Radiation damage effects in pyrochlore and zirconolite ceramic matrices for the immobilization of actinide-rich wastes
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Date
2000-07-01
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Commissariat à l'énergie atomique (CEA)
Abstract
Actinide-doping experiments using short-lived 238Pu and 244£m have demonstrated that pyrochlore and zirconolite become fully amorphous at a dose of 0.2-0.5 x 1016 cc/mg at ambient temperature and exhibit bulk swelling of 5-7%. Detailed studies of natural samples have included determination of the critical amorphization dose, long-term annealing rate, microstructural changes as a function of dose, and the thermal histories of the host rocks. Together, the laboratory based work and studies of natural samples indicate that the critical amorphization dose will increase by about a factor of 2-4 for samples stored at temperatures of 100-200 °C for up to 10 million years. These studies of alpha-decay damage have been complemented by heavy ion irradiation studies over the last ten years. Most of the irradiation work has concerned the critical amorphization dose as a function of temperature in thin films; however, some work has been carried out on bulk samples. The irradiation work indicates that most pyrochlore and zirconolite compositions will have similar critical amorphization doses at low temperatures (e.g., below 300-400 °C). Pyrochlores with Zr as the major B-site cation transform to a defect fluorite structure with increasing ion irradiation dose, but do not become amorphous.
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Keywords
Actinides, Amorphous state, Performance testing, Physical radiation effects, Pyrochlore, Radioactive waste storage, Rare earths, Zirconolite
Citation
Lumpkin, G. R., Begg, B. D., & Smith, K. L. (2000). Radiation damage effects in pyrochlore and zirconolite ceramic matrices for the immobilization of actinide-rich wastes. Paper presented at Atalante 2000: International conference on scientific research on the back-end of the fuel cycle for the 21st century, Avignon, France, 24-26 October 2000.