Spacer Grid Spring Conformal Curvature for Fuel Rod Support
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Solution Overview
Problem
Conventional spacer grid springs in nuclear fuel assemblies experience stress concentration, fretting wear, and reduced supporting performance due to inadequate conformal contact and elastic behavior, leading to potential fuel rod damage and reduced thermal performance.
Innovation Solution
The spacer grid spring is optimized with a shape that includes upper and lower plates with dimples, a spacer grid spring connecting these plates, and a conformal curvature that contacts the fuel rod, expanding the contact area and reducing plastic deformation, with bridges and supports designed to minimize twisting deformation and maintain uniform stress distribution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If the spacer grid spring uses a conventional design with limited conformal contact, then the structure is simpler, but the contact area with the fuel rod is insufficient causing stress concentration and fretting wear
Solution Approach 1:
The spacer grid spring incorporates a conformal curvature that matches the cylindrical shape of the fuel rod, transforming the contact interface from point/line contact to surface contact. This curvature design enables the spring to wrap around the fuel rod, significantly increasing the conformal contact area and distributing mechanical stresses more uniformly across the contact surface, thereby preventing stress concentration and fretting wear.
Solution Approach 2:
The invention modifies the geometric parameters of the spacer grid spring, specifically introducing a conformal curvature radius that matches the fuel rod diameter. This parameter change transforms the spring from a conventional flat or simple curved design to one that closely follows the fuel rod contour, optimizing the contact geometry to maximize surface area while maintaining structural integrity.
2Stability of the object's composition
If the spacer grid spring has high elasticity to expand contact area, then conformal contact is improved, but excessive plastic deformation may occur
Solution Approach 1:
The spacer grid spring features non-uniform thickness distribution along its length, with varying local properties optimized for different functional requirements. The spring has thicker sections for structural support and thinner sections for enhanced flexibility and conformal contact. This local quality variation allows the spring to achieve high elasticity in contact regions while maintaining sufficient strength in structural regions to prevent excessive plastic deformation.
Solution Approach 2:
The conformal curvature design distributes contact forces across a larger area of the spring, reducing peak stresses that would otherwise cause localized plastic deformation. The curved geometry allows the spring to deform elastically to match the fuel rod contour while the distributed stress field prevents any single point from exceeding the material's yield strength.
3Stress or pressure
If the spacer grid spring contacts the fuel rod at limited points, then the structure is simpler, but stress distribution is uneven causing fatigue and fretting wear
Solution Approach 1:
The conformal curvature of the spacer grid spring is designed to match the cylindrical geometry of the fuel rod, transforming discrete point contacts into continuous surface contact. This curvature matching ensures that the spring conforms to the fuel rod contour, creating uniform stress distribution across the entire contact interface and eliminating stress concentration zones that would lead to fatigue and fretting wear.
Solution Approach 2:
The invention changes the contact geometry parameters from point/line contact to surface contact by introducing a conformal curvature radius that matches the fuel rod diameter. This parameter transformation optimizes the contact interface to achieve uniform pressure distribution, reducing peak stresses and preventing fatigue failure while maintaining a relatively simple overall spring structure.
4Stability of the object's composition
If the spacer grid spring uses conventional support design, then manufacturing is easier, but twisting deformation occurs reducing supporting stability
Solution Approach 1:
The conformal curvature design inherently resists twisting deformation by distributing loads uniformly across the curved contact surface. The spring's curved geometry provides structural rigidity against torsional forces while maintaining the ability to deform elastically for conformal contact. This curvature-based structural design achieves supporting stability without requiring complex additional bracing or support elements that would complicate manufacturing.
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 design enhances the elastic behavior of the spacer grid spring, reducing fretting wear and ensuring stable support of fuel rods throughout their lifetime by improving contact pressure distribution and maintaining conformal contact, thus preventing damage and maintaining thermal performance.
Implementation Method 1
the elasticity of the spacer grid spring contacting the fuel rod is increased, the conformal contact area with a contact portion of the spacer grid spring contacting the fuel rod when the fuel rod is inserted into each cell of a spacer grid spring is expanded to realize uniform stress distribution, and excessive plastic deformation of the spacer grid spring can be reduced
Data Source
AI summary
A grid strap includes a spacer grid spring that increases the conformal contact area with a fuel rod of a nuclear fuel rod assembly. The shape of the spacer grid spring is optimized, thereby increasing the elasticity of the spacer grid spring contacting the fuel rod, expanding the conformal contact area with a contact portion between the spacer grid spring and fuel rod to obtain uniform stress distribution, and reducing excessive plastic deformation of the spacer grid spring. Further, magnitude and distribution of contact pressure between the fuel rod and the spacer grid spring are improved, thereby reducing the possibility of fretting wear caused by contact between the fuel rod and the spacer grid spring. Lastly, the elastic behavior region of the spacer grid spring is expanded, so that the fuel rod can be reliably supported until the fuel rod expires despite changes in the supporting conditions of the fuel rod.