ML20232C648
| ML20232C648 | |
| Person / Time | |
|---|---|
| Site: | Diablo Canyon  |
| Issue date: | 08/17/2020 |
| From: | Lochbaum D Public Commenter |
| To: | Blanch P Office of Nuclear Reactor Regulation |
| Lee S, 301-415-3158 | |
| References | |
| EPID L-2020-LLA-0176 | |
| Download: ML20232C648 (3) | |
Text
1 Burkhardt, Janet From:
David Lochbaum <davelochbaum@gmail.com>
Sent:
Monday, August 17, 2020 8:23 PM To:
Paul Cc:
Linda Seeley; Brian Haagensen; Skeen, David; Raspa, Rossana; Jarriel, Lisamarie; Spicher, Terri; Doane, Margaret
Subject:
[External_Sender] Re: DCL-20-066.pdf HelloPaul:
Thisrequestdoesnotappeartobetoounreasonable.
PipingdownstreamoftheLCVsbetweentheAFWpumpsandthesteamgeneratorsonUnit2wasdiscoveredtohave worntolessthantheallowablewallthickness,requiringitsreplacementlastmonth.PG&Eassumes,withreason,that thepipingonUnit1isinasimilarcondition.
Theycouldwaituntilthenextrefuelingoutagetoinspectthepipingandreplacesectionsthathavethinned.Withthis amendment,ifapproved,theycanlookatthepipingwhileUnit1continuestooperateandreplacethinnedsections.
Here'saschematicoftheAFWsystematDiabloCanyon:
TheredlinesshowthepipingdownstreamofLCVs107and111thatsupplyflowtoUnit1SteamGeneratorNo.2.
TheAFWsystemfeaturesthreepumps(oneturbinedrivenandtwomotordriven).Theturbinedrivenpumpprovides 200%oftheflowrequiredtoremovedecayheatpostshutdown.Eachmotordrivenpumpprovides100%ofthatflow.
So,onepumpandoneflowpathtoanyoneofthefoursteamgeneratorsisneededtofulfillthesafetyfunction.
TherequestedamendmentwillallowPG&Etoisolatedtheflowpathtoonesteamgeneratorforuptosevendays.
Worstcase,therewouldbetheneedtoindividuallyisolateandreplacepipingsectionsinallfourpathways(oneata time)foratotaloutagetimeofupto28days.
2
Wheneachindividualflowpathisisolated(i.e.,LCVs107and111closedorcomparablevalvesontheotherpaths),all threeAFWpumpsandthreeotherflowpathswouldremainavailable.
SupposeLCVs106and110areclosedtoreplacethepipingtosteamgenerator11.Ifthenormalfeedwatersystemis lost,theAFWsystemwillautostart.ThefullflowfromallthreeAFWpumpswouldberoutedtothreeratherthanfour steamgenerators.Giventhattherequestedamendmentispredicatedonexpectedpipinglessthantheallowablewall thickness,thegreaterthannormalflowsthroughthethreelinesathigherthannormalpressurecouldleadtothe commoncauseruptureofallthreeflowpathstothenonisolatedsteamgenerators.Thus,acompletelossofAFW concurrentwithlossofthenormalfeedwatersystem.
Theoperatorscouldremovedecayheatusingfeedandbleedmodeuntilthenormalfeedwatersystem,orportions thereof,wasrestored.
The"safetyanalysis"byPG&Einsupportoftheiramendmentrequestdancesaroundtherealityofthesituation.They seekthischangebecausetheystronglysuspectthatthepipingisthinnedtolessthanallowablelevels.Buttheiralleged safetyanalysiscuriouslyandconvenientlyassumesthatthepipingisinpristinecondition.That'sabsurd.I'dnothave signedmynametosuchabogusandincompleteanalysis(andIwouldn'tevenhavesignedyournametoit).
Frompage2oftheattachmenttoPG&E'samendmentrequest:
PG&E,inwriting,concedesthatsafetyrelatedpipinginmorethanoneAFWflowpath"maynotmeetminimumcode thicknessrequirements."Yet,theirsafetyevaluationsupportingtheamendmentimplicitlyassumesthatallpipingmeets orexceedstheminimumcodethicknessrequirements.Nopunintended,butPG&E'ssafetyanalysisisthinnerthanthe suspectedpipewallthickness.
But,itseemslessriskytoallowPG&Etoseeifthesuspectedpipeshavethinnedtoomuchandreplacethemratherthan allowUnit1tooperateblissfullyunawareofthisdegradationuntilitsnextrefuelingoutage,oruntilitsnextaccident, whichevercomesfirst.
IfIwasanNRCreviewer,I'dfeelmorecomfortableapprovingthisamendmentrequesthadPG&Eincludedinitssafety analysisanevaluationoftheasfoundpipingconditiononUnit2hadtheAFWsystemautostartedfollowingashutdown fromfullpowerwithoneofthethreeflowpathsisolated.Ifthehigherthannormalpressureinthethreeunisolated lineswouldlikelynothavefailedtheasfoundthinnedpiping,there'ssomereasontobelievethatUnit1wouldsurvive suchaneventasitreplacesthinnedpipes.
- Thanks, Dave
3
OnMon,Aug17,2020at4:53PMPaul<pmblanch@comcast.net>wrote:
Linda IcheckedwithmyNRCsafetypersonandthisisanoperationthatisahighrisk.AFWistheonlymeanstocoolthe reactorthereactor,shouldittrip.Onedoesntevenneedanaccidenttodamagethereactorcore.
Idontcarehowmanysteamgeneratorstheyhave,withouttheAFWsystem,theyareunabletopreventcoredamage assumingthisisanormalWestinghousereactor.
IamcopyingBrianHolianandothersoftheNRCandpossiblygetthisimmediateconcerntosomeoneattheNRCwho cares,butIdoubtit!
Luckmaybethefinalbarrierleft,butIdontknowallthedetails.
SentfrommyiPad