Extraction Of Plutonium Research Articles

Molecular Hosts for the Sensing and Separation of 99TcO4.

In recent years, European Union member states have hastened energy policy deliberations to address supply and sustainability concerns, placing a significant emphasis on nuclear energy as a means to achieve decarbonization goals. However, despite its significant role in power generation, nuclear energy faces significant challenges linked to fuel reprocessing and waste disposal, that hinder its broader expansion. In this context, the separation of technetium represents a concerning issue. Indeed, technetium's catalytic activity can impede the extraction of uranium, neptunium, and plutonium, affecting waste reprocessing efficiency. Additionally, the stable form of technetium in aerobic conditions, pertechnetate (TcO4 -), poses risks of groundwater contamination due to its mobility and solubility. Hence, sensing and separation of TcO4 - is imperative for both nuclear fuel processing and minimising radioactive contamination in the environment. However, the binding of TcO4 - and its separation from contaminated solutions present challenges due to the acidic (or basic) waste components and the high ionic strength in real matrices. Supramolecular chemists have addressed these issues by designing receptors inspired by molecular recognition principles. This article explores recent advancements and future directions in TcO4 - sensing and separation (using extraction and sorption) with a focus on molecular hosts. Metal-organic receptors will also be discussed.

Unique Selectivity Reversal in the Complexation of Uranium(VI) and Plutonium(IV) with Two Novel C-Pivoted Tripodal Amide Ligands: Extraction and Liquid Membrane Transport Studies

ABSTRACT Two new carbon pivoted tripodal amide-containing ligands with different spacers (L I : -CH2- spacer; L II : -CH2-CH2- spacer) have been investigated for the liquid–liquid extraction of tetravalent plutonium and hexavalent uranium from nitric acid feed solutions. The studies were carried out using the ligand solutions prepared in 95% n-dodecane + 5% isodecanol. Pu(IV) extraction was higher than that of U(VI) at 3 M HNO3 for ligand L I which was just the opposite for ligand L II . Increase of the nitric acid concentration resulted in increasing extraction of both metal ions. Isodecanol variation studies exhibited decrease in the extraction of Pu(IV) and U(VI) with increasing isodecanol content in the organic phase. Greater that 98% stripping of Pu(IV) and U(VI) was obtained from the complexes of L I and L II using 0.5 M HNO3 + 0.1 M HEDTA and 1 M Na2CO3, respectively. The slope analysis study suggested the formation of 1:2 (ML2) species with Pu(IV) as well as U(VI) with both ligands at 3 M HNO3. Temperature variation studies showed that the extraction of U(VI) and Pu(IV) with both ligands is exothermic in nature. Supported liquid membrane transport experiments using 0.11 M ligands (L I and L II ) in 95% n-dodecane + 5% isodecanol indicated poor transport (<10% after 2 h) of U(VI) and Pu(IV).

Efficient Plutonium Extraction and Electrochemical Insights in a Hydrophobic Deep Eutectic Solvent for Radioactive Waste Management

In this study, we explore the extraction and electrochemical characteristics of Plutonium using a hydrophobic deep eutectic solvent (DES) consisting of tetra-Butyl Ammonium Bromide(TBABr) as the hydrogen bond acceptor and Decanoic acid (DA) as the hydrogen bond donor in a 1:2 ratio composition. Hydrophobic DES possesses unique attributes, such as low volatility and a high affinity for metal ions, making it a promising choice for Plutonium extraction. We systematically investigate the influence of various parameters, including DES composition, acid concentration, and extraction duration. Our extraction experiments reveal that the hydrophobic DES exhibits its maximum Plutonium extraction efficiency (95%) at a 4 M HNO3 concentration, with a distribution coefficient (D) reaching nearly 71. To gain insights into the electrochemical behavior of Plutonium within the hydrophobic DES, we conduct cyclic voltammetry experiments. The resulting voltammograms offer valuable insights into the redox properties and stability of Plutonium species within the DES. Furthermore, we analyze the impact of potential scan rate on the electrochemical response, shedding light on the kinetics and mechanisms underlying Plutonium electrochemistry within the hydrophobic DES. These findings underscore the considerable potential of hydrophobic DES for efficient Plutonium extraction and electrochemical separation. This research contributes to the development of sustainable and environmentally friendly approaches for managing Plutonium, particularly in the context of nuclear waste disposal

