Plutonium Recovery from PUREX Waste Organic Phase
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Solution Overview
Problem
The PUREX process faces challenges in efficiently recovering plutonium from a waste organic phase due to the formation of complexes with degradation products, leading to retention of metal ions in the organic phase, which complicates phase separation and hinders the recovery of plutonium, especially in phases with high plutonium content that have been stored for extended periods.
Innovation Solution
A method involving the use of an aqueous back extraction solution containing 2,6-pyridinedicarboxylic acid to elute plutonium from the waste organic phase, followed by adsorption and elution using an anion exchange resin, effectively transferring plutonium into an aqueous phase, with optional deacidification and specific conditions for temperature, pH, and reagent concentrations to optimize the process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the PUREX process is used for spent fuel treatment, then plutonium and uranium can be extracted from spent fuel, but degradation products accumulate in the organic phase forming complexes with metal ions, causing retention of plutonium in the waste organic phase and making phase separation difficult
Solution Approach 1:
The patent converts the harmful effect of degradation products (HDBP, H2MBP) that cause plutonium retention into a beneficial separation mechanism. By adding a specific aqueous solution containing hydroxylamine hydrochloride and oxalic acid, the degradation products are transformed into water-soluble forms, converting the harmful retained plutonium complexes into separable forms that can be efficiently removed from the organic phase.
Solution Approach 2:
The patent changes the chemical parameters of the aqueous phase by introducing specific reagents (hydroxylamine hydrochloride at 0.1-1.0 mol/L and oxalic acid at 0.05-0.5 mol/L) to alter the solubility and complexation behavior of degradation products. This parameter change enables the degradation products to transition from organic-soluble complexes to water-soluble forms, facilitating phase separation and plutonium recovery.
2Object-generated harmful factors
If Na2CO3 is used to wash degradation products in the organic phase, then some cleaning effect is achieved, but the problem of plutonium metal retention in the waste organic phase cannot be solved
Solution Approach 1:
The patent introduces an intermediary aqueous solution containing hydroxylamine hydrochloride and oxalic acid that acts as a mediator between the organic phase and the degradation products. This intermediary solution selectively interacts with the degradation products and plutonium complexes, transferring them from the organic phase to the aqueous phase without requiring direct contact between Na2CO3 and the retained plutonium, thus solving both cleaning and recovery problems simultaneously.
Solution Approach 2:
The patent uses a composite chemical system in the aqueous phase combining hydroxylamine hydrochloride and oxalic acid. This composite reagent system works synergistically: hydroxylamine hydrochloride reduces and solubilizes plutonium complexes while oxalic acid complexes with metal ions, together achieving complete plutonium recovery that neither reagent could achieve alone.
3Duration of action of stationary object
If the waste organic phase is stored for a long time, then the complexes of degradation products and metal ions have low solubility in the organic phase, but this causes difficulties in phase separation and hinders plutonium recovery
Solution Approach 1:
The patent inverts the traditional approach by not trying to separate plutonium directly from the stored organic phase, but instead by transforming the degradation products and their complexes into water-soluble forms that naturally separate from the organic phase. This inversion of the separation strategy converts the difficult long-term storage problem into an easy phase separation 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 method achieves a high recovery rate of plutonium, with over 99% of plutonium being recovered in the aqueous phase, reducing the plutonium content in the waste organic phase to less than 0.1 mg/L, meeting the requirements for effective waste treatment.
Implementation Method 1
HDBP and H2MBP in the above degradation products are prone to form complexes with Pu (IV) and Zr (IV), and the complexes have binding energies greater than those of Pu (IV) and Zr (IV) with TBP
Implementation Method 2
contacting the waste organic phase of the PUREX process with an aqueous back extraction solution containing 2,6-pyridinedicarboxylic acid for back extraction
Implementation Method 3
contacting the back extraction product with an anion exchange resin such that plutonium in the back extraction product is adsorbed on the anion exchange resin
Data Source
AI summary
A method for treating retained plutonium in a waste organic phase of a plutonium uranium reduction extraction (PUREX) process is provided. The waste organic phase of the PUREX process contains an organic solvent and plutonium, and the method includes contacting the waste organic phase of the PUREX process with an aqueous back extraction solution containing 2,6-pyridinedicarboxylic acid for back extraction to obtain a plutonium back extraction product; and the plutonium in the back extraction solution may be loaded onto the column for adsorption, transformation and desorption by an anion exchange column, ultimately recovering plutonium in the back extraction solution.