Kinetic study on dissolution of UO2 powders in nitric acid

Ikeda, Yasuhisa; Yasuike, Yoshiyuki; Nishimura, Kenji; Hasegawa, Shuichi; Takashima, Yoichi

doi:10.1016/0022-3115(95)00059-3

Cited by 52 publications

(35 citation statements)

References 8 publications

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“…According to the results published by Ikeda et al [11], k nc = 5.0 Â 10 À7 mol 1À2.3 ·m À2+3·2.3 ·s À1 and k nc = 8.5 Â 10 À8 mol 2.3 ·m À2+3·2.3+3 ·s À1 at 50°C. With these values, v = 0.17 m 3 ·mol À1 .…”

Section: External Resistance Fraction For the Catalystmentioning

confidence: 85%

“…Ikeda and Marc include the autocatalytic aspect by defining a two-step mechanism [8,11]. First, a slow noncatalytic reaction is observed where the catalyst is produced (HNO 2 for Ikeda), and after some time, a second faster parallel catalytic reaction proceeds, where the catalyst accelerates the dissolution rate.…”

Section: An Autocatalytic Reactionmentioning

confidence: 99%

“…With these values, v = 0.17 m 3 ·mol À1 . Moreover, the order relative to the catalyst always equals 1 in the publications where a catalyst is considered [11,14]. In the event of a dissolution with no catalyst in the bulk, f e,Z must be lower than 0.29 mol·m À3 to avoid any impact of the catalyst in the boundary layer.…”

Section: External Resistance Fraction For the Catalystmentioning

confidence: 99%

“…Reaction orders relative to nitric acid and activation energies have been extensively studied by authors [8,9,11,[15][16][17]. Part of the literature data is summarized in Tables 2 and 3.…”

Section: Kinetic Studymentioning

confidence: 99%

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Formalization of the kinetics for autocatalytic dissolutions. Focus on the dissolution of uranium dioxide in nitric medium

Charlier

Canion

Gravinese

et al. 2017

EPJ Nuclear Sci. Technol.

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Abstract. Uranium dioxide dissolution in nitric acid is a complex reaction. On the one hand, the dissolution produces nitrous oxides (NO X ), which makes it a triphasic reaction. On the other hand, one of the products accelerates the kinetic rate; the reaction is hence called autocatalytic. The kinetics for these kinds of reactions need to be formalized in order to optimize and design innovative dissolution reactors. In this work, the kinetics rates have been measured by optical microscopy using a single particle approach. The advantages of this analytical technique are an easier management of species transport in solution and a precise following of the dissolution rate. The global rate is well described by a mechanism considering two steps: a non-catalyzed reaction, where the catalyst concentration has no influence on the dissolution rate, and a catalyzed reaction. The mass transfer rate of the catalyst was quantified in order to discriminate when the reaction was influenced by catalyst accumulated in the boundary layer or uncatalyzed. This first approximation described well the sigmoid dissolution curve profile. Moreover, experiments showed that solutions filled with catalyst proved to lose reactivity over time. Results pointed out that the higher the liquid-gas exchanges, the faster the kinetic rate decreases with time. Thus, it was demonstrated, for the first time, that there is a link between catalyst and nitrous oxides. The outcome of this study leads to new ways for improving the design of dissolvers. Gas-liquid exchanges are indeed a lever to impact dissolution rates. Temperature and catalyst concentration can be optimized to reduce residence times in dissolvers.

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Section: External Resistance Fraction For the Catalystmentioning

confidence: 85%

Section: An Autocatalytic Reactionmentioning

confidence: 99%

Section: External Resistance Fraction For the Catalystmentioning

confidence: 99%

“…Reaction orders relative to nitric acid and activation energies have been extensively studied by authors [8,9,11,[15][16][17]. Part of the literature data is summarized in Tables 2 and 3.…”

Section: Kinetic Studymentioning

confidence: 99%

See 2 more Smart Citations

Formalization of the kinetics for autocatalytic dissolutions. Focus on the dissolution of uranium dioxide in nitric medium

Charlier

Canion

Gravinese

et al. 2017

EPJ Nuclear Sci. Technol.

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show abstract

“…[21][22][23][24][25] The mechanism and the rate-determining step of these dissolution reactions, however, are still of controversy.…”

Section: Resultsmentioning

confidence: 99%

Dissolution Behavior of Uranium Oxides with Supercritical CO₂Using HNO₃-TBP Complex as a Reactant

Tomioka

Meguro

Enokida

et al. 2001

Journal of Nuclear Science and Technology

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Dissolution behavior of U 3 O 8 and UO 2 using supercritical CO 2 medium containing HNO 3 -TBP complex as a reactant was studied. The dissolution rate of the oxides increased with increasing the HNO 3 /TBP ratio of the HNO 3 -TBP complex and the concentration of the HNO 3 -TBP complex in the supercritical CO 2 phase. A remarkable increase of the dissolution rate was observed in the dissolution of U 3 O 8 when the HNO 3 /TBP ratio of the reactant was higher than ca. 1, which indicates that the 2:1 complex, (HNO 3 ) 2 TBP, plays a role in facilitating the dissolution of the oxides. Half-dissolution time (t 1/2 ) as an indication of the dissolution kinetic was determined from the relationship between the amount of uranium dissolved and the dissolution time (dissolution curve). A logarithmic value of a reciprocal of the t 1/2 was proportional to the logarithmic concentration of HNO 3 , C HNO 3 , in the supercritical CO 2 . The slopes of the ln(1/t 1/2 ) vs. ln C HNO 3 plots for U 3 O 8 and UO 2 were different from each other, indicating that the reaction mechanisms or the rate-determining steps for the dissolution of U 3 O 8 and UO 2 are different. A principle of the dissolution of uranium oxides with the supercritical CO 2 medium is applicable to a method for the removal of uranium from solid matrices.

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A photo-induced dissolution of UO2 sintered pellets in a simulated solution

Kim

Choung

Kim

et al. 2000

Korean J. Chem. Eng.

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Kinetic study on dissolution of UO2 powders in nitric acid

Cited by 52 publications

References 8 publications

Formalization of the kinetics for autocatalytic dissolutions. Focus on the dissolution of uranium dioxide in nitric medium

Formalization of the kinetics for autocatalytic dissolutions. Focus on the dissolution of uranium dioxide in nitric medium

Dissolution Behavior of Uranium Oxides with Supercritical CO₂Using HNO₃-TBP Complex as a Reactant

A photo-induced dissolution of UO2 sintered pellets in a simulated solution

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Kinetic study on dissolution of UO2 powders in nitric acid

Cited by 52 publications

References 8 publications

Formalization of the kinetics for autocatalytic dissolutions. Focus on the dissolution of uranium dioxide in nitric medium

Formalization of the kinetics for autocatalytic dissolutions. Focus on the dissolution of uranium dioxide in nitric medium

Dissolution Behavior of Uranium Oxides with Supercritical CO2Using HNO3-TBP Complex as a Reactant

A photo-induced dissolution of UO2 sintered pellets in a simulated solution

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Product

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Dissolution Behavior of Uranium Oxides with Supercritical CO₂Using HNO₃-TBP Complex as a Reactant