State of the Art Report for Steam Pressure Control Systems of Boiler and Nuclear Plants

Preceding techniques and patents for the steam pressure control system of boilers and nuclear power plants are described in this report. This reference information will be utilized to develop the steam pressure control system of SMART that is an integral reactor developed by KAERI for electric power generation and desalination. The control method of the boiler can be categorized into turbine following control, boiler following control, and coordinated turbine-boiler control. Traditionally the turbine following control system has been utilized for the once-through boilers. The coordinated turbine-boiler control system where the disadvantages of the turbine following control system are improved was introduced for the once-through boilers recently. In BWR (Boiling Water Reactor) plants the reactor power is first changed as the load demand signal from the grid system and then the turbine-generator response follows reactor response. On the contrary, in the case of PWR (Pressurized Water Reactor) plant, turbine-generator power is first changed as the load demand signal from the grid system and then the reactor response follows turbine-generator response. The coordinated control system was initially used in the nuclear power plant developed by the Babcock and Wilcox Company where the superheated steam was generated from the once-through steam generators. A simplified turbine following control system was suggested for the nuclear power plant with once-through steam generators in the patent registered in 1990. The once-through steam generators of SMART produce the superheated steam and include less secondary inventory than conventional nuclear plants during normal power operating mode. It is necessary to satisfy load-following requirement and control the overall plant parameters such as reactor power, feedwater flow rate, and steam pressure stably during power changing operation. To achieve this aim, the overall plant control system should be correctly organized and each sub-control system should be optimized