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{{#Wiki_filter:~~ | {{#Wiki_filter:~~BACKGROUND INFORMATION FORREACTORVESSELHEADVENTOPERATION REVISION0FEBRUARY19818i072i0423 8i07i5PDRADOCK05000315PPDR REACTORVESSELHEADVENTOPERATION I.GENERALDISCUSSION A.~PuroseTheoperatoractionsandprecautions specified inthisguideline arethoseinstructions necessary fortheremovalof'gasesfromthereactorvesselheadbyoperation ofthereactorvesselheadventsystem.8;Guideline Assumptions Thespecificdesignofthereac.orvsse'.',-ead ventsys-;eausedinthisguideline includesasirg!ecornec.'.ion to~i:avesselheadwithredundant flowpathsandisolation valves.extending fromacommonline.Thecommonlineincludesa3/8".orifice whichlimitstheflowratetowithinthemakeupcapability ofthechemicalandvolumecontrolsystem..Theredundant flowpathsdischarge tothereacto~containment building. | ||
Notethatthoseplants,whichhaveventsystemsinstalled whichventtothepressure~ | |||
erorth"r=ssur-.=er relieftankmaydesirotomodifyormake'd"i:icos | |||
-o:heexistingguideline inordertoincorporate theplantspecificdesign.2.Althoughtheguideline doesnotrequireareactorvessellevelsystemitisrecomnended thatanyventingoperation beperformed incon5unction withanaccuratevessellevelindication forbothwithandwithoutreactorcoolantpumpoperation. | |||
Forplantswithoutalevelsystem,theperformance ofAppendixA,"RCSGaseousVoidDetection andSizing"mayprovideanestimateofthetotalvolumeofgaseousvoidsintheRCS(otherthanthepressurizer). | |||
: February, 1981Revision0'Page1 b3.Thereactorcoolantsystemcanbestabilized withaconstantpressurizer levelandadequatereactorcoolantsub-cooling established. | |||
Theseconditions arerequiredtoensureadequatecore-cooling ismaintained duringtheventingperiod.4.Thepressurizer levelandpressurerequirements throughout theguideline donotincludeerrorallocations duetoanadversecontaihment environment. | |||
Therefore, itisassumed.-that containment temperature isnearnormaloperating conditions. | |||
5.Anyventingoperation mustbep'rformed priortotheinitiation- | |||
'ofsafetyinjection flowthrottl'ing duringaPOST-LOCA-cooldownanddepressurizaticn "peraton.Sever.lg"Ide;incactionsrequiresheinitiation osafe-:.y~n'ect".:-n | |||
':-ressurizer levelcannotberestore.TheO'.ST-LOCA co.lccwn"nddoresuri-zationoperation beginstothrottlesafe-.yinjecti"n.lowand-therefore fullSIflowcouldnotbedelivered totheRCSwhenrequired. | |||
6.Theheadventsystemisnotdesi'gned forandshouldnot.beusedastheprimarymeans.o<<mitigate aninadequate tcorecoolingevent.Theventflcwpa.h'.snotsi:edtoproviCe"'his capability andshouldonlybeusedincon'unction witntheInadequate CoreCoolingGuidelines. | |||
C.~S~ot~ms0Thefollowing aresymptomsthatmayindicatethepresenceofagaseousvoidinthereactorcoolantsystem.Notethatanyoneorcombination ofsymptomsmayindicatethatavoidexists.February, 1981Revision0Page2 | |||
ForPlantswithaRVlevelindication:1. | ForPlantswithaRVlevelindication: | ||
1.Reactorvessellevelindication lessthan(plantspecific) percentofspan.Theplantspecificvalueshoul'dincludeanallowance fornormalchannelaccuracy. | |||
Ifthelevelsystemdoesnotincludeareference | |||
'1egtemperature compensator | |||
'hananadditional allowance should.beincludedforconditions wheretheRCStemperature isnotequaltothechannelcalibration | |||
~'Vtemperature. | |||
ForPlants~ith/without aRYlevelindication: | |||
2.Variations fromthenorm-1pressur.,zer pressureandlevelrosponseCueto::omanchar"ingand.s".ray',ng over=.".".",.s maynotbeobserveairagaseousvoide"istsn"he.-":CS.Thepressurizer levelmaydecreasedur',ngaRCSpressurization fromchargingduetogaseousvoid.contraction andlevelmayriserapidlyduringasprayingoperation duetoagaseousvoidexpansion. | |||
3.Anindication ofreactorvesselheadtempera'tures equaltoorgreaterthansaturation temperature warrantsthepresenceofasteambubblebeinggenerated int.",eRCS.'4.Gasesinthereactorcoolantsystemmayresultfromseveraltypesofplantevents.Anaccumulator tank"discharge oracoreuncoverymayresultinnon-condensible gases(e.g.nitrogenandhydrogen) beingtrappedintheRCS.ArapidRCScooldownmayresultinthevesselheadtemperature beinggreaterthantheprimarysaturation temperature andresultinasteambubblebeingdeveloped. | |||
