Plate Nuclear Fuel Cladding Hardness Gradient Dog-Bone Control
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Solution Overview
Problem
The 'dog-bone' effect, characterized by increased thickness at the ends and reduced thickness of plate-shaped nuclear fuel elements during rolling, poses a risk of fissile material release, necessitating rebutting and limiting cladding thickness for handling and irradiation safety.
Innovation Solution
A plate-shaped nuclear fuel element design featuring a frame made of a harder metallic cladding material than the cover plates, which resists deformation during rolling, thereby minimizing the 'dog-bone' effect and maintaining cladding integrity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the rolling process is applied to reduce thickness and increase length of the nuclear fuel element, then the productivity and dimensional control are improved, but the dog-bone effect occurs causing increased thickness at ends and reduced thickness in the middle, compromising cladding integrity
Solution Approach 1:
The frame is made of a harder metallic material than the cover plates, creating local quality differentiation. The harder frame material resists deformation during rolling while the softer cover plates deform to accommodate the core, preventing the dog-bone effect and maintaining uniform cladding thickness throughout the fuel element.
2Manufacturing precision
If the cladding is made thinner to reduce the dog-bone effect, then the manufacturing precision is improved, but the strength and reliability of the cladding are reduced, increasing the risk of fissile material release
Solution Approach 1:
The frame uses a harder metallic material that maintains its thickness and strength during rolling, while the cover plates use a softer material that deforms controllably. This local differentiation allows the frame to provide structural support and maintain cladding integrity even with reduced overall thickness.
Solution Approach 2:
The cladding is constructed as a composite structure combining two different metallic materials: a harder frame material providing structural integrity and a softer cover plate material providing ductility and sealing. This composite approach maintains both precision and strength.
3Reliability
If inserts are added between the fissile core and cover plates to limit the dog-bone effect, then the cladding thickness uniformity is improved, but the device complexity and manufacturing steps are increased
Solution Approach 1:
Instead of adding separate inserts, the solution uses local quality differentiation by making the frame material harder than the cover plate material. This inherent material property difference prevents the dog-bone effect without requiring additional components, simplifying the overall structure.
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 design effectively reduces the deformation at the ends of the core, maintaining a uniform thickness and preventing fissile material release, enhancing handling and irradiation safety while allowing for higher uranium content without increasing the risk of the 'dog-bone' effect.
Implementation Method 1
the frame is made of a metallic first cladding material and the cover plates are made of a metallic second cladding material, the first cladding material having a hardness strictly greater than the hardness of the second cladding material
Implementation Method 2
The frame made of a first cladding material exhibiting a higher hardness than the second cladding material of the cover plates is more resistant to deformation than the cover plates
Data Source
AI summary
A plate-shaped nuclear fuel element includes a core made of a fissile material and a cladding. The cladding further includes a frame defining a central aperture receiving the core and two cover plates sandwiching the frame and the core. The frame is made of a metallic first cladding material. The cover plates are made of a metallic second cladding material. The first cladding material has a hardness strictly greater than the hardness of the second cladding material.