Author/Authors :
F.D’Auria، نويسنده , , M.Cherubini، نويسنده , , F.Pierro، نويسنده , , W.Giannotti، نويسنده ,
Abstract :
AcomprehensivestudyhasbeencompletedinrelationtotheaccidentanalysisofRBMKwithkeyresultsdocumentedinthreecompanionpapersinthepresentjournalvolume.ThestudyalsoaimedatthecomparisonbetweenselectedaccidentanalysistopicsinLightWaterReactors(LWR)andRBMK.TherelevanceoftheFuelChannelBlockage(FCB)eventwithintheareaofaccidentanalysiswasconfirmed.Owingtotheprobabilityofoccurrence,alsoconnectedwiththelargenumberofchannels,estimatedintheorderof10−2/reactor/year,theFCBisactuallypartoftheDesignBasisAccidents(DBA)fortheRBMK.
IncasetheFCBispartoftheDBA,anoticeabledifferenceoccursinresultsfromsafetyevaluationsbetweenLWRandRBMK:inthelattercase,aDBAcausesalossofintegrityforthepressurebarrierand,thoughtoalimitedextent,damagedfueloverpassessuchabarrier.TheFCBeventalsocausescontaminationinreactorcavityandinselectedpartsoftheoverallconfinement,damageinvariousgraphiteblocksand,evenexcludingtheMPTRriskowingtothefindingsfromthesecondcompanionpaperinthisjournalvolume,mechanicalloadsonneighbouringfuelchannels,graphitestacksandreactortankthatneedextensiveexaminationbeforereactorrestart.
Therefore,aproposalhasbeenformulatedforperformingthefeasibilityanalysisforthedesignofasystemdenominatedICM(IndividualChannelMonitoring).ThegoaloftheICMistheearlydetectionoftheFCBeventandthetriggeringofscraminsuchawaytopreventpressuretubedamageand,definitely,over-passingofthepressurebarrierbymoltenordamagedfuelduringaDBAsituation.
TheICMisbaseduponthesignalsofpressure-drop(orflow-rate)andfluidtemperaturetransducersinstalledinthebottomandtheupperpartsofthefuelchannels,respectively.Theperformedstudyshowsthatsteamsuperheatingatfuelchanneloutletoccursearlyaftertheblockageeventandtherelatedtemperaturesignalcanbeusedtocausescram.Theavailabilityofsophisticatecomputationaltoolsincludingthedetailedneutronkineticmodelforeachcorechannel,madepossiblethepreliminaryconclusionofthestudy
