ML23089A188

Request for Additional Information (E-mail Dated 3/29/2023) Spring 2022 Steam Generator Tube Inspection Report

ML23089A188
Person / Time
Site:	Millstone
Issue date:	03/29/2023
From:	Richard Guzman NRC/NRR/DORL/LPL1
To:	Olsowy T, Sinha S Dominion Energy Nuclear Connecticut
References
EPID L-2022-LRO-0142
Download: ML23089A188 (1)

Text

From: Richard Guzman To: timothy.f.olsowy@dominionenergy.com Cc: Shayan.Sinha@dominionenergy.com

Subject:

Millstone Power Station, Unit 3 - REQUEST FOR ADDITIONAL INFORMATION - Regarding Spring 2022 Steam Generator Tube Inspection Report (EPID L-2022-LRO-0142)

Date: Wednesday, March 29, 2023 6:57:26 AM

Tim,

On March 13, 2023, the U.S. Nuclear Regulatory Commission (NRC) staff sent Dominion Energy Nuclear Connecticut, Inc. (Dominion Energy, the licensee) the subject Request for Additional Information (RAI) as a draft e-mail. This RAI relates to the DENCs October 27, 2022, letter (ADAMS Accession No. ML22300A100), as supplemented on March 8, 2023 (ML23068A107), with information summarizing the results of the spring 2022 steam generator inspections performed at Millstone Power Station, Unit No. 3. The inspections were performed during refueling outage 21. As discussed w/the licensee staff on March 23, 2023, a conference call to discuss clarifications on the draft RAI were not necessary.

Updated below is the official (final) RAI. Please respond to this RAI by May 15, 2023, which is approximately 45 days from the date of this e-mail communication. A publicly available version of this message will be placed in the NRCs ADAMS system. Please contact me if you have any questions regarding this request.

Richard V. Guzman Senior Project Manager Plant Licensing Branch I Division of Operating Reactor Licensing Office of Nuclear Reactor Regulation Office: O-9C7 l Phone: (301) 415-1030 Richard.Guzman@nrc.gov

============================FINAL========================

REQUEST FOR ADDITIONAL INFORMATION SPRING 2022 STEAM GENERATOR TUBE INSPECTION REPORT DOMINION ENERGY NUCLEAR CONNECTICUT, INC MILLSTONE POWER STATION, UNIT 3 DOCKET NO. 50-423

L-2022-LRO-0142

By letter dated October 27, 2022 (Agencywide Documents Access and Management Systems Accession No. ML22300A100), as supplemented by letter dated March 8, 2023 (ML23068A107), Dominion Energy Nuclear Connecticut, Inc., submitted information summarizing the results of the spring 2022 steam generator (SG) inspections performed at Millstone Power Station, Unit No. 3 (MPS3). The inspections were performed during refueling outage 21. Technical Specification (TS) Section 6.8.4. requires that a SG Program be established and implemented to ensure SG tube integrity is maintained. TS Section 6.9.1.7 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.

To complete its review of the inspection report, the U.S. Nuclear Regulatory Commission (NRC) staff requests the following additional information:

1. The table below lists volumetric indications in SG C from the 2017 End of Cycle 18 (EOC-18) (ML18114A105) and the 2022 (EOC-21) steam generator tube inspection (SGTI) reports. Based on location, these appear to be successive inspections of three indications classified as foreign object (FO) wear in 2017 and tube support plate (TSP) wear in 2022. For each indication, the maximum through-wall (TW) depth reported in 2022 is significantly lower than the TW depth reported in 2017.

Please describe the data acquisition and analysis factors that resulted in the changes in indication classification and sizing.

The NRC staff recently asked licensees to consider including explanations in the inspection reports that may clarify information being reported, for example, such as reclassification of indications. (See NRC staff presentation to the industry Steam Generator Task Force (ML23052A123) on February 23, 2023).

Tube Reported Degradation and Location2017 2022

SG C R13-C120* FO wear, 29% TWTSP wear, 18% TW TSP 08C-0.8 inch TSP 08C-0.8 inch SG C R35-C78 FO wear, 28% TWTSP wear, 16% TW TSP 08C-0.94 inch TSP 08C-1.01 inch SG C R35-C110 FO wear, 24% TWTSP wear, 12% TW TSP 06C-1.25 inch TSP 06C-1.07 inch

• R=row, C=column

2. Table 3 of the 2022 (EOC-21) SGTI report includes three TSP wear indications in SG C with maximum depth 20 percent TW or more that were not in the previous inspection report for SG C in 2017 (ML18114A105). The indications were in tubes R17C70, R17C52, and R35C97, with TW depths of 45 percent, 33 percent, and 20 percent, respectively. Considering that the 2017 and 2022 reports include TW depth values as low as 9%, the staff requests the following information:

a. Please discuss your understanding of why two of these indications were first detected at greater than 30 percent TW depths, or whether they are considered anomalies.

b. Please describe if any of these indications were reportable based on lookback analysis to the 2017 inspection.

==

From: Richard Guzman Sent: Monday, March 13, 2023 5:17 PM To: Shayan Sinha Shayan.Sinha@dominionenergy.com Cc: Hipo Gonzalez Hipolito.Gonzalez@nrc.gov

Subject:

Millstone Power Station, Unit 3 - DRAFT Request for Additional Information Regarding Spring 2022 Steam Generator Tube Inspection Report (EPID L-2022-LRO-0142)

Shayan,

By letter dated October 27, 2022 (ADAMS Accession No. ML22300A100), as supplemented by letter dated March 8, 2023 (ML23068A107), Dominion Energy Nuclear Connecticut, Inc., submitted information summarizing the results of the spring 2022 steam generator inspections performed at Millstone Power Station, Unit No. 3. The inspections were performed during refueling outage 21. The NRC staff has determined that additional information is needed to complete its review, as described in the request for additional information (RAI) shown below. This RAI is identified as DRAFT at this time to confirm your understanding of the information needed by the NRC staff to complete its evaluation. Please let me know if a clarification call is needed, and I will coordinate availabilities w/the NRC technical staff. I would like to hold the call by March 22nd, if needed, as I plan to issue the questions as an official RAI no later than March 24th.

Thanks,

Rich Guzman Sr. PM, Division of Operating Reactor Licensing Office of Nuclear Reactor Regulation U.S. Nuclear Regulatory Commission Office: O-9C7 l Phone: (301) 415-1030 Richard.Guzman@nrc.gov