TheoperatorshouldsuspectthepresenceofgasesintheRCSifany.oftheaboveeventsoccur.February, 1981Revision0Page3 II.BASISFORSUBSEQUENT ACTIONSTheCAUTIONprecedtng Step'Iearnstheoperatortomatntatntheextsttngmodeofcorecoo11ngdurIngtheperformance ofthesubsequent actions.Trippinganoperating reacto~coolantpumpcouldresultingasesinthereactorcoolantloopscollecting inthesteamgenerator U-tubesandmaydisturbnaturalcirculation andprimarytosecondary heattransfer.'Starting reactorcoolantpumpswoulddisperseanygasesalreadycollected inthevesselheadandmaketheirremovalmorediffscult. | |||
Therefore, theexistingstatusofthereactorcoolantpumpsshouldbemaintained duringtheventfngoperation. | |||
Ifpossibleandifconditions requireso,thenareactorcoolantpumpshouldbestartedfo]lowing thecompl.so>>ofheventingoperation. | |||
TheNOTEpreceding Stepidenti.'es cer"''nsteps-(markeabyanasterisk,'hich arenotapplicable ifsafetyin~mection hasbeeninitiated andthesestepsshouldbeskippedduringtheventingoperatione l.Onceagaseousvoidisdetectedorsuspected intheRCS,thenanychangesbeingmadetotheprfnarysystemshouldbetermfnated andasteady-state condition shouldbeestablished. | |||
ThisstepreferstoeventslikeaFCST-LOCA | |||
: cooldown, anormalplantcooldown, oraplantrecoveryfromz.'esignbasisevent.TheintentistoaIIowtheRCStostabHfzesothatthesizeandpositionofthevoidcanbedetermined. | |||
NotethatanormaI-pressurizer pressurecontrolcondition'may notbeattainable duetothereasonsstatedinsymptom2.2.ThefirstactiontakentoremoveanygasesfromtheRCSfstoattempttorecombine anycondensfble gasesbyincreasing RCSpressure. | |||
Thisstepmaybeslowactingandifaupwardtrendfswitnessed onthevessellevelindicator thenmafntafnthismodeuntiltheheadisrefilledortheupwardtrendstops-thisstepissuccessful infillingthehead,thenreturntotheappropriate operating instruction. | |||
Ifthisstepisnotsuccessful, thenproceedtoStep4.February, 1981Revision0Page4 TheCAUTIONa'lertstheoperatorthatchargingfioumayresultinasuddencol'lapse ofsteambubblesintheRCSandcausearapiddecreaseinpressurizer level.Thelevelshouldberestoredbyincreasing theRCSmakeupflowrate. | |||
Iftheincreased makeupflowfailstorestorelevelthensafetyinjection shouldbeinitiated andtheoperatoristoproceedtoEOI-O,Immediate ActionsandDiagnostics. | |||
3.Theventingoperation willresultinRCSgasesbeingventedtothecontainment. | |||
Therefore thec'ontainment purgeandexhaustsystemshouldbeisolatedtopreventthereleaseofanyradioactive gasestotheenvironment. | |||
Allavailable containment aircircula-.icn ecuipment si.oui"".es;ar".adoprevens-.anyhydirognfromfor-irgagasoockezandtoersureare"rsanttivehydro".Ten concentrat';n isobtainedinS:p5.4.Increasing thereactorcoolantsub-cooling 50'Fabovetheminimum~plantspecificvalueensuresthatreactorcoolantsub-cooling willbemaintained overtheentirerangeofRCSoperating conditions iftheventingoperation isterminated following a200psidecreaseinRCSpressure. | |||
Thepreferred method-ofobtaining theadditional sub-cooling isincreasing RCSpressurtsincethis~illaidincondensing anysteambubblespresen".. | |||
Iftheadditioral 5C'Fsub-cooling isalreadyestablished thenproceedtoStep5.5.TheactionsofAppendixS"VentingTimePeriod"determine themaximumallcwable timeperiodforventingwhichwilllimitthecontainment hydrogenconcentration tolessthan3volumepercent.Thislimitisrequiredtopreventapotentially explosive hydrogenconcentration frombeingdeveloped insidethecontainment. | |||
(Thisstepmaynotbeapplicable forplantswhichventtothepressurizer orpressurizer relieftank.)February, 1981Revision0Page5 | |||
*6. | *6.Pressurizer levelisincreased togreaterthan50"forthepurposeofmaintaining RCSmassinventory duringtheventingperiod..Theoperatorisinstructed toisolateletdownin"ordertoobtainthelevelincrease. | ||
Letdownwillremainisolateduntiltheventingoperation iscomplete. | |||
a7.Thisstepandthefollowing CAUTIONearnstheoperatorthatRCS.pressurewilldecreaseduringtheventingandifin.itialpressureisnearthelowpressuresafetyinjection actuation | |||
: setpoint, thenSImay.beautomatically initiated duringtheventing.Theoperatorisinstructed:to blockthelowpressurSIactuation ifand/orwhentheblockpermissive isene.gzedtopreventaninadventn.SI.*8.Chargingflowisincrsed.omaximumtolimitthenemassdepletion oftheRCSduringtheventingperiod.Aseondc~ar,r.'g',",pimpshouldbestartedifitwillprovideadditional make-.pflou..Ifthesafetyinjection systemisin;.operation thenmaintainthecurrentplantconfiguration untiltheventingiscomplete. | |||
Theresponses indicated intheNOTEwill'provide theprobablestatJsoftheRCSforthoseplantswithoutalevelsys:em.majalsoiden=ifythepresencecfvoidsintheRCSotherthanthereactorvesselheadorpressurizer. | |||
