Lithium reduction of americium dioxide to generate americium metal

Usami, Tsuyoshi; Kato, Tetsuya; Kurata, Masaki; Inoue, Tadashi; Sims, Howard E.; Beetham, S.A.; Jenkins, J.A.

doi:10.1016/s0022-3115(02)00853-x

Cited by 36 publications

(25 citation statements)

References 4 publications

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“…• the MgO crucible was primarily periclase-MgO, with small amounts of two aluminum yttrium oxide phases, AlYO 3 and Al 2 Y 4 O 9 (believed to be residues remaining from the binder and/or grain stabilizing agents used for crucible manufacturing); and…”

Section: Crucible Materialsmentioning

confidence: 99%

The High-Temperature Chemical Reactivity of Li₂O

et al. 2010

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The ultimate purpose of this study was to investigate the use of a Li-Ca mixture for direct reduction of actinide oxides to actinide metals at temperatures below 1500 °C. For such a process to be successful, the products of the reduction reaction, actinide metals, Li 2 O, and CaO, must all be liquid at the reaction temperature so the resulting actinide metal can coalesce and be recovered as a monolith. Since the established melting temperature of Li 2 O is in the range 1427 -1700 °C and the melting temperature of CaO is 2654 °C, the Li 2 O-CaO (lithium oxidecalcium oxide) pseudo-binary system was investigated in an attempt to identify the presence of low-melting eutectic compositions.The results of our investigation indicate that there is no evidence of ternary Li-Ca-O phases or solutions melting below 1200 °C. In the 1200 -1500 °C range utilizing MgO crucibles, there is some evidence for the formation of a ternary phase; however, it was not possible to determine the phase composition. The results of experiments performed with ZrO 2 crucibles in the same temperature range did not show the formation of the possible ternary phase seen in the earlier experiment involving MgO crucibles, so it was not possible to confirm the possibility that a ternary Li-Ca-O or Li-Mg-O phase was formed. It appears that the Li 2 O-CaO materials reacted, to some extent, with all of the container materials, alumina (Al 2 O 3 ), magnesia (MgO), zirconia (ZrO 2 ), and 95% Pt-5% Au; however, to clarify the situation additional experiments are required.In addition to the primary purpose of this study, the results of this investigation led to the conclusions that:-2 -• The melting temperature of Li 2 O may be as low as 1250 °C, which is considerably lower than the previously published values in the range 1427 -1700 °C.• Lithium oxide (Li 2 O) vaporizes congruently.• Lithium carbonate and Li 2 O react with 95% Pt-5% Au, and also reacts with pure Pt.• It is likely that some or all of the past high temperature phase behavior and vaporization experiments involving Li 2 O(s) at temperatures above 1250 °C have actually involved Li 2 O(l).If these past measurements were actually measurements performed on Li 2 O(l) instead of the solid, the thermochemical data for phases and species in the Li-O system will require reevaluation.-3 -

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Section: Crucible Materialsmentioning

confidence: 99%

The High-Temperature Chemical Reactivity of Li₂O

et al. 2010

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“…For instance, Usami et al [5] successfully applied this technique to AmO 2 in LiCl-Li 2 O at 650°C and have shown that more than 99.9% of Am was recovered into a solid Am phase. This technology was also employed for UO 2 and PuO 2 with 3% of Am at 650°C [6] leaving particles of UO 2 totally reduced.…”

