Leach resistance of murataite-based ceramics containing actinides

Stefanovsky, S. V.; Yudintsev, S. V.; Перевалов, С. А.; Startseva, I. V.; Varlakova, G. A.

doi:10.1016/j.jallcom.2007.01.097

Cited by 22 publications

(7 citation statements)

References 10 publications

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“…Like in our work, in the work [9] steady-state for U has not been reached. The U leach rate at pH = 5.6 and T = 70 • C from pyrochlorebased ceramics was found to be ∼ 10 −4 g/(m 2 × d) [10] that is some higher than the value 2.4 × 10 −5 g/(m 2 × d) obtained in our previous work [6] at pH ≈ 6-6.5 and T = 90 • C. REEs (Ce, Gd, Lu) exhibit some higher leach rates from pyrochlore-based ceramics as compared with U under the same conditions [9][10][11] whereas Pu is lower leachable element -its average leach rate was found to be ∼ 8 × 10 −5 g/(m 2 × d) at pH = 2 and T = 90 • C [9] and ∼ 10 −6 -10 −5 g/(m 2 × d) at pH = 5.6 and T = 70 • C [10].…”

Section: Resultscontrasting

confidence: 70%

“…Available data on Hf release from pyrochlore-based ceramics give the value of ∼ 10 −5 g/(m 2 × d) at pH = 5.6 and T = 70 • C [10]. In our previous work [6] we obtained much lower value (∼ 10 −7 g/(m 2 × d)) but for pH = 6-6.5 and T = 90 • C. Anyway, these data may be compared. …”

Section: Resultsmentioning

confidence: 75%

“…The procedure based on contact between powdered specimen and continuously flowing leachant at various temperatures and pH values is described in details in several works (see, for example, [6,8]). …”

Section: Methodsmentioning

confidence: 99%

“…In our previous works [3][4][5] we have demonstrated high leach resistance of the murataite based ceramics under their testing with MCC-1 [3,4], ANS-16.1 [5], and a single-passflow-through (SPFT) [6] procedures. In the present work we describe new results of leach testing of the murataite ceramics using the SPFT procedure.…”

Section: Introductionmentioning

confidence: 96%

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Leach rates of uranium and thorium from murataite ceramics

Stefanovsky¹,

Varlakova²,

Startseva³

et al. 2009

Radiochimica Acta

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Leach rate / Murataite / Thorium / UraniumSummary. Samples of murataite-based ceramics with chemical composition (wt.%): 5 Al 2 O 3 , 10 CaO, 55 TiO 2 , 10 MnO, 5 Fe 2 O 3 , 5 ZrO 2 , 10 AnO 2 (An = Th, U) were produced by melting in both glassy carbon crucibles in a resistive furnace and a cold crucible followed by crystallization during slow cooling. All the ceramics were composed of predominant murataite polytypes with 5-, 8-, and 3-fold elementary fluorite unit cell, minor crichtonite and pyrophanite/ilmenite, and rare grains of perovskite and pyrochlore. More than 95% of total Th and U enter the murataite polytypes. The murataite grains have zoned structure where the 5C, 8C and 8C polytypes form their core, middle zone and rim respectively. Leach rates of Th and U were determined using a single-pass-flow-through (SPFT) procedure at pH = 2 and pH = 6.5 at a temperature of 90 ± 2 • C. Average Th leach rates from the ceramics produced in the resistive furnace and cold crucible were found to be 1.00 × 10 −5 g/(m 2 × d) and 1.97 × 10 −5 g/(m 2 × d). Uranium was found to be higher leachable element than thorium: its average leach rate was 1.42 × 10 −3 g/(m 2 × d). Higher leachability of U as compared to Th may be due to either occurrence of U in minor crichtonite phase with lower chemical durability or hydrolytic processes resulting in formation of higher leachable U(VI).

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Section: Resultscontrasting

confidence: 70%

Section: Resultsmentioning

confidence: 75%

Section: Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 96%

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Leach rates of uranium and thorium from murataite ceramics

Stefanovsky¹,

Varlakova²,

Startseva³

et al. 2009

Radiochimica Acta

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“…Data on murataite matrices have been reported in many publications (Laverov et al, 1999(Laverov et al, , 2003(Laverov et al, , 2006Lian et al, 2005;Stefanovsky et al, 2007aStefanovsky et al, , 2007bYudintsev et al, 2007). The highest murataite content is reached in ceramics of the following composition, wt %: 55 TiO 2 , 10 MnO, 10 CaO, 5 Al 2 O 3 , 5 Fe 2 O 3 , 5 ZrO 2 , 10 actinide and REE oxides.…”

Section: Results Of Previous Investigations Of Murataitementioning

confidence: 94%

Modular nature of the polysomatic pyrochlore-murataite series

et al. 2011

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Synthetic analogues of murataite, a very rare mineral-a complex oxide of REE, actinide, Ti, Fe, and other elements,-are of great interest as confinement matrices of radioactive wastes. They are produced by sintering (1200-1300°C) and melting (1500-1600°C) with subsequent crystallization of the melt. Four structural varieties of murataite distinguished by unit cell parameters have been established by TEM study. All these varieties are derivatives of the fluorite structure designated as murataite 3C, 5C, 7C, and 8C depend ing on repetition factor of a parameter of the fluorite subcell. The structural features of the synthetic murataite varieties are analyzed in this paper based on data obtained from high resolution electron micros copy, microdiffraction, and X ray refinement. The hypothesis of a modular structure of the members of poly somatic pyrochlore-murataite series has been confirmed. At the same time, the structural modules are zero dimensional rather than two dimensional as had previously been suggested. The combinations of zero dimensional modules in 3D space create the entire structural diversity of the polysomatic series.

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