ML21154A180

Response to NRC Request for Additional Information Regarding RGF-25 Steam Generator Tube Inspection Report

ML21154A180
Person / Time
Site:	Summer
Issue date:	06/03/2021
From:	Lippard G Dominion Energy South Carolina
To:	Document Control Desk, Office of Nuclear Reactor Regulation
References
21-195
Download: ML21154A180 (5)

Text

V.C.

Bradham SummerNuclear BIvd Station

& Hwy 215,Jenkinsville, SC 29065 L',7+ QQ@n jQQ Mailing Address: ry neT P.O. Box 88,Jenkinsville, SC 29065 f DominionEnergy.com June3,2021 Document Control Desk Serial No.21-195 U.S. Nuclear Regulatory Commission VCSLIC/BAB/Rev 0 Washington, DC20555 Docket No.50-395 License No.NPF-12 V

RESPONSE TONRCREQUEST FORADDITIONAL INFORMATION REGARDING RF-25 STEAMGENERATOR TUBEINSPECTION REPORT

References:

1 DESCLetter, "Special Report (SPR) 2020-002 -

Steam Generator Tube Inspection Report,"dated October20, 2020 (ADAMS Accession No.

ML20296A692)

2. E-mail fromNRCSenior Manager,Vaughn Thomas, "Summer, Project Unit 1-Final RAIsfor theSGTubeInspection Report Review," dated May11,2020 (ADAMS Accession No.ML21131A040)

InReference 1,DESCsubmitted a TechnicalSpecification required report related tosteam generator inspections performed during C.SummerUnit theVirgil 1 Twenty-Fifth Refueling Outage (RF-25). In Reference 2, the NRC Staffprovided a request for a dditional information (RAI) regarding this report. Theenclosure tothisletterprovides theDESCresponses tothe RAl.

Ifyouhaveanyquestions orrequireadditional information,please contact Mr.Michael Moore at (803) 345-4752.

Sincerely, GeorgeLippard SiteVice President V.C. Summer Nuclear Station Commitments contained inthisletter:

None

Enclosure:

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

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

NRCResident Inspector

Serial No.21-195 Docket No.:50-395 Response toRAlRegarding SGReport RF-25 Enclosure toNRCRequest Response for Additional information C.SummerNuclear Virgil Station (VCSNS) Unit 1 Energy Dominion South C arolina, (DESC)

Inc.

SerialNo.21-195 Docket No.:50-395 Enclosure -

RAlResponse: Page1of3 DESC RESPONSE TONRCREQUEST FORADDITIONAL INFORMATION REGARDING VCSNSUNIT1RF-25 STEAMGENERATOR TUBEINSPECTION REPORT 1.Please discuss ifthere wasany degradation noted during the primary side visualinspections of the channelhead bowl cladding andinternal surfaces, performed oneach SG.

2.With respect tothesecondary side inspections,please clarifythe scope (i.e.,

whether they were inallthree SGs) andresults ofthe secondary side inspections performed.

3.TheDecember 14,2020, response tothe NRC's request for additional information onthe 2018SGtube inspection report fall (ADAMS Accession No.

ML20349A326), statedthat heavy deposit formations andtube denting were identified during thevisual inspectionof the top (9th) tube support plate (TSP) ineach SG.It isstatedinthespring 2020 SG tube inspection report that Deposit Minimization Treatment (DMT) cleaning was performed during RFO

25. Please provideadditional detailregardingthe extent ofthe deposit formations andprovide anyadditional insights, including the extentofdenting, youmayhave withregards tothedenting that could be related to the heavy deposit formation.

4.Section 6.0, "Tubes Plugged during the Inspection Outage," of the spring 2020 SGtube inspection report states thata total of4 tubes wereplugged; 2 tubes were preventively plugged inSGA duetoTSPwear indications (neither exceeded the 40percent plugging criterion) and2 tubes (1 inSGA and 1in SGB)were plugged duetopossible loose parts Please (PLPs). clarify whether the PLPswere newly identified during RFO25andhowmanytotal PLPs there were inthetwotubes.

M Asnoted intheRF-25 Condition Monitoring andFinal Operational Assessment, inresponse toNSAL12-1, Revision 1,thevisual inspection oftheSteam Generator (SG) channel headbowl included inspections oftheentire channel headinternal surfaces.Specifically, theentire tubesheet, cladding, divider plate, andassociated welds/components. This visual inspection confirmed that the channel headbowl ineachSGwasinsatisfactory condition andidentified no signs ofdegradation, rust,deformation, orabnormal conditions.

