PWR Reactor Stretchout Control via Coolant Temperature
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Solution Overview
Problem
During the 'stretchout' phase of a pressurized water nuclear reactor, where boron concentration is low, conventional control methods struggle to maintain reactor stability and maneuverability due to axial xenon oscillations and limited power regulation, restricting the ability to adjust power in response to electrical energy consumption variations and requiring increased operator surveillance.
Innovation Solution
A method that controls the axial distribution of power through control rod cluster movements while allowing the mean temperature of the primary coolant to vary freely within a defined range, rather than adhering to a reference temperature profile, enabling more flexible power management and compensation for xenon growth.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional control methods are used during stretchout phase, then reactor stability is maintained, but maneuverability and power regulation capability deteriorate
Solution Approach 1:
The invention transitions from static control (fixed reference temperature profile) to dynamic control (adaptive temperature profile that varies based on real-time reactor conditions). The control system continuously adjusts the temperature profile based on measured parameters, enabling the reactor to respond dynamically to load variations and xenon oscillations while maintaining stability.
Solution Approach 2:
The invention changes the control parameter from a fixed reference temperature profile to a variable temperature profile that adapts to changing reactor conditions. By allowing the setpoint temperature to vary based on actual measurements and reactor state, the system gains maneuverability without sacrificing stability.
2Temperature
If reference temperature profile is followed during stretchout, then temperature control is maintained, but power adjustment capability deteriorates
Solution Approach 1:
The control system dynamically adjusts the temperature profile based on real-time reactor conditions rather than following a predetermined fixed profile. This enables the system to adapt power output to match electrical energy consumption variations while maintaining appropriate temperature control.
Solution Approach 2:
The invention implements feedback control where the actual reactor temperature and power measurements are continuously compared with desired values, and the control actions are adjusted based on the deviations. This feedback mechanism enables both temperature control and power adjustment capability.
3Stability of the object's composition
If control rod cluster movements are avoided during stretchout, then axial xenon oscillations are controlled, but power regulation deteriorates
Solution Approach 1:
The invention uses the primary coolant temperature as an intermediary control parameter to achieve power regulation without moving control rod clusters. By adjusting the coolant temperature, the system indirectly controls reactor power and compensates for xenon growth, maintaining axial power distribution stability while enabling power regulation.
Solution Approach 2:
The invention replaces the mechanical control rod cluster movement system with a thermal control system that uses coolant temperature adjustment. This substitution eliminates the need for control rod movements during stretchout while maintaining power regulation capability through thermal means.
4Power
If boron concentration is reduced to near zero during stretchout, then reactivity compensation is achieved, but control flexibility deteriorates
Solution Approach 1:
The invention changes the control parameter from boron concentration (which is fixed near zero during stretchout) to primary coolant temperature. By making temperature the active control parameter instead of boron concentration, the system achieves reactivity compensation while maintaining control flexibility through temperature adjustments.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach enhances reactor maneuverability and power regulation during the 'stretchout' phase, allowing for maximum power exploitation and improved frequency adjustments, reducing the need for control rod cluster movements and enabling longer operation at maximum power without adhering to a fixed temperature profile.
Implementation Method 1
a primary circuit with a core producing thermal power and a steam generator heat exchanger
Implementation Method 2
a steam generator heat exchanger
Implementation Method 3
steam generator heat exchanger
Data Source
AI summary
A method for controlling a pressurized water nuclear reactor is provided, including core producing thermal power, sensors for acquiring the mean temperature of the primary coolant and for calculating the thermal power, actuators for controlling the axial distribution of power, the control method including:a first control phase for controlling the reactor during normal operation by controlling the mean temperature of the primary coolant so as to make it correspond to a reference temperature profile (Pref) dependent on the thermal power of the reactor; anda second control phase, referred to as stretchout, that occurs after normal operation of the reactor in order to control the reactor in stretchout by controlling the axial distribution of power, the mean temperature varying freely in a temperature range delimited by an upper limit and a lower limit.