 7 ( 1996)...

Beaver 3-loop Converted 2022 -35 1088 1076 0 12 Vallev 1 Thermal Shield Uptlow..

Almaraz 3-loop.. l 2 Neutron Panel Uptlow 2022 34.5 960 957 '

1"ote: SAT - Satisfactory, RI - Relevant Indication, lll - Un-inspectable

Based on Table 2. none of the mentioned plants have ever come close to having BFB degradation that would threaten structural integrity of the baffle-former assembly. Furthermore, Wolf Creek and Callaway.

Page 2 of5 EC 639996 (Byron), Revision 1 and 640160 (Braidwood), Revision 0 Technical Evaluation for NEI 03-08 Deviation of Baffle-Former Bolts Volumetric Examinations for Byron and Braidwood

the two plants with the most similar designs to Byron and Braidwood, have the best BFB UT inspection results and did not find a single BFB with a RI. As such, the probability of significant BFB degradation (2:

5% of BFBs with indications or clustering as defined in NSAL-16-1 Revision I [2]) at Byron Units 1 and 2 and Braidwood Unit 2 is very low based on industry operating experience and lmv relative stresses on the BFBs. Plus, Byron and Braidwood had never experienced fuel failures due to baffle-jetting, which is a well-known symptom of BFB degradation at Westinghouse-designed PWRs. Therefore. performing the baseline volumetric examinations of the BFBs no later than 36 EFPY is prudent and will not be a safety concern.

The intent of the MRP-227, Revision 1-A guidance is to proactively inspect RV! components prior to them undergoing significant degradation, thereby adequately managing the aging of the components. With the RY! examination schedule for Byron Units 1 and 2 and Braidwood Unit 2 outlined in Table 1. these units will still meet this intent as demonstrated by the technical justification in this evaluation.

3. Conclusions / Findings

Based on Byron's and Braid\\vood*s history ofno fuel failures due to baffle-jetting. good industry operating experience of BFB degradation for Tier 3 and 4 plants, and low relative stresses on their BFBs due to their upfiow configuration, it is acceptable to perform the baseline volumetric examinations of the BFBs beyond 35 EFPY. but no later than 36 EFPY. Therefore, performing the baseline volumetric examinations of the BFBs no later than 36 EFPY \\Viii reduce person-rem exposure and outage complexity by bundling these with the rest of the RV! examinations while still providing an acceptable level of qua! ity and safety.

4. References

[!] MRP-227. Revision I-A, Materials Reliability Program PWR Reactor Internals Inspection and Eva! uation Guide! ine.

[21 NSAL-16-1, Revision 1, Baffle-Former Bolts.

[3] NE! 03-08. Revision 4. Guideline for the Management of Materials Issues.

[4] MRP 2014-009, 2014 Biennial Report of Recent MRP-227-A Reactor Internals Inspection Results.

[5] MRP 2016-008, 2016 Biennial Report of Recent MRP-227-A Reactor Internals Inspection Results.

[6] MRP 2018-025, 20 I 8 Biennial Report of Recent MRP-227-A Reactor Internals Inspection Results.

[7] MRP 2020-015, 2020 Biennial Report of Recent MRP-227-A Reactor Internals Inspection Results.

[8] MRP 2022-017, 2022 Biennial Report of Recent MRP-227-A Reactor Internals Inspection Results.

[9] MRP-227 Rev 1-A Reporting Tables for Westinghouse Plants, Point Beach Unit I U2R39.

[10] MRP Fall 2022 TAC Meeting, Operating Experience Technical Session, dated 11/15/2022.

[II] BB-PBD-AMP-XI-M16A, Revision 3, Byron and Braidwood PWR Vessel Internals Bases Document.

[12] TOOi BYR-23-006, Revision 0, Cycle Burnup Values for Byron Unit 1 Cycles I through 25.

[13] TOOi BYR-23-029, Revision 0, Cycle Burnup Values for Byron Unit 2 Cycles I through 24.

[14] EC 639058. Revision 0, Braidwood Unit 2 Cumulative Burnup in Effective Full Power Years Through Cycle 23 (A2R23).

[15] F-2956 and L-2956, Revision 0, Byron and Braidwood Procurement Specification for PWR In Vessel Inspections.

[16] ER-AP-333, Revision 4, Pressurized Water Reactor Internals Management Program.

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[17] ER-AP-333-100 L Revision 4. Pressurized Water Reactor (PWR) Internals Program.

[18] ER-AA-40, Revision 4, Materials Degradation Management Program (MDMP).

[19] ER-AA-400L Revision 6. Materials Degradation Management Program (MDMP) Implementation Guidance.

[20J ER-AA-4003, Revision 6. Materials Degradation Management Program (MDMP) Deviation Guidance.

[21] CC-AA-309-10 I, Revision 16. Engineering Technical Evaluations.

[22] HU-AA-1212. Revision 13. Technical Task Risk/Rigor Assessment. Pre-Job Brief. Independent Third Party Review, and Post-Job Brief.

5. Technical Review

The detailed evaluation was verified correct, and the associated conclusions are deemed reasonable through independent review of the Technical Eva] uation. The requirements of the HU-AA-1212 were reviewed and no independent third-party review was required. A human performance briefing per HU AA-1212 was completed on I 0/13/2023 by Jacky Shoulders in association with this document.

Since there are no configuration changes or plant modifications performed by this technical evaluation. it has been determined that a Design Attribute Review (DAR) is not warranted. The Programs Engineering Manager has concurred \\Vith this decision.

Preparer: Osvaldo Cruz Signature: Electronically signed in PassP011

Independent Reviewer: Kemper Young Signature: Electronically siQned in PassPort

Approver: Jackv Shoulders Signature: Electronically signed in PassPort

Page 4 ofS EC 639996 (Byron), Revision 1 and 640160 (Braidwood), Revision 0 Technical Evaluation for NEI 03-08 Deviation of Baffle-Former Bolts Volumetric Examinations for Byron and Braidwood

Attachment 1

Figure 1-Byron/Braidwood Units 1 and 2 Baffle-Former Bolts

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