ML22095A229

Summary of Conference Call Regarding the Spring 2022 Steam Generator Tube Inspections

ML22095A229
Person / Time
Site:	Vogtle
Issue date:	04/11/2022
From:	John Lamb Plant Licensing Branch II
To:	Gayheart C Southern Nuclear Operating Co
Lamb, J.
References
EPID L-2022-NFO-0002
Download: ML22095A229 (11)

Text

April 11, 2022 Ms. Cheryl A. Gayheart Regulatory Affairs Director Southern Nuclear Operating Co., Inc.

3535 Colonnade Parkway Birmingham, AL 35243

SUBJECT:

VOGTLE ELECTRIC GENERATING PLANT, UNIT 2 -

SUMMARY

OF CONFERENCE CALL REGARDING THE SPRING 2022 STEAM GENERATOR TUBE INSPECTIONS (EPID L-2022-NFO-0002)

Dear Ms. Gayheart:

On March 18, 2022, the U.S. Nuclear Regulatory Commission staff participated in a conference call with representatives of Southern Nuclear Operating Company regarding the ongoing steam generator tube inspection activities at Vogtle Electric Generating Plant, Unit 2.

A summary of the conference call is provided in the enclosure.

If you have any questions, please contact me at (301) 415-3100 or via email at John.Lamb@nrc.gov.

Sincerely, Digitally signed by John G. Lamb John G. Lamb Date: 2022.04.11 10:04:17 -04'00' John G. Lamb, Senior Project Manager Plant Licensing Branch II-1 Division of Operating Reactor Licensing Office of Nuclear Reactor Regulation Docket No. 50-425

Enclosure:

Conference Call Summary cc: Listserv

SUMMARY

OF CONFERENCE CALL HELD ON MARCH 18, 2022, REGARDING SPRING 2022 STEAM GENERATOR TUBE INSPECTIONS AT VOGTLE ELECTRIC GENERATING PLANT, UNIT 2 DOCKET NO. 50-425 Introduction On March 18, 2022, the U.S. Nuclear Regulatory Commission (NRC) staff participated in a conference call with representatives of Southern Nuclear Operating Company (SNC, the licensee), regarding the ongoing steam generator (SG) tube inspection activities at Vogtle Electric Generating Plant (Vogtle), Unit 2, during refueling outage (RFO) 22.

The NRC provided the request for the conference by emails dated February 9 and 23, 2022 (Agencywide Documents Access and Management System (ADAMS) Accession Nos.

ML22040A045 and ML22055A099, respectively). The discussion points for the conference call held on March 18, 2022, were contained in the email dated February 23, 2022. The attendees for the conference call are contained in Attachment 1.

Background

The previous time the NRC staff selected Vogtle, Unit 2, for a conference call regarding the SG tube inspection activities was March 2013. The summary of the 2013 conference calls is dated April 25, 2013 (ADAMS Accession No. ML13112A225).

By letter dated September 10, 2019 (ADAMS Accession No. ML19255F170), SNC submitted information summarizing the results of the spring 2019 SG inspections at Vogtle, Unit 2; these inspections were performed during the RFO 20. By letter dated November 15, 2019 (ADAMS Accession No. ML19282A235), the NRC staff performed a review of RFO 20 SG inspections for Vogtle, Unit 2.

By letter dated January 5, 2022 (ADAMS Accession No. ML21316A055), the NRC staff issued Amendment No. 194 to Vogtle, Unit 2. The amendment revised revise the Vogtle Steam Generator (SG) Program and the Steam Generator Tube Inspection Report technical specifications based on Technical Specifications Task Force (TSTF) Traveler TSTF-577, Revision 1, Revised Frequencies for Steam Generator Tube Inspections (TSTF-577) (ADAMS Accession No. ML21060B434), and the associated NRC staff safety evaluation (SE) of TSTF-577 (ADAMS Accession No. ML21098A188).

Vogtle, Unit 2, has four Westinghouse Model F SGs, each of which contains 5,626 U-bend thermally treated Alloy 600 tubes. Each tube has a nominal outside diameter (OD) of 0.688 inches and a nominal wall thickness of 0.040 inches. During SG fabrication, the tubes were hydraulically expanded, at both ends, over the full depth of the tubesheet. Type 405 stainless steel support plates, which have broached quatrefoil holes, support the vertical section of the tubes, and anti-vibration bars support the U-bend section of the tubes.

Enclosure

Conference Call Held on March 18, 2022 Information provided by the licensee in support of the March 18, 2022, conference call is provided as Attachment 2. The NRC staff notes that the inspection information is preliminary and subject to change upon final data analysis.

At the time of the call approximately 67 percent of the eddy current data acquisition and 64 percent of the eddy current analysis had been completed.

