ML21180A405

(Vcsns), Unit 1 - Supplement to Request for Additional Information Regarding RF-25 Stem Generator Tube Inspection Report

ML21180A405
Person / Time
Site:	Summer
Issue date:	06/29/2021
From:	Lippard G Dominion Energy South Carolina
To:	Document Control Desk, Office of Nuclear Reactor Regulation
References
.21-234
Download: ML21180A405 (4)

Text

V.C.

Bradham SummerNuclear Blvd Station

& Hwy 215,Jenk.insville, SC 29065 QQ@Q jQQ M@

Mailing Address:

P.O. Box 88,Jenkinsville, SC 29065 DominionEnergy.com June29,2021 Document Control Desk Serial No.21-234 U.S. Nuclear Regulatory Commission VCSLIC/BAB/Rev O Washington, DC20555 Docket No.50-395 License No.NPF-12 V

SUPPLEMENT TONRCREQUEST FOR ADDITIONAL INFORMATION REGARDING RF-25 STEAMGENERATOR TUBEINSPECTION REPORT

References:

1 DESCLetter, "Special Report (SPR) 2020-002Steam Generator TubeInspection Report," dated October 20,2020 (ADAMS Accession No.ML20296A692) 2.E-mail from NRCSenior Project Manager, Vaughn Thomas, "Summer, Unit 1-Final RAls for theSGTubeInspection Report Review," dated May11,2020 (ADAMS Accession No.ML21131A040)

3. DESCLetter, "Response toNRCRequest for Additional Information Regarding RF-25 Steam Generator TubeInspection Report," dated June3,2021(ADAMS Accession No.ML21154A180)

InReference 1,DESCsubmitted a Technical Specification required report related to steam generator inspections performed during theVirgil C.SummerUnit1 Twenty-Fifth Refueling Outage (RF-25). InReference 2,theNRC Staff provided a request for additional information (RAI) regarding this report. In Reference 3, DESC submitted a response totheRAI. OnJune 2 2, 2021, a clarification telephone call washeld between VCSNSandtheNRC regarding these submittals. Thisisa voluntary submittal to provide a summary ofthephone call.Theenclosure tothis letterprovides a summary of thatcall.

Serial No.21-234 No.50-395 Docket Supplement toRAIRegarding SGReport RF-25 Page2of2 Ifyouhave any questions orrequire additional information,please Mr.Michael contact Moore at(803) 345-4752.

Sincerely,

, 157 For Geore Lippard c

Site Vice President V.C.Summer Nuclear Station Commitments contained inthis None letter:

Enclosure:

Supplement toNRCRequest for Additional Information cc:G.J.Lindamood -

SanteeCooper L Dudes NRCRegion II V.Thomas NRCProject-Mgr.

NRCResident Inspector

Serial No.21-234 Docket 50-395 No.:

Supplement toRAlRegarding RF-25SGReport Enclosure Supplement toNRCRequest forAdditional Information Virgil C.SummerNuclear (VCSNS)

Station Unit 1

Dominion Energy Carolina, South (DESC)

Inc.

Serial No.21-234 Docket No.: 50-395 Enclosure -Supplement toRAIRegarding RF-25 SGReport: Page1of1 DESC SUPPLEMENT TONRCREQUEST FORADDITIONAL INFORMATION REGARDING VCSNSUNIT1 RF-25 STEAMGENERATOR TUBEINSPECTION REPORT C.Summer Nuclear Station(VCSNS)

Virgil andtheNuclear Regulatory Commission (NRC) held a clarification call on June 22, 2021 to discussthe VCSNS RAI Response regardingtheSpring2020 Steam Generator(SG) TubeInspection Report. During the VCSNSprovided call, information regarding the cause oftube denting, theprevious and deposit current quantity, and evaluation methods regarding tubefatigue atthetop supportplate.

VCSNSidentified that the most probable causeofthe newdents waselevated crossflowresulting from flow restriction inthehot leg,primarily atthe toptwoTube Support Plates (TSP). The flow restriction was caused by deposit accumulation inthe TSPflow broaches. This newdenting identified inRF-24 (Fall2018) wasoneofthe primaryreasons for emergent chemical cleaning inRF-25(Spring 2020). Prior tothe RF-25 chemical cleaning, the VCSNSSecondary Side DepositManagement Strategy (Maestro Evaluation), provided anoptimistic deposit inventory of2,228 lbs, best estimatedeposit inventory of4,722 lbs, anda pessimistic deposit inventory of7,217 lbs.

These numbers werebased oneddy current deposit mapping andcorrosion product transportestimates. During RF-25, 4,048 Ibs ofsludge was removed from theSGsvia chemical cleaning andsludge lancing Post chemical cleaning eddy currentdeposit mapping identified 3,592 lbsofdeposit inventory remaining.

VCSNS also identified that a specific evaluation for tube fatigue at the topsupport plate wasnot performed. Thenewdents identified inRF-24 andRF-25 were small and rangedfrom 2.04 volts to3.98 volts insize with nowearatthese locations. The RF-25 Condition Monitoring Operational Assessment provided discussion that cross flow will effects lessen asa result ofchemical cleaning andthat weargrowth rates and distributionsofwearscars will also lessen going forward.