Macrostructured Plate Fuel Element for High-Temperature Reactors
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current fuel elements for high-temperature reactors, such as GFRs, face challenges in achieving a significant volume fraction of fuel, ensuring mechanical resistance to internal pressure, avoiding strong interactions between fuel and structures, evacuating power efficiently, and controlling temperatures and stresses, while existing designs fail to optimize these criteria simultaneously.
Innovation Solution
A macro-structured composite fuel plate element with a honeycomb network of cells, featuring a high volume fraction of fuel (>50%) and an inert matrix, using refractory metals or ceramics for the cladding and matrix, with calibrated clearances for heat transfer and expansion, and a metal or ceramic structure to accommodate thermal and mechanical stresses.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If the volume fraction of fuel is increased to improve power density, then the power density is improved, but the mechanical resistance to internal pressure deteriorates
Solution Approach 1:
The fuel element is segmented into multiple independent cells arranged in a honeycomb pattern, each containing a fuel pellet. This segmentation allows the fuel volume fraction to be increased while maintaining structural integrity through the distributed cell structure, where each cell independently withstands internal pressure from fission gases.
Solution Approach 2:
The fuel element uses a composite structure combining fuel pellets with an inert matrix material (such as graphite or ceramic) that provides mechanical strength. This composite approach enables high fuel volume fraction (>50%) while the matrix material maintains the structural resistance to internal pressure generated by fission gases.
2Stability of the object's composition
If the fuel and structure are strongly linked to maintain geometry, then the geometric stability is improved, but the accommodation of differential deformations deteriorates
Solution Approach 1:
The connection between fuel pellets and the inert matrix structure is designed with local quality variations - the fuel is loosely held in each cell with calibrated clearances, allowing local differential deformations while maintaining overall geometric stability of the fuel element through the structured honeycomb arrangement.
3Loss of energy
If the cladding is made thin to reduce thermal resistance, then the heat transfer efficiency is improved, but the mechanical strength deteriorates
Solution Approach 1:
The inert matrix structure acts as a flexible confining medium that provides mechanical strength while maintaining thin dimensions. The structured honeycomb design allows the matrix to provide structural support with minimal thickness, reducing thermal resistance while maintaining adequate mechanical strength to contain the fuel pellets and withstand operational pressures.
4Power
If the volume fraction of fuel is increased to improve power density, then the power density is improved, but the heat transfer efficiency deteriorates
Solution Approach 1:
The segmented cell structure with fuel pellets arranged in a honeycomb pattern provides large surface area for heat transfer between the fuel and the inert matrix. This segmentation allows high fuel volume fraction while maintaining efficient heat transfer pathways through the structured arrangement, preventing thermal insulation effects that would occur with compacted fuel forms.
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 achieves efficient heat transfer, maintains structural integrity under high temperatures and power densities, and accommodates deformations without excessive stress, ensuring reliable operation and reduced fission product release, thus overcoming the limitations of existing fuel elements.
Implementation Method 1
ensure heat transfer between the fuel material and the heat transfer fluid
Implementation Method 2
Power plants producing energy from nuclear fission reactions use fuel elements in which fissions occur, releasing heat power
Implementation Method 3
fission reactions within the fuel generate solid and gaseous fission products which cause swelling of the structure of the material, a phenomenon activated by thermal which also induces mechanisms for releasing fission gases
Implementation Method 4
The cladding material adapts, through its malleability, its geometry to that of the central part of the fuel, which allows the accommodation of differential deformations
Data Source
Figure 1
Figure 2
AI summary
A novel nuclear fuel element is developed for, in particular, being used in fourth generation gas heat conductor reactors functioning with a rapid neutron flow. While being a composite plate structure, the inventive element (1) comprises a network (6) of cavities (8), preferably with a honeycomb layout, in each of which a nuclear fuel pellet (10) is placed. A radial clearance and an axial clearance are provided inside each cavity (8) in order to compensate for the differential swelling between fissile materials and structural materials inherent to the functioning of the plate (1).