Evaluation of the remaining spent extraction solvent in vermiculite after leaching tests via PIXE analysis

The spent extraction solvent, primarily comprising tributyl phosphate (TBP) and normal dodecane, is waste product generated by the solvent extraction of plutonium and uranium to develop the plutonium–uranium redox-extraction process. The spent solvent should be appropriately treated for disposal or storage. One treatment option for storing the spent solvent is the adsorption of the liquid into vermiculite. The organic liquid is trapped between the vermiculite layers. Our previous experiments on the adsorption of spent solvent into vermiculite have shown that some parts of the loaded solvent gradually leaked from the vermiculite. Therefore, the elution behavior of the loaded solvent into organic diluents, such as hexane or acetone, were evaluated to investigate the adsorption mechanism and capacity. Some loaded solvents easily leaked into the diluent, whereas some remained inside the particle, even after the leaching test. The difference in behavior might be attributed to different adsorption mechanisms, and the amount of the remaining solvent is the adsorption capacity for safely storing the solvent. This study evaluated the vermiculite adsorption capacity via the remaining solvent after washing with diluents, such as ethanol or distilled water. The remaining solvent was analyzed using particle-induced X-ray emission (PIXE) on phosphorous (P) contained in the TBP. PIXE analysis quantitatively analyzed the trace amounts of residual TBP, and n-dodecane and TBP were suggested to be adsorbed to vermiculite by different mechanisms.

Separation of neptunium and plutonium with neutral phosphorus ligands: A theoretical perspective

Effective treatment of the transuranic neptunium and plutonium from nuclear waste is of great importance and remains a challenge for developing advanced nuclear fuel cycles. Currently, novel ligands for efficient separation of actinides need to be designed urgently. Neutral extractants containing phosphorus have shown great potential for actinides separation. In this paper, we systematically explored the extraction and separation performances of neptunium(IV,V,VI) and plutonium(IV) by three phosphorus derivatives, di(1-methyl-heptyl) methyl phosphonate (P350), tri-iso-amyl phosphate (TiAP), and tributyl phosphate (TBP) by density functional theory (DFT). The outcomes showed that these neutral phosphorus reagents act as monodentate ligands through the PO group for all the extraction complexes. According to bonding nature analysis, the P350 ligand has the strongest complexing ability to the studied actinide cations. In addition, these ligands show a preference to coordination with Pu4+ and NpO22+ over Np4+ and NpO2+, respectively. As expected, the thermodynamic analysis demonstrated the potential application of these neutral extractants in Np and Pu separation, among which the P350 ligand is more promising than TBP and TiAP in acid solution system. This work can help to further understand the separation mechanism of Np/Pu with neutral phosphorus reagents and provide insight into the development of highly efficient extractants in recovery of Np and Pu.

Extraction of Neptunium, Plutonium, Americium, Zirconium, and Technetium by Di-(2-Ethylhexyl)-Iso-Butyramide (DEHiBA) at High Metal Loadings

ABSTRACT Increased focus on carbon neutral energy has generated a resurgence of interest in nuclear power, and in particular advanced reactors which are likely to utilize high assay low enriched uranium (HALEU). This in turn could increase the economic attractiveness of recovering still partially enriched uranium from used nuclear fuel. Concomitant to development of advanced reactors, advanced reprocessing schemes should be developed which address the disadvantages to well established reprocessing schemes. The present study focuses on using di-(2-ethylhexyl)-iso-butyramide (DEHiBA) under high metal loading conditions for the reprocessing of used nuclear fuel. The elements examined in the study include the dominant transuranic actinides (Np, Pu, Am) as well as the often-problematic Tc and Zr. By increasing the concentration of the extractant from the more commonly reported 1.0 M – 1.5 M, the extraction of hexavalent actinides is substantially increased, while maintaining effective rejection of tri, tetra, and pentavalent actinides, particularly in the presence of high loadings of uranium. The extraction of Zr by 1.5 M DEHiBA is noted to be negligible by comparison to tributyl phosphate (TBP), however the coextraction of Tc with U is observed to be nominally twice the quantity that is extracted by TBP indicating a need for effective Tc management.

