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Phase Composition and Leach Resistance of Actinide-Bearing Murataite Ceramics

Published online by Cambridge University Press:  26 February 2011

Sergey Stefanovsky
Affiliation:
profstef@mtu-net.ru, SIA Radon, Center of Advanced Technologies, 7th Rostovskii lane 2/14, Moscow, Russia, 119121, Russian Federation, 7 (095) 259 3739, 7 (095) 919 3194
S.V. Yudintsev
Affiliation:
Institute of Geology of Ore Deposits RAS, Staromonetnii lane 35, Moscow 119017Russia
B.S. Nikonov
Affiliation:
Institute of Geology of Ore Deposits RAS, Staromonetnii lane 35, Moscow 119017Russia
A.V. Mokhov
Affiliation:
Institute of Geology of Ore Deposits RAS, Staromonetnii lane 35, Moscow 119017Russia
S.A. Perevalov
Affiliation:
Vernadsky Institute of Geochemistry and Analytical Chemistry RAS, Kosygin st. 19, MoscowRussia
O.I. Stefanovsky
Affiliation:
SIA Radon, 7th Rostovskii lane 2/14, Moscow 119121Russia
A.G. Ptashkin
Affiliation:
SIA Radon, 7th Rostovskii lane 2/14, Moscow 119121Russia
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Abstract

Phase composition of the murataite-based ceramics containing 10 wt.% ThO2, UO2, NpO2 or PuO2 and leaching of actinides using a MCC-1 procedure were studied. The ceramics were prepared by melting of oxide mixtures in Pt ampoules in air at ∼1500 °C. They are composed of predominant murataite-type phases and contain traces of extra phases (rutile, crichtonite, perovskite). At least two murataite-related phases with five- and eight-fold elementary fluorite unit cell (5C and 8C) were simultaneously observed. Minor phase 3C (murataite) in the ceramics doped with ThO2 and UO2 was also found. In the Th-bearing sample the 5C phase prevails over the 8C phase. In the U-bearing ceramic they co-exist in comparable amounts. The sample produced at 1500 °C contains crichtonite whereas the ceramic produced at lower temperature (1400 °C) contained rutile. Higher temperature favors further rutile reactions with formation of crichtonite. The Np- and Pu-doped ceramics are also composed of major the 5C and the 8C phases and minor rutile and crichtonite (in Pu-loaded sample only). Unlike the sample prepared under slightly re-ducing conditions (in glassy carbon crucible) the Pu-doped ceramic produced under neutral conditions (in Pt ampoule) doesn’t contain perovskite-type phase. Occurrence of perovskite in the first sample was sup-posed to be due to reduction of some Pu(IV) to Pu(III) during experiment. Leach rates (7-day MCC-1 test, 90 °C) of the actinide elements from all the ceramics studied are at the level of 10-6-10-7 g/(m2·day).

Type
Research Article
Copyright
Copyright © Materials Research Society 2006

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References

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