Analysis Of Ultimate Response Guidelines For Longmen Nuclear Power Plant To Cope With Station Black Out Accident

After the compound accident, which was caused by the nature disaster of a combination ofseismic and tsunami events,occurred in Fukushima,Japan,concerns on nuclear security have beenraised once again.China mainland has adopted the relatively mature technology that is used inthe Pressurized Water Reactor.Many scholars and research institutions carry on deep-goingstudies to form complete safety analyses.Compared to China mainland，most of Nuclear PowerPlants(NPP) in Taiwan district,which possess the Boiling Water Reactor,are the advanced versionof Fukushima NPP.What’s more，Taiwan district is located in earthquake-prone area.As aresult,Ultimate Response Guidelines(URGs)for Longmen NPP is developed by Taiwan PowerCompany to deal with compound accident.This paper provides highlight of the features of URGs and validates its effectiveness in thepostulated compound accident with MAAP5.There are some conclusions as follows:(1)The parameters file that Longmen NPP has adopted possesses a relative higheraccurancy.Therefore,it could be used as a basic file to analyze severe events.(2)Existing emergency operating procedures would not be useful when compound disasteroccurs.At this very timing,ultimate response guidelines is a necessity. If plants are not equippedwith URGs,this event will transfer into the disaster similar to Fukushima and bring a crushingcalamity to surroundings.(3)The sensitivity of raw water pool is567.75L/min which ranged from50%to75%ofrated flow.It demonstrates that at least567.75l/min cooling water is needed if the peak claddingtemperature maintains below1088.6K,which leads plant to a security situation.The flow of236.56L/min could cause core to melt down and fail reactor pressure vessel and the firstcontainment.Altough three varieties of flow,which respectively are473.13L/min,709.69L/minand946.25L/min,all can maintain core water level fluctuating beteen level three and leveleight,the peak cladding temperature would be above1088.6K when the flow is473.13L/min.Also,the reaction of Zr and water becomes severely.Therefore473.13L/min isn’t asafety flow.(4)Analysis on time that RCIC is running and raw water is injecting are very important.Thelonger RCIC runs,the more possibilities plant units have of entering a safety situation.Safetyrelief value acts to depressurize the reactor vessel after reactor scrams60minutes.Coolant water with low pressure could get into the reactor core.Injecting timing of raw water reachs criticalpoint where if the time is delayed severe events would occur.