The eddy current inspection scope for each SG includes:

o A 100 percent full-length bobbin/array combination probe examination of all in-service tubes.

o +PointTM probe inspections on:

All Row 1 and 2 U-bends All hot leg (HL) top of tubesheet (TTS) tubes +3 inches to H* depth All bobbin/array I-Codes All dents/dings greater than or equal to 2 volts in the HL straight length and U-bend tube portion 50 percent dents/dings greater than 5 volts in cold leg (CL) straight length 25 percent dents/dings between 2-5 volts in CL straight length All high stress (-2 sigma) HL/CL tube support plate (TSP) intersections, HL/CL TTS transitions, and greater than or equal to 2-volt dents/dings All existing and new possible loose parts (PLP) signals (+PointTM and array probe), including a two-tube circumference around PLP signals At the time of the call, the licensee had identified:

o A total of 316 anti-vibration bars (AVB) wear indications in all SGs with the greatest wear depth measured as 42 percent through-wall.

o A total of six indications of historical foreign object wear or secondary side cleaning wall loss.

o Three potential crack indications that were going to be tested with a Ghent probe to resolve the indications. One indication was located at the HL TTS in SG1.

The other two indications were located in SG 4, at the 7th HL TSP and at the HL TTS. These indications are not historical.

o Following the call, the licensee informed the NRC that the potential crack indications discussed in the previous bullet were confirmed to be cracks. Based on the screening results, in situ pressure testing was not required.

At the time of the call all indications met the condition monitoring limits demonstrating that tube integrity was maintained. No in-situ pressure tests had been performed and none are planned.

No inspections were planned for the secondary side steam drum. In response to an NRC staff question, the licensee stated that there was no history of degradation in the moisture separators and that some flow accelerated corrosion has occurred in the feedwater distribution ring.

The licensee estimated all SG work would be completed by March 23, 2022.

Summary The NRC staff did not identify any issues that required follow-up action at this time. The NRC staff asked to be notified in the event that any new degradation mechanisms were detected or in-situ pressure testing of tube indications was planned.

ATTACHMENT 1 ATTENDEES OF CONFERENCE CALL HELD ON MARCH 18, 2022, REGARDING SPRING 2022 STEAM GENERATOR TUBE INSPECTIONS AT VOGTLE ELECTRIC GENERATING PLANT, UNIT 2 DOCKET NO. 50-425 NAME ORGANIZATION John G. Lamb U.S. Nuclear Regulatory Commission (NRC)

Paul Klein NRC Greg Makar NRC Andrew Johnson NRC Leslie Terry NRC Steve Bloom NRC Chris Safouri NRC Michael Magyar NRC DeLisa Pournaras Southern Nuclear Operating Company (SNC)

Ryan Joyce SNC Cheryl Gayheart SNC Chris Gamblin SNC Cotasha Blackburn SNC Keith Walden SNC Brett Evans SNC Jonathan Thompson SNC Michael Krinock SNC Bob Chappo SNC Jim Rockovich SNC

ATTACHMENT 2 PRELIMINARY STEAM GENERATOR TUBE INSPECTION DISCUSSION POINTS Vogtle, Unit 1, Refueling Outage 22 (2R22)

1. Discuss any trends in the amount of primary-to-secondary leakage observed during the recently completed cycle.

a. No primary-to-secondary leakage during previous inspection cycle.

2. Discuss whether any secondary side pressure tests were performed during the outage and the associated results.

a. None

3. Discuss any exceptions taken to the industry guidelines.

a. None

4. For each steam generator (SG), provide a description of the inspections performed including the areas examined and the probes used (e.g., dents/dings, sleeves, expansion-transition, U-bends with a rotating probe), the scope of the inspection (e.g.,

100 percent of dents/dings greater than 5 volts and a 20 percent sample between 2 and 5 volts), and the expansion criteria.

Exam Percentage Probe Extent Expansion Criteria X-Probe Tube End to Tube None Full Length 100%

(Bobbin/Array) End Bobbin Candy Cane from None Array Only Hot Leg (HL)

Rows 3-5 Row 1 and 2 U-Low Row U-Bend 100% bends from the

+Point top tube support plate (TSP) on the HL to the top TSP on the Cold Leg (CL)

HL tubes from top None of tubesheet HL Top of (TTS) to licensed 100% +Point Tubesheet H* ARC depth

(+3/-15.2 inches) /

HL bulge and

Exam Percentage Probe Extent Expansion Criteria overexpansion populations Special Interest I-Codes 100% +Point None Dings/Dents 2 None volts in HL HL Straight straight Lengths Lengths and U-100% +Point and U-Bends Bends (New and (New and existing)

Existing)

Dings/Dents > Expansion 5.0 Volts in CL CL Straight on an as straight lengths 50% +Point Length (New and needed (New and Existing) basis Existing)

Dings/Dents Expansion between 2.0-5.0 on an as In CL Straight Volts in CL needed 25% +Point Lengths (New and Straight Lengths basis Existing)

(New and Existing)

TSP HL/CL None Intersections, TTS 2-Sigma High 100% +Point HL/CL Expansion Stress Tubes Transitions, and 2 Volts Existing Possible 100% +Point / X-Probe TTS None Loose Parts (PLPs)

New PLPs 100% +Point / X-Probe TTS None

5. For each area examined (e.g., tube supports, dent/dings, sleeves, etc.), provide the following:

a. A summary of the number of indications identified to date for each degradation mode (e.g., number of circumferential primary water stress corrosion cracking indications at the expansion transition).

