Automatic steam generator control at low power

Abstract

The steam generator water level, the feed water temperature, and the reactor power are continuously measured and a level signal (76), a temperature signal (78), and a power signal (80) commensurate with these measurements are respectively generated. From the power signal and the temperature signal, a target flow signal (84) is generated corresponding to the feedwater flow rate that would produce a stable steam generator water level at the steady state condition of the power signal and the temperature signal. The level signal is compared to a level signal setpoint (54) and a resulting level error signal (86) is generated. The level error signal is adjusted by a gain factor (88) that is dependent on the temperature signal to produce an adjusted level error signal (90). The feedwater flow through the bypass valve is then controlled in response to the target flow signal (84') and the adjusted level error signal. In a preferred implementation of the invention, the transition between low power control using the bypass valve and high power control using the main feed water valve is accomplished by generating a main valve position signal (118), and generating an enable signal (124) when the power signal is within a desired transition power range. When the power is in the transition range, the feedwater flow through the bypass valve is ramped down or up in response to the target flow signal, the adjusted level error signal, and the main valve position signal, as the main feedwater flow increases or decreases.

Dependencies are inferred from the claim text.