FuelassemblydesignstudyforareactorwithsupercriticalwaterOriginalResearchArticle

TheEuropeanconceptoftheHighPerformanceLightWaterReactor(HPLWR)differsfromcurrentlightwaterreactorsinahighersystempressurebeyondthecriticalpointofwater,aswellasahigherheat-upofthecoolantwithinthecoreandthushighercoreoutlettemperatures,leadingtoasignificantincreaseinturbinepowerandthermalefficiencyofthepowerplant.ThemotivationtodevelopanovelfuelassemblyfortheHPLWRiscausedbythehighvariationofcoolantdensityinthecorebymorethanafactorofseven.Asystematicdesignstudyshowsthatasquarefuelassemblywithtworowsoffuelrodsandacentralmoderatorboxisbesttominimizethestructuralmaterial,tooptimizethemoderatortofuelratioandtoreducedifferencesoffuelrodpower.Usingneutronicandthermal-hydraulicanalyses,adetailedmechanicaldesignofafuelassemblyoftheHPLWRhasbeenworkedout.Moreover,conceptsfortheheadpiece,thefootpiece,thesteamplenumandthelowermixingplenum,includingthelowercoreplate,havebeendevelopedtoaccountfortheindividualflowpathsofthisreactor.Theseallowaleak-tightcountercurrentflowofmoderatorwaterandcoolantaswellasuniformmixingofdifferentmassflows.Theassemblydesignconceptcanbeusedasageneralkeycomponentforanyadvancedcoredesignofthisreactor.