Utilizing deep eutectic solvent for facile, selective and sustainable sequestration of plutonium

In the recent surge of green and cheap energy for future generation; nuclear industry is going to play a pivotal role and reprocessing of nuclear fuel through safe and systematic approach is the key. In that direction recent literature has shown that there is lack of better and improved methods towards efficient extraction of highly radiotoxic and hazardous plutonium from nuclear waste. Herein, we have utilized a greener and cost effective indigenously synthesized deep eutectic solvent (DES) for the selective extraction of plutonium from (Am, Pu, U) waste. The maximum D value achieved for Pu was 67.42 at 5 mol L−1 HNO3 media and the equilibrium uptake capacity was found to be 107.28 ± 5 μg of Pu/g of C12DES. This was followed by solidified floating organic drop micro-extraction (SFODME) technique for its quantification. High radiation stability of this DES (upto 750 kGy) highlighted its great potential in nuclear fuel reprocessing. Several other reprocess parameters were studied and optimized such as DES volume, alkyl chain length attached to hydrogen bond acceptor (HBA), actinide concentration and speciation and its acidity to achieve best extraction of plutonium ion form the waste stream. Regeneration capability and reusability of the DES employing stripping agents gave encouraging results as 95% of Pu could be stripped in a single cycle using 1 M hydroxylamine hydrochloride as the stripping agent. The developed method was applied for recovery and quantification of Pu from real samples, viz. (U,Pu) Carbide fuel solution, radioactive research waste and synthetic dissolver solution. We believe this work is a way forward in resolving a variety of issues that exist in health physics and reprocessing laboratories of nuclear installation pertaining to selective and efficient extraction of Pu (IV).

Hybrid extractive scintillator resin for simultaneous concentration and detection of plutonium from aqueous solutions

A scoping study of a commercially available resin selective for aqueous plutonium (Pu), AnaLig® Pu-02, modified with scintillator was investigated as a scheme to simultaneously concentrate and detect Pu in aquatic matrices. The extractive scintillating resin was comprised of a silica base, functionalized for plutonium extraction, grafted with plastic scintillator of polyvinyl toluene (PVT) and 2-(1-naphthyl)-4-vinyl-5- phenyloxazole (vNPO) fluor. Scintillator was incorporated onto the AnaLig® Pu-02 resin in a two-step process of silanization followed by surface-polymerization. Successful modification was facilitated by grinding the resin beads prior to silanization to expose cleaved silica surface sites appropriate for scintillator grafting. The modified resin was subjected to initial characterization of batch uptake and radioluminosity measurements where a total detection efficiency of 32.5% was observed. The modified resin was then subjected to pH 1 simulants containing environmental relevant groundwater constituents of varying concentration. Concentrations of 0.001M Fe(III) interfered with Pu uptake, while concentrations of up to 0.01M Ca(II) and 0.001 mM concentration of natural uranium and thorium had minimal influence on plutonium uptake. A translucent column packed with the modified AnaLig® Pu-02 was placed in a commercial flow-cell radiation detector for real-time detection of plutonium; a total detection efficiency of 20.4% was achieved for on-line measurements. The modification of AnaLig® Pu-02 results in a minimum detection limit capable of meeting the EPA limit for gross alpha activity in drinking water given a sufficient counting time of 15 min and approximately 300 mL of solution volume.

