Canoe-Shaped Spring Spacer Grid for Nuclear Fuel Rod Wear
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Solution Overview
Problem
Current spacer grids in nuclear fuel assemblies cause fretting wear of fuel rods due to flow-induced vibrations and irradiation growth, leading to damage from irregular contact and abrasion, despite attempts to enhance thermal performance and maintain surface contact.
Innovation Solution
An anti-fretting wear spacer grid with canoe-shaped springs that provide extended linear contact from initial to final contact, featuring a flat fuel rod-contacting part, curved connecting part, and obliquely formed legs to maintain constant contact surface shape and reduce wear.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional springs are used in spacer grids, then the fuel rods are supported and positioned, but fretting wear occurs on the fuel rod surfaces due to flow-induced vibrations and irregular contact
Solution Approach 1:
The spring contact surface is designed with a curved shape matching the fuel rod curvature, enabling surface contact instead of point contact. This curved contact surface distributes the contact pressure and prevents fretting wear by maintaining continuous surface contact during flow-induced vibrations
Solution Approach 2:
The spring geometry is modified with specifically designed parameters including contact surface curvature radius, leg angle, and leg length to optimize the contact characteristics. These parameter changes ensure the spring maintains surface contact with the fuel rod while providing adequate support force
2Reliability
If the spring contact surface is curved to match fuel rod curvature, then surface contact is achieved, but manufacturing precision becomes more difficult to maintain
Solution Approach 1:
The design specifies precise geometric parameters for the curved contact surface, including curvature radius and arc length, that can be accurately controlled during manufacturing. These parameter definitions enable consistent reproduction of the contact surface geometry while maintaining the curved shape necessary for surface contact
3Object-affected harmful factors
If linear contact is extended from initial to final contact, then fretting wear depth is reduced, but the spring structure becomes more complex
Solution Approach 1:
The curved contact surface naturally extends linear contact from initial to final contact by matching the fuel rod curvature. This geometric approach achieves extended linear contact without requiring complex mechanical structures, as the curvature itself enables the prolonged surface contact necessary to reduce fretting wear depth
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 canoe-shaped springs significantly reduce fretting wear depth and maintain contact surface integrity throughout the fuel rod's manufacturing and operational life, minimizing abrasion and damage from irregular contact.
Implementation Method 1
each of the canoe-shaped springs having a given elastic force so as to support the fuel rod together with the dimples
Data Source
AI summary
The present invention relates to an anti-fretting wear spacer grid having a plurality of canoe-shaped springs formed thereon, wherein each of the canoe-shaped springs includes: a fuel rod-contacting part having a flat surface having a predetermined longitudinal length so as to have linear contact with the fuel rod; a curved face-connecting part formed on the upper and lower portions of the fuel rod-contacting part; a leg-connecting part formed on the end portion of the curved face-connecting part; and legs each being formed of a plate shape having a predetermined length and connecting the both sides of the leg-connecting part with one unit grid cell surface.