ML13098A431
| ML13098A431 | |
| Person / Time | |
|---|---|
| Site: | South Texas  |
| Issue date: | 04/08/2013 |
| From: | Sande T Enercon Services |
| To: | Plant Licensing Branch IV |
| Singal B | |
| Shared Package | |
| ML13098A368 | List: |
| References | |
| TAC MF0613, TAC MF0614 STP‐RIGSI191‐V03.6.1, Rev 0 | |
| Download: ML13098A431 (8) | |
Text
SouthTexasProjectRiskInformedGSI191Evaluation
DevelopmentofChemicalEffectsModulesforRisk InformedGSI191Resolution
Document:STPRIGSI191V03.6.1 Revision:0 Date:March28,2013
Preparedby:
TimothyD.Sande,EnerconServices,Inc.
Reviewedby:
BlakeStair,EnerconServices,Inc.
JanetLeavitt,UniversityofNewMexico KerryHowe,UniversityofNewMexico ZahraMohaghegh,UniversityofIllinois SeyedReihani,UniversityofIllinois
Approvedby:
ErnieKee,SouthTexasProject
SouthTexasProjectRiskInformedGSI191Evaluation DevelopmentofChemicalEffectsModules STPRIGSI191V03.6.1 Revision0
Page2of8 Purpose Thepurposeforthisdocumentistoprovideadescriptionofthegenericmethodologyforevaluatingthe impactofchemicaleffectswithinariskinformedframework.Althoughtheapproachisgeneric,allfour ofthechemicaleffectsmodulesthataredescribedmustbedevelopedbasedonplantspecific parameters.Thedescriptionofthemodulesincludeshighleveldiscussionofthetypesoftestingand analysisrequiredforeachmodule.However,thenumerousdetailsrequiredforfullydevelopingand implementingeachmodulewillbedescribedinotherdocuments.
Introduction Toevaluatethepossibleoutcomesshouldalossofcoolantaccident(LOCA)occur,theriskinformed approachforresolvingGSI191reliesonanevaluationofthousandsofscenarios(differentbreaksizes andlocations,variationsindebrischaracteristics,rangesofpossiblewaterlevelsandflowrates,etc.).
Eachinputhasarangeofpossiblevaluesdependentonbothrandomandsystematicvariations.The inputvariableprobabilitydistributionsarethoroughlyevaluatedusingstatisticalsamplingmethods.
However,physicalmodelsortestdataarenecessarytounderstandtheoutcomeofagivensetof conditions.
ForthechemicaleffectsportionoftheGSI191evaluation,theinputvariablesincludetimedependent pooltemperatureandpH,insulationandcoatingsdebrisquantities,exposedsurfaceareasforconcrete andreactivemetalsincontainment,initialchemistryoftheRCSandRWST,buffertypeandquantity,and otherfactors.Thegoalofthechemicaleffectsevaluationistoquantifytheeffectsofinsolublechemical products1ondebrisbedheadloss.Thiscanbedifficultbecausechemicalproductswon'tnecessarily forminallscenarios.Also,manyoftheinputparametershavecompetingeffectsthattendtooffset eachother.Forexample,maximizingthetemperatureprofilewilltendtomaximizethequantityof aluminumreleasedintosolution,butwillalsoraisethesolubilitylimitforaluminumprecipitatesto form.
Fordeterministicevaluations,theapproachthathastypicallybeenusedbytheindustry(asdescribedin WCAP16530NP)istocalculatethequantityofmaterialsreleasedintosolutionbasedonbounding inputconditionsandtoassumefullprecipitationofaluminum(andinsomecases,calciumandsilicon)to determinethetotalquantityofprecipitatesforagivenscenario.Theheadlossinducedbythese precipitatesisdeterminedbyperformingheadlosstestswithsurrogatemixturesthatarerecognizedas averyconservativerepresentationoftheactualprecipitatesthatmayform.
1Thetermchemicalproductsisusedinthisdocumenttorefertoinsolubleproductsthatmayresultfrom precipitationinthebulksolution,formationofscaleonmetalsurfaces,nucleationandgrowthofcrystalsonfiber surfaces,oranyotherformationmechanism.