Supercritical Fluid Extraction of Uranium, Plutonium and Thorium

In recent decades, extraction of actinides (U,Pu,Th) employing supercritical CO2has drawn attention owing to its inherent potential to minimize liquid waste generation. Supercritical Fluid Extraction (SFE) offers faster extraction with fine control over extraction process by means of varying pressure , temperature conditions. Supercritical Fluids have hybridproperties of liquid and gas. Liquid like solvation and gas like diffusivity enable topenetrate deep inside solid matrix, extracting component of interest, thus capable of extraction from liquid as well as solid matrix. Metal ion is complexed withsuitable organic compound, which gets soluble in SC CO2 . SC CO2 acts as a solvent and after extractionescapes as gas leaving behind extractant. Various types of ligands such organophosphorus compounds, -diketones, macrocyclic compounds, amides, dithiocarbamates are employed.SFE offers attractive alternative to reprocessing of spent nuclear fuel and radioactive waste.In this paper, research work carried out on the SFE of actinides (U,Pu,Th) has been reviewed.

Supercritical Fluid Extraction of Uranium, Plutonium and Thorium: A Review

In recent decades, extraction of actinides (U,Pu,Th) employing supercritical CO2has drawn attention owing to its inherent potential to minimize liquid waste generation. Supercritical Fluid Extraction (SFE) offers faster extraction with fine control over extraction process by means of varying pressure , temperature conditions. Supercritical Fluids have hybridproperties of liquid and gas. Liquid like solvation and gas like diffusivity enable topenetrate deep inside solid matrix, extracting component of interest, thus capable of extraction from liquid as well as solid matrix. Metal ion is complexed withsuitable organic compound, which gets soluble in SC CO2 . SC CO2 acts as a solvent and after extractionescapes as gas leaving behind extractant. Various types of ligands such organophosphorus compounds, -diketones, macrocyclic compounds, amides, dithiocarbamates are employed.SFE offers attractive alternative to reprocessing of spent nuclear fuel and radioactive waste.In this paper, research work carried out on the SFE of actinides (U,Pu,Th) has been reviewed.

Development of a rapid technique for sequential separation of plutonium/americium in nasal swab using solvent extraction and liquid scintillation spectrometry

A rapid radiochemical method has been developed for estimation of plutonium and americium in nasal swab using extractive liquid scintillation spectrometry. The method involves solvent extraction of plutonium and americium from pre-treated nasal swab using 0.2 M Di-(2-ethylhexyl)phosphoricacid prepared in toluene scintillator & back extraction of americium in aqueous phase using 0.35 M HNO3. Activity assessment was carried out using liquid scintillation spectrometry. Overall recovery obtained was 96% for plutonium and 76% for americium with a sample turnaround time of 3 h.

Cyphos nitrate: A potential ionic liquid for the extraction and selective separation of plutonium (IV) from other metal ions present in nitric acid

Cyphos nitrate (Trihexyl(tetradecyl)phosphonium nitrate: [P66614][NO3]) is a well-known ionic liquid which is strongly hydrophobic and sustainable for the recovery of metal ions from waste matrix. In the present study, the ionic liquid was explored for the selectively separation of plutonium(IV) from uranium(VI), zirconium(IV), americium(III) and europium(III) present in the nitric acid medium in conjunction with 1,3-diisopropyl benzene (DIPB) as the diluent. The extraction factors of Pu(IV) were evaluated as a function of various experimental parameters such as the concentration of feed acidity, the concentration of ionic liquid, equilibration time, temperature, type of ionic liquid ions, etc. Facile formation of the anionic nitrato complex of Pu(IV) in the ionic liquid phase was found to be the driving force for the preferential extraction of Pu(IV) over other metal ions. Effect of radiation dose suggested the stability of the proposed ionic liquid by acquiring the similar extraction factors like that in the unirradiated ionic liquid phase. Remarkable separation factors of Pu(IV) over the aforementioned metal ions were computed and presented in the paper. Various thermodynamic parameters accompanied by the extraction as well as the back extraction processes of Pu(IV) from the loaded ionic liquid phase have been presented in detail.

