Kinetics of dissolution of Th0.25U0.75O2 sintered pellets in various acidic conditions

Dalger, Thomas; Szenknect, Stéphanie; Tocino, Florent; Claparède, Laurent; Mesbah, Adel; Moisy, Philippe; Dacheux, Nicolas

doi:10.1016/j.jnucmat.2018.07.050

Cited by 12 publications

(6 citation statements)

References 55 publications

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“…Furthermore, since concentrations of catalytic species were expected to remain at a low level in solution, their impact on the dissolution rates was expected to be low. Nevertheless, their concentration were gradually increasing during this step due to the dissolution reaction [29]. Then, when their concentration reached about 10 -3 mol.L -1 , the dissolution was accelerating significantly.…”

Section: Characterisations Of the Sintered Pelletsmentioning

confidence: 98%

“…The first one could be associated to the development of redox reaction located at the metallic particles/UO 2 /solution interface, leading to the reduction of nitrate ions into nitrogen oxide species. These latter could produce nitrous acid (HNO 2 ) and thus induce autocatalytic dissolution mechanism (according to equations 9-11) [29].…”

Section: Discrimination Of Pgm Contributionsmentioning

confidence: 99%

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Impact of platinum group metals (Ru, Pd, Rh) on the dissolution of UO2

Cordara¹,

Bertolotto²,

Claparède³

et al. 2020

Journal of Nuclear Materials

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Section: Characterisations Of the Sintered Pelletsmentioning

confidence: 98%

Section: Discrimination Of Pgm Contributionsmentioning

confidence: 99%

Impact of platinum group metals (Ru, Pd, Rh) on the dissolution of UO2

Cordara¹,

Bertolotto²,

Claparède³

et al. 2020

Journal of Nuclear Materials

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View full text Add to dashboard Cite

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“…The normalized weight loss, N L geo (t) (g.m -2 ), and the apparent dissolved thickness e geo (t) (µm) were calculated according to equation (12):…”

Section: Calculationmentioning

confidence: 99%

“…According to literature [7][8][9][10][11], the most likely mechanism is initiated by a redox reaction between UO2 and HNO3 at the solid/solution interface following reaction (1): UO2(s) + HNO3(aq) + 2 H +  UO 2 2+ (aq) + HNO2(aq) + H2O (1) The rate of this reaction is considered to be slow [10]. According to this reaction, the increase of the nitrous acid concentration is proportional to the concentration of uranyl nitrate in solution [9,12]. A second reaction between UO2 and nitrous acid is suspected to be much faster than reaction (1) […”

Section: Introductionmentioning

confidence: 99%

Effect of surface orientation on dissolution rate and surface dynamics of UO2 single crystals in nitric acid

et al. 2020

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“…Moreover, the morphological characterization of the samples was performed by SEM with an FEI Quanta 200 environmental scanning electron microscope using a back-scattered electron detector (BSED) or a secondary electron detector (SED) in vacuum conditions with an acceleration voltage of 25 kV. SEM micrographs recorded at low magnification were also used to evaluate the initial specific surface area (S SA in m².g -1 ) of the pellets as already described in previously published works 27,42 .…”

Section: Accepted Manuscriptmentioning

confidence: 99%

Microstructural evolution of UO2 pellets containing metallic particles of Ru, Rh and Pd during dissolution in nitric acid solution: 3D-ESEM monitoring

et al. 2019

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Uranium dioxide containing 3 mol.% platinum group metals (PGMs) (Ru, Rh, Pd) was synthesized by hydroxide precipitation. The powders were converted to oxides, pelletized and sintered to prepare dense pellets of UO 2 incorporating PGMs particles. The characterization techniques performed revealed a microstructure similar to that of spent nuclear fuel (SNF). Dissolution tests in nitric acid demonstrated that in the presence of PGMs, the uranium dissolution rate was increased and the induction period was shortened. We used a new method based on the acquisition of Environmental Scanning Electron Microscopy (ESEM) micrographs recorded at three tilt angles and at different dissolution times. This method allowed the reconstruction of the topography of the solid/liquid interface. By monitoring the evolution of the solid/liquid interface during dissolution by means of 3D reconstructions, we were able to observe preferential dissolution zones in the vicinity of the PGMs particles and to determine microscopic dissolution rates for several regions of interest. PGMs particles were found mainly at the grain boundaries. In 0.1 M HNO 3 solution at 60˚C, the normalized dissolution rate for uranium at the grain boundaries reached R L (U) = (7 ± 1)×10-2 g.m-2 .d-1 , a value similar to the normalized dissolution rate determined for the whole image over the first 30 days of the experiment. This result showed that the dissolution occurred mainly at the UO 2 grain boundaries in the vicinity of PGMs particles. Furthermore, the 3D reconstructions of the solid/liquid interface were used to determine the evolution of the surface area of the pellet. By combining the weight losses determined at the macroscopic scale using the uranium concentrations in solution with the reactive surface area values, it was possible to estimate an effective normalized dissolution rate for the whole pellet.

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Kinetics of dissolution of Th0.25U0.75O2 sintered pellets in various acidic conditions

Cited by 12 publications

References 55 publications

Impact of platinum group metals (Ru, Pd, Rh) on the dissolution of UO2

Impact of platinum group metals (Ru, Pd, Rh) on the dissolution of UO2

Effect of surface orientation on dissolution rate and surface dynamics of UO2 single crystals in nitric acid

Microstructural evolution of UO2 pellets containing metallic particles of Ru, Rh and Pd during dissolution in nitric acid solution: 3D-ESEM monitoring

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