| 摘要 |
Excessive primary cooldown and start up of the auxiliary feedwater system in a pressurized water reactor (PWR) following a reactor trip are avoided by switching to primary coolant Tavg programmed, main feedwater flow control in place of normal level programmed control. The Low Tavg set point at which the main feedwater isolation valves are closed is lowered below the no load Tavg temperature set point and the flow rate is decreased gradually to zero at a Tavg between these two set points. In addition, the low-low level set point at which the auxiliary feedwater system is started is lowered if possible, and/or the level signal is filtered, or the start signal delayed, to increase the margin to the low-low set point. |
