Hexagonal Fuel Rack Design for Spent Nuclear Storage
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Solution Overview
Problem
Existing fuel racks for spent nuclear fuel assemblies are inadequate for accommodating non-rectangular fuel assemblies, such as those with a hexagonal cross-section, and fail to efficiently manage neutron radiation and heat dissipation, leading to suboptimal storage and transfer solutions.
Innovation Solution
A fuel rack design featuring hexagonal tubes connected to a base plate in a vertical orientation, with flux trap spaces between tubes to prevent criticality and allow natural thermosiphon cooling, and a fuel basket with a honeycomb-like grid structure that maximizes packing density and structural integrity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If rectangular cells are used in fuel racks, then manufacturing is simpler and structural strength is easier to achieve, but the ability to accommodate non-rectangular fuel assemblies (such as hexagonal cross-section) is compromised
Solution Approach 1:
The patent applies asymmetry by transitioning from conventional rectangular cells to hexagonal cells that match the non-rectangular cross-section of the fuel assemblies. This geometric adaptation allows the fuel rack to accommodate hexagonal fuel assemblies without requiring complex asymmetric modifications, thereby improving adaptability while maintaining manufacturing feasibility through systematic geometric transformation.
Solution Approach 2:
The fuel rack is segmented into modular hexagonal cells that can be independently manufactured and assembled. Each hexagonal cell is designed as a discrete unit that can be produced using standardized processes, then assembled to form the complete fuel rack structure, balancing manufacturing simplicity with the ability to accommodate non-rectangular fuel assemblies.
2Productivity
If fuel assemblies are placed closer together to increase storage density, then packing efficiency improves, but neutron radiation interaction between adjacent assemblies increases leading to criticality risks
Solution Approach 1:
The patent introduces neutron absorbing material as an intermediary substance placed between adjacent fuel assemblies. This intermediary layer absorbs excess neutron radiation and prevents harmful interactions between assemblies, allowing the fuel rack to maintain higher storage density while mitigating the criticality risk associated with closely spaced assemblies.
Solution Approach 2:
The fuel rack employs local quality by incorporating neutron absorbing material selectively in specific regions where neutron interaction is most problematic. Rather than uniformly treating all assemblies, the neutron absorbing material is strategically positioned between adjacent hexagonal cells to address local neutron flux issues while maintaining overall storage efficiency.
3Object-affected harmful factors
If solid neutron shield sheets are placed between cells to protect from radiation, then radiation shielding improves, but the structural integrity and corrosion resistance in water environments deteriorates
Solution Approach 1:
The patent replaces solid neutron shield sheets with thin film or shell-like neutron absorbing materials that can be positioned between hexagonal cells. These thin film structures provide sufficient neutron radiation shielding while maintaining compatibility with water environments, avoiding the corrosion problems associated with solid shield sheets and preserving structural integrity in aqueous conditions.
4Ease of manufacture
If conventional rectangular fuel racks are used, then manufacturing processes are simpler and more standardized, but the efficiency of heat dissipation and cooling for non-rectangular fuel assemblies is reduced
Solution Approach 1:
The patent applies curvature by adopting hexagonal cell geometries that naturally conform to the shape of the fuel assemblies. This geometric curvature allows for improved heat dissipation surfaces and more efficient cooling water flow patterns compared to flat rectangular cells, while the hexagonal shape can still be manufactured using standardized processes adapted from conventional rectangular designs.
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 provides a cost-effective, compact, and corrosion-resistant fuel rack that maintains structural stability under radiation exposure, effectively managing neutron radiation and heat dissipation while accommodating non-rectangular fuel assemblies with enhanced packing density and ease of manufacturing.
Implementation Method 1
it is necessary that the neutron and gamma radiation emitted from the spent fuel assemblies be adequately contained at all times upon being removed from the reactor
Implementation Method 2
The pool water also serves to cool the spent fuel assemblies by drawing the heat load away from the fuel assemblies
Implementation Method 3
The pool water also serves to cool the spent fuel assemblies by drawing the heat load away from the fuel assemblies
Implementation Method 4
The water may also contain a dissolved neutron shielding substance
Data Source
AI summary
Apparatus for supporting radioactive fuel assemblies, such as spent nuclear fuel. In one aspect, the invention is an apparatus, which can be in the form of a fuel basket, fuel rack, or the like, in which hexagonal storage tubes are used not only for their internal cells but are also strategically patterned to create resultant cells with their outside surfaces. In another aspect, the invention is an apparatus having flux traps surrounding each cell wherein the size of the flux traps decrease with distance from the center of the storage grid.