Graphitic Carbon Thermal Bridge for HTGR Fuel Block Heat Transfer
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Solution Overview
Problem
High temperature gas cooled nuclear reactors face inefficiencies due to the fuel channel gap and the use of low thermal conductivity gases like nitrogen, which reduces thermal transfer and overall reactor efficiency, and the immaturity of turbomachinery designs for helium coolant poses a significant commercial barrier.
Innovation Solution
Incorporating a thermal bridge with a high melting point, such as graphitic carbon powder, to fill the fuel channel gap and enhance heat transfer between the fuel element and the fuel channel, and using nitrogen as a coolant compatible with existing turbomachinery designs, which improves thermal conductivity and reactor efficiency without the need for increased coolant mass flow.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If nitrogen is used as coolant gas, then compatibility with existing turbomachinery is improved, but thermal transfer efficiency deteriorates due to lower thermal conductivity
Solution Approach 1:
The patent introduces a thermal bridge as an intermediary substance filling the fuel channel gap. This thermal bridge has high thermal conductivity and acts as a mediator to transfer heat from the fuel element to the nitrogen coolant, overcoming nitrogen's inherently low thermal conductivity while maintaining compatibility with existing turbomachinery designs.
Solution Approach 2:
The patent employs a composite approach by combining the thermal bridge material with the nitrogen coolant system. The thermal bridge serves as a thermal conduit that complements the nitrogen coolant, creating a hybrid heat transfer system that leverages both the chemical inertness and turbomachinery compatibility of nitrogen and the high thermal conductivity of the thermal bridge material.
2Ease of manufacture
If fuel channel gap is maintained for manufacturing tolerance, then assembly flexibility is improved, but thermal transfer deteriorates due to increased thermal resistance
Solution Approach 1:
The thermal bridge acts as an intermediary that fills the fuel channel gap while maintaining the gap's functional benefits. It provides a high thermal conductivity pathway through the gap region, converting the gap from a thermal barrier into a controlled thermal management zone that preserves assembly flexibility while enhancing heat transfer.
Solution Approach 2:
The thermal bridge can be implemented as a porous or particulate material that fills the fuel channel gap. This porous structure allows the thermal bridge to conform to manufacturing tolerances and assembly variations while maintaining continuous thermal contact with both the fuel element and the coolant, thus preserving assembly flexibility without compromising thermal transfer.
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 thermal bridge significantly improves heat transfer from the fuel element to the coolant, enhancing reactor efficiency and reducing the temperature difference across the fuel channel gap, thereby achieving higher thermal efficiencies compared to helium coolant without a thermal bridge and more efficient than nitrogen coolant without one.
Implementation Method 1
the thermal bridge thermally linking the fuel element and the fuel channel, wherein the thermal bridge comprises a melting point greater than the working temperature of the reactor fuel block, thereby improving thermal transfer from the fuel element to the fuel block
Implementation Method 2
a coolant gas is flowed through the coolant channels in order to absorb heat generated by the fuel element in use
Data Source
AI summary
A thermal bridge for improving thermal transfer between a fuel element to a fuel block wherein there is provided a high temperature gas cooled nuclear reactor fuel block comprising a fuel channel and a coolant channel wherein the fuel channel comprises a fuel element, the fuel channel further comprising a thermal bridge thermally linking the fuel element and the fuel channel, wherein the thermal bridge comprises a melting point greater than the working temperature of the fuel block, thereby improving thermal transfer from the fuel element to the fuel block, thereby improving thermal transfer to the coolant channel.