PWR Axial Offset Control via Parallel Boration Prediction
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Solution Overview
Problem
Pressurized water reactors face challenges in controlling axial offset (AO) during power maneuvers, particularly in preventing xenon oscillations, as existing methods are complex, inaccurate, and not fast enough, especially in reactors without movable heavy banks.
Innovation Solution
A method for controlling a pressurized water reactor that involves acquiring measurable reactor process variables and obtaining simulated non-measurable variables, calculating future axial offsets for different boration/dilution actions, determining the optimal action based on reference axial offsets, and commanding the boration/dilution action in the primary cooling circuit.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If manual boration/dilution function is used to keep axial offset, then reactor operation is maintained, but control response is slow (around 5 min) and inaccurate
Solution Approach 1:
The system performs preliminary calculation of required boration/dilution masses before actual injection is needed. By predicting future axial offset values and pre-calculating the necessary correction masses, the system eliminates the slow trial-and-error process of manual control, achieving both fast response and accurate control.
Solution Approach 2:
The system continuously monitors actual axial offset measurements and compares them with predicted values. This feedback loop allows the system to adjust boration/dilution actions in real-time, improving both the speed and accuracy of control response compared to manual methods.
2Measurement precision
If phenomenological method with test injection is used, then operators can see the reaction, but the procedure is difficult, inaccurate and not fast enough for power maneuvering
Solution Approach 1:
Instead of performing test injections to determine control effectiveness, the system pre-calculates the required boration/dilution masses based on predicted axial offset values. This eliminates the time-consuming trial-and-error process while maintaining or improving accuracy through physics-based predictions.
Solution Approach 2:
The system creates a virtual copy of the reactor state through simulation models, allowing operators to predict the effects of boration/dilution actions before implementing them. This virtual experimentation replaces physical test injections, providing accurate predictions instantly without the time and complexity of actual test runs.
3Reliability
If pre-calculation of injection masses is performed, then control accuracy may be improved, but the reactor physics complexity makes pre-calculation difficult
Solution Approach 1:
The system uses simulation models that create virtual copies of the reactor core, allowing complex physics calculations to be performed in silico rather than requiring real-time complex calculations during actual control operations. This pre-computation approach simplifies the control system while maintaining high accuracy.
Solution Approach 2:
The system performs complex physics-based pre-calculations of boration/dilution masses before control actions are needed. By preparing these calculations in advance using simplified models, the actual control execution becomes much simpler and faster, resolving the contradiction between accuracy and complexity.
Data Source
AI summary
A method for controlling a pressurized water reactor, computer program product and control system, the pressurized water reactor includes a reactor core and a primary cooling circuit. The primary cooling circuit includes a primary cooling medium, which includes: acquiring a plurality of measurable reactor process variables and obtaining a plurality of non-measurable reactor process variables. The method further includes calculating future axial offsets at the end of a predetermined prediction time interval for a plurality of different possible boration/dilution actions based on the plurality of measurable reactor process variables and the plurality of non-measurable reactor process variables, the axial offset being a normalized difference between power of an upper half of the reactor core and a lower half of the reactor core. The calculation of the future axial offset for each of the plurality of different possible boration/dilution actions is performed in parallel.