Nuclear Steam Generator Level Control Oscillation Prevention
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Solution Overview
Problem
In nuclear power plants with pressurized water reactors, frequent switching of the high-level priority control function in the feedwater control system leads to oscillation of the steam generator level, potentially causing reactor shutdown due to inadequate shutdown margins at high steam generator levels.
Innovation Solution
A steam generator level control system that includes a comparator, proportional integral control unit, high-level priority control signal generator, and receiver, which reduces the proportional integral control value after deactivating the high-level priority mode to prevent oscillation by controlling the main feedwater pump and feedwater control valve outputs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the high-level priority control function is frequently switched on/off when steam generator level changes, then the steam generator level can be controlled within the high range, but the steam generator level oscillates due to drastic switching of control signals
Solution Approach 1:
The system performs preliminary action by outputting a reduced proportional integral control value in advance before the high-level priority control mode is fully deactivated. This prevents the drastic switching of control signals that causes oscillation, by gradually transitioning the control output rather than making abrupt changes when switching between control modes.
2Speed
If the proportional integral control value is not reduced after deactivating high-level priority mode, then the control response is fast, but the steam generator level oscillates and may cause reactor shutdown
Solution Approach 1:
The system applies preliminary anti-action by reducing the proportional integral control value in advance before normal control mode fully engages. This counteracts the potential for oscillation and reactor shutdown by preemptively adjusting the control output to a safer level, preventing the harmful effect of drastic control signal switching.
3Ease of operation
If the high-level priority control mode is deactivated when steam generator level reaches 80%, then normal control is restored, but the control signal switches drastically causing level oscillation
Solution Approach 1:
When the steam generator level reaches 80% and high-level priority control mode is deactivated, the system performs preliminary action by outputting a reduced proportional integral control value. This gradual transition prevents the drastic switching of control signals that would otherwise occur when restoring normal control, thereby maintaining control signal stability.
Data Source
AI summary
Provided are a method and system for improving control of a steam generator level for preventing oscillation of the steam generator level in a nuclear power plant. In order to prevent oscillation of a steam generator level and resultant shutdown of a nuclear reactor, which may be caused when a high-level priority control function is frequently and repeatedly turned on/off as the steam generator level is excessively increased, by improving a feedwater control system in the nuclear power plant, a proportional integral control value may be controlled to be reduced, and thus, output while a certain condition is met after a high-level priority mode is deactivated or a signal instructing to enter the high-level priority control mode may be controlled not to be output.