Nuclear Fuel Assembly Threaded End Caps
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Solution Overview
Problem
Existing fuel assembly manufacturing processes for nuclear thermal propulsion are complex and prone to failure due to difficulties in connecting individual fuel elements end to end using methods like resistance welding and diffusion bonding.
Innovation Solution
A nuclear fuel assembly design featuring elongated shells with lattice structures, flow channels, and end caps with matching cross-sectional shapes, allowing for threadedly connected fuel elements that eliminate the need for resistance welding and enable axial movement during thermal expansion and contraction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If resistance welding or diffusion bonding is used to connect fuel elements end to end, then the fuel assembly can be constructed, but the manufacturing process becomes complex and prone to failure
Solution Approach 1:
The patent replaces complex thermal welding processes (resistance welding, diffusion bonding) with a simpler mechanical expansion and insertion system. Fuel elements are expanded axially to engage with adjacent elements mechanically, eliminating the need for difficult welding operations and their associated reliability issues.
Solution Approach 2:
The patent utilizes changes in the physical state and dimensions of fuel elements through thermal expansion and contraction. By controlling temperature parameters, fuel elements expand to engage with adjacent elements or contract to allow for insertion and assembly, simplifying the manufacturing process while ensuring reliable connections.
2Strength
If fuel elements are connected rigidly, then structural integrity is maintained, but thermal expansion and contraction during operation causes stress and potential failure
Solution Approach 1:
The patent introduces dynamic capability into the fuel assembly by allowing fuel elements to expand and contract axially during operation. The expansion joints and mechanical connection system accommodate these dimensional changes, maintaining structural integrity while adapting to thermal cycling conditions.
Solution Approach 2:
The patent explicitly accounts for and utilizes thermal expansion effects in the fuel element design and connection system. By designing expansion joints and flexible mechanical connections, the system accommodates the natural thermal expansion and contraction of fuel elements during reactor operation, preventing stress buildup and potential failure.
3Strength
If complex welding processes are used to ensure strong connections, then joint strength is achieved, but the manufacturing time and complexity increase
Solution Approach 1:
The patent replaces complex thermal welding processes with simpler mechanical expansion and insertion operations. The strong connections are achieved through controlled mechanical engagement of expanded fuel elements rather than through complex welding procedures, reducing manufacturing complexity while maintaining joint strength.
Solution Approach 2:
The patent performs preliminary expansion of fuel elements before final assembly and insertion into the reactor core. This preliminary action prepares the fuel elements for easy mechanical connection without requiring complex welding operations during the assembly process, thereby reducing overall manufacturing complexity.
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 solution provides a robust and reliable fuel assembly construction method that simplifies the assembly process, reduces the risk of failure, and allows for material gradients along the fuel assembly's axial length, optimizing performance and efficiency in nuclear thermal propulsion systems.
Implementation Method 1
end caps with matching cross-sectional shapes, allowing for threadedly connected fuel elements
Implementation Method 2
allowing for threadedly connected fuel elements that eliminate the need for resistance welding and enable axial movement during thermal expansion and contraction
Data Source
AI summary
A nuclear fuel assembly for a nuclear reactor core, the fuel assembly having at least one fuel element including an elongated shell defining an interior volume, a lattice structure disposed within the interior volume, at least one flow channel extending through the lattice structure, at least one lattice site disposed in the lattice structure, and at least one fuel compact disposed within a corresponding one of the at least one lattice site, a first end cap including a boss having a first cross-sectional shape, the first end cap being affixed to a first end of the shell, and a second end cap including a first bore having a second cross-sectional shape, the second end cap being affixed to a second end of the shell, wherein the first cross-sectional shape of the boss is the same as the cross-sectional shape of the bore.