New conditionings for separated long-lived radionuclides

Guy, Christophe; Audubert, Fabienne; Lartigue, Jean-Éric; Latrille, Christelle; Advocat, T.; Fillet, C.

doi:10.1016/s1631-0705(02)01377-4

Cited by 90 publications

(98 citation statements)

References 15 publications

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“…A typical value of the initial corrosion rate of ceramics measured at 90°C is on the order of 10 m yr −1 , respectively. 198,199 Both pH and temperature significantly impact the corrosion rate of ceramics, and several orders of magnitude difference in the corrosion rate can be observed from highly acidic to near-neutral pH values. The time to achieve steady state varies from days to years.…”

Section: Silicate Glass Crystalline Ceramic and Metal Corrosion: Simentioning

confidence: 99%

A comparative review of the aqueous corrosion of glasses, crystalline ceramics, and metals

et al. 2018

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All materials can suffer from environmental degradation; the rate and extent of degradation depend on the details of the material composition and structure as well as the environment. The corrosion of silicate glasses, crystalline ceramics, and metals, particularly as related to nuclear waste forms, has received a lot of attention. The corrosion phenomena and mechanisms of these materials are different, but also have many similarities. This review compares and contrasts the mechanisms of environmental degradation of glass, crystalline ceramics, and metals, with the goal of identifying commonalities that can seed synergistic activities and advance the current knowledge in each area.npj Materials Degradation (2018) 2:15 ; doi:10.1038/s41529-018-0037-2 INTRODUCTIONNew research activity focused on the environmental degradation of silicate glasses, crystalline ceramics, and metals relevant to nuclear waste forms and containers has recently been described.

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Section: Silicate Glass Crystalline Ceramic and Metal Corrosion: Simentioning

confidence: 99%

A comparative review of the aqueous corrosion of glasses, crystalline ceramics, and metals

et al. 2018

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“…In the frame of long-term storage of nuclear wastes, several ceramic matrices were already proposed as good candidates for the immobilization of minor actinides such as Np, Am or Cm [1]. Zirconolite Ca 1-x and β-TPD/monazite composites and finally apatites (with general formula Me 10 (XO 4 ) 6 Y 2 with Me = Ca 2+ , Ln 3+ , An 3+ or An 4+ , X = Si or P and Y = F or O) were considered for the simultaneous incorporation of An(III) and An(IV) [2].…”

Section: Introductionmentioning

confidence: 99%

Synthesis and characterization of thorium-bearing britholites

Terra

Audubert

Dacheux

et al. 2006

Journal of Nuclear Materials

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In the field of the immobilization of tri-and tetravalent minor actinides, apatites and especially britholites were already proposed as good candidates. In order to simulate tetravalent minor actinides, the incorporation of thorium, through dry chemical routes, was studied in britholite samples of general formula Ca 9 Nd 1-x Th x (PO 4 ) 5-x (SiO 4 ) 1+x F 2 . The study showed that the incorporation of thorium was effective whatever the thorium reagent used or the grinding conditions considered. Nevertheless, it appeared necessary to use mechanical grinding (30 Hz, 15 minutes) before heating treatment (T = 1400°C, 6 hours) to improve the reactivity of powders and the sample homogeneity. In these conditions, the incorporation of thorium in the britholite structure occurred above 1100°C. The heating treatment at 1400°C led to single phase and homogeneous compounds. This work also underlined the necessity to prefer the coupled substitution (Nd 3+ , PO 4 3-) ⇔ (Th 4+ , SiO 4 4-) instead of (Nd 3+ , F -) ⇔ (Th 4+ , O 2-), in order to prepare pure and single phase samples in all the range of composition examined.3

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“…The fluorapatite accepts many substitutions on each of the three Ca, PO 4 , and F sites. Examples of ions that can be substituted in the fluorapatite structure are listed in Table I.…”

Section: Fluorapatite Structurementioning

confidence: 99%

“…This study is part of the extensive research performed in our Institute on potential host phases for long-life radioactive elements, or radionuclides, separated from French nuclear waste. We focus on minerals called apatites, which form a very large and abundant family with the general formula Me 10 (XO 4 ) 6 Y 2 , where Me stands for a divalent cation, XO 4 for a trivalent anion, and Y for a monovalent ion. The most common and simple example of apatite is the fluorapatite: Ca 10 (PO 4 ) 6 F 2 .…”

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Optimizing the formula of rare earth‐bearing materials: A computational chemistry investigation

Bertolus

Defranceschi

2006

Int J of Quantum Chemistry

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ABSTRACT:We present a computational investigation into the nature of bonds formed by rare earth elements (REE) in materials. This study focuses on the incorporation of neodymium in minerals called apatites, which are derived from fluorapatite: Ca 10 (PO 4 ) 6 F 2 . These minerals, which allow many substitutions on all three Ca, P, and F sites, are considered as potential host phases for radioactive elements separated from nuclear waste. Nd and trivalent actinides have very similar physical and chemical properties, and Nd is not radioactive and much more easily handled. It is therefore very often used as a surrogate for actinides with oxidation degree three in experimental studies. Several formulas can be considered to substitute Nd 3ϩ to Ca 2ϩ and maintain charge balance of the apatite. Existing experimental and theoretical studies, however, mostly concern the Ca 9 Nd(PO 4 ) 5 SiO 4 F 2 formula, where the Nd incorporation is compensated by the replacement of one PO 4 3Ϫ by a SiO 4 4Ϫ group. Moreover, only the cation position has been studied, whereas the silicate position and its influence on stability are unknown. We present a more general investigation of possible charge compensations on the one hand, and of the various resulting configurations on the other. All possible configurations of the two formulas Ca 9 Nd(PO 4 ) 5 SiO 4 F 2 and Ca 8 NdNa(PO 4 ) 6 F 2 have been considered. Calculations have been performed within the framework of density functional theory (DFT). A computation scheme that permits good accuracy in these systems within reasonable computation times is determined. The results obtained for cohesion energies, geometries, and electronic densities are discussed. As for the formulation, it is shown that the Ca 8 NdNa(PO 4 ) 6 F 2 formula is less stable than the fluorapatite, while Ca 9 Nd(PO 4 ) 5 SiO 4 F 2 is more stable. For the structures, it is found that Nd substitutes preferably in the second cationic site. Moreover, the most stable structures exhibit the shortest Na-Nd or Nd-Si distances. Local charge balance therefore seems favorable. Then, it is shown that Nd forms covalent bonds both in apatite and in britholite, while Na forms ionic bonds. Finally, a first correlation between the material stability and the covalent character of the bonds formed is established.

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New conditionings for separated long-lived radionuclides

Cited by 90 publications

References 15 publications

A comparative review of the aqueous corrosion of glasses, crystalline ceramics, and metals

A comparative review of the aqueous corrosion of glasses, crystalline ceramics, and metals

Synthesis and characterization of thorium-bearing britholites

Optimizing the formula of rare earth‐bearing materials: A computational chemistry investigation

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