ML22140A336
| ML22140A336 | |
| Person / Time | |
|---|---|
| Issue date: | 03/08/2022 |
| From: | Christopher Hunter NRC/RES/DRA |
| To: | Office of Nuclear Reactor Regulation |
| References | |
| Download: ML22140A336 (14) | |
Text
WeatherRelatedLossofOffsite PowerTrendsandRiskInsights ChrisHunter OfficeofNuclearRegulatoryResearch DivisionofRiskAnalysis PerformanceandReliabilityBranch
Overview Evaluationsofrecenteventscausedbysevereweatherconditionshave providedimportantriskinsights.
Severeweathereventsaremostlikelytoleadtolossesofoffsitepower (LOOPs).
AreviewofcurrentLOOPdataandtrendscanbeusedtoevaluatewhethermoreextreme weathereventsaffectnuclearpowerplants.
KeyQuestions ArethefrequencyanddurationofweatherrelatedLOOPschanging?
WhatdotheresultsandinsightsfromrecentweatherrelatedLOOPstellus?
LOOPDataandTrends
LOOPFrequencies TheoverallfrequencyofallLOOPsisdecreasingoverthepast 15years(2006-2020).
ThereisnostatisticallysignificanttrendforweatherrelatedLOOPs duringthepastdecade(2011-2020).
WeatherRelatedLOOPs(2006-2020)
EventDate Plant Cause PowerOps/
Shutdown Duration (hours) 8/10/2020 DuaneArnold Hurricane PowerOps 25.3 8/3/2020 Brunswick1 Hurricane PowerOps 14.0 3/13/2018 Pilgrim SnowandWind Shutdown 12.0 10/8/2016 ShearonHarris Hurricane Shutdown 7.4 1/27/2015 Pilgrim SnowandWind PowerOps 0.03 2/8/2013 Pilgrim SnowandWind PowerOps 21.0 10/29/2012 OysterCreek HighWinds Shutdown 14.4 4/27/2011 BrownsFerry1 Tornado PowerOps 0.03 4/27/2011 BrownsFerry2 Tornado PowerOps 0.03 4/27/2011 BrownsFerry3 Tornado PowerOps 0.03 4/16/2011 Surry1 Tornado PowerOps 5.1 4/16/2011 Surry2 Tornado PowerOps 5.1 8/19/2009 WolfCreek Lightning PowerOps 2.2 2/24/2007 DuaneArnold Ice Shutdown 17.5
LOOPDuration ThedurationofallLOOPsshowedanincreasingtrendduringthe 1997-2020period.
Thereisnostatisticallysignificanttrendforthedurationof weatherrelatedLOOPsduringthissameperiod.
DurationsbyLOOPType Parameter Plant Switchyard Grid Weather LOOPeventcount 16 32 17 19 Mu(µ)
0.70 0.44 0.35 1.37 Standarderrorofµ 0.53 0.29 0.33 0.51 Sigma()
2.13 1.66 1.36 2.24 Standarderrorof 0.38 0.21 0.23 0.36 Fittedmedian,hour 2.00 1.56 1.41 3.94 Fittedmean,hour 19.17 6.21 3.55 48.23 Fitted95th percentile,hour 66.10 24.03 13.19 156.51 Errorfactor 32.97 15.42 9.33 39.70
RecentEvents
BrunswickLOOPduringHurricaneIsaias StormgenerateddebrisresultedinaLOOPtoUnit1inAugust2020.
TheLOOPlastedapproximately14hours.
Themeanconditionalcoredamageprobability(CCDP)was2x105.
LOOPtransientscenariosdominatedrisk;stationblackout(SBO)riskwasminimal.
DuaneArnoldLOOPduringDerecho Severewinds(100-130milesperhour)duringaderechoresultedina LOOPinAugust2020.
Thestormcausedseveredamagetononsafetyrelatedcoolingtowersandminordamageto afewbuildings.
Thehighwindsalsoresultedinincreaseddebrisloadingtotheessentialservicewater systemandresultedinacloggedstrainer.
TheLOOPlastedapproximately25hours.
ThemeanCCDPwas8x104.
SBOscenarioswerethedominantriskcontributors.
WaterfordLOOPduringHurricaneIda Thehighwinds,heavyrain,andlocalizedfloodingresultedindamageto bothsourcesofoffsitepower.
Thesupplementaldieselgeneratorexperiencedafailedbatterydueto rapiddischargeaftertheLOOPoccurred.
TheLOOPlastedapproximately53hours.
ThepreliminaryanalysisindicatesameanCCDPfrommid1x104 tolow 1x103.
SBOscenarioswerethedominantriskcontributors.
GeneralRiskInsights SBOriskisdominantfortwoemergencydieselgenerator(EDG)plants forlongdurationLOOPs.
MultiunitsiteswithsharedEDGstypicallyhavemuchlowerrisk.
HavinganEDGnotincludedinthesamecommoncausecomponentgroupastheother safetyrelatedEDGscanbeasignificantbenefit.
Modelingofcommoncausefailuresacrosstheunitsintroducessignificantuncertainties becausethedatadonotsupportthismodeling.
LOOPdurationhassignificantimpactonplantsthathavedominantSBOrisk.
FLEXcreditcanhavesignificantimpactontheresults.