Aldoxime Anti-Nitrous Agents for Plutonium Stripping
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Solution Overview
Problem
Current reductive plutonium stripping operations in spent nuclear fuel processing, particularly in the PUREX process, face inefficiencies due to the limited extractability of anti-nitrous agents like hydrazine and butanal oxime, leading to high reagent consumption and toxicity issues, as well as the formation of azohydric acid, which restricts industrial application.
Innovation Solution
The use of aldoximes with at least five carbon atoms, such as pentanal oxime and hexanal oxime, as anti-nitrous agents in reductive plutonium stripping operations, which are more extractable by the organic phase and can function alone or in combination with other oximes to stabilize both phases, reducing the need for hydrazine and minimizing reagent consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If hydrazine is used as anti-nitrous agent in aqueous phase, then it effectively stabilizes the aqueous phase, but it is not extractable by organic phase leading to high reagent consumption and formation of azohydric acid
Solution Approach 1:
The patent divides the anti-nitrous function into two separate agents: one for the aqueous phase (hydrazine) and one for the organic phase (aldoxime with 5+ carbon atoms). This segmentation allows each agent to function optimally in its respective phase without the limitations of cross-phase extraction issues, thereby reducing overall reagent consumption while maintaining stability in both phases.
Solution Approach 2:
The aldoxime acts as an intermediary substance that transfers the anti-nitrous function to the organic phase. By introducing this intermediate agent with specific properties (5+ carbon atoms, appropriate solubility), the system achieves stable protection against nitrous acid formation in the organic phase without requiring excessive hydrazine, thus reducing reagent consumption.
2Loss of substance
If butanal oxime is used to stabilize organic phase, then it reduces hydrazine consumption, but its extraction by organic phase is greatly reduced when saturated with actinides making it poorly suited for U/Pu partition step
Solution Approach 1:
The patent changes the key parameter of carbon chain length from 4 carbons (butanal oxime) to 5 or more carbons (aldoximes). This parameter change fundamentally alters the extraction behavior and actinide interaction properties, enabling the anti-nitrous agent to maintain effectiveness in the organic phase even when saturated with actinides, thus resolving the reliability issue in U/Pu partition operations.
Solution Approach 2:
The patent applies the principle of local quality by selecting aldoximes with specific carbon chain lengths (5+ carbons) that exhibit appropriate solubility and extraction characteristics for the organic phase. This localized optimization of molecular structure ensures the agent performs effectively in the specific environment of the organic phase during U/Pu partition, addressing the extraction efficiency problem.
3Reliability
If large quantities of butanal oxime are introduced to achieve effective concentration in organic phase, then anti-nitrous action is improved, but process complexity and reagent cost increase
Solution Approach 1:
By changing the carbon chain length parameter to 5 or more carbons, the patent fundamentally improves the extraction coefficient and phase distribution behavior of the aldoxime. This parameter change enables effective anti-nitrous action at much lower concentrations, thereby simplifying the process and reducing reagent quantities needed, which directly addresses the device complexity issue.
4Reliability
If hydrazine is used as anti-nitrous agent, then it effectively destroys nitrous acid, but it is toxic and classified as CMR substance restricting industrial application
Solution Approach 1:
The patent extracts the harmful property (toxicity) from the system by replacing hydrazine in the organic phase with aldoximes. The aldoxime with 5+ carbon atoms performs the necessary anti-nitrous function in the organic phase, allowing hydrazine to be eliminated or minimized in the aqueous phase, thereby removing the CMR classification and toxicity concerns from the overall process.
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 significantly reduces the quantities of reagents required, enhances plutonium stripping efficiency, and eliminates the use of hydrazine, leading to more concentrated aqueous phases and simplified equipment design, while maintaining effective anti-nitrous action and stability of uranium and plutonium.
Implementation Method 1
The use of aldoximes with at least five carbon atoms, such as pentanal oxime and hexanal oxime, as anti-nitrous agents in reductive plutonium stripping operations, which are more extractable by the organic phase
Implementation Method 2
The reduction of plutonium(IV) to plutonium(III) is induced by a reducing agent which is added to the aqueous phase used for stripping
Data Source
Figure 1~2A
Figure 2B~3
Figure 4~5
AI summary
The invention relates to the use of aldoximes comprising at least five carbon atoms as anti-nitrous agents in operations for the reductive back-extraction of plutonium. The invention is applicable in any method for processing spent nuclear fuels that comprises one or more operations for the reductive back-extraction of plutonium and, in particular, in the PUREX method as implemented in modern plants for processing spent nuclear fuels and in the methods derived therefrom.