a)Duringadepressurization, anygaseousvoidsthatexistintheRCS,otherthanthevesselhoad,willrapidlyexpand'ndresult.inanincreaseinthepressurizer level.b).Theorificeintheheadventdischarge lineissizedtolimitwaterrelieftowithinthemake-upcapability ofacharging'pump.Therefore, ifnogasesarepresentinthevesselhead,thentheventflowratewil.lmatchthechargingflowrateandthepressurizer levelwillremainconstant. | |||
: February, 1981Revision0Pag'e6 c)Theventingofgaseswillresultinarapiddecreasefnpressurizer levelduetothemassflowrateofthegasesbeinggreaterthanthenthemassinputbeingprovidedbythemakeupflow.9.Bothisolation va1vesinoneventflowpathmustbeopenedtoinitiatetheventingoperation. | |||
TheNOTEinstructs the.operatortoclosebothisolation valvesintheflowpathff..':oneor,bothofthevalvesfailtoopen.'Thefsolatfon valvesfntheredundant flowpathshouldthen.beopened.Thfspreventstwoflowpaths'being openifthefailedvalvesuddenlyopens.10.Theventingis'terminated whenthereactorvess=lheadfsrefilledorwhenthefollowing criteriaareme=.b)lhemaximumtimeperiodallowable forventingwhicnli..itsccntainment hydrogenconcentration-to lessthan3volumepercent(determined byAppendixB,"VentingTimePeriod").c,d;e)Theselimitingconditions areconsistent withthesafetyfngection re-initiation criteriaoftheemergency operating instructions. | |||
Theyprovidesuffjcient ope.atingmarginfortheventingan'datthesametime,providei'mtscnt.".etransient whichensuresadequate'system controlcanbemaintained. | |||
rf)Oncethereactorvesselheadisventedandrefilledthenwaterreliefth~oughtheventpathwillbegin.Atthistime,therateofRCSdepressurization andtherateofpressurizer leveldecreaseshouldchangeanymayeventerminate. | |||
Thismaybeusedonani'ndication that.theheadhasbeen'refilled forthoseplantswithoutavessellevelsystem.Bothisolation valvesintheventflowpathshouldbeclosedtoterminate theventing.February, 1981Revision0Page7 TheCAUTIONinstructs theoperatortomaintaintheRCSventingiflossofreactorcoolantpumpoperation occurs.Theventingismaintained toremoveasmuchgasaspossiblefromthevesselheadduringtheRCPcoastdown andonsoughtofnatural'irculation. | |||
Thiswillminimizetheamountofgasbubblesinthereactorcoolantloopsandsteamgenerator U-tubes.TheoperatorshouldrefertoAOI-4"NaturalCirculation" toensureadequatecorecoolin'gisbeingmaintained. | |||
*II.Nornialpressurizer pressureandlevelcontrolisrestoredafterthecompletion oftheventing.Astablelevelandpressureshouldbemaintained while,itisdetermined iffurtherventingisreouired. | |||
I"12.Ifa'gasbubbleexistednthevesselheadandtheventingwasterminated priortothevesselheadbeingcomolezely | |||
;f'.llthen*theoperatorshouldreturntoStep4andrepeattheventingoperation untilthereactorvesselheadhasbeencompletely refi1Ied.TheNOTEalertstheoperatorthatif~thetimeperiodforventingdetermined inAppendix8ismetheft<rethevesselhad'.sre-,illted,; | |||
thenthecontainment hydrogenconcentration musbereducedandanewventingperiodcalcula:ed priortoperforming additional | |||
.Nventing.Thehydrogenconcentration couldbereducedthroughtheuse,ofthecontainment hydrogenre-combiners orbythepurge'.andexhaustsystemifradioactive gasconcentrations arewithinlimits.Thenewventingperiodwillbebaseduponthereducedhydrogenconcentration. | |||
13.Theoperatorshouldreturntotheappropriate operating instruction following thesuccessful completion ofventing'thereactorvesselhead.If,duringsubsequent actions,agaseousbubblereformsinthevesselhead,thentheoperatorshouldreturntoStepIandrepeattheventingoperation. | |||
: February, 1981Revision0Page8 III.BASISFORAPPENDIXA"RCSGASEOUSVOIDDETECTION ANDSIZING"PIfgasesarepresentinthereactorcoolant'system,thenthepressurizer pressureandlevelcontrolswillnotrespondastheynormallywould.Thetotalgasvolumecanbeestimated byperforming aroutinepressurizer controloperation andthencomparing theexpectedresultswith.theactualresults,,:This isthetechnique utilizedinthefallowing steps..Ifthesafetyinjection systemisinservice,thenthefoll'owing stepsarenotapplicable sincenormalpressurizer controlwillnotbemaintained. | |||
1,Theop"=rator isinstructed toachievo=-.-.-ablepressurizer pressurewithnormalcontrolsbeingmainai.;ed.2.Systempressureandlevelareplacedon.rendrecorde.s"'.oachievebetteraccuracyforrecording theirvalves.;hcransie",-. | |||
isnotexpectedtoexceeda150psi.or.'.1NofspanchargeinRCSconditions. | |||
3..Theserecordings willbecometheinitialparameters inthefollow'.ng calculation. | |||