SouthTexasProjectRiskInformedGSI191Evaluation DevelopmentofChemicalEffectsModules STPRIGSI191V03.6.1 Revision0
Page3of8 CalculatingtheimpactofchemicaleffectsoverthewiderangeofpossiblepostLOCAconditionsrequires thedevelopmentoffourchemicaleffectsmodules:(1)asolubilitylimitcalculatortodeterminethe concentrationwhereachemicalproductcouldformasafunctionoftemperatureandpH;(2)achemical releasemoduletodeterminethetimedependentconcentrationofimportantchemicalconstituents basedoncorrosionordissolutionreleaserates,materialquantities,andtemperatureandpHprofiles; (3)aproductformationmoduletodeterminethetypeandquantityofchemicalproducts,thelocation wheretheproductswouldform,andthecharacteristicmorphologyandsizeoftheproducts;and(4)a chemicalheadlossmoduletodeterminetheeffectoftheproductsondebrisbedheadloss.These modulesaredescribedinmoredetailbelow.
Module1:SolubilityLimits Thesolubilitylimitistheaqueousconcentrationrequiredforagivenproducttoform.Thislimitvaries dependingonthetypeandmorphologyoftheproduct.Ingeneral,thesolubilitylimitforagiven chemicalproductdecreaseswithdecreasingtemperature.However,somechemicalproductsexhibit retrogradesolubility,whichmeansthatthesolubilitylimitincreaseswithdecreasingtemperature.The solubilitylimitisalsodependentonthepH,andthereisgenerallyauniquepHvaluethatminimizesa chemicalproductssolubilitylimitforanygiventemperature(i.e.,thesolubilitylimitincreasesasthe solutionbecomesmoreacidicorbasic).
Basedonextensivetestingwithinthechemicalindustry,equilibriumconditionshavebeenestablished forawiderangeofchemicalproducts.Usingtheexistingdatabasesandcurrentliterature,thesolubility limits(basedonequilibriumconditions)forrelevantplantspecificproductscanbeestimatedwith thermodynamicmodeling.Aswithotheraspectsoftheriskinformedevaluation,thethermodynamic modelpredictionsincludealevelofuncertainty(duetouncertaintiesintheinputvariables)thatmust beconsideredintheevaluation.Figure1illustratesthesolubilitylimit(withuncertaintybands)fora chemicalproductasafunctionoftemperature.
SouthTexasProjectRiskInformedGSI191Evaluation DevelopmentofChemicalEffectsModules STPRIGSI191V03.6.1 Revision0
Page4of8
Figure1:IllustrationofaluminumsolubilitylimitversustemperatureataconstantpH
Thekeyfordevelopingthismoduleistoidentifythechemicalproductsthataremostlikelytoform underplantspecificconditions.ForSouthTexasProject(STP),whichusestrisodiumphosphate(TSP)as abufferingagent,themostlikelyproductsareconsideredtobealuminumhydroxide(Al(OH)3)orother aluminumproducts,calciumphosphate(Ca3(PO4)2),andzincphosphate(Zn3(PO4)24H2O).Althoughthe thermodynamicmodelsarebasedonextensivetesting,additionalbenchtoptestingmayberequiredto confirmthepotentialchemicalproductsthatwillbeevaluatedforModule1.
Module2:CorrosionandDissolutionRelease Thesecondmoduleprovidesapredictionofthetimedependentreleaseofvariousmaterials(Al,Ca,Si, Zn,etc.)intosolutionbasedonthecorrosion/dissolutionreleaserates,exposedquantityorsurfacearea ofcontributingmaterials(e.g.,insulationandcoatingsdebrisandmetalsincontainment),and containmentconditions.ThismoduleisessentiallyequivalenttotheWCAP16530NPcalculator.
However,somemodificationsmaybenecessarytomoreaccuratelycalculatetimedependentmaterial releaseforplantspecificconditions.Thepotentialmodificationsinclude:
AnadjustmenttothealuminumreleaseratetoaddressNRCconcernsthattheWCAPcalculator underpredictstherate(althoughnotthetotalquantityreleasedover30days)byapproximately afactorof2.
Incorporationofazinccorrosionrate(i.e.,forgalvanizedsteelandinorganiczinccoatings).
SouthTexasProjectRiskInformedGSI191Evaluation DevelopmentofChemicalEffectsModules STPRIGSI191V03.6.1 Revision0
Page5of8 IncorporationoftheinhibitionofaluminumcorrosionbysiliconandphosphatebasedonWCAP 16785NP.
Incorporationoftheinhibitionofaluminumcorrosionbyzinc.
