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1、Nuclear Engineering ReactorPassive Safety System ContentDefinition1ThePCSofPWR2ThePXSofPWR3PassivesafetysystemofAP1000Foundationofthecourse Students should know about the basic components of PWR nuclear power station,especially the special safety system,including residual heat removal system,safety
2、injection system,etc.We recommend some references for you to have a better understanding of PWRs.Coursecontent In this class,we mainly introduce passive safety technology.First,we will have a brief introduce of passive safety system according AP1000 nuclear power plant.Then,we have a discussion on p
3、assive safety technology to extend our vision.At the same time,we also provide references for you to study passive safety technology in depth after class.AdvancedPWRAP1000 Much has been done to improve neutron economy,system and component reliability.Also,equipment design and layout have been rework
4、ed to reduce cost and simplify plant operation.Finally,dramatic changes have been made in Safeguards Systems to provide for passive measures that would operate after a severe accident,assuming no operator action is possible in the containment vessel for a considerable period of time Remark Passivesa
5、fetysystemofAP1000Definition Passive safety technology is a design approach for safety features that does not require any active intervention on the part of the operator or electrical feedback in order to bring the reactor to a safe shutdown state,in the event of a particular type of emergency.It ty
6、pically takes advantage of natural forces or phenomena such as gravity,buoyancy,pressure differences,conduction or natural heat convection to accomplish safety functions without requiring an active power source.Active safety system needs external trigger and power source.Passive safety system requir
7、es little or no outside power or human controlPassivesafetysystemofAP1000ComponentPassivesafetysystemPassivecorecoolingsystemSafetyinjectionanddepressurizationPassiveresidualheatremovalsystemPassivecontainmentcoolingsystemPassivesafetysystemofAP1000Passivecorecoolingsystem The passive core cooling s
8、ystem(PXS),shown in picture,protects the plant against RCS leaks and ruptures of various sizes and locations.The PXS including PRHR HX,CMT,ACC,IRWST,ADS.PassivesafetysystemofAP1000Passiveresidualheatremovalsystem The PRHR HX is connected through inlet and outlet lines to RCS loop.The IRWST provides
9、the heat sink for the PRHR HX.The IRWST water absorbs decay heat for more than one hour before the water begins to boil.Once boiling starts,steam passes to the containment.The steam condenses on the steel containment vessel and,after collection,drains by gravity back into the IRWST.The PRHR HX and t
10、he passive containment cooling system provide indefinite decay heat removal capability with no operator action required.PassivesafetysystemofAP1000PassiveresidualheatremovalsystemPRHR startPassivesafetysystemofAP1000SafetyinjectionanddepressurizationPassivesafetysystemofAP1000Safetyinjectionanddepre
11、ssurization In the case of water loss accident,PXS uses four different kind of water sources for passive safety injection:A.Long time high flow injection of CMT;B.Several minutes of very high flow injection of ACC;C.Long time low flow injection of IRWST;D.The containment system becomes a long-term c
12、ooling hot trap after the vessel is submerged by water.PassivesafetysystemofAP1000SafetyinjectionanddepressurizationCoremakeuptankinjection70.8m3PassivesafetysystemofAP1000SafetyinjectionanddepressurizationAccuminjection56.6m3PassivesafetysystemofAP1000SafetyinjectionanddepressurizationIRWSTinjectio
13、n2100m3PassivesafetysystemofAP1000SafetyinjectionanddepressurizationContainmentsumpwatercyclePassivesafetysystemofAP1000PassivecontainmentcoolingsystemPassivesafetysystemofAP1000Passivecontainmentcoolingsystem The passive containment cooling system(PCS)provides the safety-related ultimate heat sink
14、for the plant.The PCS cools the containment following an accident so that design pressure is not exceeded and pressure is rapidly reduced,dropping to 40%of the design pressure in less than 5 h.The steel containment vessel provides the heat transfer surface that removes heat from inside the containme
15、nt and transfers it to the atmosphere.The heat is removed from the containment vessel by the continuous,natural circulation of air.During an accident,air cooling is supplemented by water evaporation.PassivesafetysystemofAP1000PassivecontainmentcoolingsystemPassivesafetysystemofAP1000Passivecontainme
16、ntcoolingsystemPassivesafetysystemofAP1000Safetythroughsimplicity Passive systems increase safety,enhance public acceptance of nuclear power,and ease licensingthey also simplify overall plant systems,equipment,and operation and maintenance.The simplification of plant systems,combined with large plan
17、t operating margins,greatly reduces the actions required by the operator in the unlikely event of an accident.Passive systems use only natural forces and there are no pumps,fans or other rotating machinery required for the safety systems.This eliminates the need for safety-related AC power sources.A few simple valves align the passive safety systems when they are automatically actuated.In most cases,these valves are“fail safe.”They require power to stay in their normal,closed position.Loss of power causes them to open into their safety alignment.