4.Letdownflowisisolated, pressurizer heatersaretriooe",andpressurizer sprayisterminated toestablish acondit".on wherethepressurizer levelwillchangeonlyasaresultofmassbeinginjectedintotheRCS.UII5.Theoperatorisinstructed toallowthesystempressuretoincrease100psiorthepressurizer levelincreaseby5percentofspan(pressurizer levelisthepreferred response). | |||
Theseconditions areobtainedbyaslowcontinuous chargingrate.6.Theserecordings willbecomethefinalparameters inthefollowing calculation.'ebruary, 1981Revision0Page9 7.NormalRCSpressureandlevelcontrolsarere-established andmaintained untilotherwise directedbystepsofthisinstruction. | |||
8.Theoperatorisinstructed tocalculate thetotalvolumeofthepressurizer vaporspace.Thetotalcylindrical pressurizer vol.:meisthetotalvolumeofthepressurizer excluding theupperandlowersph'erical domes.9.ThetotalchargedvolumeintotheRCSisthedifference betweenthe(charging andsealinjection flows)andthesealleakoffflowandthenconverted tocubicfe't;Anexpectedpressurizer levelchangecanLedeirminedthetotalchargedvolumeinthepreced'.rc s-.ep.11.Iftheactualpressurizer levelchangeislessthantheexpec.edchange(orifnolevelchangewaswitnessed} | |||
thengaseousvoidsexistinthereactorcoolantsystem.~Thisisaresultofthegaseousvoidscontracting whenthepressurewasincreased bythechargingflow.Thiswilllimit,orpreventanormalpressurizer, levelincrease. | |||
Thevoidcontractio;. | |||
mayevenbelargeenougr.tocausear.actualdecreaseinthepressuriz rlevel.Step12shouldthenbeperformed toestimatethetotalvolumeofthegasvoids.intheRCS..12.TheRCSvoidvolumecontraction, isequaltothechangeinpressurizer levelconverted tovolume.AlsotheratiooffinalvoidvolumetoinitialvoidvolumeisequaltotheratioofinitialRCSpressuretofinalRCSpressure. | |||
Fromthesetwoequations thetwounknown(initialandfinalRCSvoidvolume)canbedetermined byinserting oneequationintoanother.The.initialvoidvolumeifcalculated firstandthenfitintothevolume/pressure ratiotodetermine thefinalvoidvolume.February, 1981Revision0Page10 IY.BASISFORAPPEHOIX8YEHTINGTIi"IEPERIOD'uring acoreuncoveryevent,thereexiststhepotential forasignificant amount'of hydrogengenerated inthecorewhichcouldbetrappedinthereactorvesselheadandreleasedtothecontainment atmosphere duringtheventingoperation. | |||
Thecontainment hydrogenconcentration islimitedtolessthan4volumepercenttopreventapotential explosive mixturewithoxygen,therefore, theamountofhydrogenthat,.canbeventedtothecontainment isrestricted. | |||
Amaximumallowable timeperiodforventingisdetermined tolimitthecontainment hydrogen..'oncentration. | |||
1.Theto.alcontainment volumeincubicfeetis-.'rs=de:a~ne"andthenconvrtedtostancard.e..oera..r'e andorossurec"nditons.Ho.e"'..atthepressure~ermfor:neconvetsionisi..iya"iicabietosub-atmospheric containments andcanbedeleted;-'ar='..eremaining | |||
:plants.'2,Thecontainment hydrogenconcentration, isthendetermined involumepercert'units. | |||
Thisvaluecanbefoundbydirectsamplingorbyhydrogenmonitors. | |||
Sufficient timeshouldbeallowedfortheaircirculation equipment tomixthecontainmnta--..osph reprio~tosamplinginor"ertodetermine arepresenta iveconcentration. | |||
aTheNOTEidentifies totheoperatorthatthecontainment hydrogenconcentration willbeinsignificant iftherehasbeennoleakagefromtheRCStothecontainment. | |||
Theoperatormayassumethe.HZconcentration tobe.0volumepercent.3.Themaximumvolumeofhydrogenthatcanbeventediscalculated whichwilllimitthecontainment hydrogenconcentration tolessthan3volume.percent.February, 1981Revision0'page11 0L'~~l~,l,}} |
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Issue date: | 02/28/1981 |
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Text
~~BACKGROUND INFORMATION FORREACTORVESSELHEADVENTOPERATION REVISION0FEBRUARY19818i072i0423 8i07i5PDRADOCK05000315PPDR REACTORVESSELHEADVENTOPERATION I.GENERALDISCUSSION A.~PuroseTheoperatoractionsandprecautions specified inthisguideline arethoseinstructions necessary fortheremovalof'gasesfromthereactorvesselheadbyoperation ofthereactorvesselheadventsystem.8;Guideline Assumptions Thespecificdesignofthereac.orvsse'.',-ead ventsys-;eausedinthisguideline includesasirg!ecornec.'.ion to~i:avesselheadwithredundant flowpathsandisolation valves.extending fromacommonline.Thecommonlineincludesa3/8".orifice whichlimitstheflowratetowithinthemakeupcapability ofthechemicalandvolumecontrolsystem..Theredundant flowpathsdischarge tothereacto~containment building.