Pyridine diglycolamide: A novel ligand for plutonium extraction from nitric acid medium

A novel ligand N, N, N’, N’ tetra-isobutyl pyridine diglycolamide (PDGA) was synthesized and tested for extraction of actinides and fission products present in high level liquid waste (HLLW). The ligand was studied in presence of two different diluents- nitrobenzene (NB), a molecular diluent and 3-methyl-1-octyl immidazolium bis[(trifluoromethyl)sulfonyl] imide, an Ionic Liquid (IL). Unusual selectivity towards tetravalent plutonium over minor actinides and alkali & alkaline metal ions present in nuclear waste was showed by PDGA in presence of NB as diluent. The trend in kinetics of extraction as well as dependency of DPu(IV) values with nitric acid concentration was found to be different for two diluents studied. Mechanism of extraction was also varied for the two diluents studied. It followed solvation mechanism for NB whereas for IL it was a combination of solvation and ion-exchange mechanism. The calculated Gibbs free energy of extraction, ΔGext for Pu(IV) using density functional theory was found to be higher than that of other competitive metal ions corroborating the results from solvent extraction experiment. Further, ΔGext was found to be highly negative for metal and ionic liquid cations thus complimenting the experimental findings of ion exchange mechanism for a metal cation with cation of the ionic liquid.

Highly efficient Plutonium(IV) uptake from acidic feeds using four extraction chromatography resins containing diglycolamides and ionic liquid

Quantitative recovery of plutonium from lean effluents is one of the most challenging tasks for separation scientists. Four extraction chromatography (XC) resins containing substituted diglycolamide ligands viz. N,N,N',N'-tetra-n-pentyl diglycolamide (TPDGA), N,N,N',N'-tetra-n-hexyl diglycolamide (THDGA), N,N,N',N'-tetra-n-octyl diglycolamide (TODGA) and N,N,N',N'-tetra-n-decyl diglycolamide (TDDGA) and a room temperature ionic liquid (RTIL) were tested for the extraction of plutonium (IV) from nitric acid feed solutions. The relative efficiency of uptake of the metal ion in the entire range of HNO3 studied was: TPDGA > THDGA > TODGA > TDDGA, which was opposite to the chain length of the attached alkyl groups. Also, for all the four XC resins the uptake of Pu(IV) was found to decrease with increasing nitric acid concentration in the lower acidity range followed by an increase thereafter. The uptake of Pu(IV) with all the four XC resins was fitted into different kinetic and isotherm models. It was found that all the four resins followed the pseudo-second order kinetic model and Langmuir monolayer adsorption model. Column studies with these XC resins using a loading solution containing 1.2g/L Pu(IV) in 3M HNO3 showed early breakthrough for the higher homolog DGA ligands as compared to the lower homologs. Effective elution of the loaded Pu(IV) from the column was done in about 5.5 column volumes using a solution containing 0.5M oxalic acid in 0.5M HNO3.

A comparison of the efficiency of extraction of americium and plutonium on solid-phase extractants TODGA, DN Resin-B, and TEVA Resin-B from model pulps of accumulated higher activity waste

A comparison of the efficiency of extraction of americium and plutonium on solid-phase extractants TODGA, DN Resin-B, and TEVA Resin-B from model pulps of accumulated higher activity waste

Extraction of Uranium(VI) and Plutonium(IV) by New Tri Alkylcarbamides

ABSTRACT The use of tri-alkylcarbamides (TrAC) as novel extractants for the separation of uranium(VI) and plutonium(IV) by solvent extraction from spent nuclear fuels is investigated. The comparison between extraction properties of different tri-alkylcarbamides and tetra-alkylcarbamides indicates their higher ability to co-extract uranium(VI) and plutonium(IV). Moreover, tri-alkylcarbamides present very high separation factors SFU/Pu (up to 100) at lower nitric acid concentration showing that they are good candidates for U(VI)/Pu(IV) separation without redox chemistry. The addition of branched 2-ethylhexyl chains induces a decrease of distribution ratios and U/Pu separation factor. Due to the formation of intermolecular hydrogen bond between carbonyl and -NH functions, the viscosity of tri-alkylcarbamides is higher compared to tetra-alkylcarbamides. Nevertheless, the introduction of branched alkyl chains decreases the viscosity of the solvent and increases the limit organic concentration (LOC) for uranium(VI), preventing from third phase formation.

