Helically Fluted Tubular Fuel Rod Support Grid
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional support grids for nuclear fuel assemblies are difficult to assemble and can cause fretting wear between the grids and fuel rods, leading to potential nuclear contamination due to vibrations and pressure drops, which complicates water flow and torque issues within the reactor core.
Innovation Solution
A support grid design featuring helically fluted tubular members that engage fuel rods, eliminating the need for mixing vanes and reducing assembly complexity by using a frame assembly with cylindrical tubular members and a transition portion, minimizing pressure drops and torque while securely holding fuel rods.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional support grids with interleaved straps, springs, and dimples are used to support fuel rods, then fuel rod positioning and vibration resistance are improved, but assembly complexity and time consumption increase significantly
Solution Approach 1:
The patent combines multiple support functions (positioning, vibration resistance, lateral support) into a single integrated tubular member with helical flutes, eliminating the need for separate straps, springs, and dimples. This merging reduces the number of components and simplifies assembly while maintaining all necessary support functions.
Solution Approach 2:
The tubular member is segmented into distinct functional zones: a cell contact portion for positioning within the grid, a transition portion for structural integrity, and a helically fluted fuel rod contact portion for vibration damping and lateral support. This segmentation allows each zone to optimize its specific function while forming an integrated whole.
2Use of energy by moving object
If mixing vanes are added to support grids to facilitate water mixing and heat exchange, then convective heat exchange is improved, but pressure drop and torque in the reactor core increase
Solution Approach 1:
The patent removes mixing vanes from the support grid system entirely. Instead, water mixing and heat exchange functions are achieved through the natural flow patterns created by the helically fluted tubular members, which guide water flow along helical paths without requiring additional mixing components.
Solution Approach 2:
The helically fluted tubular member performs multiple functions simultaneously: it supports and positions fuel rods, dampens vibrations, and facilitates water mixing for heat exchange. This multi-functionality eliminates the need for separate mixing vanes while maintaining energy efficiency.
3Reliability
If conventional straps with springs and dimples are used to engage fuel rods, then fuel rod support at multiple points is achieved, but fretting wear and potential nuclear contamination occur due to vibrations
Solution Approach 1:
The patent uses a helically fluted surface on the tubular member that provides continuous curved contact with the fuel rod. This curved, helical contact surface distributes vibrational stresses more evenly and reduces localized fretting wear compared to discrete spring and dimple contact points, thereby preventing cladding breach and nuclear contamination.
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 helically fluted tubular member design simplifies assembly, reduces fretting wear, maintains efficient water mixing, and minimizes pressure drops and torque, enhancing the stability and safety of nuclear fuel assemblies by securely supporting fuel rods without the need for additional mixing vanes.
Implementation Method 1
the helical shape of the flutes induces a rotational flow in water passing through the fuel assembly
Implementation Method 2
Each of the springs and dimples includes an arcuate, concave platform having a radius generally the same as a fuel rod. This concave platform helps distribute the radial load on the sides of the fuel rods.
Data Source
AI summary
A support grid for a nuclear fuel assembly, the fuel rod assembly having a generally cylindrical fuel rod with a diameter, wherein the support grid includes a frame assembly having a plurality of outer straps and a plurality of helical frame members. The helical frame members have a contact portion structured to contact an adjacent helical frame member and at least one helical fuel rod contact portion with a lesser diameter. The lesser diameter is generally equivalent to the fuel rod diameter such that a fuel rod disposed in the helical frame member would engage the inner helical frame member at helical fuel rod contact portion. The helical frame members are coupled to each other at the contact portions thereby forming a grid. The plurality of outer straps are disposed about the perimeter of the helical frame members.