Notethatthoseplants,whichhaveventsystemsinstalled whichventtothepressure~
erorth"r=ssur-.=er relieftankmaydesirotomodifyormake'd"i:icos
-o:heexistingguideline inordertoincorporate theplantspecificdesign.2.Althoughtheguideline doesnotrequireareactorvessellevelsystemitisrecomnended thatanyventingoperation beperformed incon5unction withanaccuratevessellevelindication forbothwithandwithoutreactorcoolantpumpoperation.
Forplantswithoutalevelsystem,theperformance ofAppendixA,"RCSGaseousVoidDetection andSizing"mayprovideanestimateofthetotalvolumeofgaseousvoidsintheRCS(otherthanthepressurizer).
- February, 1981Revision0'Page1 b3.Thereactorcoolantsystemcanbestabilized withaconstantpressurizer levelandadequatereactorcoolantsub-cooling established.
Theseconditions arerequiredtoensureadequatecore-cooling ismaintained duringtheventingperiod.4.Thepressurizer levelandpressurerequirements throughout theguideline donotincludeerrorallocations duetoanadversecontaihment environment.
Therefore, itisassumed.-that containment temperature isnearnormaloperating conditions.
5.Anyventingoperation mustbep'rformed priortotheinitiation-
'ofsafetyinjection flowthrottl'ing duringaPOST-LOCA-cooldownanddepressurizaticn "peraton.Sever.lg"Ide;incactionsrequiresheinitiation osafe-:.y~n'ect".:-n
':-ressurizer levelcannotberestore.TheO'.ST-LOCA co.lccwn"nddoresuri-zationoperation beginstothrottlesafe-.yinjecti"n.lowand-therefore fullSIflowcouldnotbedelivered totheRCSwhenrequired.
6.Theheadventsystemisnotdesi'gned forandshouldnot.beusedastheprimarymeans.o<<mitigate aninadequate tcorecoolingevent.Theventflcwpa.h'.snotsi:edtoproviCe"'his capability andshouldonlybeusedincon'unction witntheInadequate CoreCoolingGuidelines.
C.~S~ot~ms0Thefollowing aresymptomsthatmayindicatethepresenceofagaseousvoidinthereactorcoolantsystem.Notethatanyoneorcombination ofsymptomsmayindicatethatavoidexists.February, 1981Revision0Page2
ForPlantswithaRVlevelindication:
1.Reactorvessellevelindication lessthan(plantspecific) percentofspan.Theplantspecificvalueshoul'dincludeanallowance fornormalchannelaccuracy.
Ifthelevelsystemdoesnotincludeareference
'1egtemperature compensator
'hananadditional allowance should.beincludedforconditions wheretheRCStemperature isnotequaltothechannelcalibration
~'Vtemperature.
ForPlants~ith/without aRYlevelindication:
2.Variations fromthenorm-1pressur.,zer pressureandlevelrosponseCueto::omanchar"ingand.s".ray',ng over=.".".",.s maynotbeobserveairagaseousvoide"istsn"he.-":CS.Thepressurizer levelmaydecreasedur',ngaRCSpressurization fromchargingduetogaseousvoid.contraction andlevelmayriserapidlyduringasprayingoperation duetoagaseousvoidexpansion.
3.Anindication ofreactorvesselheadtempera'tures equaltoorgreaterthansaturation temperature warrantsthepresenceofasteambubblebeinggenerated int.",eRCS.'4.Gasesinthereactorcoolantsystemmayresultfromseveraltypesofplantevents.Anaccumulator tank"discharge oracoreuncoverymayresultinnon-condensible gases(e.g.nitrogenandhydrogen) beingtrappedintheRCS.ArapidRCScooldownmayresultinthevesselheadtemperature beinggreaterthantheprimarysaturation temperature andresultinasteambubblebeingdeveloped.
