Thermal Hydraulic Calculation And Design Of Secondary Passive Residual Heat Removal System In1000MWe PWR

The passive residual heat removal system has been widely used in the third generationreactor, which is forced by potential difference between the heat and cool core. Application ofPRHR system has the advantage of reduce compulsive safety equipment in PWR plant, alsoreduce the possibility of careless action of operator and improve the inherent safety of theplant. As for the second generation100MWe PWR, study on design an additional PRHRsystem, for use in failure accident of reactor compulsive cooling system, is very important forimproving the safety and reliability of the present PWR plant.In this paper, the thermal-hydraulic system analysis program, RELAP5has been used todesign a secondary side passive residual heat removal system for PWR plant, also it’s thermalhydraulic character has been investigated. Firstly, design of the condensation heat exchangerfor PRHR of CPR1000plant has been implemented, whose main thermal hydraulicparameters and the key influence factor had been investigated. Secondary, the PRHR systemfor the CPR1000plant and the RELAP simulation model has been put forward. The steadystate analysis was first completed and tested with the designed parameters to verify the heatremoval and natural circulation capability. Then, the heat removing capacity of the PRHRsystems were discussed during the station blackout and main feedwater line rupture accidents.The transient startup stability, violation of pressure, flow rate and SG water level wereinvestigated. The typical unstable phenomenon in startup of PRHR, steam hammer has beenstudied deeply, and effect of starting mode and opening speed of valves on intensity andduration of pressure wave have been put forward.Study in this paper shows that the PRHR system can continually carry out residual heat ofthe core in station blackout accident, which can make temperature and pressure of the primaryloops come down to a safety low value without any human action. In main feedwater piperupture accident, availability of two set PRHR systems could take away the reactor decay heatin designed time, while only one PRHR system couldn’t play the role. A suitable start-upmode and opening speed of valve, for mitigate or avoid the steam hammer phenomenon instartup of PRHR system have also put forward. The designs of condensation heat exchanger,RELAP simulation model of PRHR system, and methods for improve the startup stability has helpful guideline for PRHR design of actual CPR1000plant.