Combustion Engineering, Inc.

Abb Combustion Engineering Nuclear Power, Inc.

James E Robertson

Stephen J Wilkosz

Deva R Chari

A feedwater control system and method for a pressurized water reactor steam generating system having first and second output signals. The first output signal is determined by first and second input signals, and, when combined with a third input signal automatically controls at least one feedwater pump and first designated valves which regulate water flow from the one or more feedwater pumps to a steam generator when a steam generator steam load and reactor are operating at a first predetermined power level. The first input signal is determined by a downcomer feedwater flow differential pressure. The second input signal is determined by a reactor power level. The third input signal is determined by a steam generator level. The second output signal, determined by a steam generator water level, automatically controls at least one startup feedwater control valve when the steam generator steam load and the reactor are operating at a second predetermined power level. In a preferred embodiment, the first designated valves include at least one economizer feedwater control valve and at least one downcomer feedwater control valve. Also, in a preferred embodiment, the first predetermined power level is between about 5 and about 20 percent, and the second predetermined power level is between zero and about 5 percent.

Feedwater control over full power range for pressurized water reactor

The operator of a nuclear steam supply system manually selects a lineup of either one, two, or three main feedwater pumps for normal reactor operation to generate power. This selection sets or resets a status latch for each pump, representative of intended pump operation. A system (RPCS) for implementing a step reduction in the power output of the reactor, includes an associated logic circuit which combines signals indicative of tripping of one or more pumps, with the pump status latches, to achieve the following outcomes: (a) with one pump selected, a trip of this one pump does not produce an RPCS trip demand signal (because the reactor will be tripped); (b) with two pumps selected, (i) a trip of one pump will produce an RPCS trip demand signal, whereas (ii) a trip of these two pumps will not produce an RPCS trip demand signal; (c) with three pumps selected, (i) a trip of one pump will not produce an RPCS trip demand signal (because the transient can be handled by the basic control system), (ii) a trip of two pumps will produce an RPCS trip demand signal, and (iii) a trip of three pumps will not produce an RPCS trip demand signal.

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South Glastonbury, CT, United States of America

James E Robertson