TheoperatorshouldsuspectthepresenceofgasesintheRCSifany.oftheaboveeventsoccur.February, 1981Revision0Page3 II.BASISFORSUBSEQUENT ACTIONSTheCAUTIONprecedtng Step'Iearnstheoperatortomatntatntheextsttngmodeofcorecoo11ngdurIngtheperformance ofthesubsequent actions.Trippinganoperating reacto~coolantpumpcouldresultingasesinthereactorcoolantloopscollecting inthesteamgenerator U-tubesandmaydisturbnaturalcirculation andprimarytosecondary heattransfer.'Starting reactorcoolantpumpswoulddisperseanygasesalreadycollected inthevesselheadandmaketheirremovalmorediffscult.
Therefore, theexistingstatusofthereactorcoolantpumpsshouldbemaintained duringtheventfngoperation.
Ifpossibleandifconditions requireso,thenareactorcoolantpumpshouldbestartedfo]lowing thecompl.so>>ofheventingoperation.
TheNOTEpreceding Stepidenti.'es cer"nsteps-(markeabyanasterisk,'hich arenotapplicable ifsafetyin~mection hasbeeninitiated andthesestepsshouldbeskippedduringtheventingoperatione l.Onceagaseousvoidisdetectedorsuspected intheRCS,thenanychangesbeingmadetotheprfnarysystemshouldbetermfnated andasteady-state condition shouldbeestablished.
ThisstepreferstoeventslikeaFCST-LOCA
- cooldown, anormalplantcooldown, oraplantrecoveryfromz.'esignbasisevent.TheintentistoaIIowtheRCStostabHfzesothatthesizeandpositionofthevoidcanbedetermined.
NotethatanormaI-pressurizer pressurecontrolcondition'may notbeattainable duetothereasonsstatedinsymptom2.2.ThefirstactiontakentoremoveanygasesfromtheRCSfstoattempttorecombine anycondensfble gasesbyincreasing RCSpressure.
Thisstepmaybeslowactingandifaupwardtrendfswitnessed onthevessellevelindicator thenmafntafnthismodeuntiltheheadisrefilledortheupwardtrendstops-thisstepissuccessful infillingthehead,thenreturntotheappropriate operating instruction.
Ifthisstepisnotsuccessful, thenproceedtoStep4.February, 1981Revision0Page4 TheCAUTIONa'lertstheoperatorthatchargingfioumayresultinasuddencol'lapse ofsteambubblesintheRCSandcausearapiddecreaseinpressurizer level.Thelevelshouldberestoredbyincreasing theRCSmakeupflowrate.
Iftheincreased makeupflowfailstorestorelevelthensafetyinjection shouldbeinitiated andtheoperatoristoproceedtoEOI-O,Immediate ActionsandDiagnostics.
3.Theventingoperation willresultinRCSgasesbeingventedtothecontainment.
Therefore thec'ontainment purgeandexhaustsystemshouldbeisolatedtopreventthereleaseofanyradioactive gasestotheenvironment.
Allavailable containment aircircula-.icn ecuipment si.oui"".es;ar".adoprevens-.anyhydirognfromfor-irgagasoockezandtoersureare"rsanttivehydro".Ten concentrat';n isobtainedinS:p5.4.Increasing thereactorcoolantsub-cooling 50'Fabovetheminimum~plantspecificvalueensuresthatreactorcoolantsub-cooling willbemaintained overtheentirerangeofRCSoperating conditions iftheventingoperation isterminated following a200psidecreaseinRCSpressure.
Thepreferred method-ofobtaining theadditional sub-cooling isincreasing RCSpressurtsincethis~illaidincondensing anysteambubblespresen"..
Iftheadditioral 5C'Fsub-cooling isalreadyestablished thenproceedtoStep5.5.TheactionsofAppendixS"VentingTimePeriod"determine themaximumallcwable timeperiodforventingwhichwilllimitthecontainment hydrogenconcentration tolessthan3volumepercent.Thislimitisrequiredtopreventapotentially explosive hydrogenconcentration frombeingdeveloped insidethecontainment.
(Thisstepmaynotbeapplicable forplantswhichventtothepressurizer orpressurizer relieftank.)February, 1981Revision0Page5
- 6.Pressurizer levelisincreased togreaterthan50"forthepurposeofmaintaining RCSmassinventory duringtheventingperiod..Theoperatorisinstructed toisolateletdownin"ordertoobtainthelevelincrease.
