Nuclear Fuel Cladding with Ceramic-Metal Composite Hermeticity
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Solution Overview
Problem
Ceramic matrix composite materials (CMCs) used in nuclear fuel cladding lack hermeticity beyond their elastic limit, making them unsuitable for applications requiring airtightness over their entire operating range, particularly in nuclear reactors where they are prone to multi-cracking and loss of hermeticity under mechanical stress and high temperatures.
Innovation Solution
A nuclear fuel cladding design featuring a metallic tubular body sandwiched between two layers of ceramic matrix composite material, with the metallic layer acting as a hermeticity layer between the inner and outer CMC layers, maintaining hermeticity until the CMCs break, and using materials like niobium and its alloys for the metallic layer and SiCf/SiC for the CMC layers to ensure mechanical integrity and resistance to cracking.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If CMC material is used for nuclear fuel cladding, then mechanical strength and high temperature resistance are improved, but hermeticity is lost beyond the elastic limit due to multi-cracking
Solution Approach 1:
The invention uses a composite structure combining CMC material and metallic material. The CMC layer provides mechanical strength and high temperature resistance, while the metallic layer ensures hermeticity. This composite approach allows the cladding to maintain both structural integrity and airtightness under operating conditions including beyond the elastic limit of the CMC material.
Solution Approach 2:
The invention employs a layered structure where the metallic layer is positioned between two CMC layers (inner and outer CMC layers). The metallic layer is nested within the CMC structure, creating a sandwich configuration that allows each material to perform its optimal function while protected by the other layers.
2Reliability
If a metallic layer is placed inside the CMC cladding to ensure hermeticity, then hermeticity is maintained, but the metallic layer becomes vulnerable to thermochemical attacks from fuel and fission products
Solution Approach 1:
The metallic layer is nested between two CMC layers, with the inner CMC layer serving as a protective barrier between the metallic layer and the fuel. This nested configuration shields the metallic layer from direct exposure to thermochemical attacks from fuel and fission products while maintaining hermeticity.
Solution Approach 2:
The inner CMC layer acts as an intermediary protective barrier between the metallic hermeticity layer and the aggressive fuel environment. It mediates the interaction by preventing direct contact between the metallic layer and fuel/fission products, thus protecting the metallic layer from thermochemical attacks.
3Stability of the object's composition
If CMC material is used beyond its elastic limit, then mechanical ductility is improved, but hermeticity is compromised due to crack formation
Solution Approach 1:
The composite structure allows the CMC material to be utilized beyond its elastic limit for improved mechanical ductility, while the metallic layer compensates for the hermeticity loss by maintaining airtightness even when the CMC layers develop cracks under high stress conditions.
Data Source
AI summary
The invention relates to a multilayer tubular part (1) comprising: a metal layer forming a metal tubular body (3); and two layers of ceramic-matrix composite material covering the metal tubular body, in which one of the two layers of ceramic-matrix composite material covers the internal surface of the metal tubular body in order to form an internal tubular body (4), while the other of the two layers of ceramic-matrix composite material covers the external surface of the metal tubular body in order to form an external tubular body (2), the metal tubular body thus being sandwiched between the internal and external tubular bodies. The metal tubular body is made from metal or metal alloy. Furthermore, the metal tubular body has an average thickness less than the average thicknesses of the internal and external tubular bodies. Such a part can in particular be used to produce nuclear fuel cladding.