Fuel Rod Sensor System Inductive Coupling
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Solution Overview
Problem
Current sensors for monitoring centerline fuel temperature, fuel pellet stack elongation, and internal fuel rod pressure in nuclear reactors have limited sensitivity, necessitating an improvement in measurement accuracy.
Innovation Solution
A sensor system comprising a wireless interrogator and a passive sensor component with a linear differential variable transformer (LVDT) core, which moves in conjunction with fuel pellet stack expansion or contraction, and temperature changes, allowing for enhanced sensitivity in monitoring fuel rod characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a passive sensor component with inductor and capacitor is used to monitor fuel rod characteristics, then the sensor can operate wirelessly within the fuel rod, but the measurement sensitivity is limited
Solution Approach 1:
The sensor system is divided into two separate components: a passive sensor component (inductor, capacitor, ferrite core) installed within the fuel rod that remains simple and minimally intrusive, and an external interrogator system that performs the complex signal processing and measurement functions. This segmentation allows the internal sensor to maintain simplicity while achieving high measurement sensitivity through the external system.
Solution Approach 2:
An external interrogator system acts as an intermediary between the simple passive sensor component inside the fuel rod and the measurement/analysis functions. The interrogator wirelessly communicates with the sensor component, excites the resonant circuit, and processes the response signals to extract precise measurements of temperature, elongation, and pressure, thereby achieving high sensitivity without complicating the internal sensor structure.
2Measurement precision
If a ferrite core is passed through the inductor to detect fuel pellet stack elongation, then elongation measurement is enabled, but the overall sensor sensitivity remains limited
Solution Approach 1:
The system utilizes changes in the resonant frequency and impedance parameters of the LC circuit in response to mechanical stress, temperature variations, and ferrite core position changes. By precisely measuring these parameter changes through the external interrogator, the system achieves high sensitivity for detecting elongation, temperature, and pressure without requiring additional sensor components.
Solution Approach 2:
The passive sensor component serves multiple functions simultaneously: the inductor and capacitor form a resonant circuit that responds to temperature changes, the ferrite core detects fuel pellet stack elongation through position changes, and the overall circuit impedance changes reflect internal pressure variations. This multi-functionality is achieved with a minimal component set, avoiding the need for separate sensors for each measurement type.
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
The system provides increased measurement sensitivity for centerline fuel temperature, fuel pellet stack elongation, and internal fuel rod pressure, enabling more accurate monitoring and reducing common temperature-related drift issues.
Implementation Method 1
The sensor operates by passing current through the transmitter 22, which causes it to generate an interrogation signal that is received by and excites the passive component 10
Implementation Method 2
The passive component 10 includes an inductor 12 and a capacitor 14 which together form a resonant circuit
Implementation Method 3
In some methodologies, a ferrite core coupled to a stack of fuel pellets is passed through the inductor 12, which results in changes in the inductance of the inductor 12 as the stack of fuel pellets elongates
Data Source
AI summary
A sensor system for a fuel rod including a fuel pellet stack, the sensor system including a wireless interrogator disposed outside the fuel rod and a passive sensor component disposed within the fuel rod. The passive sensor component includes a receiver structured to receive an interrogation signal and output an excitation signal in response to receiving the interrogation signal, a reference transmitter structured to output a reference signal to the reference receiver in response to the excitation signal, a sensing transmitter structured to output a sensing signal to the sensing receiver in response to the excitation signal, and a core at least partially disposed within the sensing transmitter and coupled to move in conjunction with expansion or contraction of the fuel pellet stack, to move based on changes in pressure within the fuel rod, or to change temperature based on temperature changes within the fuel rod.