ModelingofWWER-440fuelpinbehavioratextendedburn-up

Currently,thereisanongoingefforttoincreasefueldischargeburn-upofallLWRsfuelincludingWWERsasmuchaspossibleinordertodecreasepowerproductioncost.Therefore,burn-upisexpectedtobeincreasedfrom60to70MWd/kgU.Thechangeinthefuelradialpowerdistributionasafunctionoffuelburn-upcanaffecttheradialfueltemperaturedistributionaswellasthefuelmicrostructureinthefuelpelletrim.Bothofthesefeatures,commonlytermedthe“rimeffect.”Highburn-upphenomenainWWER-440UO2fuelpin,whichareimportantforfissiongasrelease(FGR)weremodeled.Theradialburn-upasafunctionofthepelletradiusandenrichmenthastobeknowntodeterminethelocalthermalconductivity. Inthispaper,theradialburn-upandfissileproductsdistributionsofWWER-440UO2fuelpinwereevaluatedusingMCNP4BandORIGEN2codes.TheimpactofthethermalconductivityonpredictedFGRcalculationsisneeded.Fortheanalysis,atypicalWWER-440fuelpinandsurroundingwatermoderatorareconsideredinahexagonalpinwell.Thethermalreleaseandtheathermalreleasefromthepelletrimweremodeledseparately.Thefractionoftherimstructureandtheexcessiveporosityintherimstructureinisothermalirradiationasafunctionofthefuelburn-upwaspredicted.Acomputerprogram;RIMSC-01,isdevelopedtoperformtherequiredFGRcalculations.Finally,therelevantphenomenaandthecorrespondingmodelstogetherwiththeirvalidationarepresented