Gas-cooledfastreactors—StatusofCEApreliminarydesignstudiesOriginalResearchArticle

Thegas-cooledfastreactor(GFR)isoneofthesixreactorconceptsselectedintheframeoftheGenerationIVinitiative.ThemostsignificantGFRoptionistheuseofaheliumhightemperatureprimarycoolant.Theheliumoptionisveryattractive(chemicalinertness,neutrontransparency,etc.)butitleadstoveryspecificthermal-hydraulicissues. Asfarasthereactorcoredesignisconcerned,aceramicfuelconceptwithagoodthermalconductivityhasbeenchosen.Themainrequirementistoobtainanaverageexitcoretemperatureof850°C(energyconversionefficiency)withamaximumfueltemperatureofabout1200°Candwithalowcorepressuredrop(inordertoeasethedecayheatremoval).Themaincorecharacteristicshavebeendeterminedfortworeactorpowers:amediumone(600MWth)andalargeone(2400MWth).Forvariousreasons,thislatterbecametheCEAreferencechoice.Aconsistentsetofcoreparametershasbeendeterminedtakingintoaccountthedifferentconstraintsincludingthethermal-hydraulics.Thereferencearrangementproposedisbasedonplatefuelelements. AsignificantissuefortheGFRisthedecayheatremoval.Aninnovativeapproachhasbeenchosenincaseoflossofcoolantaccidents(LOCAs).A“guardcontainment”enclosingtheprimarysystemisusedtomaintainamediumgaspressure(10bar)inordertoremovethedecayheatbylowpowerforcedconvectionsystemsintheshorttermandnaturalconvectionsystemsinthelongterm.Thisguardcontainmentisnotpressurizedduringnormaloperationsandcanbeametallicstructure. Asfarastheenergyconversionsystemisconcerned,anindirect-combinedcyclehasbeenchosen.Thesignificantadvantagesofthischoiceare:amoderatecoreinlettemperature(400°Cinsteadof480°Cforthedirectcycle)andanattractivecompactnessoftheprimarysystem(facilitatingtheguardcontainmentdesign). Duetothenoveltyoftheseoptions,asignificanteffortofcomponentspre-sizinganddesigncalculationshasbeenachieved.Followingthiseffort,aCATHAREmodelofthereactorsystemhasbeenmadeandthecalculationofthereactorsteady-stateconfirmstheconsistencyoftheoverallsystempre-sizing.Thismodelhasbeenusedforafirsttransientcalculation.Othertypesoftransientshavetobeanalyzed,however,itisthoughtthattheproposedGFRdesigncanreachthesafetyrequirementsofGenerationIVsystems.