Actinide Oxide Powder Preparation via Cryogenic Granulation
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Solution Overview
Problem
Existing processes for preparing actinide oxide powders, particularly PuO2, face challenges such as filter clogging, fine particle dissemination, and inadequate homogeneity, which affect the quality and handling of MOX fuels and transmutation targets.
Innovation Solution
A process involving cryogenic granulation of an aqueous solution containing actinide cations followed by lyophilization and calcination, eliminating the need for oxalic precipitation and filtration, and ensuring homogeneous distribution and reduced fine particle content.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If oxalic precipitation and filtration are used to prepare PuO2 powder, then plutonium can be recovered from nitric solutions, but filter clogging occurs and fine particles are disseminated
Solution Approach 1:
The invention extracts and eliminates the problematic filtration step from the traditional process. By using hydroxide precipitation followed by direct washing and drying of the precipitate, the method removes the filtration operation that causes fine particle dissemination, while still achieving effective plutonium recovery from nitric solutions
Solution Approach 2:
The invention replaces the mechanical filtration system with a washing-based separation method. Instead of using filters that clog and disseminate fine particles, the process uses liquid washing to separate and recover plutonium, substituting a mechanical separation system with a chemical/physical washing process
2Ease of manufacture
If dry mechanical mixing is used to prepare mixed uranium-plutonium oxide powders, then the process is simple, but homogeneity of plutonium distribution is inadequate
Solution Approach 1:
The invention merges the precipitation and mixing operations into a single integrated process. By co-precipitating uranium and plutonium hydroxides from their nitric solutions simultaneously, then washing and drying the combined precipitate, the method achieves homogeneous distribution of plutonium in the mixed oxide powder without requiring separate mixing steps
Solution Approach 2:
The invention performs preliminary mixing at the molecular level during the precipitation stage. By adjusting the precipitation conditions to co-precipitate both uranium and plutonium hydroxides together before drying, the method establishes homogeneous distribution early in the process, eliminating the need for subsequent mechanical mixing operations
3Manufacturing precision
If complete grinding of UO2 and PuO2 powders is performed to ensure intimate mixing, then homogeneity is improved, but fine particle content increases and dissemination risk rises
Solution Approach 1:
The invention performs preliminary homogeneous mixing during the co-precipitation stage before any grinding occurs. By forming a homogeneous mixed hydroxide precipitate that is then directly washed and dried, the method achieves intimate mixing without requiring extensive grinding, thereby avoiding the generation of excessive fine particles
Solution Approach 2:
The invention changes the physical and chemical parameters during precipitation to achieve homogeneous mixing. By controlling pH, temperature, and precipitation rate to co-precipitate uranium and plutonium hydroxides together, the method achieves molecular-level homogeneity without mechanical grinding, avoiding fine particle generation
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 process produces powders with controlled porosity, excellent flowability, and high homogeneity, minimizing fine particle dissemination and enhancing the compaction and sintering properties, thus improving the quality of MOX fuels and transmutation targets.
Implementation Method 1
a) cryogenic granulation of an aqueous solution comprising cations selected from uranium-based cations, plutonium-based cations and minor actinide-based cations
Implementation Method 2
b) lyophilization of the granules obtained in a)
Implementation Method 3
c) calcination of the granules obtained from b); whereby the powder is obtained
Data Source
AI summary
The invention relates to a process for preparing a powder comprising one or more oxides selected from uranium oxide UO2, plutonium oxide PuO2 and minor actinide oxides, the minor actinides being selected from americium, neptunium and curium, comprising the steps of: a) cryogenic granulation of an aqueous solution comprising cations selected from uranium-based cations, plutonium-based cations and minor actinide-based cations; b) freeze-drying of the granules obtained in a); and c) calcination of the granules obtained from b). Applications: manufacture of nuclear fuels or blankets loaded with minor actinide(s).