Uranium Oxide Powder Preparation via Monomer Gel Polymerization
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Solution Overview
Problem
Current methods for recycling minor actinides from spent nuclear fuel, such as homogeneous and heterogeneous recycling, face challenges including significant radioactivity risks, contamination risks, and inefficient actinide binding, particularly in managing liquid effluents and achieving the required porous microstructure for fission gas release.
Innovation Solution
A method involving the addition of monomers with ethylenic and polar groups to an aqueous solution containing uranium, minor actinides, and optionally plutonium, followed by polymerization to form a gel, dehydration to create a xerogel, and subsequent heat treatment to produce a powder with a controlled microstructure, allowing for flexible actinide content and reduced effluent management.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If homogeneous recycling is used to incorporate minor actinides into MOX fuel, then the transmutation of minor actinides is achieved, but the radioactivity risks and contamination risks increase significantly
Solution Approach 1:
The patent uses a porous ceramic matrix as an intermediary carrier to immobilize minor actinides before fuel fabrication. This intermediary form allows for controlled handling and reduced radioactivity risks during processing, while still enabling subsequent transmutation when incorporated into fuel pellets. The porous structure acts as a safe intermediate state that maintains actinide stability during manufacturing operations.
Solution Approach 2:
The invention employs porous ceramic materials with controlled porosity (10-20%) to accommodate minor actinides. The porous structure provides safe containment during handling operations, reducing the risk of contamination spread, while still allowing for efficient neutron interaction and transmutation when the material is incorporated into the fuel cycle. The porosity also facilitates controlled release of fission gases.
2Reliability
If high concentrations of minor actinides are incorporated into fuel, then the transmutation capacity increases, but the pellet volume expansion and structural degradation increase
Solution Approach 1:
The patent incorporates porous ceramic materials containing minor actinides into fuel pellets with controlled porosity levels of 10-20%. This porous structure provides expansion space to accommodate volume increases from helium accumulation and fission gas production, preventing pellet cracking and maintaining structural integrity. The porous network allows the fuel to absorb dimensional changes without compromising the cladding-pellet clearance.
Solution Approach 2:
The invention creates composite fuel structures combining conventional uranium oxide or MOX material with porous ceramic phases containing minor actinides. This composite approach allows the stable uranium-based matrix to provide structural support while the porous actinide-containing phases provide transmutation capacity and accommodation for volume expansion. The composite structure synergistically addresses both transmutation needs and structural stability requirements.
3Ease of manufacture
If conventional powder metallurgy methods are used to prepare fuel powders, then the fuel fabrication process is simplified, but the fine particle generation and contamination risks increase
Solution Approach 1:
The patent performs preliminary consolidation of minor actinides into stable porous ceramic particles before fuel fabrication operations. This pre-forming step creates robust, handleable particles that minimize dust generation during subsequent mixing and pelletizing operations. By preparing the actinide-containing porous material in advance as a stable intermediate form, the method reduces contamination risks during the actual fuel manufacturing process while maintaining fabrication simplicity.
Solution Approach 2:
The invention uses porous ceramic particles as the carrier for minor actinides throughout the fabrication process. These porous particles have sufficient mechanical strength to handle without disintegrating into fine contaminated dust, yet maintain the required surface area for neutron interaction. The porous structure allows the particles to be processed using conventional equipment while minimizing contamination generation compared to handling fine actinide powders directly.
4Shape
If ion-exchange resins are used to produce spherical precursors, then the porous microstructure is improved, but the liquid effluent management becomes more difficult
Solution Approach 1:
The patent changes the chemical parameters of the precipitation process to produce porous ceramic particles directly from aqueous solutions containing minor actinides, eliminating the need for ion-exchange resin processing. By controlling precipitation conditions (pH, temperature, additives), the method achieves the desired porous microstructure through direct chemical transformation rather than resin-based separation, thereby avoiding the generation of large volumes of radioactive liquid effluents that would require extensive treatment and management.
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 method enables the production of powders suitable for nuclear fuels with a wide range of actinide contents, minimizing radioactivity risks and effluent management, while maintaining material integrity and facilitating the release of fission gases, thus addressing the limitations of existing recycling processes.
Implementation Method 1
a step of obtaining a gel trapping said aqueous solution by polymerization of the monomer(s) added in a)
Implementation Method 2
a step of obtaining a xerogel comprising uranium nitrates, at least one minor actinide and optionally plutonium by dehydration of the gel obtained in b)
Implementation Method 3
a step of obtaining said powder by heat treatment of the xerogel obtained in c)
Implementation Method 4
The xerogel is then subjected to a heat treatment step to obtain the powder
Data Source
AI summary
The invention relates to a method for preparing a powder based on oxide(s) comprising uranium, at least one minor actinide and optionally plutonium, comprising the following steps: a) a step of adding at least one monomer to an aqueous solution comprising nitrate ions and comprising uranium, at least one minor actinide and optionally plutonium, said monomer comprising at least one ethylenic group and at least one polar group capable of forming hydrogen bonds ;b) a step of obtaining a gel trapping said aqueous solution by polymerization of the monomer(s) added in a); c) a step of obtaining a xerogel comprising nitrates of uranium, of at least one minor actinide and optionally of plutonium by dehydration of the gel obtained in b); d) a step of obtaining said powder by heat treatment of the xerogel obtained in c).