Leaching studies

Three principal conditions in the leaching studies differed markedly from those in the single-phase studies ... 

Leaching studies, ground-water composition and Pu transport... 

Evidence for the firm binding of Zn comes from studies using labelled zinc polyacrylate containing Zn and C. Only small amounts of these ions were lost to a saline solution over a three-month period, even in the presence of calcium (Peters et al., 1972 Peters, Jackson Smith, 1974). There is some evidence, from leaching studies, that Zn is more firmly bound to a copolymer of acrylic and itaconic adds than to poly(acrylic acid), and less firmly bound to a copolymer of maleic and acrylic adds. 

Schreiner, M., I. Prohaska, J. Rendl, and C. Weigel (1998), Leaching studies of potash-lime-silica glass with medieval glass composition using AAS and IRRS, in Tennent, N. (ed.), Conservation of Glass and Ceramics, James and James, London. 

It should be noted that in leaching the rate of reaction is of great importance, since the temperature used is relatively low and many factors combine to keep the rate slow. For practical reasons, leaching studies are performed on a homogenized sample, testing the temperature dependency of the rate of reaction (concentration and time) in various leaching mixtures. The most important variables in aqueous systems are pH and redox... 

Four surficial soils were collected from along a traverse across the projected position of the blind Northern Pods mineralisation (450 m below surface). This traverse was originally made to conduct a partial leach study over the Northern Pods, with samples 138538 and 138539 being soils with low mobile metal ion (MMI) response 250 m east of samples 138440 and 138441 which are directly over the mineralisation and show anomalous MMI response. 

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 chemical modelling to predict the formation of secondary phases and the mobility of trace elements in the CCB disposal environment requires detailed knowledge of the primary and secondary phases present in CCBs, thermodynamic and kinetic data for these phases, and the incorporation of possible adsorp-tion/desorption reactions into the model. As noted above, secondary minerals are typically difficult to identify due to their low abundance in weathered CCB materials. In many cases, appropriate thermochemical, adsorption/desorp-tion and kinetic data are lacking to quantitatively describe the processes that potentially affect the leaching behaviour of CCBs. This is particularly tme for the trace elements. Laboratory leaching studies vary in the experimental conditions used (e.g., the type and concentration of the extractant solution, the L/S ratio, and other parameters such as temperature and duration/ intensity of agitation), and therefore may not adequately simulate the weathering environment (Rai et al. 1988 Eary et al. 1990 Spears Lee, 2004). 

Wolfsberg, K., "Sorption-Desorption Studies of Nevada Test Site Alluvium and Leaching Studies of Nuclear Explosion Debris," Los Alamos Scientific Laboratory, Kept. LA-7216-MS, (April, 1978). 

A long term leaching study to compare the behavior of a titanate waste with glassy waste forms and to attempt to elucidate a leaching mechanism has been in progress for l6 months (15) ... 

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. 

---