Aswiththesolubilitymodule,uncertaintyinthecorrosionanddissolutionratesmustbeconsideredin theevaluation.Figure2illustratesthetimeandtemperaturedependentconcentrationthatwouldbe determinedfromModule2andthetemperaturedependentsolubilitylimitthatwouldbedetermined fromModule1(includinguncertainties).Thepointwherethetwolinescross(i.e.,wherethe concentrationexceedsthesolubilitylimit)isrepresentativeofthetimewhenachemicalproductcould firstbegintoform.Notethatsincecontainmentpooltemperaturegenerallydecreasesovertime,the solubilitycurveshowninFigure1isinvertedinFigure2.
Figure2:Comparisonoftimedependentsolubilitylimitandaqueousconcentration
ThemajorityofthereleasemoduleisbasedonexistingtestdatadocumentedinWCAP16530NPand WCAP16785NP.However,additionalbenchtopcorrosiontestsmayberequiredtoaddressthe corrosionofgalvanizedsteelandIOZcoatingsaswellastheinhibitoryeffectsofzinconaluminum corrosion.
SouthTexasProjectRiskInformedGSI191Evaluation DevelopmentofChemicalEffectsModules STPRIGSI191V03.6.1 Revision0
Page6of8 Module3:ProductFormation Theproductformationmoduleisintendedtopredictthetype,quantity,location,morphology,size,and transportofthechemicalproducts.Theproducttypes(e.g.,aluminumproductsorzincphosphate)can bedeterminedbasedonwhethertheconcentrationexceedsthesolubilitylimit.Similarly,thequantity (includinguncertainty)canbecalculatedbasedonachemicalmassbalancefromtheresultsofthefirst twomodules.
Chemicalproductscouldformatthefollowinglocations:(1)precipitationwithinthebulksolution,(2) thebuildupofscaleonmaterialsurfaces,or(3)growthwithinthedebrisbeditself.Aslongasa significantquantityofchemicalproductforms,precipitationwithinthebulksolutioncanbereadily identifiedbytakingwatersamplesduringatestandmeasuringturbidityorcomparingthechemical concentrationsoffilteredandunfilteredsamples.Forexample,ifthealuminumconcentrationinan unfilteredsampleissignificantlyhigherthaninafilteredsample,itisagoodindicationthatan aluminumprecipitatehasformedinthebulksolution.Ifasignificantquantityofchemicalproductforms asascaleonmetalsurfaceswithinatest,thiscanbeobservedbycomparingthesurfacesbeforeand afterthetest.Forexample,duringthe2012largebreakCHLEtest,asignificantquantityofzinc phosphateformedonthegalvanizedsteelcoupons.Ifthechemicalproductsformwithinthedebrisbed itself,itmaybedifficulttodirectlyobservetheproductsattheendofthetest,andthefilteredand unfilteredwatersampleswouldbeapproximatelythesame.However,significantproductgrowthwithin thedebrisbedcanbeindirectlyobservedbyotherwiseunexplainedincreasesinthedebrisbedhead loss.
Themorphologyandsizecanbedeterminedifthequantityoftheproductformedissufficienttopermit itscollectionandcharacterization.Themorphologyisimportantbecauseanamorphousprecipitatemay havesignificantlydifferentheadlosscharacteristics(andwouldgenerallybemoredetrimental)thana crystallineproduct.Thesizeisalsoimportantbecauseprecipitatesthatforminthebulksolutioncould passthroughadebrisbediftheyaresubstantiallysmallerthanthevoidspacedimensionsofthebed, whereasprecipitatesthataremuchlargercouldbereadilycapturedbyadebrisbed.
Thetransportforchemicalproductsdependsonthelocationwheretheproductsareformedaswellas thesizeandmorphology.Iftheproductsformwithinthedebrisbeditself,thetransportisirrelevant.
However,iftheproductsformonmetalsurfaces,theymayormaynotdetachfromthesurfacesand transporttothedebrisbed.
ThekeytodevelopingModule3istoconducttestsinwhichthequantityofproductformationislarge enoughtoobservethelocationwhereitoccursandtocollectandcharacterizetheproduct.Asdiscussed above,threetypesofchemicalproducts(aluminum,calcium,orzincproducts)couldpotentiallyformfor thefullrangeofSTPconditions.Asignificantquantityofzincphosphatewasobservedtoformasa crystallineproductonthesubmergedgalvanizedsteelcouponsandbagsofzincgranulesintheSTP
SouthTexasProjectRiskInformedGSI191Evaluation DevelopmentofChemicalEffectsModules STPRIGSI191V03.6.1 Revision0
Page7of8 largebreakCHLEtest.Asmallportionofthezincproductdetachedfromthesurfaceswhereitformed andsettledontheflooroftheCHLEtankortransportedtothedebrisbeds.Nosignificantquantitiesof aluminumorcalciumproductswereobservedinthistest,however.Therefore,additionaltestingis requiredtoidentifytheformationlocationsandcharacteristicsofaluminumproductsandcalcium phosphateproductsunlesstestingandModules1and2demonstratethataproductwillneverform undertherangeofplantspecificconditions.Toaccomplishthis,thetestsshouldbedesignedto encouragethepotentialformationofeachoftheseproducts.Thisisonepurposeforthetwo10day testsdescribedinthecurrentCHLEtestplan.
