Mixed Uranium-Plutonium Oxide Reprocessing via Partial Separation
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Solution Overview
Problem
Current nuclear fuel reprocessing methods, such as PUREX, separate uranium and plutonium completely, leaving plutonium unattended, risking misappropriation and requiring extensive radiological protection and costly infrastructure for handling radioactive fission products, which is not suitable for all reactor types.
Innovation Solution
A process that partially separates uranium and plutonium, maintaining their presence together until a mixed uranium-plutonium oxide is formed, using liquid-liquid extraction techniques with specific solvent phases and acidity controls to minimize fission product contamination and achieve a suitable U/Pu mass ratio for MOX fuel production.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If complete separation of uranium and plutonium is performed using PUREX process, then decontamination from fission products is achieved, but plutonium security risk increases and extensive radiological protection infrastructure is required
Solution Approach 1:
The patent merges uranium and plutonium into a mixed oxide form (MOX fuel) where both elements remain together throughout the process. Instead of completely separating them as in traditional PUREX, the invention maintains their association by converting them simultaneously into a mixed ceramic oxide, thereby eliminating security risks associated with isolated plutonium while achieving effective decontamination from fission products
2Manufacturing precision
If complete separation of uranium and plutonium is performed, then pure streams are obtained, but infrastructure complexity and costs increase due to need for extensive radiological protection
Solution Approach 1:
The invention combines uranium and plutonium processing into a single integrated flow where both elements are co-extracted, co-purified, and co-converted into mixed oxide fuel. This merging eliminates the need for separate handling infrastructure for highly radioactive plutonium streams, reducing overall facility complexity and radiological protection requirements while maintaining high purification standards
3Manufacturing precision
If traditional PUREX process with multiple purification cycles is used, then effective decontamination is achieved, but process time and operational complexity increase
Solution Approach 1:
The patent applies partial action by performing a reduced number of purification cycles compared to traditional PUREX. Instead of multiple sequential separation cycles for uranium and plutonium, the invention uses a streamlined approach with fewer extraction and back-extraction cycles, achieving sufficient decontamination levels more quickly by focusing on key impurity removal steps
4Object-affected harmful factors
If uranium and plutonium are kept together as mixed oxide, then security risks are minimized, but flexibility for different reactor types is reduced
Solution Approach 1:
The invention uses parameter changes by varying the uranium-to-plutonium mass ratio in the mixed oxide fuel according to the specific reactor type requirements. For fast reactors, a higher plutonium content (e.g., 40-70% Pu) is used, while for light-water reactors, a lower plutonium content (e.g., 3-10% Pu) is employed. This flexibility in compositional parameters maintains security benefits of mixed oxide form while adapting to different reactor applications
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 process effectively decontaminates uranium and plutonium from fission products, minimizes the risk of plutonium misappropriation, and produces a mixed uranium-plutonium oxide suitable for both fast and light-water reactors, reducing the need for extensive radiological protection and infrastructure costs.
Implementation Method 1
carrying out several purification cycles using the liquid-liquid extraction technique (that is to say by mixing an aqueous phase and a solvent phase that are mutually immiscible, followed by separation of these two phases by settling)
Implementation Method 2
an operation for the purpose of back-extracting the plutonium from the solvent phase by means of an aqueous nitric phase of low acidity, containing a reducing agent capable of reducing plutonium(IV), which is highly extractable by TBP, to plutonium(III) which is itself only barely extractable
Data Source
AI summary
The invention relates to a process for reprocessing a spent nuclear fuel and for preparing a mixed uranium-plutonium oxide, which process comprises:a) the separation of the uranium and plutonium from the fission products, the americium and the curium that are present in an aqueous nitric solution resulting from the dissolution of the fuel in nitric acid, this step including at least one operation of coextracting the uranium and plutonium from said solution by a solvent phase;b) the partition of the coextracted uranium and plutonium to a first aqueous phase containing plutonium and uranium, and a second aqueous phase containing uranium but no plutonium;c) the purification of the plutonium and uranium that are present in the first aqueous phase; andd) a step of coconverting the plutonium and uranium to a mixed uranium/plutonium oxide.Applications: reprocessing of nuclear fuels based on uranium oxide or on mixed uranium-plutonium oxide.