3D Printed Nuclear Fuel Spacer Grid Design
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Solution Overview
Problem
Conventional spacer grid manufacturing processes, relying on sheet metal working and welding, limit design freedom and result in reduced impact strength, particularly at end-of-life conditions, making it challenging to achieve sufficient seismic performance and mechanical integrity for nuclear fuel assemblies.
Innovation Solution
The use of 3D printing technology to manufacture spacer grids, excluding sheet metal working and welding, allows for enhanced design freedom and simplifies the manufacturing process, incorporating square grid cells with curved springs, flow channels, and mixing vanes that improve impact strength and reduce pressure drop.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If sheet metal working and welding processing are used to manufacture spacer grids, then manufacturing precision and structural integrity are maintained, but design freedom is limited and impact strength is reduced
Solution Approach 1:
The patent merges multiple separate manufacturing operations (sheet metal working, welding, assembly) into a single 3D printing process. The spacer grid is manufactured as an integrated structure where grid plates, grid springs, dimples, and mixing vanes are all formed in one additive manufacturing process, eliminating the need for separate welding and assembly operations.
Solution Approach 2:
The invention changes the manufacturing method from subtractive (sheet metal working) and joining (welding) processes to additive manufacturing. This parameter change enables complex geometries and optimized structures that cannot be achieved with conventional methods, thereby improving design freedom while simplifying the overall manufacturing process.
2Strength
If conventional welding processes are used to assemble grid plates, then structural integrity is maintained, but impact strength is reduced particularly at end-of-life conditions
Solution Approach 1:
The patent eliminates the welding process entirely by manufacturing the entire spacer grid as a single integrated component using 3D printing. The grid plates, grid springs, and other structural elements are formed as one monolithic structure, removing the weak points that would otherwise exist at weld joints and thereby improving both impact strength and seismic performance.
Solution Approach 2:
The invention utilizes metal powder materials in the 3D printing process to create a homogeneous microstructure throughout the spacer grid. This composite approach using metallic powders enables optimized material distribution and microstructure that enhances mechanical properties including impact strength and fatigue resistance under seismic conditions.
3Manufacturing precision
If sheet metal working is used to create grid springs and dimples, then manufacturing precision is maintained, but design freedom and geometric flexibility are limited
Solution Approach 1:
The invention transitions from conventional sheet metal forming processes to additive manufacturing, fundamentally changing the manufacturing parameter set. This enables the creation of complex three-dimensional geometries including optimized grid spring configurations, variable dimple patterns, and integrated mixing vanes with precise dimensional control, achieving both high geometric precision and design freedom.
Solution Approach 2:
The patent applies local quality optimization by enabling different geometric features and material properties at different locations within the spacer grid through 3D printing. Grid springs, dimples, and mixing vanes can be locally optimized for their specific functional requirements while maintaining overall structural integrity, something not achievable with uniform sheet metal working processes.
4Productivity
If multiple manufacturing steps including welding are used, then structural integrity is ensured, but manufacturing time and complexity increase
Solution Approach 1:
The patent consolidates multiple discrete manufacturing steps (cutting, forming, welding, assembly) into a single 3D printing operation. The spacer grid is manufactured as one integrated component in a single additive manufacturing process, eliminating all intermediate handling, fixture setup, and joining operations, thereby dramatically improving manufacturing efficiency and reducing process complexity.
Solution Approach 2:
The 3D printing process is self-service in nature, building the spacer grid layer by layer automatically without requiring external intervention for each feature. The machine autonomously creates complex geometries including grid springs, dimples, and mixing vanes in one continuous process, eliminating the need for multiple manual operations and reducing manufacturing complexity.
Data Source
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AI summary
Disclosed is a spacer grid of a nuclear fuel assembly, which may be manufactured using 3D printing with a high degree of design freedom with the exclusion of sheet metal working and welding processing and may simplify the structure, improve impact strength, and reduce pressure drop. The spacer grid of a nuclear fuel assembly of the present invention includes square grid cells (110) having respective inner walls (111) and constituting a square lattice structure, wherein each of the grid cells (110) includes: a plurality of springs (120) for elastically supporting a fuel rod, each of the plurality of the springs having a fixed end (121) along a vertical direction in each of the inner walls (111) and having a free end (122) by being curvedly provided in a horizontal direction from the fixed end (121); a plurality of flow channels (130) each provided in the vertical direction to the grid cells (110) ; and a plurality of mixing vanes (140) protrudingly provided in a downstream direction of coolant flow at end parts of the grid cells (110).