ML21154A180
| 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.SummerNuclear Station QQ@njQQ Bradham BIvd& Hwy 215,Jenkinsville, SC 29065 L',7+
Mailing Address:
r y 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 REGARDINGRF-25 STEAMGENERATOR TUBEINSPECTION REPORT
References:
1 DESCLetter, "Special Report (SPR) 2020-002
- SteamGenerator Tube Inspection Report,"
datedOctober20, 2020 (ADAMSAccession No.
ML20296A692) 2.E-mail fromNRCSenior Project Manager,Vaughn Thomas, "Summer, Unit 1-Final RAIsfortheSGTubeInspection Report Review,"
datedMay11,2020 (ADAMS Accession No.ML21131A040)
InReference 1,DESCsubmitted a Technical Specification required report related tosteam generator inspections performed during theVirgil C.SummerUnit1 Twenty-Fifth Refueling Outage(RF-25).
InReference 2,theNRCStaff provided a request for additional information (RAI) regarding this report.
Theenclosure tothis letter provides theDESCresponses tothe RAl.
Ifyouhaveanyquestions orrequire additional information, please contact Mr.Michael Moore at (803) 345-4752.
Sincerely, GeorgeLippard Site VicePresident V.C.SummerNuclear Station Commitments contained inthis letter:
None
Enclosure:
Response
toNRCRequest forAdditional Information cc: G.J.Lindamood
- Santee Cooper L.Dudes
- NRCRegion II V.Thomas
- NRCProject Mgr.
NRCResident Inspector
Serial No.21-195 Docket No.:
50-395
Response
toRAlRegarding RF-25SGReport Enclosure
Response
toNRCRequest for Additional information Virgil C.SummerNuclear Station (VCSNS)
Unit1 Dominion Energy SouthCarolina, Inc.(DESC)
Serial No.21-195 Docket No.:
50-395 Enclosure
- RAlResponse:
Page1of3 DESC
RESPONSE
TONRCREQUEST FORADDITIONAL INFORMATION REGARDING VCSNSUNIT1RF-25STEAMGENERATOR TUBEINSPECTION REPORT 1.Please discuss ifthere wasanydegradation noted during theprimary side visual inspections ofthechannelheadbowlcladding andinternal
- surfaces, performed oneach SG.
2.With respect tothe secondary side inspections,please clarify thescope(i.e.,
whether theywereinallthree SGs)andresults ofthesecondary side inspections performed.
3.TheDecember 14,2020, response totheNRC'srequest foradditional information onthefall 2018SGtube inspection report (ADAMS Accession No.
stated that heavy deposit formations andtubedenting were identified during thevisual inspectionof the top(9th) tubesupport plate (TSP) ineachSG.Itisstated inthespring 2020 SG tube inspection report that Deposit Minimization Treatment (DMT) cleaning wasperformed during RFO 25.Please provide additional detail regardingthe extent ofthedeposit formations andprovide anyadditional
- insights, including theextent ofdenting, youmayhavewith regards tothedenting that could be related totheheavy deposit formation.
4.Section 6.0,"Tubes Plugged during theInspection Outage,"
ofthespring2020 SGtubeinspection report states that atotal of4tubes wereplugged; 2tubes werepreventively plugged inSGA duetoTSPwearindications (neither exceeded the40percent plugging criterion) and2tubes(1inSGA and 1in SGB)wereplugged duetopossible loose parts (PLPs).
Please clarify whether thePLPswerenewly identified during RFO25andhowmanytotal PLPs there wereinthetwotubes.
M Asnoted intheRF-25Condition Monitoring andFinal Operational Assessment, inresponse toNSAL12-1, Revision 1,thevisual inspection oftheSteam Generator (SG) channel headbowlincluded inspections oftheentire channel headinternal surfaces.
Specifically, theentire tubesheet,
- cladding, divider
- plate, andassociated welds/components.
Thisvisual inspection confirmed that the channel headbowlineachSGwasinsatisfactory condition andidentified no signs ofdegradation,
- rust, deformation, orabnormal conditions.
Serial No.21-195 Docket No.:
50-395 Enclosure
- RAIResponse:
Page2of3 M
As noted inSpecialReport 2020-02
- SteamGenerator TubeInspection
- Report, secondary sideinspections(SSl) wereperformed during RF-25forthetopofthe tubesheet (TTS), flow distribution baffle (FDB),
andtop(9th) tubesupport plate (TSP) inall three SGs.Inspection results fromtheRF-25Condition Monitoring andFinal Operational Assessment arediscussed below.
