Crystalline ceramic waste forms

Lumpkin, G. R., Smith, K. L., Gier6, R. Williams, C. T. 2004. Geochemical behaviour of host phases for actinides and fission products in crystalline ceramic nuclear waste forms. In Giere, R. Stille, P. (eds). Energy, Waste, and the Environment a Geochemical Perspective. Geological Society, London, Special Publications, 236, 89-111. 

Geochemical behaviour of host phases for actinides and fission products in crystalline ceramic nuclear waste forms... 

The preparation, composition, structure and leaching characteristics of a crystalline, ceramic radioactive waste form have been discussed, and where applicable, compared with vitrified waste forms. The inorganic ion exchange materials used such as sodium titanate were prepared from the corresponding metal alkoxide. The alkoxides were reacted in methanol with a base containing the desired exchangeable cation and the final powder form was produced by hydrolysis in an acetone-water mixture followed by vacuum drying the precipitate at ambient temperature. 

During the past ten years, there has been considerable research devoted to the development of crystalline waste forms for actinide immobilization [7,8,24,27, 28,39,40,67,68,41-43,69]. Many of the phases are based on studies of minerals that contain Th and U, such as pyrochlore [16-18], zirconolite [70,71], zircon [1,72], monazite [73], britholite [74]. Based on their degrees of alteration, most of the minerals are considered to have an acceptable chemical durability. In addition, closely related mineral structures, such as murataite and garnet, which do not contain U or Th have been synthesized with actinides [29,75,76]. Multiphase ceramics. Ceramic matrices were initially designed for the immobilization of non-partitioned HLW from SNF reprocessing and considered... 

Table 1. A selection of crystalline ceramic waste forms, applications, and mineralogy...

Solomah, A. G. Matzke, Hj. 1989. Leaching studies of synroc crystalline ceramic waste forms. In Lutze, W. Ewing, R. C. (eds) Scientific Basis for Nuclear Waste Management XII. Materials Research Society Symposium Proceedings, 127, 241-248. 

The use of inorganic ion exchangers to solidify liquid radioactive waste followed by pressure sintering to produce a ceramic waste form appears to be a viable alternative to calcina-tion/vitrification processes. Both the process and waste form are relatively insensitive to changes in the composition of the waste feed. The stability of the ceramic waste form has been shown to be superior to vitrified wastes in leaching studies at elevated temperatures. Further studies on the effects of radiation and associated transmutation and the influence of temperature regimes associated with potential geologic repositories are needed for a more definitive comparison of crystalline and amorphous waste forms. 

Dacheux N, Clavier N, Le Coustumer P, Podor R (in press) Immobilization of tetravalent actinides in the TPD structrrre. Proc 10th Inti Ceramics Congress. Vincenzini P (ed) Techna Publishers, Florence, Italy Davis DD, Vance ER, McCarthy GJ (1981) Crystal chemistry and phase relations in the synthetic miner s of ceramic waste forms. II. Studies of uranirrm-containing monazites. In Scientific Basis for Nuclear Waste Management, vol. 3. Moore JG (ed) Plentrm Press, New York, p 197-200 Day DE, Wu Z, Ray CS, Hrma P (1998) Chemically durable iron phosphate glass waste forms. J Non-Crystalline Solids 241 1-12... 

Ewing RC, Weber WJ, Lutze W (1995a) Crystalline ceramics waste forms for the disposal of weapons plutonium. In Disposal of Weapon Plutonium Approaches and Prospects. Merz ER, Walter CE (eds) Kluwer Academic Publishers, Dordrechf The Netherlands, p 65-83 Ewing RC, Weber WJ, Chnard FW, Jr (1995b) Radiation effects in nuclear waste forms for high-level radioactive waste. Progress Nucl Energy 29 63-112... 

Low-temperature treatment of low-level mixed wastes has also been accomplished by solidification/stabilization with chemically bonded phosphate ceramics (CBPC). These are made by hydrothermal chemical reaction rather than by sintering. Chemical bonding develops when acid phosphates react with oxides to form crystalline orthophosphate (Singh et al. 1997). The ceramic matrix stabilizes the wastes by microencapsulation. The low temperature of the reaction allows volatile radionuclides to be treated (Singh et al. 1997). 

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