Letdownwillremainisolateduntiltheventingoperation iscomplete.
a7.Thisstepandthefollowing CAUTIONearnstheoperatorthatRCS.pressurewilldecreaseduringtheventingandifin.itialpressureisnearthelowpressuresafetyinjection actuation
- setpoint, thenSImay.beautomatically initiated duringtheventing.Theoperatorisinstructed:to blockthelowpressurSIactuation ifand/orwhentheblockpermissive isene.gzedtopreventaninadventn.SI.*8.Chargingflowisincrsed.omaximumtolimitthenemassdepletion oftheRCSduringtheventingperiod.Aseondc~ar,r.'g',",pimpshouldbestartedifitwillprovideadditional make-.pflou..Ifthesafetyinjection systemisin;.operation thenmaintainthecurrentplantconfiguration untiltheventingiscomplete.
Theresponses indicated intheNOTEwill'provide theprobablestatJsoftheRCSforthoseplantswithoutalevelsys:em.majalsoiden=ifythepresencecfvoidsintheRCSotherthanthereactorvesselheadorpressurizer.
a)Duringadepressurization, anygaseousvoidsthatexistintheRCS,otherthanthevesselhoad,willrapidlyexpand'ndresult.inanincreaseinthepressurizer level.b).Theorificeintheheadventdischarge lineissizedtolimitwaterrelieftowithinthemake-upcapability ofacharging'pump.Therefore, ifnogasesarepresentinthevesselhead,thentheventflowratewil.lmatchthechargingflowrateandthepressurizer levelwillremainconstant.
- February, 1981Revision0Pag'e6 c)Theventingofgaseswillresultinarapiddecreasefnpressurizer levelduetothemassflowrateofthegasesbeinggreaterthanthenthemassinputbeingprovidedbythemakeupflow.9.Bothisolation va1vesinoneventflowpathmustbeopenedtoinitiatetheventingoperation.
TheNOTEinstructs the.operatortoclosebothisolation valvesintheflowpathff..':oneor,bothofthevalvesfailtoopen.'Thefsolatfon valvesfntheredundant flowpathshouldthen.beopened.Thfspreventstwoflowpaths'being openifthefailedvalvesuddenlyopens.10.Theventingis'terminated whenthereactorvess=lheadfsrefilledorwhenthefollowing criteriaareme=.b)lhemaximumtimeperiodallowable forventingwhicnli..itsccntainment hydrogenconcentration-to lessthan3volumepercent(determined byAppendixB,"VentingTimePeriod").c,d;e)Theselimitingconditions areconsistent withthesafetyfngection re-initiation criteriaoftheemergency operating instructions.
Theyprovidesuffjcient ope.atingmarginfortheventingan'datthesametime,providei'mtscnt.".etransient whichensuresadequate'system controlcanbemaintained.
rf)Oncethereactorvesselheadisventedandrefilledthenwaterreliefth~oughtheventpathwillbegin.Atthistime,therateofRCSdepressurization andtherateofpressurizer leveldecreaseshouldchangeanymayeventerminate.
Thismaybeusedonani'ndication that.theheadhasbeen'refilled forthoseplantswithoutavessellevelsystem.Bothisolation valvesintheventflowpathshouldbeclosedtoterminate theventing.February, 1981Revision0Page7 TheCAUTIONinstructs theoperatortomaintaintheRCSventingiflossofreactorcoolantpumpoperation occurs.Theventingismaintained toremoveasmuchgasaspossiblefromthevesselheadduringtheRCPcoastdown andonsoughtofnatural'irculation.
Thiswillminimizetheamountofgasbubblesinthereactorcoolantloopsandsteamgenerator U-tubes.TheoperatorshouldrefertoAOI-4"NaturalCirculation" toensureadequatecorecoolin'gisbeingmaintained.
- II.Nornialpressurizer pressureandlevelcontrolisrestoredafterthecompletion oftheventing.Astablelevelandpressureshouldbemaintained while,itisdetermined iffurtherventingisreouired.
I"12.Ifa'gasbubbleexistednthevesselheadandtheventingwasterminated priortothevesselheadbeingcomolezely
- f'.llthen*theoperatorshouldreturntoStep4andrepeattheventingoperation untilthereactorvesselheadhasbeencompletely refi1Ied.TheNOTEalertstheoperatorthatif~thetimeperiodforventingdetermined inAppendix8ismetheft<rethevesselhad'.sre-,illted,;
thenthecontainment hydrogenconcentration musbereducedandanewventingperiodcalcula:ed priortoperforming additional
.Nventing.Thehydrogenconcentration couldbereducedthroughtheuse,ofthecontainment hydrogenre-combiners orbythepurge'.andexhaustsystemifradioactive gasconcentrations arewithinlimits.Thenewventingperiodwillbebaseduponthereducedhydrogenconcentration.
13.Theoperatorshouldreturntotheappropriate operating instruction following thesuccessful completion ofventing'thereactorvesselhead.If,duringsubsequent actions,agaseousbubblereformsinthevesselhead,thentheoperatorshouldreturntoStepIandrepeattheventingoperation.
