Separation of Plutonium-238 from Fission Products by Solvent Extraction Using HDEHP

Akatsu, J.

doi:10.1080/18811248.1973.9735475

Cited by 9 publications

(4 citation statements)

References 9 publications

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“…The oxidation state of Pu in the aqueous phase was determined for selected samples using the liquid-liquid extraction method described in Neck et al [2]. The method is a combination of previously reported approaches [29][30][31][32][33], and allows the quantification of Pu(III), Pu(IV), Pu(V), Pu(VI) and colloidal Pu(IV) with an uncertainty of 20 % (for the Pu concentration-range evaluated in this study). Note further that the reliability of the method is greater for the separation/identification of the groups (Pu(III) + Pu(IV)) and (Pu(V) + Pu(VI)), because of the slower redox transformation kinetics of Pu n+ ⇔ PuO 2 z+ .…”

Section: Liquid-liquid Extractionmentioning

confidence: 99%

Redox behavior and solubility of plutonium under alkaline, reducing conditions

et al. 2018

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The solubility and redox behavior of hydrous Pu(IV) oxide was comprehensively investigated by an experimental multi-method approach as a function of different redox conditions in 0.1 M NaCl solutions, allowing a detailed characterization of Pu(IV) and Pu(III) solubility and solid phase stability in these systems. Samples were prepared at ~3≤pHm≤~6 (pHm=–log${{\text{m}}_{{{\text{H}}^{\text{ + }}}}})$and ~8≤pHm≤~13 atT=(22±2)°C under Ar atmosphere. No redox buffer was used in one set of samples, whereas mildly and strongly reducing redox conditions were buffered in two series with hydroquinone or SnCl2, respectively, resulting in (pe+pHm)=(9.5±1) and (2±1). XRD, XANES and EXAFS confirmed the predominance of Pu(IV) and the nanocrystalline character of the original, aged PuO2(ncr,hyd) solid phase used as a starting material. Rietveld analysis of the XRD data indicated an average crystal (domain) size of (4±1) nm with a mean cell parameter of (5.405±0.005) Å. The solubility constant of this solid phase was determined as log$^ * K{^\circ _{{\text{s}},0}}$=–(58.1±0.3) combining solubility data in acidic conditions and redox speciation by solvent extraction and CE–SF–ICP–MS. This value is in excellent agreement with the current thermodynamic selection in the NEA-TDB. Synchrotron-basedin-situXRD, XANES and EXAFS indicate that PuO2(ncr,hyd) is the solid phase controlling the solubility of Pu in hydroquinone buffered samples. Under these redox conditions and ~8≤pHm≤~13, the solubility of Pu is very low (~10−10.5m) and pH-independent. This is consistent with the solubility equilibrium PuO2(am,hyd)+2H2O(l)⇔ Pu(OH)4(aq). Althoughin-situXRD unequivocally shows the predominance of PuO2in Sn(II)-buffered systems, XANES analyses indicate a significant contribution of Pu(III) (30±5%) in the solid phases controlling the solubility of Pu at (pe+pHm)=(2±1). For this system, EXAFS shows a systematic shortening of Pu–O and Pu–Pu distances compared to the starting Pu material and hydroquinone-buffered systems. The solubility of Pu remains very low (~10−10.5m) at pHm>9, but shows a very large scattering (~10−9–10−10.5m) at pHm=8. Experimental observations collected in Sn(II) buffered systems can be explained by the co-existence of both PuO2(ncr,hyd) and Pu(OH)3(am) solid phases, but also by assuming the formation of a sub-stoichiometric PuO2−x(s) phase. This extensive study provides robust upper limits for Pu solubility in alkaline, mildly to strongly reducing conditions relevant in the context of nuclear waste disposal. The potential role of Pu(III) in the solid phases controlling the solubility of Pu under these conditions is analysed and discussed in view of the current NEA-TDB thermodynamic selection, which supports the predominance of PuO2(am,hyd) and constrains the formation of Pu(OH)3(am) at pHm>8 outside the stability field of water.

