Theindividualchannelmonitoring(ICM)proposaltoimprovethesafetyperformanceofRBMKOriginalResearchArticle

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