EvaluationoftheburstcharacteristicsforaxialnotchesonSGtubings

Someeventsofsteamgeneratortubeshavebeenreportedinsomenuclearpowerplantsaroundtheworld.Maincausesoftheleakagearefromvarioustypesofcorrosioninthesteamgenerator(SG)tubing.Primarywaterstresscorrosioncracking(PWSCC)ofsteamgeneratortubinghaveoccurredinmanytubesinKoreanplants,andtheywererepairedusingsleevesorplugs.Inordertodevelopproperrepaircriteria,itisnecessarytoascertaintheleakbehaviorofthetubings.Ahigh-pressureleakandbursttestingsystemwasmanufactured.Varioustypesofelectro-discharged-machined(EDM)notcheshavingdifferentlengthsweremachinedontheo.d.oftesttubestostudySGtubebehavior.Leakrateandligamentrupturepressureaswellastheburstpressureweremeasuredforthetubesatroomtemperature.Rupturepressureofthepartthrough-walldefecttubesdependsonthedefectdepthandlength.Waterflowratesaftertherupturewereindependentoftheflawtypes;tubeshaving20–60mmlongEDMnotchesshowedsimilarflowratesregardlessoftheinitialdefectdepth.Afastpressurizationrategeneratedalowerburstpressurethanthecaseofaslowpressurization.