Study On Load Switching And Steam Emission Characteristics Of Marine Nuclear Power Secondary Loop System

Marine nuclear power plant has limited space volume,high frequency and wide range of load fluctuation during operation.The off design control strategy plays an important role in the smooth load transition.In this paper,the control characteristics of a secondary system are simulated.At the same time,the simulation study of the steam emission characteristics under the condition of the power mismatch between the primary and secondary circuits is carried out.In this paper,the simulation model and the corresponding control model of a ship’s nuclear power secondary system are established based on GSE simulation platform,and the simulation model is verified and modified by design parameters.Two kinds of control strategies are developed: the first loop average temperature method and the switching control method.The control switching points are 55%,50% and 45% of the main turbine load respectively.Different control strategies and different switching point load simulation are carried out;different steam emission control strategies are formulated: control the average temperature of the primary circuit,control the main steam header pressure and the combination of the two control methods,and the steam emission process is simulated.The simulation results of different control strategies show that: compared with the temperature control scheme,the control switching scheme has a greater disturbance on the average temperature of coolant,the liquid level of steam generator,the reactor power and the steam pressure of steam generator,and the stability time is longer.Under the control switching scheme,the average temperature of coolant,the reactor power and the steam pressure of steam generator at low load are less than the temperature control scheme and it has a better advantage to the equipment life and economy of the system.The simulation results of different switching points show that the lower the turbine load corresponding to the selected switching point,the smaller the disturbance to the system parameters.Among them,the average temperature of the coolant,the liquid level of the steam generator,the power of the reactor,the fluctuation amplitude and the stable time of the steam generating pressure of the steam generator decrease in turn.It shows that the smaller the load corresponding to the switching point,the more conducive to the stable operation of the system.The dynamic simulation results of the steam exhaust system show that: under the temperature control mode,the response of the steam exhaust valve is fast,and the control effect of the average temperature of the primary circuit and the pressure of the main steam header is good at the initial stage of regulation,but the main steam pressure will rise again after the exhaust valve is closed.In the pressure control mode,the average temperature of the primary circuit and the main steam header pressure overshoot are large,but this control mode can effectively prevent the secondary rise of the main steam pressure.The integrated control mode can respond to the primary coolant temperature quickly,and effectively restrain the main steam pressure from being too high.The system economy under the pressure mode is better than that under the temperature mode and the integrated mode.