Additive Manufacturing of Nuclear Fuel Structures
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Solution Overview
Problem
Conventional methods for forming fissile fuel structures in nuclear reactor cores, such as extrusion and sintering, often result in structures with surface and internal cracking, reduced density, and impurity due to the use of resin or binder materials, which also increase the likelihood of oxidation and porosity.
Innovation Solution
The method involves additive manufacturing using a powder mixture with a high graphite content, where layers of fuel and graphite are compacted and exposed to defocused laser radiation to form inter-granular bonds without the need for binder materials, resulting in a structure with a graphite to total carbon ratio of 1:1, enhancing thermal conductivity and reducing operating temperatures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If resin or binder materials are used in extrusion or sintering processes, then the structure can be formed, but surface and internal cracking occur and density is reduced
Solution Approach 1:
The patent removes resin and binder materials from the powder mixture entirely, using only graphite and fuel particles. This extraction of harmful binding agents eliminates the source of cracking and density reduction while maintaining structural integrity through direct particle-to-particle bonding achieved via laser irradiation.
Solution Approach 2:
The patent replaces mechanical binding mechanisms (resin/binder adhesion) with thermal bonding mechanisms (laser-induced sintering). The laser energy directly fuses graphite and fuel particles together without requiring organic binders, substituting a physical-chemical bonding process for a mechanical binding approach.
2Ease of manufacture
If resin or binder materials are added to facilitate sintering, then green structure formation is enabled, but outgassing creates pores and reduces total density
Solution Approach 1:
The patent extracts and eliminates resin and binder materials from the formulation, relying solely on the graphite matrix and fuel particles. This removal prevents outgassing entirely, as there are no organic materials to decompose and release gases that would create pores during sintering.
Solution Approach 2:
The patent changes the chemical composition parameters by eliminating organic binders and using only inorganic graphite and fuel materials. This parameter change transforms the sintering process from one requiring binder removal to one where all materials are stable and non-outgassing under processing conditions.
3Ease of manufacture
If resin and binder materials are used in the powder mixture, then structure formation is facilitated, but purity of the final structure is reduced
Solution Approach 1:
The patent extracts all resin and binder materials from the powder mixture, leaving only graphite and fuel components. This extraction ensures that the final sintered structure contains only the desired fuel and graphite phases, eliminating contamination from organic binder residues and achieving high purity.
4Productivity
If conventional extrusion or sintering processes are used, then fuel structures can be manufactured, but thermal conductivity is reduced due to binder materials and porosity
Solution Approach 1:
The patent removes resin and binder materials that act as thermal insulators and create porosity. By using only graphite (a material with high thermal conductivity) and fuel particles directly bonded together, the resulting structure achieves superior thermal conductivity compared to conventional processes.
Solution Approach 2:
The patent creates a composite structure of graphite and fuel particles where the graphite matrix provides both structural integrity and high thermal conductivity. This composite approach leverages the excellent thermal properties of graphite while maintaining the fuel's functional characteristics.
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 approach produces fuel structures with increased thermal conductivity, reduced porosity, and lower operating temperatures, minimizing oxidation and improving neutronic performance by eliminating binder-related issues, while allowing for lower temperature and pressure processing.
Implementation Method 1
exposing the first layer of the powder to defocused laser radiation to form a first layer of a structure comprising inter-granular bonds between particles of the powder
Implementation Method 2
exposing the first layer of the powder to laser radiation to form a first layer of material comprising the fuel dispersed within a graphite matrix material and to form inter-granular bonds between the second layer and the first layer
Data Source
AI summary
A method of forming one or more structures by additive manufacturing comprises introducing a first layer of a powder mixture comprising graphite and a fuel on a surface of a substrate. The first layer is at least partially compacted and then exposed to laser radiation to form a first layer of material comprising the fuel dispersed within a graphite matrix material. At least a second layer of the powder mixture is provided over the first layer of material and exposed to laser radiation to form inter-granular bonds between the second layer and the first layer. Related structures and methods of forming one or more structures are also disclosed.