Silicon Carbide Coated Nuclear Fuel Preventing Sintering Cracks
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Solution Overview
Problem
Current nuclear fuels face challenges such as cracking and porosity issues during sintering due to shrinkage differences between silicon carbide matrix and three-layer-structured isotropic nuclear fuel particles, leading to reduced accident tolerance and increased risk of reactor damage.
Innovation Solution
A fully ceramic capsulated nuclear fuel material is developed with a coating layer having higher shrinkage than the matrix phase, using a silicon carbide precursor, silicon carbide, and sintering additives, allowing for normal pressure sintering at 1700-1800°C to prevent cracking and enhance thermal conductivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If normal pressure sintering is performed on silicon carbide matrix with three-layer-structured isotropic nuclear fuel particles, then mass production and cost-effectiveness are improved, but cracking and porosity occur due to shrinkage differences
Solution Approach 1:
The patent modifies the shrinkage parameter of the nuclear fuel particles by incorporating a silicon carbide precursor that undergoes thermal decomposition to generate excessive shrinkage (greater than 15% volume reduction). This parameter change allows the particles to compensate for the matrix shrinkage during sintering, preventing cracking while enabling normal pressure sintering for mass production
Solution Approach 2:
The patent creates a composite structure where the coating layer contains a silicon carbide precursor (polycarbosilane or polysilicon oxycarbide) combined with silicon carbide particles and sintering additives. This composite material design enables the coating to provide both structural integrity and controlled shrinkage behavior during sintering
2Reliability
If silicon carbide precursor is added to coating layer to increase shrinkage, then cracking is prevented, but phonon scattering increases reducing thermal conductivity
Solution Approach 1:
The patent optimizes the precursor content parameter within a specific range (5-30 wt%) to balance two opposing effects: generating sufficient shrinkage to prevent cracking while limiting phonon scattering to maintain thermal conductivity above 80 W/mK. This precise parameter control resolves the contradiction between crack resistance and thermal performance
Solution Approach 2:
The patent creates local quality differentiation within the coating layer by combining the silicon carbide precursor with silicon carbide particles and sintering additives in specific proportions. The precursor provides shrinkage compensation locally, while the silicon carbide particles maintain thermal conductivity, achieving both functions in the same coating 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
The solution effectively prevents cracking and pores, enhances accident tolerance by minimizing phonon scattering, and facilitates mass production with a cost-effective process, ensuring stable nuclear reactor operation and safe storage of nuclear fission by-products.
Implementation Method 1
a coating layer cladding the nuclear fuel particles and configured to include a silicon carbide precursor, silicon carbide, and sintering additives
Implementation Method 2
when shrinkage of the coating layer of the three-layer-structured isotropic nuclear fuel particles during a sintering process is given as ΔLC, and when the shrinkage of the silicon carbide matrix phase during the sintering process is given as ΔLm, a condition of ΔLC>ΔLm may be satisfied
Implementation Method 3
performing normal pressure sintering of the pre-sintered body processed with thermal decomposition
Data Source
AI summary
The present invention relates to a method for preparing a fully ceramic capsulated nuclear fuel material containing three-layer-structured isotropic nuclear fuel particles coated with a ceramic having a composition which has a higher shrinkage than a matrix in order to prevent cracking of ceramic nuclear fuel, wherein the three-layer-structured nuclear fuel particles before coating is included in the range of between 5 and 40 fractions by volume based on after sintering. More specifically, the present invention provides a composition for preparing a fully ceramic capsulated nuclear fuel containing three-layer-structured isotropic particles coated with the substance which includes, as a main ingredient, a silicon carbine derived from a precursor of the silicon carbide wherein a condition of ΔLc>ΔLm at normal pressure sintering is created, where the sintering shrinkage of the coating layer of the three-layer-structured isotropic nuclear fuel particles is ΔLc and the sintering shrinkage of the silicon carbide matrix is ΔLm; material produced therefrom; and a method for manufacturing the material. The residual porosity of the fully ceramic capsulated nuclear fuel material is 4% or less.