Silicon Carbide Composite Channel Box for Nuclear Fuel Assembly
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Solution Overview
Problem
Zirconium-based alloys used in nuclear reactor channel boxes undergo exothermic oxidation at high temperatures, leading to rapid hydrogen generation and potential hydrogen explosions, necessitating a material with improved high-temperature resistance and earthquake resilience.
Innovation Solution
A silicon carbide composite material with a laminated structure, comprising a silicon carbide matrix, silicon carbide fibers, and an intermediate solid lubricant layer, is used to create a channel box that enhances strength, fracture toughness, and fracture energy, while preventing hydrogen generation and radioactivation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If zirconium-based alloy is used for channel box, then corrosion resistance and low neutron absorption are achieved, but hydrogen generation occurs at high temperature leading to potential hydrogen explosion
Solution Approach 1:
The patent applies composite materials by combining silicon carbide matrix with zirconium-based alloy layers. The silicon carbide provides high-temperature resistance and prevents hydrogen generation, while the zirconium-based alloy layers maintain corrosion resistance and low neutron absorption properties. This composite structure resolves the contradiction by integrating materials with complementary properties.
2Reliability
If zirconium-based alloy is used for channel box, then excellent corrosion resistance is achieved, but earthquake resistance is insufficient
Solution Approach 1:
The composite structure combines silicon carbide's high strength and fracture toughness with zirconium-based alloy's corrosion resistance. The silicon carbide matrix provides superior mechanical properties and earthquake resistance, while embedded zirconium-based alloy layers maintain corrosion protection and neutron absorption characteristics.
3Temperature
If silicon carbide composite material is used for channel box, then high temperature resistance and earthquake resistance are improved, but manufacturing complexity increases
Solution Approach 1:
The channel box is segmented into multiple functional layers: silicon carbide matrix for high-temperature resistance, zirconium-based alloy layers for corrosion protection, and intermediate layers for bonding. This segmentation allows each layer to be optimized independently and facilitates manufacturing by enabling separate production and assembly of layers.
Solution Approach 2:
The patent uses composite materials to achieve high temperature resistance through silicon carbide while managing manufacturing complexity through controlled layering. The composite structure allows selection of materials based on specific functional requirements rather than requiring a single material to satisfy all constraints simultaneously.
4Ease of manufacture
If conventional channel box shape is used, then manufacturing ease is maintained, but coolant flow efficiency is insufficient
Solution Approach 1:
The patent applies local quality by modifying the channel box shape in specific regions to enhance coolant flow. The outer peripheral surface includes protruding portions and recesses that create turbulence and improve heat transfer in critical areas, while maintaining a generally conventional overall shape for manufacturing ease. This localized modification optimizes coolant flow without requiring complete redesign.
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 silicon carbide composite channel box effectively suppresses hydrogen generation and radioactivation, provides improved mechanical properties, and increases earthquake resistance, allowing for thinner designs and enhanced coolant flow paths, thereby improving the safety and performance of the fuel assembly.
Implementation Method 1
When these zirconium-based alloys are exposed to high temperature, such as during an accident, the following reaction with surrounding moisture occurs. Zr+2H2O→ZrO2+2H2 (1) Here, the reaction expressed in Equation (1) is an exothermic reaction... use of a ceramic composite material that is chemically and mechanically resistant to high temperature... In particular, the use of a silicon carbide composite material... is expected
Implementation Method 2
A silicon carbide composite material with a laminated structure, comprising a silicon carbide matrix, silicon carbide fibers, and an intermediate solid lubricant layer
Data Source
AI summary
A channel box has a hollow elongated portion and accommodates a plurality of nuclear reactor fuel rods inside the hollow elongated portion, wherein the hollow elongated portion is constituted by a plurality types of silicon carbide composite materials. The channel box has a shape that can be achieved by applying the silicon carbide composite material and can increase earthquake resistance and improve functions and performance as a fuel assembly.