Abstract :
Periodicsafetyreviews(PSRs)areperformedtoverifyand/orimprovethesafetyofoperatingnuclearpowerplants.WhenthePSRofGoriUnits3/4inSouthKoreawasperformed,afewsafety-relatedheatexchangerswerepointedoutascomponentsinneedofanageingmanagementprogram.Thisstudysharesthemotivationwiththenecessityoftheageingmanagementprogram.Wedevelopedaconditionmonitoringmethodologyforidentifyingoneoftheageingmechanismsinthesafety-relatedheatexchangersandnameditthefoulingmonitor.Thefoulingmonitoriscomposedof(1)themodelfordeterminingthetestfoulingresistanceandtheprojecteddesignfoulingresistanceatatestcondition,and(2)themonitoringanddetectionoftheirdeviation.Themathematicalmodelfordeterminingtheprojecteddesignfoulingresistanceatatestconditionneedstobeconsideredcarefullybecausetheheatexchanger,andparticularlyinthisstudy,theletdownheatexchanger,isnormallytestedunderoperatingconditionsthatdifferconsiderablyfromthedesignconditions.Thisneedwasmetbydevelopingindependentphysicalandempiricalcorrectionmethodsofwhichconsistencyiscross-checked.Eitherorbothcorrectionmethod(s)convertthedesignfoulingresistanceintoaprojectedfoulingresistance,whichisfinallycomparablewiththetestfoulingresistance.Themonitoringanddetectionmethodtracksthedeviationofthetestfoulingresistanceandtheprojectedfoulingresistance.Consideringthestochasticcharacteristicsoffoulingphenomena,weadoptedthesequentialprobabilityratiotesttodetermineappropriateschedulingforcost-andsafety-optimizedmaintenanceoftheheatexchanger.
