22312 engineering of nuclear reactors：22312工程的核反应堆

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1、22.312ENGINEERINGOFNUCLEARREACTORSDueNovember16,2007by12:00pmTAKEHOMEQUIZ2Problem1(45%)–EffectofinternalcoolingonfueltemperaturesConsiderthefollowingthreeUO2pellets:•Solidpellet•Annularpelletwithonlyexternalcooling•AnnularpelletwithsimultaneousinternalandexternalcoolingThedimensionsforallthreepell

2、etsareinthetablebelow.Assumethatthefuelthermalconductivityiskf=3W/m⋅K(independentoftemperature),thepelletsurfacetemperatureis700°Candthelinearpowerisq′=40kW/minallthreecases.GeometryofthepelletsID(mm)OD(mm)SolidpelletN/A8.2Annularpelletwithonlyexternal2.08.44coolingAnnularpelletwithinternaland9.91

3、4.1externalcoolingi)Calculatethemaximumtemperatureforthesolidpellet.(5%)ii)Calculatethemaximumtemperaturefortheannularpelletwithonlyexternalcooling.(5%)iii)Calculatethemaximumtemperaturefortheannularpelletwithsimultaneousexternalandinternalcooling.(20%)iv)Fortheannularpelletwithsimultaneousinterna

4、landexternalcoolingcalculatealsotheheatfluxattheinnerandoutersurfaces.(10%)v)Whatareinyourjudgmenttheadvantagesanddrawbacksoftheannularfuelpelletwithsimultaneousinternalandexternalcooling?(5%)Citeas:JacopoBuongiorno,coursematerialsfor22.312EngineeringofNuclearReactors,Fall2007.MITOpenCourseWare(ht

5、tp://ocw.mit.edu/),MassachusettsInstituteofTechnology.Downloadedon[DDMonthYYYY].Problem2(55%)–Flow-levitatedcontrolrodinaPWRProf.Driscollhasrecentlyproposedanovelcontrolroddesignbasedonflowlevitation,tobeusedinPWRs.Thecontrolrodconsistsofaslugofabsorbingmaterial(boroncarbide,B4C)thatcanslidewithin

6、aguidetube(seeFigure1).Duringnormaloperatingconditionsthecontrolrodisheldoutofthecorebythecoolantflow.Ifthecoolantflowsuddenlydecreases,thecontrolrodfallsbackintothecore.Theideaistocreateascramsystemthatwouldautomatically(passively)shutdownthereactorincaseoflossofflowandlossofcoolantaccidents.Thec

7、ontrolrodslugdiameterisD=2cmanditslengthisL=3.7m.TheguidetubediameterisDo=2.6cm.ThepropertiesofB4Candcoolantarereportedinthetablebelow.MechanicalstopDgLControlrodslugGuidetubeActivecoreDoregionFigure1.Theflow-lev