Fuel Rod Resonant Circuit Sensing Through Intact Cladding

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Solution Overview

Problem

Existing nuclear reactor sensors cannot directly monitor conditions within a nuclear fuel rod during reactor operation, and the testing of advanced fuel cladding materials is lengthy, requiring several years and only providing critical data during post-irradiation examinations.

Innovation Solution

A detection apparatus is placed within a fuel rod, comprising an electrical circuit apparatus with a resonant circuit and a pressure/temperature transmission apparatus, which communicates wirelessly with an interrogation apparatus outside the fuel rod, allowing for the monitoring of temperature, elongation, and ambient pressure without penetrating the fuel rod cladding.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If in-core sensors are used to measure radioactivity and power distribution, then measurement capability is improved, but the sensors cannot directly monitor conditions within the fuel rod itself

Engineering Contradiction:
Improvepower distribution measurementVSAvoidfuel rod internal condition data
Core Design Contradiction:
Measurement precisionVSLoss of information

Solution Approach 1:

The detection apparatus is nested within the fuel rod structure itself. The electrical circuit apparatus with resonant circuit is placed inside the fuel rod, allowing direct measurement of internal conditions (temperature, pressure, elongation) while the fuel rod remains intact. This nested configuration enables the system to obtain information from within the fuel rod without requiring external penetration or separate monitoring systems.

Inventive Principle:
Principle #7Nested doll (Nesting)

Solution Approach 2:

The patent replaces traditional mechanical sensor systems with a wireless resonant circuit system. Instead of using conventional sensors that require physical connections and signal leads, the invention uses an electrical circuit apparatus that generates resonant signals detectable by external interrogation equipment. This substitution eliminates the need for mechanical penetrations through the fuel rod cladding while maintaining measurement capability.

Inventive Principle:
Principle #28Mechanics substitution (Replace mechanical system)

2Ease of manufacture

If advanced fuel cladding materials are tested without in-pile monitoring, then testing can be performed, but critical data is only obtained during lengthy post-irradiation examinations taking several years

Engineering Contradiction:
Improvefuel cladding testing capabilityVSAvoidtesting duration
Core Design Contradiction:
Ease of manufactureVSLoss of time

Solution Approach 1:

The detection apparatus is installed within the fuel rod before irradiation testing begins. This preliminary installation of monitoring equipment allows continuous data collection during the testing process itself, rather than waiting for post-irradiation examination. The system captures critical information about temperature, pressure, and structural changes as they occur during reactor operation, eliminating the several-year waiting period for data acquisition.

Inventive Principle:
Principle #10Preliminary action

Solution Approach 2:

The resonant circuit system provides real-time feedback about fuel rod conditions during operation. The electrical circuit apparatus continuously monitors parameters and can transmit data about temperature, pressure, and elongation changes occurring during irradiation. This feedback mechanism enables researchers to observe material behavior under actual reactor conditions without delaying data acquisition until post-irradiation examination.

Inventive Principle:
Principle #23Feedback

3Reliability

If sensors are installed within the fuel rod, then real-time monitoring is enabled, but the fuel rod cladding integrity must be maintained without penetrations

Engineering Contradiction:
Improvereal-time monitoring capabilityVSAvoidsensor installation complexity
Core Design Contradiction:
ReliabilityVSDevice complexity

Solution Approach 1:

The patent replaces mechanical sensor installation methods with a wireless resonant circuit system. Instead of drilling holes or creating penetrations in the fuel rod cladding to install traditional sensors, the invention uses an electrical circuit apparatus that can be placed inside the fuel rod and communicates wirelessly through the cladding. The resonant circuit generates electromagnetic signals that can be detected externally, eliminating the need for physical penetrations and maintaining cladding integrity while enabling real-time monitoring.

Inventive Principle:
Principle #28Mechanics substitution (Replace mechanical system)

4Productivity

If traditional testing methods are used for fuel cladding materials, then testing can be performed, but critical operational data is unavailable during reactor operation

Engineering Contradiction:
Improvetesting efficiencyVSAvoidoperational condition data
Core Design Contradiction:
ProductivityVSLoss of information

Solution Approach 1:

The detection apparatus provides continuous feedback about fuel rod operational conditions during reactor operation. The electrical circuit apparatus monitors temperature, pressure, and elongation in real-time, transmitting data about the actual operational environment experienced by the fuel cladding materials. This feedback enables researchers to correlate material performance with specific operational conditions, providing critical information that was previously unavailable during the testing period.

Inventive Principle:
Principle #23Feedback

Solution Approach 2:

The monitoring system is installed in advance within the fuel rod before irradiation testing begins. This preliminary configuration ensures that data collection is already underway when the fuel rod is subjected to reactor conditions, capturing critical operational data as it occurs rather than relying on post-test analysis. The system is ready to record temperature, pressure, and structural changes from the moment irradiation begins.

Inventive Principle:
Principle #10Preliminary action

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

Enables real-time monitoring of fuel rod conditions, providing critical data during reactor operation and reducing the testing time for advanced fuel cladding materials, while maintaining the integrity of the fuel rod cladding.

Implementation Method 1

an electrical circuit apparatus (44) which is situated within an interior region (36) of the fuel rod (6) and which includes a resonant electrical circuit (50) that outputs a response pulse (78) having a frequency that is adjusted responsive to a change in ambient pressure within the interior region (36) of the fuel rod (6)

Methodology Applied
Scientific EffectPressure-induced frequency shift in resonant circuit: Resonance

Implementation Method 2

The electrical circuit apparatus (144) includes a temperature transmission apparatus (184) that detects the temperature of the fuel pellets (38) and that includes a ferritic rod (188) that is abutted with the fuel pellets (38) and that conducts heat from the fuel pellets (38)

Methodology Applied
Scientific EffectThermal conduction: Conduction (thermal)

Implementation Method 3

The electrical circuit apparatus (44) includes an elongation transmission apparatus (84) that detects an extent of elongation of the fuel pellets (38) and that includes a ferritic rod (88) that is abutted against the fuel pellets (38) and that transmits elongation of the fuel pellets (38)

Methodology Applied
Scientific EffectMechanical conduction: Mechanical Force

Data Source

PatentEP3721450B1Detection apparatus usable in a nuclear reactor, and associated method
Publication Date: 2025.04.30 WESTINGHOUSE ELECTRIC CORP
  • EP3721450B1 patent drawingFigure 1
  • EP3721450B1 patent drawingFigure 2~3
  • EP3721450B1 patent drawingFigure 4~6

AI summary

A detection apparatus includes a resonant electrical circuit supported within an interior of a nuclear fuel rod generates a response pulse in response to an excitation pulse and transmits the response pulse through a cladding of the fuel rod to another location within a reactor in which the fuel rod is housed and without any breach in the cladding. A characteristic of the response pulse is indicative of a condition of the fuel rod. The detection apparatus also includes a transmitter positioned outside the cladding, in the reactor, in the vicinity of the fuel rod and configured to generate the excitation pulse and transmit the excitation pulse through the cladding to the resonant electrical circuit. A receiver is supported within the reactor outside of the cladding and, in response to the response pulse, communicates a signal to an electronic processing apparatus outside of the reactor.