Studies on the Thoria Fuel Recycling Loop Using Triflic Acid: Effects of Powder Characteristics, Solution Acidity, and Radium Behavior

Tyrpekl, Václav; Lommelen, Rayco; Wangle, T.; Cardinaels, Thomas; Binnemans, Koen; Zhang, Fei; Verwerft, Marc

doi:10.1007/s40831-018-0205-1

Cited by 4 publications

(3 citation statements)

References 23 publications

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“…In a direct strike precipitation, the acidity of the solution in which the precipitation occurs (which contains free HNO3 from the starting solution), is significantly higher than in a reverse strike. The increasing solubility of the oxalates of Th 4+ [39][40][41][42] and Np 4+ [43] with increasing acidity, together with the coarse nature of the holes suggests that the holes are formed by a local precipitation-dissolution equilibrium. The precipitation of Th(C2O4)2 forms HNO3, see eq.…”

Section: Resultsmentioning

confidence: 99%

Morphology dependent sintering path of nanocrystalline ThO2

Wangle

Beliš

Tyrpekl

et al. 2020

Journal of Nuclear Materials

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Thorium is most commonly precipitated as oxalate, because of the high efficiency regardless of precipitation conditions. Thorium oxalate readily decomposes into fine-grained ThO2 during heating, but keeps the macrostructure of the oxalate platelets. To assess the effects of precipitate macrostructure on the sintering behavior, different platelet morphologies were prepared and sintered. There are two factors which influence the sintering: the presence of holes within the platelets and the size of the platelets. Small platelets or precipitates with holes generally sinter to thorium dioxide pellets of a higher density and smaller grain size. I. Introduction Thorium dioxide is a candidate fuel for several types of nuclear reactors. Hania and Klaassen [1] extensively reviewed the preparation, properties and use of thorium oxide as a nuclear fuel. The production process, however, still needs to be further developed to meet high industrial efficiency and standards. ThO2 is a refractory ceramic with the highest oxide melting point reported for binary oxides at 3665±70 K [2] or 3624±86 K [3]. As such, the temperature needed to efficiently sinter ThO2 to closed porosity (desired densities of ≥ 95%) often exceed the 1700-1750 °C achievable in commercial highvolume continuous furnaces. One may expect to improve sinterability by introducing defects on the cation or anion lattice. At elevated temperatures (T > 2000 K), a narrow non-stoichiometry domain develops under highly reducing atmospheres [4, 5]. Electrical conductivity measurements indicated that deviation of stoichiometry starts already at 1673 K [6]. Alternatively, sintering-enhancement can be achieved by suitable dopants that induce anion or cation lattice defects. Previous reports have shown that the addition of divalent M 2+ (Ca, Mg) [7], trivalent M 3+ (Y, Al) [8-11], or pentavalent M 5+ (V, Nb, Ta) [12] cations to ThO2 can increase the sinterability significantly. In mixed oxides (Th1−yUy)O2+x and (Th1−yPuy)O2-x deviations from stoichiometry readily occur as the substituting cations, U and Pu are also in valence states other than (IV). [13, 14]. The formation of defects on anion or cation sites in the fluorite crystal structure of ThO2promotes the diffusion of the sintering-limiting cation. This diffusion rate is a function of the square of the deviation from stoichiometry (x) in fluorite UO2±x [15] and in fluorite ThO2±x. In ThO2 without additives, this deviation is determined by the presence of impurities and the oxygen potential in the sintering atmosphere. Thus, both heavily reducing and oxidizing atmosphere can be used to promote sintering above about 1400 °C. Additionally, the morphology of the ThO2 plays a significant role in the packing density and sintering behavior. Most commonly, ThO2 is prepared from oxalates, according to eq. (1).

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Section: Resultsmentioning

confidence: 99%

Morphology dependent sintering path of nanocrystalline ThO2

Wangle

Beliš

Tyrpekl

et al. 2020

Journal of Nuclear Materials

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“…Triflic acid finds some applications in niche applications in hydrometallurgy such as the recycling of thoria (ThO 2 ) from thorium-based nuclear-fuel production scrap. 196,197 Critical reflection on the green character of MSA MSA is endorsed by numerous scholars and industry associates as a green acid that harbors immense potential for the advancement of novel clean technologies. These range from its use as catalysts in organic synthesis, to electrolytes for metal electroplating, to a lixiviant for metal recycling via urban mining, and even its application in redox flow batteries.…”

Section: Comparison With Other Acidsmentioning

confidence: 99%

“…Triflic acid finds some applications in niche applications in hydrometallurgy such as the recycling of thoria (ThO 2 ) from thorium-based nuclear-fuel production scrap. 196,197…”

Section: Comparison With Other Acidsmentioning

confidence: 99%

Methanesulfonic acid (MSA) in clean processes and applications: a tutorial review

Binnemans,

Jones

2024

Green Chem.

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Methanesulfonic Acid (MSA) in Hydrometallurgy

Binnemans

Jones

2022

J. Sustain. Metall.

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This paper reviews the properties of methanesulfonic acid (MSA) and its potential for use in hydrometallurgy. Although MSA is much less known than sulfuric, hydrochloric or nitric acid, it has several appealing properties that makes it very attractive for the development of new circular flowsheets in hydrometallurgy. Unlike other organic acids such as acetic acid, MSA is a very strong acid (pKa = − 1.9). In addition, it is very stable against chemical oxidation and reduction, and has no tendency to hydrolyze in water. In terms of its environmental impact, MSA has low toxicity and is biodegradable. In nature, it is part of the geochemical sulfur cycle. A useful property is the high solubility of its salts in water: methanesulfonate salts have a much higher solubility in water than sulfate salts. Additionally, MSA and its salts are compatible with the electrowinning of metals because the anode reaction involves the formation of oxygen gas (unlike chlorine gas formation in chloride electrolytes) and no cathodic reduction of the anion occurs (unlike nitrate reduction in nitrate electrolytes). MSA is particularly interesting for lead hydrometallurgy, where it offers more environment-friendly alternatives to HBF4 and H2SiF6. However, MSA can also be adopted in all hydrometallurgical processes that require strong Brønsted acids. It can be used in the metallurgy of copper, zinc, cobalt, nickel, and rare earths, as well as in the recycling of metals from end-of-life products. Although MSA itself is a non-oxidizing acid, in combination with hydrogen peroxide it yields strongly oxidizing lixiviants that can leach copper from chalcopyrite or dissolve metallic silver. The global production of MSA is expected to increase rapidly in the near future thanks to both the industrialization of a new sustainable synthesis process and its many applications (cleaning fluids, electrolytes for electroplating, redox-flow batteries, catalysts in organic synthesis, and as a solvent for high-molecular-weight polymers). As a result, MSA will become more widely available and a lower price will make it an increasingly attractive option. Graphical Abstract

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Studies on the Thoria Fuel Recycling Loop Using Triflic Acid: Effects of Powder Characteristics, Solution Acidity, and Radium Behavior

Cited by 4 publications

References 23 publications

Morphology dependent sintering path of nanocrystalline ThO2

Morphology dependent sintering path of nanocrystalline ThO2

Methanesulfonic acid (MSA) in clean processes and applications: a tutorial review

Methanesulfonic Acid (MSA) in Hydrometallurgy

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