i. Anti-Vibration Bar Wear [AVB]:

SG1: ~94 indications SG2: ~76 indications SG3: ~40 indications SG4: ~106 indications ii. Historical Foreign Object Wear [FOW] / Secondary Side [SS]

Cleaning Loss:

SG1: 5 indications SG4: 1 indication

iii. Other indications of interest:

SG1: One I-code awaiting Ghent probe retest on Tube support hot leg side (TSH), not historical SG4: Two I-codes awaiting Ghent probe retest on 7th tube support on hot leg side (7H) and TSH, both are not historical.

b. For the most significant indications in each area, provide an estimate of the severity of the indication (e.g., voltage, depth, and length of the indication),

including whether SG tube integrity (structural and accident induced leakage integrity) was maintained during the previous operating cycle. In addition, discuss any analyses performed specifically for the most significant indications to demonstrate tube integrity.

i. Structural and leakage integrity was maintained during the previous inspection interval ii. Max AVB wear, 42% through wall (TW), less than CM [condition monitoring] limit iii. Max historical FOW / SS Cleaning Loss 22% TW, less than CM limit

c. Discuss whether any location exhibited a degradation mode that had not previously been observed at this location at Vogtle, Unit 2 (e.g., observed circumferential primary water stress corrosion cracking at the expansion transition for the first time at this unit).

i. Pending special interest exams

6. Describe repair/plugging plans.

a. Any tube wear 40% TW will be plugged on detection, any confirmed crack will be plugged on detection, and any additional tubes will be plugged on an as-needed basis to support the operational assessment.

Circumferential cracks or accelerated growth rates will be stabilized.

7. Describe in-situ pressure test and tube pull plans and results (as applicable and if available).

a. As of the data at 0800 EST [Eastern Standard Time], there are no indications that require in-situ pressure testing. For any confirmed cracks, line-by-line sizing will be completed to start the screening process. The line by line sizing information will then be used in parallel with the Vogtle 2R22 DAs [degradation assessment] instructions for in-situ pressure test screening.

b. No tube pulls are planned to be performed.

8. Discuss the following regarding loose parts:

a. The inspections performed to detect loose parts.

i. TTS Visual Inspection in all SGs ii. Sludge Lance in all SGs iii. Foreign object search and retrieval (FOSAR) TTS in all SGs iv. Top Support Plate Visual Inspection SG2

b. A description of any loose parts detected and their location within the SG (including the source or nature of the loose part, if known).

i. See Table 1

c. If the loose parts were removed from the SG.

i. See Table 1

d. Indications of SG tube damage associated with the loose parts.

i. There have been no new instances of FOW, only indications from previous inspections

9. Discuss the scope and results of any secondary side inspection and maintenance activities (e.g., in-bundle visual inspections, feedring inspections, sludge lancing, assessing deposit loading, etc.).

a. See response to Question 8

b. Additionally, sludge profiling will be completed post-outage from SG4 sludge.

10. Discuss any unexpected or unusual results.

a. None

11. Provide the schedule for SG-related activities during the remainder of the current outage

a. ECT [eddy current testing] in all SGs is estimated to be completed on Wednesday, March 23.

TABLE 1 Height Foreign Foreign SG Retrieval Leg / above Beginning End Beginning End Is Length Width Height Object Object No. Status Region Support Row Row Column Column Legacy (In.) (In.) (In.)

No. Description (In.)

Will Not Sludge SG1 1001 Tubelane 0.01 0 0 75 76 New 0.25 0.25 0.3 Retrieve Rock Will Not Sludge SG1 1002 Tubelane 0.01 0 1 63 64 New 0.3 0.25 0.5 Retrieve Rock Will Not Sludge SG1 1003 Tubelane 0.01 36 37 20 20 New 0.292 0.292 0.292 Retrieve Rock Will Not Sludge SG1 1004 Tubelane 1.5 44 44 97 98 New 0.292 0.292 0.292 Retrieve Rock Will Not Sludge SG2 2001 Hot Leg 0.01 21 22 8 8 New 0.29 0.29 0.29 Retrieve Rock Will Not Other -

SG2 2004 Hot Leg 0.01 21 21 61 62 Legacy 0.175 0.03 0.175 Retrieve Unkown Will Not Sludge SG2 2002 Cold Leg 0.01 51 52 33 33 New 0.29 0.2 0.29 Retrieve Rock Will Not Sludge SG4 4001 Hot Leg 0.001 21 22 5 6 New 0.292 0.292 0.35 Retrieve Rock Will Not Sludge SG4 4002 Cold Leg 0.001 49 50 87 88 New 0.25 0.25 0.25 Retrieve Rock

ML22095A229 OFFICE NRR/DORL/LPL2-1/PM NRR/DORL/LPL2-1/LA NRR/DNRL/NCSG/BC NAME JLamb KGoldstein SBloom DATE 4/5/2022 04/06/2022 4/4/2022 OFFICE NRR/DORL/LPL2-1/BC NRR/DORL/LPL2-1/PM NAME MMarkley JLamb DATE 4/11/2022 4/11/2022