Nuclear Reactor Mixing Grid Trihedral Cell Deflector Design
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Solution Overview
Problem
Prior art mixing and spacing grids in nuclear reactor fuel assemblies suffer from high hydraulic resistance, which is unsuitable for fuel assemblies releasing much energy, and existing designs are difficult to manufacture and install due to complex geometries and potential contact with fuel elements.
Innovation Solution
A mixing grid design featuring a hoop with intersecting plates forming hexahedral and trihedral cells, where trihedral cells have deflectors bent towards hexahedral cells to enhance coolant flow agitation, and a second field of hexagonal cells with supports for fuel elements, reducing contact risks and improving coolant circulation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If complex deflecting elements are used to agitate coolant flow, then coolant mixing is improved, but device complexity and manufacturing difficulty increase
Solution Approach 1:
The mixing grid is divided into multiple simple plate elements arranged in a crosswise pattern, rather than using complex three-dimensional deflecting structures. Each plate is a simple flat element that is easy to manufacture, and collectively they achieve effective coolant agitation through their arrangement and interaction with the flow.
Solution Approach 2:
Instead of using complex protruding deflectors that extend into the coolant flow path, the invention uses flat plates with deflectors at their ends that bend toward adjacent cells. This inverted approach simplifies the main body of each element while maintaining mixing effectiveness through the deflector geometry.
2Ease of operation
If multiple deflecting elements are placed in secondary channels, then coolant turbulence is improved, but risk of contact with fuel elements increases
Solution Approach 1:
The deflectors are positioned locally at the ends of plates and bent toward adjacent trihedral cells, creating turbulence in specific regions where it is most needed for coolant mixing, while leaving other areas clear of obstructions that could contact fuel elements.
Solution Approach 2:
The deflectors are bent in a specific direction toward adjacent cells rather than extending perpendicular to the plate surface. This directional bending in a different dimension creates effective turbulence while reducing the probability of contact with fuel elements that pass through the grid.
3Ease of operation
If high hydraulic resistance structures are used for flow control, then coolant mixing is improved, but energy loss increases
Solution Approach 1:
The hydraulic resistance parameters are optimized by adjusting the number, size, and arrangement of the plate elements and their deflectors. The design achieves effective flow control and coolant mixing while maintaining acceptable pressure drop by carefully selecting these geometric parameters rather than using maximally resistant structures.
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 design effectively agitates coolant, improves heat removal from fuel elements, and enhances fuel cycle operation with increased energy release efficiency by minimizing hydraulic resistance and facilitating easy manufacture and installation.
Implementation Method 1
mixing grids provided with deflectors to produce turbulence in the coolant flow
Data Source
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AI summary
The invention relates to nuclear reactor elements, in particular to the structural design of spacing and mixing grids of fuel assemblies. The mixing grid comprises a hoop and a set of intercrossing plates which form a field of cells for accommodating fuel elements and the supporting elements of the fuel assembly. The cells for accommodating the supporting elements have a circle cross-section. The cells for accommodating fuel elements are hexahedral and the cells for passing a coolant which are adjacent thereto are trihedral. Two faces of each trihedral cell are concave, the third face being provided with a plate deflector