ML18012A724
| ML18012A724 | |
| Person / Time | |
|---|---|
| Issue date: | 01/12/2018 |
| From: | Jay Collins, Stephen Cumblidge, Ali Rezai NRC/NRR/DMLR/MPHB |
| To: | |
| Rezai A, NRR-DMLR 415-1328 | |
| Shared Package | |
| ML18002A510 | List: |
| References | |
| Download: ML18012A724 (9) | |
Text
UpperHeadInspections StephenCumblidgeandJayCollins NRC/IndustryNDETechnical InformationExchangeMeeting January1618,2018
Motivation Inalicensee,whichhadreplacedtheirheadwitharesistanthead,claimedthat significantboricaciddepositswereallleakagefromabove,powerwashedthe headwithoutperforminganysupplementalexaminations.Otherdiscussions withotherlicenseeshavesincefollowed.
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NRCGoals Maintainrigoronupperheadinspections PreventsituationwheretheNRCstaffanda licenseehavealengthydebatetherequirements forupperheadinspectionsduringanoutage 3
LeaksHappen Boricacidontheupperhead cancomefromtwomain sources
- Leakagefromsealsorweld leaksintheCRDMhousings
- Leakagethroughtheannulus formPWSCCofthenozzle
- Both Determiningthesource oftheboricacidcanbe challenging 4
PhotographsfromEPRIReport1007842
DeterminingtheSourceofBoricAcid Chemicalorisotopicanalysismybe used,dependingonthesourceofhe leak EPRIprovidesguidelinesinthe publicallyavailableVisualExamination forLeakageofPWRReactorHead PenetrationsRevision2EPRIReport 1007842 Compressedair,intherangeof40-60 psi(276-414kPa),oravacuumdirected atdepositshasbeenusedtodistinguish whetheradepositisloosebuildupof materialsimplyrestingagainsta penetrationthatiseasilyremovedoris atightlyadheringdeposit,originating fromtheannulusofaleaking penetration.
Ifonewashestherelevant conditionsawaywithoutany analysis,itisessentially impossibletoruleoutthe possibilitythatsomeofthe leakagemayhavecomefroma leak 5
VERelevantConditions Currentrulesrequire thatareaswithboric acidorsignsof corrosionbeevaluated todeterminethe sourceofleakage Ifleakagecannotbe ruledout,volumetric inspectionsofthe nozzleorrepairare required FromN7294 6
RecentOE PaloVerdeRelief PaloVerdeUnit1leakedreactorcoolantfrom aventvalve 14nozzleshadboricacidindicationsatthe nozzleannuli Additionally,fibrousinsulationparticleswere blownaroundbyventilation PaloVerdeinitiallylefttheareaswith suspectedfibrousinsulationoutoftherelief anddidnotinitiallyperformanyadditional evaluations 7
PaloVerdeReliefcont.
AfterdiscussionswiththeNRCstaff,thelicensee performedsufficientevaluations(airblastingand additionalphotographs)oftheadditionalnozzles tosatisfytheheadquartersandregionalstaff ReliefwasgrantedtoperformaVEexaminationon the14originalnozzlesduringthenextrefueling outage 8
Future TohelpgettheNRCstaffandlicenseesin agreementandunderstandwhatisexpected,a draftRISClarificationoftheRequirementsfor ReactorPressureVesselUpperHeadBareMetal VisualExaminationsiscurrentlygoingthrough concurrence TheRISwillbeoutforpubliccommentsinearly 2018andisprojectedtobeineffectbytheFall of2018 9