ML20246G561

Request for Additional Information (E-mail Dated 9/2/2020) License Amendment Request for a One-Time Deferral of the Steam Generator Inspections

ML20246G561
Person / Time
Site:	Millstone
Issue date:	09/02/2020
From:	Richard Guzman NRC/NRR/DORL/LPL1
To:	Sinha S Dominion Energy Nuclear Connecticut
Guzman R
References
COVID-19, EPID L-2020-LLA-0178
Download: ML20246G561 (2)

Text

From: Guzman, Richard To: Shayan.Sinha@dominionenergy.com

Subject:

Millstone Power Station, Unit 3 - REQUEST FOR ADDITIONAL INFORMATION - License Amendment Request for a One-Time Deferral of the Steam Generator Inspections (EPID: L-2020-LLA-0178)

Date: Wednesday, September 02, 2020 10:25:00 AM

Shayan, On August 31, 2020, the U.S. Nuclear Regulatory Commission (NRC) staff sent Dominion Energy Nuclear Connecticut, Inc. (DENC, the licensee) the subject Request for Additional Information (RAI) as a draft e-mail. This RAI relates to the licensees August 11, 2020, license amendment request (ADAMS Accession No. ML20224A457), proposing changes to the Millstone Power Station, Unit 3 (MPS3) Technical Specifications to allow a one-time deferral of steam generator tube inspections currently scheduled for the MPS3 refueling outage in the fall 2020 (RFO-20).

You indicated today that a clarification call was not necessary to respond to the information request. I understand DENC will provide a response to this RAI by September 18, 2020.

Updated below is the official RAI. A publicly available version of this e-mail and RAI will be placed in the NRCs ADAMS system. Please contact me should you have any questions in regard to this request.

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

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REQUEST FOR ADDITIONAL INFORMATION (RAI) REGARDING LICENSE AMENDMENT REQUEST FOR A ONE-TIME DEFERRAL OF THE STEAM GENERATOR INSPECTIONS FOR MILLSTONE POWER STATION, UNIT NO. 3 DOCKET NO. 50-423 (EPID: L-2020-LLA-0178)

By letter dated August 11, 2020 (Agencywide Documents Access and Management System (ADAMS) Accession No. ML20224A457), Dominion Energy Nuclear Connecticut, Inc. (the licensee) submitted a license amendment request (LAR) to Renewed Facility Operating License No. NPF-49 for Millstone Power Station Unit 3 (MPS3). The proposed change would allow a one-time deferral of steam generator tube inspections currently scheduled for Refueling Outage 20 in fall 2020.

The U.S. Nuclear Regulatory Commission (NRC) staff has reviewed the information provided in the submittal and has determined that additional information as requested in the below is needed to complete its review.

RAI-1

Section 3.1.1, AVB Wear, of the operational assessment (Attachment 4 to the LAR) states that the anti-vibration bar (AVB) growth rate used is the largest 95th percentile at 50 percent confidence value measured among the four MPS3 steam generators (SGs) at the most recent inspection. Please discuss why this upper bound growth rate value from the last inspection is appropriate in terms of the observed plant specific AVB wear rate trends.

RAI-2

Section 3.2.1, Axial ODSCC at Tube Support Plates, of the operational assessment (Attachment 4 to the LAR) states that the probability of detection (POD) curve for axial outside diameter stress corrosion cracking (ODSCC) at tube support plates (TSPs) was developed using the more limiting eddy current noise measurements from Surry Power Station, Unit 2 (Surry 2) with the model-assisted POD (MAPOD) methodology. Figure 3-1 of the MPS3 operational assessment shows the corresponding POD curve.

The NRC staff observed that the POD curve in Figure 3-1 is different than the corresponding POD curve in the operational assessment for Surry 2, SG B, for the same degradation mechanism (Figure 3-2 of Surry LAR dated April 14, 2020 (ADAMS Accession No. ML20105A223)). Therefore, please explain the apparent difference for the two POD curves. Are the differences due solely to variability with the MAPOD process? Was the noise data input for MPS3 the exact same noise input as for Surry (i.e., Surry 2 SG B) or something different?

RAI-3

The LAR proposes to defer the SG inspection. The proposed TS language states that the SG inspection may be extended. The NRC staff notes that deferred is an appropriate term, while extended is not accurate for the proposed TS change. Discuss your plans to revise the TS wording to accurately reflect the proposed action.