Module4:ChemicalHeadLoss Thepurposeofthechemicalheadlossmoduleistoquantifytheoveralleffectsofchemicalproduct formation.Insomecases,thefirstthreemodulesmaypredictthatchemicalproductswouldnotformor thatthechemicalproductsthatformwouldnotbetransportedtothedebrisbed.Forthesecases,there wouldbenochemicalheadloss.However,incaseswhereasignificantquantityofchemicalproducts formandtransporttothedebrisbed(orgrowwithinthedebrisbed),theincreaseindebrisbedhead lossmustbedetermined.Ifthemorphologyofthechemicalproductsiscrystalline,itmaybepossibleto treatitsimilartoparticulatedebriswithintheconventionaldebrisheadlosscorrelation.However, amorphousprecipitatesdonotbehavelikeconventionalparticulatedebrisandgenerallyhaveamuch greaterimpactonheadloss.Thechangeinheadlossduetochemicalproductsisalsodependentonthe existingconventionaldebrisbed.Athinbedoffiberdebriswithnegligiblequantitiesofparticulate wouldlikelyhaveasignificantlydifferentresponsetoagivenquantityofchemicalproductsthanwould athickfiberbedwithlargequantitiesofparticulate.
Theapproachthatisproposedforquantifyingtheeffectsofchemicalproductsonheadlossisto developabumpupfactorcorrelationfortherangeofplantspecificconditions.Thisdiffersfrom previousattemptstodevelopauniversalbumpupfactor.Instead,arangeofbumpupfactorswillbe determinedthatcorrespondtoavarietyofchemicalconditionsandconventionalfiberglassdebrisloads.
ThetestingrequiredtodevelopModule4includesaseriesofverticallooptestswithchemical conditionsfocusedonthemoreproblematicscenarios(i.e.,caseswheremaximumquantitiesof chemicalproductsarepredictedbasedonModules13)andthatconsidervariationsindebrisbeds(i.e.,
combinationsofthinandthickfiberbedswithlowandhighparticulatequantities).
Conclusions ToimplementariskinformedGSI191resolutionapproach,fourchemicaleffectsmodulesarerequired.
ThefirstmodulewillbeusedtodeterminethesolubilitylimitasafunctionoftemperatureandpHfor potentialchemicalproductsthatmayform.Thismodulewillbebasedonthermodynamicmodeling, althoughtestingmayberequiredtoverifythemodule.Thesecondmodulewillbeusedtopredictthe timedependentconcentrationofvariouschemicalsasafunctionofthequantityandsurfaceareaof
SouthTexasProjectRiskInformedGSI191Evaluation DevelopmentofChemicalEffectsModules STPRIGSI191V03.6.1 Revision0
Page8of8 variousmaterialsandofthetemperatureandpH.Thismodulewillbebasedprimarilyonthe corrosion/dissolutionequationsinWCAP16530NP,althoughsomeadditionalbenchtoporintegrated tanktestsmaybenecessary.
Thefirsttwomodulesfeedintothethirdmodule,whichwillbeusedtodeterminethetype,quantity, location,andcharacteristicsofthechemicalproducts.Thetypeandquantityofproductwillbe determinedbycomparingtheresultsofModules1and2,andthelocationandcharacteristicsofthe productswillbedeterminedbasedonintegratedtanktestswheretheproductsareobservedtoform.
Thefourthmodulewillquantifytheheadlossduetothechemicalproductspredictedtoformbythe thirdmodule.Thechemicalheadlossmodulewillbebasedonintegratedverticallooptestingwith prototypicaldebrisbedswheretheincreaseinheadlosscanbemeasuredasafunctionofthechemical productsformedandthedebrisbedwheretheproductsarecollected.
Onceallofthesemodulesarefullydeveloped,itwillbepossibletofullyevaluatechemicaleffectsfor therangeofplantspecificconditions.Atthispoint,itmaybebeneficialtoconducta30dayintegrated testforthelimitingscenario(aspredictedbythefourmodules)toconfirmthatthemodulesprovidea reasonableprediction.