OPDT Signal Processing for Nuclear Reactor Margin Optimization
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Solution Overview
Problem
Unwanted Over Power Delta Temperature (OPDT) actuations in nuclear reactors lead to reduced power operations due to temperature streaming and incomplete mixing of reactor coolant flow, causing fluctuations and potential false alarms or tripping.
Innovation Solution
Applying filtering to the hot leg temperature signal and lead/lag compensation to the cold leg temperature signal, with the turbine runback activated when the temperature difference exceeds a set point, allowing for higher lag time constants and reduced measurement fluctuations without affecting Over Temperature Delta Temperature (OTDT) responses.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If lead/lag compensation is applied to the hot leg temperature signal, then the response speed of the OPDT system is improved, but measurement fluctuations are amplified
Solution Approach 1:
The patent separates the signal processing paths for hot leg and cold leg temperatures. Lead/lag compensation is applied only to the cold leg temperature signal, while the hot leg temperature signal undergoes filtering without lead/lag compensation. This segmentation prevents amplification of measurement fluctuations while maintaining system response speed.
Solution Approach 2:
Different signal processing treatments are applied to different parts of the temperature measurement system. The cold leg temperature signal receives lead/lag compensation to improve response, while the hot leg temperature signal receives only filtering to reduce fluctuations. This local differentiation resolves the contradiction by optimizing each signal path according to its specific characteristics.
2Reliability
If filtering is applied to reduce measurement fluctuations, then the reliability of temperature measurement is improved, but the response time of the system increases
Solution Approach 1:
The patent divides the signal processing into two distinct paths: filtering is applied to the hot leg temperature signal to reduce fluctuations, while lead/lag compensation is applied to the cold leg temperature signal to maintain response speed. This segmentation allows each signal to be optimized independently, resolving the trade-off between reliability and response time.
Solution Approach 2:
The cold leg temperature signal acts as an intermediary that provides lead/lag compensation to compensate for the lag introduced by filtering the hot leg temperature signal. This intermediary processing maintains overall system response time while allowing aggressive filtering of the hot leg signal to improve measurement reliability.
3Reliability
If turbine runback is activated to prevent unwanted OPDT actuations, then reactor safety is improved, but power output is reduced
Solution Approach 1:
The patent implements a feedback mechanism where the OPDT system monitors temperature differences and activates turbine runback only when necessary to prevent unwanted actuations. By improving the accuracy and reliability of temperature measurements through selective filtering and compensation, the system reduces false positives, thereby maintaining safety while minimizing unnecessary power reductions.
Solution Approach 2:
The patent modifies the parameters of temperature signal processing (filtering characteristics and lead/lag compensation) to optimize the balance between safety and productivity. By adjusting these parameters, the system achieves more reliable detection of actual temperature excursions, reducing spurious OPDT actuations and their associated power output reductions while maintaining adequate safety margins.
Data Source
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AI summary
Overpower and overtemperature turbine runback and reactor trip (OPDT, OTDT) on pressurized water reactors (PWR) use the temperature difference between hot and cold leg temperature measurements. The difference between filtered hot leg temperature and lead/lag compensated cold leg temperature is used to maximize OPDT margin to hot leg fluctuations, while enabling safety margin increase for secondary accidents mitigated OPDT.