In-Pile Fuel Rod Temperature Sensor System
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Solution Overview
Problem
Current nuclear reactor systems lack direct monitoring of fuel rod internal temperatures during operation, relying on indirect inferences that lead to conservative assumptions and increased energy costs, as existing sensors cannot be placed within fuel rods to endure multiple fuel cycles without penetrating them.
Innovation Solution
A method involving an in-pile sensor system that directly measures internal fuel rod temperatures at multiple axial locations, using a resonant circuit or liquid metal thermometer to determine the maximum measured internal fuel rod temperature and peak clad temperature, which are then used to calculate the peak clad temperature based on heat transfer characteristics and coolant parameters.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If in-core sensors are used to measure power distribution, then radial and axial power distribution can be monitored, but direct monitoring of fuel rod internal temperatures is not achieved
Solution Approach 1:
The temperature sensor is placed inside the fuel rod, nested within the fuel assembly structure. The sensor housing is positioned within the fuel rod bore, allowing direct measurement of internal temperatures while maintaining the hierarchical structure of fuel rods within fuel assemblies within the reactor core.
Solution Approach 2:
A thermal conductor element serves as an intermediary between the fuel pellets and the temperature sensor. This thermal conductor transfers heat from the fuel pellets to the sensor, enabling indirect measurement of fuel temperature when direct contact is not feasible, while still providing accurate temperature data for protection systems.
2Reliability
If advanced fuel cladding materials are tested over several fuel cycles, then regulatory approval can be obtained, but critical data is only available after several years during post irradiation examination
Solution Approach 1:
Temperature sensors are installed in fuel rods during fuel assembly fabrication, before the fuel is irradiated. This preliminary installation allows continuous temperature monitoring throughout the fuel cycle and multiple cycles, providing critical data in real-time rather than waiting for post-irradiation examination after several years.
3Reliability
If conservative assumptions are made about fuel rod temperatures, then safety margins are maintained, but energy production costs increase
Solution Approach 1:
Real-time temperature data from sensors in the fuel rods provides feedback to the reactor protection system. This actual measurement feedback replaces conservative assumptions, allowing operators to optimize power levels and cooling parameters based on actual thermal conditions, thereby reducing unnecessary energy losses while maintaining safety through monitored thresholds.
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 allows for more accurate monitoring of critical temperatures, reducing the need for conservative assumptions and lowering energy production costs by enabling safer operation closer to safety limits, potentially improving energy generation efficiency by 28%.
Implementation Method 1
using a resonant circuit or liquid metal thermometer to determine the maximum measured internal fuel rod temperature
Implementation Method 2
using a resonant circuit or liquid metal thermometer to determine the maximum measured internal fuel rod temperature
Implementation Method 3
using a resonant circuit or liquid metal thermometer to determine the maximum measured internal fuel rod temperature
Implementation Method 4
determining the peak clad temperature based on heat transfer characteristics and coolant parameters
Implementation Method 5
determining the peak clad temperature based on heat transfer characteristics and coolant parameters
Data Source
AI summary
A system that provides a direct indication of peak fuel rod centerline temperature and peak fuel rod clad temperature than conventionally inferred from the power distribution by directly and continuously measuring the fuel temperatures of the fuel pellets in one or more of the hottest fuel elements in the core. The peak fuel rod clad temperature is then obtained from the maximum measured peak fuel rod centerline temperature in combination with the maximum coolant core exit temperature and the minimum coolant flow rate.