A Novel Methodology for Processing of Plutonium-Bearing Waste as Ammonium Plutonium(III)-Oxalate

Sali, S.K.; Noronha, D. M.; Mhatre, H. R.; Mahajan, Muktar A.; Chander, Keshav; Venugopal, V.

doi:10.13182/nt05-a3651

Cited by 12 publications

(9 citation statements)

References 5 publications

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“…The decomposition mechanism in air is consistent with the work of Subramanian7b and Sali,7d as they both consider that the dehydrated oxalate is obtained prior to the decomposition of the oxalate groups, unlike Rao7a and Kozlova7c who proposed a monohydrated intermediate instead. As for the thermal decomposition mechanism under argon, it is in agreement with the one proposed by Rao 7a…”

Section: Resultssupporting

confidence: 85%

“…It appeared that even without vacuum, the starting oxalate was a nonahydrate, thus the first dehydration step under static air accounts for the loss of one water molecule. On the other hand, the first dehydration step under argon accounts only for five water molecules, and the experimental mass loss for the oxalate decomposition step is smaller than expected because of the residual carbon present in the oxide at the end of the calcination 7d. By superimposing the TG curves of the thermal decomposition of plutonium oxalate in air and under argon (cf.…”

Section: Resultsmentioning

confidence: 99%

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Insights into the Thermal Decomposition of Lanthanide(III) and Actinide(III) Oxalates – from Neodymium and Cerium to Plutonium

et al. 2012

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Lanthanides are often used as surrogates to study the properties of actinide compounds. Their behaviour is considered to be quite similar as they both possess f valence electrons and are close in size and chemical properties. This study examines the potential of using two lanthanides (neodymium and cerium) as surrogates for plutonium during the thermal decomposition of isomorphic oxalate compounds, in the trivalent oxidation state, into oxides. Thus, the thermal decomposition of neodymium, cerium and plutonium(III) oxalates are investigated by several coupled thermal analyses (TG-DTA/DSC-MS/FTIR) and complementary characterisation [a] CEA Marcoule, Nuclear Energy Division, DRCP/SCPS/LC2A, 4986techniques [XRD, UV/Vis and FTIR spectroscopy, scanning electron microscopy (SEM), carbon analysis] under both oxidizing and inert atmospheres. The thermal decomposition mechanisms determined in this study confirmed some previously reported results, among diverging propositions, and also elucidated some original mechanisms not previously considered. The calculated thermodynamic and kinetic parameters for the studied systems under both atmospheres are reported and compared with available literature data. Similarities and differences between the thermal behaviour of plutonium(III) and lanthanide(III) oxalates are outlined.The residual carbon contents in the neodymium and cerium oxides obtained after calcination of the oxalate pre-Eur.

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Section: Resultssupporting

confidence: 85%

Section: Resultsmentioning

confidence: 99%

Insights into the Thermal Decomposition of Lanthanide(III) and Actinide(III) Oxalates – from Neodymium and Cerium to Plutonium

et al. 2012

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“…Five hydrates of Pu(III) oxalates with the general formula Pu 2 (C 2 O 4 ) 3 · n H 2 O are reported in air or argon, with the hydration number n equal to 10, 9, 2, 1, or 0 (only in Ar) depending on the temperature . Sali et al reports different thermal behavior in air, with the Pu(III) oxalate decahydrate dehydrating to a monohydrate at 100 °C and then to the anhydrous form at 150 °C . In the range between 25° and 50 °C, Am 2 (C 2 O 4 ) 3 ·7H 2 O dehydrates to form the tetrahydrate, continuing to the anhydrous Am(III) oxalate at 240 °C via 3 additional hydrates .…”

Section: Introductionmentioning

confidence: 99%

Directed Synthesis of Crystalline Plutonium(III) and (IV) Oxalates: Accessing Redox-Controlled Separations in Acidic Solutions

et al. 2009

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Both binary and ternary solid complexes ofPu(III) and Pu(IV) oxalates have been reported in the literature. However, uncertainties regarding the coordination chemistry and the extent of hydration of some compounds remain due to the absence of any crystallographic characterization. We synthesized single crystals of hydrated oxalates of Pu(III), PU2(C204)3(H20)6-3H20 (I), and Pu(IV), KPU(C204)2(OH)-2.5H20 (II), under moderate hydrothermal conditions and characterized them spectroscopically and by using single crystal X-ray diffraction. Compounds I and II are the first plutonium III or IV oxalate compounds to be structurally characterized, and II contains the first overall

