ML22157A090

NRR E-mail Capture - RAIs - Vogtle, Unit 1 - Refueling Outage (RFO) 1R23 Steam Generator (SG) Tube Inspection Report

ML22157A090
Person / Time
Site:	Vogtle
Issue date:	06/06/2022
From:	John Lamb Plant Licensing Branch II
To:	Lowery K Southern Nuclear Operating Co
References
L 2022-LRO-0030
Download: ML22157A090 (3)

Text

From: Lamb, John Sent: Monday, June 6, 2022 11:14 AM To: Lowery, Ken G.

Cc: Pournaras, DeLisa S.

Subject:

RAIs - Vogtle, Unit 1- Refueling Outage (RFO) 1R23 Steam Generator (SG)

Tube Inspection Report (EPID L 2022-LRO-0030)

Importance: High

Ken, By letter dated April 1, 2022 (Agencywide Documents Access and Management System (ADAMS) Accession No. ML22091A261), Southern Nuclear Operating Company (SNC) submitted information summarizing the results of the fall 2021 steam generator (SG) inspections performed at Vogtle Electric Generating Plant (Vogtle), Unit 1, during the twenty-third refueling outage (1R23).

After reviewing the report, the NRC staff requests response to the request for additional information (RAI) given below.

On May 27, 2022, the NRC staff provided a draft RAI question to SNC to make sure that the RAI is understandable, the regulatory basis is clear, to ensure there is no proprietary information, and to determine if the information was previously docketed. On June 6, 2022, a clarifying call was held and SNC stated that it would provide the RAI response within 45 days of the date of this email.

If you have any questions, you can contact me at 301-415-3100.

Sincerely, John Thanks.

John REQUEST FOR ADDITIONAL INFORMATION (RAI)

By letter dated April 1, 2022 (Agencywide Documents Access and Management System (ADAMS) Accession No. ML22091A261), Southern Nuclear Operating Company (SNC, the licensee) submitted information summarizing the results of the fall 2021 steam generator (SG) inspections performed at Vogtle Electric Generating Plant (Vogtle), Unit 1, during the twenty-third refueling outage (RFO) (1R23).

All pressurized water reactors have Technical Specifications (TS) according to Section 50.36 of Title 10 of the Code of Federal Regulations that include a SG Program with specific criteria for the structural and leakage integrity, repair, and inspection of SG tubes. Vogtle Unit 1, TS Section 5.6.10 requires that a report be submitted within 180 days after the initial entry into hot shutdown (MODE 4) following completion of an inspection of the SGs performed in accordance with TS Section 5.5.9, which requires that a SG Program be established and implemented to ensure SG tube integrity is maintained.

To complete its review of the inspection report, the NRC staff requests the following additional information:

1. Vogtle, Unit 1, has recurring circumferential outside diameter stress corrosion cracking (ODSCC) at the hot leg top of tubesheet in the expansion transition. The 1R23 inspection report (Table 6) provides information about eight tubes with ODSCC in the hot leg top of tubesheet region. Knowing the indication location, SNC reviewed previous inspection data to determine if an eddy current precursor signal was present. Review of previous inspection data is valuable since it helps with early recognition of ODSCC indications and informs growth rate estimates. Previously, a tube in Vogtle, Unit 1, SG 4, with circumferential ODSCC at the top of the tubesheet, was pulled from the SG in 2008 and destructively analyzed (ML100560265). Comparison of the destructive analysis results to the eddy current analysis results confirmed the challenges related to detection of shallow stress corrosion cracking (SCC) cracks.

a. Based on the information gained from eddy current analysis (including review of previous inspection data) and laboratory analysis of the pulled tube, please discuss the depth of circumferential ODSCC in the tubesheet expansion transition region that is associated with reliable detection.

b. If arc length is included as an input for the operational assessment (OA) of circumferential ODSCC in the tubesheet expansion transition region, please discuss how the OA accounts for the differences that were previously observed between destructive analysis results and eddy current measurements.

Hearing Identifier: NRR_DRMA Email Number: 1660 Mail Envelope Properties (MN2PR09MB508466A6DB2ED7700D20ADDCFAA29)

Subject:

RAIs - Vogtle, Unit 1- Refueling Outage (RFO) 1R23 Steam Generator (SG)

Tube Inspection Report (EPID L 2022-LRO-0030)

Sent Date: 6/6/2022 11:13:39 AM Received Date: 6/6/2022 11:13:00 AM From: Lamb, John Created By: John.Lamb@nrc.gov Recipients:

"Pournaras, DeLisa S." <DSPOURNA@SOUTHERNCO.COM>

Tracking Status: None "Lowery, Ken G." <KGLOWERY@southernco.com>

Tracking Status: None Post Office: MN2PR09MB5084.namprd09.prod.outlook.com Files Size Date & Time MESSAGE 3736 6/6/2022 11:13:00 AM Options Priority: High Return Notification: No Reply Requested: No Sensitivity: Normal Expiration Date: