• Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
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• v.16 no.3
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• pp.347-357
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• 2018

The applicability of room temperature ionic liquids (RTILs), 1-alkyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ([$C_nmim$] [$Tf_2N$]), was investigated for the extraction of Am(III) and Eu(III) from nitric acid using n-octyl(phenyl)-N,N-diisobutyl carbamoylmethyl phosphine oxide (CMPO) and tri-n-butylphosphate (TBP) as extractants. The distribution ratios of Am(III) and Eu(III) in CMPO-TBP/[$C_nmim$][$Tf_2N$] were measured as a function of various parameters such as the concentrations of nitric acid, CMPO, and TBP. The results were compared with those obtained in CMPO-TBP/n-dodecane (n-DD). With comparable concentrations of the extractants, the distribution ratios obtained with RTILs were much higher than those obtained with n-DD. It was observed that the extraction efficiency was less for Eu(III) than for Am(III). The extraction of Am(III) and Eu(III) decreased with increases in the feed acidity for all three RTILs. The results suggest that the extraction of Am(III) and Eu(III) by CMPO in RTILs from nitric acid proceeds through the cation-exchange mechanism. The distribution ratios of Am(III) and Eu(III) increased with increases in the concentration of CMPO for all three RTILs. A linear regression analysis of the extraction data resulted in a straight line with a slope of about 3, suggesting the involvement of 3 molecules of CMPO during the extraction process.

• Proceedings of the Korean Nuclear Society Conference
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• 1996.05c
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• pp.559-564
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• 1996

다작용기 유기인산 추출제인 octyl(phenyl)-N, N-diisobutyl carbamoylmethylphosphine oxide(CMPO)의 Am(III)에 대한 추출특성을 조사하였다. 0.2M CMPO-1.4M TBP/n-dodecane 추출제, 추출온도 30 $^{\circ}C$, 수용액의 질산농도 2M인 조건에서 Am(III)은 95.8%가 추출되었다. CMPO 추출제에 첨가되는 TBP 농도가 0.5M 까지는 Am(III)의 추출율이 감소시키는 영향을 나타냈으나, 0.5M 이상인 영역에서는 Am(III) 추출율에 미치는 영향이 작게 나타났다. 그리고 Am(III) 추출에 미치는 옥살산농도의 영향은 옥살산농도가 증가할수록 Am(III)의 추출율이 감소하였으며 추출온도가 높을수록 Am(III) 추출율이 감소하는 실험결과를 얻었다. CMPO 추출제는 제 3상을 매우 잘 형성하여 특징을 나타냈으며 이를 방지할 수 있는 조건을 규명하였다.

• Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
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• v.20 no.4
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• pp.371-382
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• 2022

Carbonates are inorganic ligands that are abundant in natural groundwater. They strongly influence radionuclide mobility by forming strong complexes, thereby increasing solubility and reducing soil absorption rates. We characterized the spectroscopic properties of Am(III)-carbonate species using UV-Vis absorption and time-resolved laser-induced fluorescence spectroscopy. The deconvoluted absorption spectra of aqueous Am(CO₃)₂^- and Am(CO₃)₃^3- species were identified at red-shifted positions with lower molar absorption coefficients compared to the absorption spectrum of aqua Am³⁺. The luminescence spectrum of Am(CO₃)₃^3- was red-shifted from 688 nm for Am³⁺ to 695 nm with enhanced intensity and an extended lifetime. Colloidal Am(III)-carbonate compounds exhibited absorption at approximately 506 nm but had non-luminescent properties. Slow formation of colloidal particles was monitored based on the absorption spectral changes over the sample aging time. The experimental results showed that the solubility of Am(III) in carbonate solutions was higher than the predicted values from the thermodynamic constants in OECD-NEA reviews. These results emphasize the importance of kinetic parameters as well as thermodynamic constants to predict radionuclide migration. The identified spectroscopic properties of Am(III)-carbonate species enable monitoring time-dependent species evolution in addition to determining the thermodynamics of Am(III) in carbonate systems.

• Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
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• v.16 no.4
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• pp.397-410
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• 2018

When considering the long-term safety assessment of spent-nuclear fuel management, americium is one of the most radio-toxic actinides. Although spectroscopic methods are widely used for the study of actinide chemistry, application of those methods to americium chemistry has been limited. Herein, we purified $^{241}Am$ to obtain a highly pure stock solution required for spectroscopic studies. Quantitative and qualitative analyses of purified $^{241}Am$ were carried out using liquid scintillation counting, and gamma and alpha radiation spectrometry. Highly sensitive absorption spectrometry coupled with a liquid waveguide capillary cell and time-resolved laser fluorescence spectroscopy were employed for the study of Am(III) hydrolysis and oxalate (Ox) complexation. $Am^{3+}$ ions under acidic conditions exhibit maximum absorbance at 503 nm, with a molar absorption coefficient of $424{\pm}8cm^{-1}{\cdot}M^{-1}$. $Am(OH)_3(s)$ colloidal particles formed under near neutral pH conditions were identified by monitoring the absorbance at around 506-507 nm. The formation of ${Am(Ox)_3}^{3-}$ was detected by red-shifts of the absorption and luminescence spectra of 4 and 5 nm, respectively. In addition, considerable enhancements of the luminescence intensities were observed. The luminescence lifetime of ${Am(Ox)_3}^{3-}$ increased from 23 to 56 ns, which indicates that approximately six water molecules are replaced by carboxylate ligands in the inner-sphere of the Am(III). These results suggest that ${Am(Ox)_3}^{3-}$ is formed through the bidentate coordination of the oxalate ligands.

• Proceedings of the Korean Nuclear Society Conference
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• 1995.05a
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• pp.841-846
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• 1995

대전지역 토양에서 추출한 흄산(TJHA)과 Am(III), Eu(III)의 착물형성에 대한 안정도상수를 추출용매 di-2-ethylhexyl phosphoric acid와 희석제 toluene을 사용하여 용매추출법으로 구하였다. 이온강도가 0.1M NaCIO$_4$에서 TJHA의 총 carboxylate capacity를 직접 전위차적정법으로 분석한 결과 3.757 meq/g이고, apparent pKa는 5.15 이었다. TJHA와 Am(III) 및 Eu(III)의 조건부 안정도상수의 log$\beta$1 값과 log$\beta$2 값을 흄산의 이온화도 함수로 구한 결과, Eu-TJHA은 0.1M NaClO$_4$일때 log $\beta$1=5.948$\alpha$ + (6.83 $\pm$ 0.3) 및 log $\beta$2 = 5.687$\alpha$ + (10.44 $\pm$ 0.4)이며, Am-TJHA은 log$\beta$$_1$= 4.004 $\alpha$ + (6.96 $\pm$ 0.2) 및 log$\beta$$_2$= 3.719 $\alpha$ + (11.71 $\pm$ 0.2)이었다.

• Proceedings of the Korean Radioactive Waste Society Conference
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• 2004.02a
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• pp.245-256
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• 2004

The extraction of three kinds of amido podands, N,N,N'N'-tetrabutyl-3-oxa-pentanedi- amide (TBDGA), N,N,N'N'-tetra-isobutyl-3-oxa-pentanediamide(TiBDGA) and N,N,N'N'-tetra- butyl-3,6-dioxa-oct-anediam- ide(TBDOODA) on U(VI),Pu(IV), Am(III), Eu(III) and other metal ions is studied in nitric acid solutions. 40%octanol-kerosene is chosen as diluents to eliminate third phase and emulsion. TBDGA and TiBDGA show extraction selectivity to An(III) and Ln(III) much higher than to U(VI) and Pu(IV). Fe, Ru and Mo is poorly extracted by the three kinds of amid podands in 2~3mol/L $HNO_3$ solutions. Aiming to eliminate interface crude when using simulated HLLW solution in the system of 0.2mol/L TBDGA/Octanol＋kerosene, acetohydroxyamic acid was adapted. Distribution ratio of zirconium was decreased when adding acetohydroxyamic acid in aqueous solution, and interface crude disappeared as mixing extractant with HLLW. The counter-current extraction test is carried out in a set of miniature mixer-settler, with 0.2mol/L TBDGA/ 40% octanol-kerosene as extractant to separate U(VI), Pu(IV), Am(III) and Eu(III) from simulated high level liquid waste(HLLW) solution. In battery A, lanthanides and actinides are coextracted into organic phase with the recovery of 99.98% for U(Ⅵ), >99.99% for Pu(IV), and >99.99% for Am(III) and Eu(III) respectively. In battery R1, 99.99% U, 86.2% Pu and a part of Am or Eu are stripped into aqueous phase by 0.2mol/L acetohydroxyamic acid (AHA) in 0.01mol/L $HNO_3$ solution. In battery $R_2$, Am, Eu and remained Pu are completely back-extracted by 0.2mol/L AHA. This separation process contains no salt reagent, and it is not necessary to dilute HLLW feed.

• Proceedings of the Korean Nuclear Society Conference
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• 1998.05b
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• pp.533-538
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• 1998

추출제 Cyanex 301에 대한 NaN $O_3$ 매질에서 Am과 Eu의 추출 및 상호분리 거동에 대해 고찰하였다. Cyanex 301에 대한 Am과 Eu의 추출거동은 매우 유사하여 상호 분리할 수 없었으나 Cyanex 301을 8M NaOH로 비누화 처리하여 NaN $O_3$ 용액 매질에서 Eu에 대한 미량의 Am의 분배계수를 측정한 결과 Am에 대한 선택적 추출성이 높게 나타났다. Cyanex 301의 비누화을, 수용상의 pH 및 Eu 농도가 높아질수록 Am과 Eu의 상호 분리계수인 S $F_{AM}$Eu/는 930까지 증가되었으나 Cyanex 301에 옥탄올을 첨가할 경우에는 S $F_{Am}$ Eu/는 32.3까지 감소하였으며, Am과 Eu의 추출에 미치는 NaN $O_3$ 농도 영향은 없는 것으로 나타났다. Cyanex 301에 추출된 Am과 Eu은 pH가 4인 lM NaN $O_3$ 용액으로는 97.7% 그리고 0.05M DTPA/1.5M Lactic acid에 의해서 99% 이상 역추출되었다.

• Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
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• v.6 no.1
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• pp.25-33
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• 2008

A selective separation of Actirlide(III) by a nPr-BTP/nitrobezene extraction system was studied. The nPr-BTP (2.6-Bis-(5.6-n-propyl-1.2.4-triazin-3-yl)-pyridine) of a environmentally -friendly CHN type was self-synthesized and its compatability with diluent and stability with nitric acid were investigated. At the 0.1M nPr-BTP/nitrobenzene-1M $HNO_3$ and O/A=2, extraction yields of Am used as a representative of Actinide(III) and Eu were about 85% and 8%, respectively, and the other RE elements such as Nd, Ce and Y were extracted less than 3% (separation factor of Am and Eu was about 60). Thus, there was no problems in the selective extraction of Actinide(III) from RE. The stripping yield of Am with 0.05M $HNO_3$ at O/A= 1, however, was about 43% and the maximum stripping yield was 65% at O/A=0.3. It is necessary to develop the stripping system including the stripping agent instead of nitric acid solution.

• Applied Chemistry for Engineering
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• v.10 no.1
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• pp.143-147
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• 1999

The present paper describes the solvent extraction behaviors and the mutual separation of Am and Eu by sulphur bearing Cyanex 301 acidic extractant in sodium nitrate solutions. Original Cyanex 301 was not able to separate the Am and Eu because of their similar extraction behaviors. The saponification of commercial Cyanex 301 was performed by small amounts of 8 M NaOH solutions and saponified Cyanex 301 was able to separate of Am from Eu with high selectivity in sodium nitrate aqueous solution. The separation factors ($SF_{Am/Eu}$) were increased with saponified ratio of commercial Cyanex 301, pH of sodium nitrate solution and initial concentration of Eu. To obtain the homogeneous saponified Cyanex 301, heterogeneous saponified Cyanex 301 was treated with addition of octyl alcohol or filtration. The observed $SF_{Am/Eu}$ was 32.3 for the former and 930 for the latter. Finally, the stripping behaviors of Am and Eu were similar and stripping yields showed 96.1% for the 1 M $NaNO_3$(pH=1.3) and 99% for the mixture solution of 0.05 M DTPA and 1.5 M lactic acid.

• Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
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• v.20 no.4
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• pp.399-410
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• 2022

The solubility and species distribution of radionuclides in groundwater are essential data for the safety assessment of deep underground spent nuclear fuel (SNF) disposal systems. Americium is a major radionuclide responsible for the long-term radiotoxicity of SNF. In this study, the solubility of americium compounds was evaluated in synthetic groundwater (SynDB3), simulating groundwater from the DB3 site of the KAERI Underground Research Tunnel. Geochemical modeling was performed using the ThermoChimie_11a thermochemical database. Concentration of dissolved Am(III) in Syn-DB3 in the pH range of 6.4-10.5 was experimentally measured under over-saturation conditions by liquid scintillation counting over 70 d. The absorption spectra recorded for the same period suggest that Am(III) colloidal particles formed initially followed by rapid precipitation within 2 d. In the pH range of 7.5-10.5, the concentration of dissolved Am(III) converged to approximately 2×10^-7 M over 70 d, which is comparable to that of the amorphous AmCO₃OH(am) according to the modeling results. As the samples were aged for 70 d, a slow equilibrium process occurred between the solid and solution phases. There was no indication of transformation of the amorphous phase into the crystalline phase during the observation period.