SerialNo.21-195 Docket No.:50-395 Enclosure -

RAIResponse: Page2of3 M

As noted inSpecial Report 2020-02 -

Steam Generator TubeInspection Report, secondary side inspections (SSl) wereperformed during RF-25 forthetopofthe tubesheet (TTS), flow distribution baffle (FDB), andtop(9th) tube support plate (TSP) in all three SGs. Inspection results from t heR F-25 C onditionMonitoring andFinal Operational Assessment arediscussed below.

TopoftheTubesheet (TTS)/FlowDistribution Baffle (FDB)

TheDeposit Minimization Treatment (DMT) process results inremoval oftube deposition. Therefore, post-DMT lancing wasperformed ontopoftheFDB first followed bylancing onthe TTS. Prior totheremoval ofthelancing equipment at each location, quick look visual inspections were performed ontheFDBandTTS toassess the thoroughness of the lancing process. After removal ofthelancing equipment, post-lance SSIwereperformed.

TheFDBpost-lance inspections included innerbundle passes approximately every 20columns (H/L C/L).

and The TTS post-lance inspections included the no-tube lane, annulus regions, andinnerbundle passes. Foreign object search andretrieval (FOSAR) inspections at the FDB and TTS were also performed as needed.

Other than foreign objects that wereidentified butdid not causetube wear, no abnormal conditions wereidentified during the TTSinspections. All foreign object-related findings resulted ineither removal offoreign material orplugging of tubes for possible loose parts (PLP) located onthe 1st TSP that couldnot be visually inspected.

Top(9th) TubeSupport Plate (TSP)

Visual inspections ofthe topTSP(9th TSP) along thenotube laneregion were performed ineachSG.Theinspections focused ongeneral conditionof the TSP looking for general condition ofsludge/fouling oftheno-tube lane, TSP ligaments, andlowrowU-bends. Theinspection also looked for webbing or bridging between thetubes/broaches, tube-to-tube bridging andblocked/partially blocked flow/broached holes. inner bundle passes (H/L andC/L) atright angles tothe 9th support notube lane wasalso performed totheextent possible.The results ofthese inspections identified noconditions quality.

adverse to M

TheV.C. SummerSteam Generator Secondary Side Management Evaluation (Framatome Maestro Evaluation), dated 11/13/2019 (priortocleaning), describes that small, discrete deposit accumulation begins atthe3rd TSPandbecome moreextensive ateachhigher support level. "More extensive" inthis context meansincreased eddy current amplitudes aswell asa greater number of affected broaches. Thedeposition predominantly affects thehotleg; however, at higher elevations thecold legs become moreinvolved. The9th TSPisthemost

Serial No.21-195 Docket No.:

50-395 Enclosure -

RAIResponse: Page3of3 impacted support inall three SGs,atwhich a substantial portion ofthehotleg broaches have large amplitude deposit indications, andmorethan half ofthecold leg broaches have detectibledeposit indications. TheSGA deposition atall support levels is very similarinmagnitude anddistribution tothat ofSGB.SGC hasexperienced moreadvanced accumulation than SGA andSGB atall levels.

InSGC,the hot leg broaches in both TSP8andTSP9 arebroadly affected by large amplitude deposit indications.

During RF-24 (Fall 2018), eight newly formed dents were identified atupper TSP intersections SGC at9th inthehot legs ofSGB andSGC During RF-25, six newdents (one inSGB at8th wereidentified TSP,seven inthehot leg in of TSP).

SGC formed (one at8th byverifying TSPand five at9th that TSP) T nodent signals werepresent hedents were confirmed intheprevious as eddy newly current inspection data. Nowear has beenidentified atanyofthedent locations.

TheMaestro Report concluded that, although nowear hasbeenidentified atthe tubes, themost probable cause ofthe new dentsiselevated crossflow resulting from flow restriction inthe hotleg, primarily atthe toptwoTSPs. This tube denting first identified inRF-24 wasa driving factor for chemical cleaning performed inRF-25 (Spring 2020) that resulted inremoval of 4,048 lbs ofsludge through a combination ofthe DMTprocess and subsequent sludge lancing.

M FromtheRF-25 Condition Monitoring andFinal Operational Assessment, there weretwo(2) tubes plugged duetoPLPs. o f Both these tubes had new PLP single indications whose locations werenot accessible bySSl/FOSAR. These indications wereatlocations onthe 01HTSPthat donothaveinspection ports.