ML20140B003

NRR E-mail Capture - Request for Additional Information - Oconee Nuclear Station - LPSW Relief Request RA-20-0036 (L-2020-LLR-0036)

ML20140B003
Person / Time
Site:	Oconee
Issue date:	05/19/2020
From:	Michael Mahoney NRC/NRR/DORL/LPL2-1
To:	Sigmon C Duke Energy Carolinas
References
L-2020-LLR-0036
Download: ML20140B003 (3)

Text

From: Mahoney, Michael Sent: Tuesday, May 19, 2020 12:41 PM To: Sigmon, Chet Austin Cc: Arthur.Zaremba@duke-energy.com; Wasik, Christopher J

Subject:

Request for Additional Information - Oconee Nuclear Station - LPSW Relief Request RA-20-0036 (L-2020-LLR-0036)

Chet, By letter RA-20-0036, dated March 2, 2020 (Agencywide Documents Access and Management System (ADAMS) Accession No. ML20062G131), Duke Power Carolinas, LLC (Duke, the licensee), submitted Relief Request (RR) RA-20-0036 which proposes an alternative to the requirements in Subarticle IWA-4421 of the American Society of Mechanical Engineers Boiler and Pressure Vessel Code (ASME Code),Section XI, Rules for Inservice Inspection of Nuclear Power Plant Components, 2007 Edition through 2008 Addenda, regarding removal of defects in accordance with IWA-4411, IWA-4461, or IWA-4462 on the subject Low Pressure Service Water (LPSW) piping identified in the request, prior to performing repair/replacement activities at Oconee Nuclear Station, Unit Nos. 1 and 2. The licensee is proposing to install a modification/repair of a welded encapsulation, over the defect in the subject LPSW piping.

The NRC staff has reviewed the application and, based upon this review, determined that additional information is needed to complete our review. Please provide a response on the docket within 30 days of this correspondence.

Request for Additional Information (RAI-01)

The letter dated March 2, 2020, does not discuss the nature of the degradation mechanism which resulted in the through-wall leak discovered on September 26, 2019.

a. Please provide a discussion of the degradation mechanism which caused the through-wall leak.

b. Please provide a map of the as found pipe wall thickness readings this should also identify the locations where the encapsulation is proposed to be attached to the existing piping.

RAI-02

Section 5.1.6 of the letter dated March 2, 2020, discusses ultrasonic thickness measurements being performed prior to installation of the encapsulation to confirm that that the material thickness has remained adequate for the encapsulation design.

Please define what the material thickness needs to be, to be adequate for the encapsulation design.

RAI-03

Sections 5.1.1 and 5.1.2 of the letter dated March 2, 2020, discuss that the design, replacement pressure-retaining materials, and welding of the encapsulation will comply with the Construction

Code (American Society of Mechanical Engineers (ASME), Section B31.1) and Owner's requirements.

a. Please clarify how the outer pipe is analyzed to satisfy the allowable stresses in ASME B31.1.

b. Please provide a discussion on how the applied loads (i.e., forces and moments) on the outer pipe are calculated or obtained.

RAI-04

Please provide a discussion on the rate of degradation used in the design of the encapsulation to ensure that propagation of the defect into the material credited for structural integrity in the modification does not occur in the design life of the modification. This discussion should include a comparison of the rate of degradation used in the design to the actual measured rate of degradation.

RAI-05

Please provide a description of the wall thickness examinations in the vicinity of the modification and relevant pipe base metal which will be performed after the installation of the encapsulation to ensure propagation of the defect into the material credited for structural integrity does not occur during the design life of the modification.

Once this email is added to ADAMS, I will provide the accession number for your reference.

Thanks Mike Michael Mahoney McGuire and Catawba Project Manager, Division of Operating Reactor Licensing Office of Nuclear Reactor Regulation U. S. Nuclear Regulatory Commission Desk: (301)-415-3867 Email: Michael.Mahoney@NRC.GOV

Hearing Identifier: NRR_DRMA Email Number: 593 Mail Envelope Properties (MN2PR09MB35179A38531367AB9FBA0583E5B90)

Subject:

Request for Additional Information - Oconee Nuclear Station - LPSW Relief Request RA-20-0036 (L-2020-LLR-0036)

Sent Date: 5/19/2020 12:41:26 PM Received Date: 5/19/2020 12:41:28 PM From: Mahoney, Michael Created By: Michael.Mahoney@nrc.gov Recipients:

"Arthur.Zaremba@duke-energy.com" <Arthur.Zaremba@duke-energy.com>

Tracking Status: None "Wasik, Christopher J" <Christopher.Wasik@duke-energy.com>

Tracking Status: None "Sigmon, Chet Austin" <Chet.Sigmon@duke-energy.com>

Tracking Status: None Post Office: MN2PR09MB3517.namprd09.prod.outlook.com Files Size Date & Time MESSAGE 3631 5/19/2020 12:41:28 PM Options Priority: Normal Return Notification: No Reply Requested: No Sensitivity: Normal Expiration Date: