Nuclear Reactor Fuel Assembly Hexagonal Mixing Lattice
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current nuclear reactor fuel assemblies face challenges in maintaining reliable and safe operation at increased power levels due to spotty coolant distribution and reduced critical power ratio, leading to inefficiencies in heat transfer and safety concerns.
Innovation Solution
The design incorporates a hexagonal mixing lattice with shaped tube cells featuring sagging facets and no gaps, promoting circular translation of coolant and forming vortices that enhance heat transfer by separating water and vapor, minimizing drag coefficient and torque transmission.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If power generation and operation duration are increased, then productivity and fuel utilization efficiency are improved, but reliability and safety deteriorate due to severe operating conditions
Solution Approach 1:
The mixing lattice is divided into multiple separate bars instead of a continuous structure, allowing each bar to be independently positioned to optimize coolant flow paths and reduce stress concentration points, thereby maintaining safety under high power conditions
Solution Approach 2:
The mixing lattice acts as an intermediary structure between the coolant flow and fuel elements, creating controlled mixing zones that enhance heat transfer and prevent hot spots, enabling safe operation at increased power levels
2Productivity
If power generation is increased, then productivity is improved, but critical power ratio decreases due to spotty coolant distribution
Solution Approach 1:
The mixing lattice bars are positioned to create dynamic mixing patterns that adapt to varying coolant flow conditions, ensuring uniform coolant distribution across the fuel assembly cross-section even at high power levels where flow patterns change
3Temperature
If deflectors are added to enhance heat transfer, then heat transfer is improved, but device complexity increases and coolant flow fluctuation worsens
Solution Approach 1:
The deflector function is extracted from a complex lattice structure and implemented through simple angled bars that create sufficient mixing without the complexity of intersecting plates and multiple deflector elements
Solution Approach 2:
The mixing lattice uses simple, easily manufacturable bar elements rather than complex precision-machined components, reducing manufacturing complexity and cost while achieving the required mixing effect
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
This configuration significantly enhances heat transfer in the coolant two-phase flow, increasing the critical power ratio and ensuring safer reactor operation by uniformly distributing coolant parameters and increasing reactor power capacity.
Implementation Method 1
the proposed selection of geometry of mixing lattice cells facets comprising the middle and two extreme portions ensures circular translation motion of the coolant passing through the said cell in between the cells facets and the fuel elements installed into the cells, with formation of vortex
Implementation Method 2
In the coolant two-phase flow comprising water and vapour, due to centrifugal forces of formed vortex the heavy particles of the flow (water) are thrown back to neighbouring fuel elements and destruct the vapour film on their surface
Data Source
Figure 1
Figure 2
Figure 3~3(b)
AI summary
The invention is related to the nuclear power industry sphere, specifically to the design of fuel assemblies of nuclear reactors, and is aimed at supporting efficient mixing of the heat carrier for the purpose of improving heat removal from fuel elements. The nuclear reactor fuel assembly contains upper and lower end caps, guide channels, fuel elements situated in triangular network points, and at least one array consisting of cells integrally connected in between. Each cell is made in the form of a shaped tube, with the longitudinal axis thereof coinciding with the longitudinal axis of the fuel element and having hexagon-shaped cross-section, with its edges consisting of middle and two outermost sections. Outermost sections, at least near edges of cells from the upper end cap side, have deflection with a steady change in value along the longitudinal axis of the cell. Outermost sections of neighboring edges adjacent to common top of hexagon have deflection direction opposite to the cell centerpoint. Directions of deflections of adjacent cells' edges contacting with each other are opposite relatively to centerpoints of their specific cells. There is no gap between array cells.