Nuclear Fuel Spacer Grid with Seamless Corner Straps
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Solution Overview
Problem
In pressurized water nuclear reactors, maintaining adequate support and heat transfer for fuel rods is challenging due to dimensional changes and vibrations, leading to corrosion fretting and potential cladding failure, while existing grid designs are complex and costly to manufacture.
Innovation Solution
A nuclear fuel assembly with a spacer grid featuring elongated interior intersecting straps and a bordering strap with overlapping sections and anti-snag projections, allowing for reduced pressure drop and improved heat transfer, and enabling manufacturing with longitudinal material and dies, simplifying production.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional grid designs with interleaved straps are used, then fuel rod support and spacing are maintained, but manufacturing complexity and cost increase
Solution Approach 1:
The patent merges multiple separate straps into a single integrated grid structure with continuous perimeter straps and interior support straps. This consolidation maintains the fuel rod support function while eliminating multiple welding joints and simplifying manufacturing, directly resolving the contradiction between reliability and complexity.
2Strength
If multiple welding joints are used in grid straps, then structural strength is achieved, but corrosion risk and manufacturing cost increase
Solution Approach 1:
The patent extracts and eliminates the welding joints from the grid structure by using a continuous perimeter strap design. This removal of welding joints eliminates the corrosion pathways that would exist at joint locations, while the continuous strap structure maintains structural strength through its integrated design.
3Manufacturing precision
If complex grid manufacturing processes are used, then precise fuel rod spacing is achieved, but production time and cost increase
Solution Approach 1:
The patent segments the grid manufacturing process into modular components (perimeter straps, interior support straps, spring-dimple assemblies) that can be fabricated separately and assembled efficiently. This segmentation enables parallel production and simplifies quality control, achieving precise fuel rod spacing without sacrificing manufacturing productivity.
Data Source
AI summary
A nuclear fuel assembly grid that has fuel rod support features that take up a substantial portion of the width of the corner fuel rod support cells. The nuclear fuel assembly grid has an outer strap that is joined around a corner of the grid to another outer strap segment and a mating inner strap end at the intersection with the inner strap. The juncture accommodates the width of the rod support feature, enables grid-to-grid anti-snag capabilities and facilitates the use of longitudinal feed materials and dies.