Nuclear Fuel Assembly Mixed Grid Pattern Design
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
CANDU heavy-water reactors face inefficiencies in fuel assembly design, leading to underutilization of space within reactor tubes and limitations in fuel burnup and safety, as conventional fuel assemblies occupy less than optimal areas within the reactor core.
Innovation Solution
A fuel assembly design featuring a mixed grid pattern of rectangular and triangular grid patterns with fuel elements arranged in concentric circles and having a multi-lobed profile with spiral ribs, allowing for self-spacing and increased packing density within a shroud, optimizing the use of space within the reactor tubes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If conventional fuel assemblies with square or triangular grid patterns are used, then the assembly structure is simple and easy to manufacture, but the space utilization within the reactor tube is suboptimal (occupying only 63.7% or 82.7% of the tube area)
Solution Approach 1:
The patent applies asymmetry by transitioning from symmetric square or equilateral triangular grid patterns to an asymmetric arrangement where fuel elements are positioned at different centerline-to-centerline distances. The fuel elements are arranged such that some have spacing equal to their circumscribed diameter while others have different spacing, creating an asymmetric pattern that achieves superior space utilization (greater than 82.7% of tube area) while maintaining structural integrity
Solution Approach 2:
The patent employs dimensionality change by arranging fuel elements in a mixed grid pattern that combines rectangular and triangular configurations, effectively utilizing both 2D plane arrangements. The fuel elements are positioned in concentric circles with varying radial distances, transforming the traditional uniform 2D grid into a multi-dimensional arrangement that maximizes space occupation within the circular tube cross-section
2Area of stationary object
If fuel elements are arranged in a mixed grid pattern with varying centerline-to-centerline distances, then space utilization increases to greater than 82.7% of tube area, but the manufacturing and assembly complexity increases
Solution Approach 1:
The patent applies segmentation by dividing the fuel assembly into distinct zones with different grid patterns. The assembly includes an inner region with one spacing configuration and an outer region with another spacing configuration. This segmentation allows each zone to be manufactured and assembled independently using standardized procedures, reducing overall manufacturing complexity while achieving high space utilization through the combination of different patterns
Solution Approach 2:
The patent utilizes parameter changes by systematically varying the centerline-to-centerline distance parameter across different regions of the fuel assembly. Instead of using a single uniform spacing parameter, the design incorporates multiple spacing parameters (some equal to the fuel element circumscribed diameter, others different), optimizing the geometric arrangement to maximize area occupation while maintaining manufacturability through controlled parameter variation
3Productivity
If conventional fuel assemblies are used, then the assembly design is proven and reliable, but the fuel burnup power and operating time are limited due to underutilization of reactor tube space
Solution Approach 1:
The patent applies spheroidality by arranging fuel elements along concentric circular patterns rather than straight linear grids. The fuel elements are positioned at radial distances that create circular or near-circular boundaries, better matching the circular cross-section of the reactor tube. This curved arrangement eliminates the wasted corner spaces inherent in rectangular or triangular grids, achieving greater than 82.7% tube area occupation and thereby increasing fuel burnup power and operating time
Data Source
Figure 1A~1B
Figure 2
Figure 3
AI summary
A fuel assembly for use in a core of a nuclear power reactor. The assembly includes a frame shaped and configured to fit within the nuclear reactor internal core structure; and a plurality of helically twisted fuel elements supported by the frame in a fuel rod bundle. Each of the fuel elements includes fissile material. When viewed in a cross-section that is perpendicular to an axial direction of the fuel assembly, the outermost fuel elements of the fuel rod bundle define a substantially circular perimeter. Other features, and a nuclear reactor, are also described.