К ВОПРОСУ О ЦЕНЕ ПЛУТОНИЯ В ДВУХКОМПОНЕНТНОЙ ЯЭС

A possible approach to accounting for the specific present value of plutonium produced in fast reactors of a two-component nuclear power system (NPS) with thermal and fast reactors is described. The approach is based on taking into account the additional income that can be obtained by selling at the market price the natural uranium released when thermal reactors are replaced with fast reactors with MOX-fuel based on plutonium produced in NPS. At the same time, along with the sale of natural uranium, the sale at market value of other products made on its basis, for example, enriched uranium or fuel assemblies for a thermal reactors, can be considered. Relations between the main fuel characteristics of the considered nuclear reactors and the economic parameters characterizing the efficiency of nuclear reactors and the fuel cycle of a NPS are obtained. Using the methodology described in this paper, a computational study of the specific present value of plutonium in a two-product nuclear power model with commercial sodium high-power fast reactor and VVER-1200 reactors was carried out. The calculation results in all considered cases indicate very significant present value of plutonium. Comparison of the obtained cost of plutonium, which is ultimately based on the energy equivalent of plutonium and uranium, and the cost of plutonium, determined on the basis of the costs of the back-end of the fuel cycle (plutonium extraction from SNF), show the economic efficiency of closing the fuel cycle even at existing uranium prices.

Development of small-scale plutonium electrorefining in molten CaCl2

Molten salt extraction and electrorefining of plutonium were successfully conducted with only a 200-g initial charge. Due to this small scale, the electrorefining cell components were redesigned relative to conventional, multi-kg standards. The efficiency and yield of this small-scale process are comparable to those of larger-scale exemplars. Chemical analysis of the plutonium product and the anode heel is presented. The product was 99.8% pure. The anode heel was able to be depleted beyond the expected freezing point without significant impurity carryover.

Effect of acetohydroxamic acid on the extraction of plutonium by dilute tri-n-butyl phosphate/n-dodecane in the presence of a high concentration of Al(NO3)3

Effect of acetohydroxamic acid on the extraction of plutonium by dilute tri-n-butyl phosphate/n-dodecane in the presence of a high concentration of Al(NO3)3

Insights from quantum chemical calculations into inner and outer-sphere complexation of plutonium(iv) by monoamide and carbamide extractants

The strong influence of the structure of amide derivatives on their extraction properties has been demonstrated in several studies in the literature. To investigate and rationalize the influence of the nature and length of the monoamide alkyl chains on Pu(iv) extraction/complexation, a theoretical study was performed using the Density Functional Theory (DFT) method in the scalar relativistic framework. For that, the geometries for the inner/outer-sphere complexes and interaction energies of [Pu(NO3)4] and [Pu(NO3)6]2- with different ligands have been calculated. For both inner and outer-sphere complexes, it is found that the introduction of a bulky alkyl group on the carbonyl side strongly diminishes the complexation energy. This is fully consistent with monamide extraction properties. The influence of the bulkiness of the alkyl group is as or even more important for outer than for inner-sphere interactions. This result was unexpected when considering that there are less flexibility and stronger steric constraints in the inner sphere compared to the outer one. However, this can be attributed to specific electrostatic interactions between the two outer-sphere amide ligands and two nitrate ions of [Pu(NO3)6]2-. By increasing the polarity of the solution, such interactions diminish and the outer-sphere ligands move away from [Pu(NO3)6]2-. Consequently, the solvent effects were found to be very significant for outer-sphere complexation while rather small for inner-sphere complexation. This gives the key possibility to tune the substituent effect by changing the polarity of the solution. As for carbamide ligands, it was found that the weak interactions (dispersion) have remarkable effects on both inner and outer-sphere complexations.