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“…This task is extremely challenging due to the very narrow electrochemical window of working electrodes in an acidic medium, leading to the occurrence of hydrogen (H 2 ) evolution way before Pu and U electrodeposition. 6,12 Herein, we report a simple electrochemical method in which Pu and U can be recovered separately from the aqueous acidic waste solutions as solid potassium plutonium(III) sulfate [K 2 (K 0.5 Pu 0.5 )(SO 4 ) 2 ] and potassium uranium(IV) sulfate [K 2 (K 0.67 U 0.33 )(SO 4 ) 2 ], respectively, with an efficiency>97.5% (which is close to that achieved by traditional techniques), 1,5,8 just by varying the electrode potential. First, electrochemistry and bulk electrolysis of pure PuO 2 2+ and UO 2 2+ in 0.1 M HNO 3 /K 2 SO 4 sat.…”

Section: ■ Introductionmentioning

confidence: 92%

A “Two-Step” Electrochemical Approach for Recovery of Plutonium and Uranium from Aqueous Acidic Waste Solutions

Agarwal,

Gamare,

Nandi

et al. 2024

Inorg. Chem.

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Chemical quality control of nuclear fuel, particularly the determination of Pu and U contents by chemical methods, results in analytical acidic aqueous waste solutions from which Pu and U must be recovered efficiently for the remediation of radioactive wastes. Reported methods involve several complicated steps requiring addition of chemical oxidants/reductants for valence adjustments and generation of secondary wastes, thereby making the recovery process cumbersome. Herein, we report a novel two-step electrochemical approach for Pu and U recovery from acidic aqueous waste solutions containing different metallic impurities (Fe, Cr, Mn, Cd, Al, Ni, Co, Zn, and Mg) by bulk electrolysis using a Pt gauze electrode. Pu and U are recovered from these waste solutions in a two-step process: (i) bulk electrolysis of the mixed solution at a constant potential of 0.1 V vs Ag/AgCl/3 M KCl that results in the reduction of PuO 2 2+ to Pu 3+ followed by the precipitation of Pu 3+ as K 2 (K 0.5 Pu 0.5 )(SO 4 ) 2 , which is then filtered and separated and (ii) the filtrate solution is again subjected to bulk electrolysis at a constant potential of −0.35 V vs Ag/AgCl/3 M KCl resulting in the reduction of UO 2 2+ to U 4+ . The U 4+ is then precipitated as K 2 (K 0.67 U 0.33 )(SO 4 ) 2 , which is filtered and separated, leading to a Pu-and U-free aqueous acidic waste solutions. Biamperometry shows that 97.8% and 99.1% recovery of Pu and U, respectively, is possible, and emission spectrometry confirms the purity of K 2 (K 0.5 Pu 0.5 )(SO 4 ) 2 and K 2 (K 0.67 U 0.33 )(SO 4 ) 2 . Because of its operational simplicity, potential for remote handling, and excellent extraction efficiency, the present methodology can easily replace traditional methods for the recovery of Pu and U from acidic aqueous waste solutions.

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A Novel Methodology for Processing of Plutonium-Bearing Waste as Ammonium Plutonium(III)-Oxalate

Cited by 12 publications

References 5 publications

Insights into the Thermal Decomposition of Lanthanide(III) and Actinide(III) Oxalates – from Neodymium and Cerium to Plutonium

Insights into the Thermal Decomposition of Lanthanide(III) and Actinide(III) Oxalates – from Neodymium and Cerium to Plutonium

Directed Synthesis of Crystalline Plutonium(III) and (IV) Oxalates: Accessing Redox-Controlled Separations in Acidic Solutions

A “Two-Step” Electrochemical Approach for Recovery of Plutonium and Uranium from Aqueous Acidic Waste Solutions

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