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Natural Annealing of Alpha-Recoil Damage in Metamict Minerals of the Thorite Group

Published online by Cambridge University Press:  28 February 2011

Y. Eyal ,
G. R. Lumpkin  and
R. C. Ewing
Y. Eyal
Affiliation:
Department of Nuclear Engineering, Technion - Israel Institute of Technology, Haifa 32000, Israel
G. R. Lumpkin
Affiliation:
Department of Geology, University of New Mexico, Albuquerque, New Mexico 87131, USA
R. C. Ewing
Affiliation:
Department of Geology, University of New Mexico, Albuquerque, New Mexico 87131, USA
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Abstract

Minerals of the thorite (ThSiO4) mineral group have been leached as fine powders in bicarbonate-carbonate solutions for time periods up to 288 days.The radioactivities of the solutions were measured for 238U, 234U, 232Th, 230Th and 228Th by alpha spectrometry, preceded by chemical separation and purification of U and Th. The results confirm the preservation of disordered regions of higher chemical reactivity in an already fully-damaged aperiodic structure. The damage is most evident for the short-lived nuclide 228Th and to a much lesser extent for the long-lived nuclide 234U because the alpha-recoil tracks anneal with time. The calculated mean life of an alpha-recoil track in these metamict thorium silicates is approximately 1,500 to 6,000 years. This study demonstrates that alpha-decay products are selectively leached from damaged, aperiodic materials, but the damage is subject to low-temperature annealing over relatively short periods of time.

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 84: Symposium L – Scientific Basis for Nuclear Waste Management X , 1986 , 635
Copyright
Copyright © Materials Research Society 1987

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