Hydraulically Balanced Mixing Vane Spacer Grid
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Solution Overview
Problem
Conventional spacer grids in nuclear fuel assemblies experience hydraulic imbalance and coolant flow-induced vibration due to uneven mixing vane patterns, leading to fretting wear of fuel rods and reduced thermal performance.
Innovation Solution
A spacer grid with hydraulically balanced mixing vane patterns is designed, where the positions and directions of mixing vanes are arranged in uniform patterns parallel to standard lines passing through the center, ensuring symmetry and minimizing coolant flow-induced vibrations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If mixing vanes are arranged in conventional patterns to promote coolant mixing, then heat transfer performance is improved, but hydraulic imbalance and coolant flow-induced vibration occur
Solution Approach 1:
The patent applies asymmetry by introducing mixing vanes with non-uniform spacing and orientation angles that vary across different regions of the spacer grid. Specifically, mixing vanes are arranged with different spacing intervals in first and second regions, and with different orientation angles relative to the coolant flow direction, creating an asymmetric configuration that balances hydraulic forces while maintaining effective coolant mixing and heat transfer performance
2Temperature
If mixing vanes are added to enhance coolant mixing, then thermal performance improves, but coolant flow-induced vibration and fretting wear increase
Solution Approach 1:
The patent applies the counterweight principle by designing mixing vanes with specific orientation angles and spacing configurations that create hydraulic forces balancing each other out. The asymmetric arrangement of mixing vanes in different regions generates counterbalancing hydraulic moments that cancel out net vibration forces, thereby reducing coolant flow-induced vibration and preventing fretting wear of fuel rods while maintaining thermal performance enhancement
3Ease of manufacture
If uniform mixing vane patterns are used across the spacer grid, then manufacturing is simplified, but hydraulic imbalance occurs in central regions
Solution Approach 1:
The patent applies local quality by differentiating the mixing vane configuration across different regions of the spacer grid. Specifically, mixing vanes in the first region have different spacing intervals and orientation angles compared to those in the second region, with central mixing vanes having distinct characteristics from peripheral mixing vanes. This localized variation in mixing vane properties optimizes hydraulic balance in central regions while maintaining manufacturability through modular design principles
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 solution maintains hydraulic balance and reduces coolant flow-induced vibrations, enhancing the thermal performance and stability of the spacer grid by distributing hydraulic forces evenly around the center.
Implementation Method 1
a plurality of mixing vanes, integrated to inner strips inside the spacer grid, protruded to downstream of coolant flow, wherein positions and directions of the mixing vanes are formed in a pattern when facing to an upper plane of the spacer grid
Implementation Method 2
the spacer grid is equipped with a plurality of mixing vanes 8 (see FIGS. 2 and 3) that integrated to the strips inside, protruded to downstream of coolant flow and bent for surrounding the fuel rod 3 to promote heat transfer caused by mixing coolant around the fuel rod 3
Implementation Method 3
The spring 6 and the dimple 7 are contacted to the fuel rod 3 (see FIG. 1) to maintain the interval of the fuel rods 3 (see FIG. 1), arrange the fuel rods 3 at determined positions and fix the fuel rod 3 due to elasticity of the spring 6
Data Source
AI summary
Disclosed is a spacer grid assembly with mixing vanes supporting fuel rods of nuclear fuel assemblies and mixing coolant that flows around the fuel rods, and more particularly, a spacer grid equipped with mixing vanes that mix coolant flowing around fuel rods.The spacer grid with hydraulically balanced mixing vane patterns, in the spacer grid equipped with a strip dividing a plurality of unit grid cells and a plurality of springs, protruded in uniform directions of vertical and horizontal directions on a grid surface of the strip and supporting nuclear fuel rods, which includes: a plurality of mixing vanes protruded to the downstream of coolant on an upper end of the inner grid surface, wherein positions and directions of the mixing vanes are formed in regular patterns on the spacer grid. Thus, it can minimize coolant flow induced vibration of the spacer grid by balancing hydraulic load generated by the mixing vanes, around the center of the spacer grids.