Section: Introductionmentioning

confidence: 99%

Direct electrochemical reduction of solid uranium oxide in molten fluoride salts

Gibilaro¹,

Cassayre²,

Lemoine³

et al. 2011

Journal of Nuclear Materials

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International audienceThe direct electrochemical reduction of UO2 solid pellets was carried out in LiF-CaF2 (+ 2 mass. % Li2O) at 850°C. An inert gold anode was used instead of the usual reactive sacrificial carbon anode. In this case, oxidation of oxide ions present in the melt yields O2 gas evolution on the anode. Electrochemical characterisations of UO2 pellets were performed by linear sweep voltammetry at 10mV/s and reduction waves associated to oxide direct reduction were observed at a potential 150mV more positive in comparison to the solvent reduction. Subsequent, galvanostatic electrolyses runs were carried out and products were characterised by SEM-EDX, EPMA/WDS and XRD. In one of the runs, uranium oxide was partially reduced and three phases were observed: non reduced UO2 in the centre, pure metallic uranium on the external layer and an intermediate phase representing the initial stage of reduction taking place at the grain boundaries. In another run, the UO2 sample was fully reduced. Due to oxygen removal, the U matrix had a typical coral-like structure which is characteristic of the pattern observed after the electroreduction of solid oxides

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“…In the lithium reduction process, Li 2 O which is produced from an electrolytic reduction reaction drop off the conversion rate of the uranium oxide and TRU oxides, creates a complex oxide or acid chloride by reacting with the rare earth oxides. 6,7) In order to promote the conversion rate of the reduction and restrain the side reaction, the Li 2 O concentration in the LiCl molten salt is kept to less than 5.1 wt% as shown in other references. 6,7) ANL has reported on the experimental results of an electrochemical reduction of uranium oxide fuel in a bench-scale apparatus with a cyclic voltammetry, and it has designed high-capacity reduction (HCR) cells and conducted three kg-scale UO 2 reduction runs.…”

Section: Introductionmentioning

confidence: 99%

“…6,7) In order to promote the conversion rate of the reduction and restrain the side reaction, the Li 2 O concentration in the LiCl molten salt is kept to less than 5.1 wt% as shown in other references. 6,7) ANL has reported on the experimental results of an electrochemical reduction of uranium oxide fuel in a bench-scale apparatus with a cyclic voltammetry, and it has designed high-capacity reduction (HCR) cells and conducted three kg-scale UO 2 reduction runs. 8,9) Gourishankar et al 10) classified the mechanisms of the electrolytic reduction of the metal oxides in a LiCl-Li 2 O molten salt system into two types: a direct and an indirect electrolytic reduction.…”

Section: Introductionmentioning

confidence: 99%

Electrochemical Study on the Reduction Mechanism of Uranium Oxide in a LiCl-Li₂O Molten Salt

Seo

Park

et al. 2006

Journal of Nuclear Science and Technology

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By means of a linear sweep voltammetry, a cyclic voltammetry and a chronopotentiometry, the electrolytic reduction of uranium oxide has been studied to establish the reduction mechanisms, which are based on a simultaneous uranium oxide reduction and a Li 2 O electrowinning, and the formation and electrolysis of lithium uranate. From the voltammograms, the reduction potentials of the uranium oxide and Li 2 O were obtained. From the chronopotentiometries based on the results of the voltammograms, the uranium oxide was reduced to uranium metal through the reduction mechanisms showing a more than 99% conversion. For a verification of the reduction mechanisms feasibility, basic data on the electrolytic reduction of the uranium oxide was obtained from the experiments and the characteristics of the closed recycle of Li 2 O were discussed.

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Lithium reduction of americium dioxide to generate americium metal

Cited by 36 publications

References 4 publications

The High-Temperature Chemical Reactivity of Li₂O

The High-Temperature Chemical Reactivity of Li₂O

Direct electrochemical reduction of solid uranium oxide in molten fluoride salts

Electrochemical Study on the Reduction Mechanism of Uranium Oxide in a LiCl-Li₂O Molten Salt

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Lithium reduction of americium dioxide to generate americium metal

Cited by 36 publications

References 4 publications

The High-Temperature Chemical Reactivity of Li2O

The High-Temperature Chemical Reactivity of Li2O

Direct electrochemical reduction of solid uranium oxide in molten fluoride salts

Electrochemical Study on the Reduction Mechanism of Uranium Oxide in a LiCl-Li2O Molten Salt

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The High-Temperature Chemical Reactivity of Li₂O

The High-Temperature Chemical Reactivity of Li₂O

Electrochemical Study on the Reduction Mechanism of Uranium Oxide in a LiCl-Li₂O Molten Salt