Full Scope Nodeling And Analysis On The Secondary Circuit Of PWR Based On RELAP5 Code

As an important clean and economical source,nuclear energy has important significance in the sustainable development of human society.At the same time of nuclear power plant(NPP)construction,accident sequences prediction and operators training are also in progress.Since there are some possible events in secondary circuit may lead to accident in NPP,the simulation and analysis of secondary circuit are necessary.The simulation can not only used in the safety assessment before NPP construction,but also in operators traning,decreasing human errors and improving conventional island accident procedures etc.Meanwhile,with an increasing proportion of nuclear power in the electric power in China,it will participate in regulating peak load in power network,which puts forward higher requirements for the accuracy calculation and control of secondary circuit.Chinese large-capacity advanced PWR under construction in China is an advanced reactor type with passive technology.This demonstration project has been listed in the national medium and long-term development plan of nuclear power.Chinese large-capacity advanced PWR is not only the milestone of the innovotion of Generation III nuclear power technology in China,but also an indispensable reactor type in the developing process of nuclear power plant fields in the world.In order to achieve real-time and full scope simulation of the secondary circuit,RELAP5 code has been adopted to model Chinese large-capacity advanced PWR in the power change transient for its advantage of high calculation accuracy.This paper describes the model of steady state and turbine load transient from 100%to 40%of secondary circuit using RELAP5 according to the practical layout of the NPP.Meanwhile,this paper provides a reasonable equivalent method to solve the calculation divergence problem in heaters caused by dramatic two-phase condition change while guaranteeing the heat transfer efficiency.The validation of the main parameters shows that all the errors between the calculation values of steady state for turbine load of 100%and practical design values are less than 2%.The errors of key parameters in steady state calculation of turbine load from 100%to 40%are acceptable.The transient trend of turbine load from 100%to 40%is reasonable,which shows the model has high validity and reliability.