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Section: Liquid-liquid Extractionmentioning

confidence: 99%

Redox behavior and solubility of plutonium under alkaline, reducing conditions

et al. 2018

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“…The presence of Pu (IV) was evidenced in some experiments by extraction of plutonium in compartment A with HDEHP (bis(2ethylhexyl)phosphoric acid) in hexane, which extracts the +IV and +VI oxidation state but not the +III and +V oxidation states. 21 In an experiment with a double spike of 238 Pu at +IV and 239 Pu at +V oxidation states, SPE (solid phase extraction) on TEVA resin was used to specifically extract Pu (IV) from the B compartment in nitric acid media. Pu (V) was not extracted in these conditions.…”

Section: ■ Experimental Sectionmentioning

confidence: 99%

“…In one experiment designed to control the +IV oxidation state of plutonium, all the solutions were degassed with N 2 until the oxygen probe (CellOx 325) read <0.5 ppm, and the diffusion experiment was carried out in a glovebox under N 2 flux. The presence of Pu (IV) was evidenced in some experiments by extraction of plutonium in compartment A with HDEHP (bis(2-ethylhexyl)phosphoric acid) in hexane, which extracts the +IV and +VI oxidation state but not the +III and +V oxidation states . In an experiment with a double spike of 238 Pu at +IV and 239 Pu at +V oxidation states, SPE (solid phase extraction) on TEVA resin was used to specifically extract Pu (IV) from the B compartment in nitric acid media.…”

Section: Experimental Sectionmentioning

confidence: 99%

A DGT Technique for Plutonium Bioavailability Measurements

Cusnir

Steinmann

Bochud

et al. 2014

Environ. Sci. Technol.

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The toxicity of heavy metals in natural waters is strongly dependent on the local chemical environment. Assessing the bioavailability of radionuclides predicts the toxic effects to aquatic biota. The technique of diffusive gradients in thin films (DGT) is largely exploited for bioavailability measurements of trace metals in waters. However, it has not been applied for plutonium speciation measurements yet. This study investigates the use of DGT technique for plutonium bioavailability measurements in chemically different environments. We used a diffusion cell to determine the diffusion coefficients (D) of plutonium in polyacrylamide (PAM) gel and found D in the range of 2.06-2.29 × 10(-6) cm(2) s(-1). It ranged between 1.10 and 2.03 × 10(-6) cm(2) s(-1) in the presence of fulvic acid and in natural waters with low DOM. In the presence of 20 ppm of humic acid of an organic-rich soil, plutonium diffusion was hindered by a factor of 5, with a diffusion coefficient of 0.50 × 10(-6) cm(2) s(-1). We also tested commercially available DGT devices with Chelex resin for plutonium bioavailability measurements in laboratory conditions and the diffusion coefficients agreed with those from the diffusion cell experiments. These findings show that the DGT methodology can be used to investigate the bioaccumulation of the labile plutonium fraction in aquatic biota.

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“…The dependency is linear with negative slope as shown in Figure 4-2. For plutonium, it had been reported that HDEHP has high affinity to both trivalent and pentavalent plutonium [55].…”

Section: Theory and Backgroundmentioning

confidence: 99%

Development of Novel Method for Rapid Extract of Radionuclides from Solution using Polymer Ligand Film

Rim¹

2013

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Accurate and fast determination of the activity of radionuclides in a sample is critical for nuclear forensics and emergency response. Radioanalytical techniques are well established for radionuclides measurement, however, they are slow and labor intensive, requiring extensive radiochemical separations and purification prior to analysis. With these limitations of current methods, there is great interest for a new technique to rapidly process samples. This dissertation describes a new analyte extraction medium called Polymer Ligand Film (PLF) developed to rapidly extract radionuclides. Polymer Ligand Film is a polymer medium with ligands incorporated in its matrix that selectively and rapidly extract analytes from a solution. The main focus of the new technique is to shorten and simplify the procedure necessary to chemically isolate radionuclides for determination by alpha spectrometry or beta counting. Five different ligands were tested for plutonium extraction: bis(2-ethylhexyl) methanediphosphonic acid (H 2 DEH[MDP]), di(2-ethyl hexyl) phosphoric acid (HDEHP), trialkyl methylammonium chloride (Aliquat-336), 4,4'(5')-di-t-butylcyclohexano 18crown-6 (DtBuCH18C6), and 2-ethylhexyl 2-ethylhexylphosphonic acid (HEH[EHP]). The ligands that were effective for plutonium extraction further studied for uranium extraction. The two ligands, H 2 DEH[MDP] and HDEHP, which showed effectiveness in plutonium extraction were extensively studied. The extraction of strontium was exclusively studied with DtBuCH18C6. This particular ligand was effective for strontium separation in resin bead form. However, in PLF form, the ligand became completely ineffective for strontium extraction. vii

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Separation of Plutonium-238 from Fission Products by Solvent Extraction Using HDEHP

Cited by 9 publications

References 9 publications

Redox behavior and solubility of plutonium under alkaline, reducing conditions

Redox behavior and solubility of plutonium under alkaline, reducing conditions

A DGT Technique for Plutonium Bioavailability Measurements

Development of Novel Method for Rapid Extract of Radionuclides from Solution using Polymer Ligand Film

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