Vase-like Compression Spring for Nuclear Fuel Rod Stability
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Solution Overview
Problem
Existing nuclear fuel rod assembly designs face issues with stress concentration and reduced stability due to irregular spring forces from clip type compression springs, leading to potential damage and decreased productivity.
Innovation Solution
A vase-like compression spring with incised portions is used, which expands to fit snugly within the cladding tube, providing a constant force distribution and increased internal volume to accommodate fission gases, enhancing burn-up performance and mechanical integrity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a coil type compression spring is used to compress fuel pellets, then the fuel pellets are prevented from moving and damage, but buckling of the spring may occur during assembly reducing productivity and welding quality
Solution Approach 1:
The compression spring is segmented into multiple radial blades that are separated by gaps. This segmentation prevents the spring from buckling as a single coil structure while maintaining the compression function. The segmented design allows the spring to flex radially without the buckling issues that affect coil-type springs during assembly operations.
2Reliability
If a compression spring is inserted into the cladding tube, then fuel pellets are supported, but the spring occupies internal volume reducing space for fission gases
Solution Approach 1:
The compression spring is designed as a thin-walled hollow cylindrical structure with radial blades. This thin-film approach minimizes the material volume occupied by the spring while maintaining its structural integrity and compression function. The hollow cylindrical design with thin walls provides the necessary mechanical support for fuel pellets while maximizing the internal volume available for fission gases.
3Reliability
If a compression spring applies force to fuel pellets, then pellets are held in position, but irregular spring forces cause stress concentration on the cladding tube
Solution Approach 1:
The spring structure features localized radial blades that distribute compression forces evenly across the fuel pellet surfaces and cladding tube inner wall. Each blade acts as a localized support element, creating uniform pressure distribution rather than concentrated point loads. This local quality approach ensures stable fuel pellet positioning while preventing stress concentration on the cladding tube structure.
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 vase-like compression spring ensures stable assembly and operation by evenly distributing forces, preventing buckling and stress concentration, thus improving the fuel rod's burn-up performance and mechanical integrity.
Implementation Method 1
an elastic means inserted into the cladding tube in such a manner as to be disposed between the upper end plug and the fuel pellets, for elastically supporting the fuel pellets by using a given elastic force generated therefrom
Data Source
AI summary
The present invention relates to a fuel rod of a nuclear fuel assembly having a vase-like compression spring adapted to increase the internal volume thereof wherein when the vase-like compression spring is inserted into a cladding tube, it has a relatively smaller volume occupied inside the fuel rod when compared with the existing coil type compression spring, such that the vase-like compression spring can ensure a sufficient space portion receiving the fission gases generated during the operation of the fuel rod, thereby increasing the burn-up performance of the fuel rod and the mechanical integrity thereof.