Synthesis of Actinide-Doped Ceramics: From Laboratory Experiments to Industrial Scale Technology
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Alexander A. Kitsay, Vladimir M. Garbuzov and Boris E. Burakov Laboratory of Applied Mineralogy and Radiogeochemistry, the V.G. Khlopin Radium Institute, 28, 2-nd Murinskiy ave., St. Petersburg, 194021, Russia, fax: +7-812-346-1129; $%675$&7 The experience of the Laboratory of Applied Mineralogy and Radiogeochemistry of the V.G. Khlopin Radium Institute on synthesis of Pu-Am-doped ceramics is summarized. During the last 5 years, dozens of actinide doped polycrystalline samples and single crystals have been successfully synthesized such as zircon, hafnon, cubic zirconia, monazite, Ti-pyrochlore, perovskite and garnet. Actinide loading has been varied as follows: - 239Pu – from 5-6 wt.% in zircon (polycrystalline and single crystals), hafnon, garnet and perovskite to 10 wt.% in Ti-pyrochlore and up to 37 wt.% in zirconia; 238 Pu – from 2.5 wt.% in zircon single crystals to 5 wt. % in polycrystalline zircon and 10 wt.% in monazite and cubic zirconia; - 243Am – 20-23 wt.% in cubic zirconia and monazite. The weight of each single ceramic pellet varied from 0.2 to 2.0 grams. Special furnaces developed in KRI for ceramic synthesis allowed obtaining up to 7 ceramic pellets simultaneously during the same experiment. The highest amounts of actinides used under glove-box conditions in the same experiment were: 1.5-2.0 g for 239Pu, 0.6 g for 238Pu and 0.3 g for 243Am. Most experiments on synthesis of ceramics and single crystals doped with 239Pu, 238Pu and 243Am carried out at the KRI did not lead to contamination of internal walls of glove boxes. No release of Pu-Am-aerosols was observed as a result of sintering or melting at 1300-1600°C. These results allowed us to conclude that at the present the KRI has developed the experimental basis for transferring laboratory innovations to the industry of actinide immobilization. It is important that adopting ceramic synthesis methods at industrial scale does not require development of new special equipment. ,1752'8&7,21 Actinide materials and wastes in Russia are numerous and characterized by different phase and chemical compositions. These include: 1) surplus weapons and civilian Pu (e.g., in the forms of metal, alloys or oxides); 2) actinide/rare earth element fractions (e.g., nitrate solutions or calcined oxides) of high-level wastes from spent nuclear fuel reprocessing; 3) Pu and Amcontaining residue wastes (e.g., alkaline solutions and residues of complex chemical compositions) from nuclear weapons production; and 4) separated concentrates of actinides (e.g., oxides). According to the approach of the V.G. Khlopin Radium Institute (KRI), the immobilization of actinides should include as the first stage their complete conversion into chemically durable ceramics [1]. Then these ceramics might be directly buried in geological formations or used before geological disposal as the targets for actinide transmutation including burning of Pu-ceramic fuel. Development of industrial scal
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