- February, 1981Revision0Page8 III.BASISFORAPPENDIXA"RCSGASEOUSVOIDDETECTION ANDSIZING"PIfgasesarepresentinthereactorcoolant'system,thenthepressurizer pressureandlevelcontrolswillnotrespondastheynormallywould.Thetotalgasvolumecanbeestimated byperforming aroutinepressurizer controloperation andthencomparing theexpectedresultswith.theactualresults,,:This isthetechnique utilizedinthefallowing steps..Ifthesafetyinjection systemisinservice,thenthefoll'owing stepsarenotapplicable sincenormalpressurizer controlwillnotbemaintained.
1,Theop"=rator isinstructed toachievo=-.-.-ablepressurizer pressurewithnormalcontrolsbeingmainai.;ed.2.Systempressureandlevelareplacedon.rendrecorde.s"'.oachievebetteraccuracyforrecording theirvalves.;hcransie",-.
isnotexpectedtoexceeda150psi.or.'.1NofspanchargeinRCSconditions.
3..Theserecordings willbecometheinitialparameters inthefollow'.ng calculation.
4.Letdownflowisisolated, pressurizer heatersaretriooe",andpressurizer sprayisterminated toestablish acondit".on wherethepressurizer levelwillchangeonlyasaresultofmassbeinginjectedintotheRCS.UII5.Theoperatorisinstructed toallowthesystempressuretoincrease100psiorthepressurizer levelincreaseby5percentofspan(pressurizer levelisthepreferred response).
Theseconditions areobtainedbyaslowcontinuous chargingrate.6.Theserecordings willbecomethefinalparameters inthefollowing calculation.'ebruary, 1981Revision0Page9 7.NormalRCSpressureandlevelcontrolsarere-established andmaintained untilotherwise directedbystepsofthisinstruction.
8.Theoperatorisinstructed tocalculate thetotalvolumeofthepressurizer vaporspace.Thetotalcylindrical pressurizer vol.:meisthetotalvolumeofthepressurizer excluding theupperandlowersph'erical domes.9.ThetotalchargedvolumeintotheRCSisthedifference betweenthe(charging andsealinjection flows)andthesealleakoffflowandthenconverted tocubicfe't;Anexpectedpressurizer levelchangecanLedeirminedthetotalchargedvolumeinthepreced'.rc s-.ep.11.Iftheactualpressurizer levelchangeislessthantheexpec.edchange(orifnolevelchangewaswitnessed}
thengaseousvoidsexistinthereactorcoolantsystem.~Thisisaresultofthegaseousvoidscontracting whenthepressurewasincreased bythechargingflow.Thiswilllimit,orpreventanormalpressurizer, levelincrease.
Thevoidcontractio;.
mayevenbelargeenougr.tocausear.actualdecreaseinthepressuriz rlevel.Step12shouldthenbeperformed toestimatethetotalvolumeofthegasvoids.intheRCS..12.TheRCSvoidvolumecontraction, isequaltothechangeinpressurizer levelconverted tovolume.AlsotheratiooffinalvoidvolumetoinitialvoidvolumeisequaltotheratioofinitialRCSpressuretofinalRCSpressure.
Fromthesetwoequations thetwounknown(initialandfinalRCSvoidvolume)canbedetermined byinserting oneequationintoanother.The.initialvoidvolumeifcalculated firstandthenfitintothevolume/pressure ratiotodetermine thefinalvoidvolume.February, 1981Revision0Page10 IY.BASISFORAPPEHOIX8YEHTINGTIi"IEPERIOD'uring acoreuncoveryevent,thereexiststhepotential forasignificant amount'of hydrogengenerated inthecorewhichcouldbetrappedinthereactorvesselheadandreleasedtothecontainment atmosphere duringtheventingoperation.
Thecontainment hydrogenconcentration islimitedtolessthan4volumepercenttopreventapotential explosive mixturewithoxygen,therefore, theamountofhydrogenthat,.canbeventedtothecontainment isrestricted.
Amaximumallowable timeperiodforventingisdetermined tolimitthecontainment hydrogen..'oncentration.
1.Theto.alcontainment volumeincubicfeetis-.'rs=de:a~ne"andthenconvrtedtostancard.e..oera..r'e andorossurec"nditons.Ho.e"'..atthepressure~ermfor:neconvetsionisi..iya"iicabietosub-atmospheric containments andcanbedeleted;-'ar='..eremaining
- plants.'2,Thecontainment hydrogenconcentration, isthendetermined involumepercert'units.
Thisvaluecanbefoundbydirectsamplingorbyhydrogenmonitors.
Sufficient timeshouldbeallowedfortheaircirculation equipment tomixthecontainmnta--..osph reprio~tosamplinginor"ertodetermine arepresenta iveconcentration.
aTheNOTEidentifies totheoperatorthatthecontainment hydrogenconcentration willbeinsignificant iftherehasbeennoleakagefromtheRCStothecontainment.
Theoperatormayassumethe.HZconcentration tobe.0volumepercent.3.Themaximumvolumeofhydrogenthatcanbeventediscalculated whichwilllimitthecontainment hydrogenconcentration tolessthan3volume.percent.February, 1981Revision0'page11 0L'~~l~,l,