Nuclear Fuel Rod Retainer Spring Installation Method
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Solution Overview
Problem
The existing methods for maintaining fuel pellets under compression in a nuclear fuel rod are complex, costly, and difficult to automate due to the intricate design of the coil spring retainer and installation tooling, which complicates the assembly process.
Innovation Solution
A method involving an elongated retainer spring with distinct diameter sections for an interference and clearance fit is used, where a tool with matching sections is inserted to apply axial preload, allowing for simplified installation and automation by reducing the complexity of the spring and tooling design.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a coiled spring retainer with torsion application features is used, then the fuel pellets can be maintained under compression, but the installation process becomes complex and time-consuming
Solution Approach 1:
The patent removes the complex torsion application features from the spring design. Instead of requiring torsion to reduce coil diameter for insertion, the spring is designed with a constant diameter that fits directly into the fuel rod without requiring complex installation tooling or torsion application steps.
Solution Approach 2:
The spring is divided into two distinct sections: an upper coiled section with constant diameter for direct insertion, and a lower solid section that provides the compression force. This segmentation eliminates the need for torsion features while maintaining the compression function.
2Volume of moving object
If torsion is applied to reduce spring coil diameter for insertion, then the spring can be located inside the fuel rod, but the installation process becomes cumbersome and difficult to automate
Solution Approach 1:
The patent eliminates the torsion application step entirely from the installation process. The spring is designed with a constant diameter that allows direct insertion into the fuel rod without requiring torsion tools or complex manipulation steps, thereby enabling automation.
3Reliability
If multiple spring features (tang, wafer, partial coil) are incorporated, then the spring can be retained in position, but the manufacturing cost and production difficulty increase
Solution Approach 1:
The patent removes complex retention features such as tangs, wafers, and partial coils from the spring design. Instead, the spring uses a simple constant diameter configuration that is easily manufactured and requires minimal additional components, reducing both manufacturing complexity and cost.
4Manufacturing precision
If the installation tool requires precise positioning and torsion maintenance, then the spring can be installed correctly, but the assembly time increases
Solution Approach 1:
The patent eliminates the need for precise tool positioning and torsion maintenance during installation. The spring's constant diameter design allows for simple insertion without requiring complex alignment or torsion application, significantly reducing assembly time while maintaining proper installation precision.
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 method enables efficient and cost-effective axial preload maintenance of fuel pellets within the fuel rod, simplifying the installation process and allowing for manual or automated assembly, while maintaining the required compression without the need for intricate spring features or tooling.
Implementation Method 1
a fuel column retainer using a coiled spring to maintain the fuel pellets under compression within the nuclear fuel rod
Implementation Method 2
the large diameter section of a size for an interference fit with the interior diameter of the tube
Data Source
Figure 1~3
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Figure 6~7
AI summary
A method for installing a locking retainer in a tube to maintain internal components within the tube under compression comprising the steps of: a) providing an elongated retainer spring having large and small diameter sections with the large diameter section of a size for an interference fit with the interior diameter of the tube and the smaller diameter section of a size having a clearance with the interior diameter of the tube; b) inserting a smaller diameter section of an elongated tool into the larger diameter section of the elongated retainer spring; c) engaging a transition between the smaller and larger diameter sections of the tool against a transition between the larger and smaller diameter sections of the elongated retainer spring; d) inserting the combined tool and retainer spring into an open end of the tube containing internal components with an end of the smaller diameter section of the retainer spring entering the tube first; e) advancing the combined tool and retainer spring within the tube to compress the smaller diameter spring against an adjacent internal component until an end of the tool engages the adjacent internal component enabling the spring to apply a selected axial preload on the internal components in the tube; and f) withdrawing the tool from the retainer spring while maintaining the larger diameter section of the retainer spring in engagement with the interior diameter of the tube to maintain the axial preload on the internal components.