TopoftheTubesheet (TTS)/FlowDistribution Baffle (FDB)
TheDeposit Minimization Treatment (DMT) process results inremoval oftube deposition.
Therefore, post-DMT lancing wasperformed first ontopoftheFDB followed bylancing onthe TTS.
Priortotheremoval ofthelancing equipment at eachlocation, quick look visual inspections wereperformed ontheFDBandTTS toassess thethoroughnessof the lancing process.
After removal ofthelancing equipment, post-lance SSIwereperformed.
TheFDBpost-lance inspections included innerbundle passes approximately every 20columns (H/L andC/L).
TheTTS post-lance inspections included the no-tube
- lane, annulus
- regions, andinnerbundle passes. Foreign object search andretrieval (FOSAR) inspections atthe FDB and TTSwerealsoperformed as needed.
Other thanforeign objects that wereidentified butdid notcausetubewear,no abnormal conditions wereidentified during theTTSinspections.
Allforeign object-related findings resulted ineither removal offoreign material orplugging of tubes forpossible loose parts(PLP) located onthe1st TSP that couldnotbe visually inspected.
Top(9th)
TubeSupport Plate(TSP)
Visual inspections ofthetopTSP(9th TSP) along thenotube laneregion were performed ineachSG.Theinspections focused ongeneral conditionof the TSP looking forgeneral condition ofsludge/fouling oftheno-tube
- lane, TSP ligaments, andlowrowU-bends.
Theinspection alsolooked forwebbing or bridging between thetubes/broaches, tube-to-tube bridging andblocked/partially blocked flow/broached holes.
inner bundle passes(H/L andC/L) atright angles tothe9thsupport notubelanewasalsoperformed totheextent possible.
The results oftheseinspections identified noconditions adverse toquality.
M TheV.C.SummerSteamGenerator Secondary SideManagement Evaluation (Framatome Maestro Evaluation),
dated11/13/2019 (prior tocleaning),
describes that
- small, discrete deposit accumulation begins atthe3rdTSPandbecome moreextensive ateachhigher support level.
"Moreextensive" inthis context meansincreased eddycurrent amplitudes aswell asagreater number of affected broaches.
Thedeposition predominantly affects thehotleg;
- however, at higher elevations thecoldlegs becomemoreinvolved.
The9thTSPisthemost
Serial No.21-195 Docket No.:
50-395 Enclosure
- RAIResponse:
Page3of3 impacted support inall three SGs,atwhichasubstantial portion ofthehotleg broaches havelarge amplitude deposit indications, andmorethanhalf ofthecold leg broaches havedetectible deposit indications.
TheSGAdeposition atall support levels isverysimilar inmagnitude anddistribution tothat ofSGB.SGC hasexperienced moreadvanced accumulation thanSGAandSGBatall levels.
InSGC,the hot leg broaches inboth TSP8andTSP9arebroadly affected by large amplitude deposit indications.
During RF-24(Fall2018),
eightnewly formed dents wereidentified atupper TSP intersections inthe hot legs ofSGBandSGC(one inSGBat8thTSP,seven in SGCat9thTSP).
During RF-25, sixnewdents wereidentified inthehotlegof SGC(one at8thTSPandfive at9thTSP)Thedents wereconfirmed asnewly formed byverifying that nodent signals werepresent intheprevious eddy current inspection data.
Nowear has beenidentifiedatanyofthedentlocations.
TheMaestro Report concluded
- that, although nowearhasbeenidentified atthe
- tubes, themostprobable causeofthe new dentsiselevated crossflow resulting fromflow restriction inthehotleg, primarily atthetoptwoTSPs.Thistube denting first identified inRF-24wasa driving factor forchemical cleaning performed inRF-25(Spring 2020) that resulted inremoval of4,048lbsofsludge through acombination oftheDMTprocess and subsequent sludge lancing.
M FromtheRF-25Condition Monitoring andFinal Operational Assessment, there weretwo(2) tubes plugged duetoPLPs.Bothofthese tubes had newPLP single indications whoselocations werenotaccessible bySSl/FOSAR.
These indications wereatlocations onthe01HTSPthat donothave inspection ports.