Basaltic dykes in evaporites: a natural analogue
We present rare earth element (REE) data of basalt and salt samples from central Germany where basaltic dykes of Tertiary age crosscut Upper Permian rock and potash salt. The glassy rims of the dykes can be considered as a natural analogue for the corrosion of nuclear waste glass in a salt repository, whereas the REE data from the salt can serve as an analogue for radionuclide migration in salt next to a leaking nuclear waste repository because the light rare earths (LREE) have a geochemical behavior similar to that of some actinides.
Our basalt data demonstrate mobility and fractionation of the REE during postintrusive circulation of salt brines. The processes controlling this behavior of the REE were dissolution and reprecipitation of phosphate minerals. The salt data show that a small portion of the REE has left the basalt during postintrusive fluid circulation and migrated into the salt where a strong depletion of the LREE can be observed with increasing distance from the basalt contact. This fractionation is most probably due to precipitation of LREE-enriched accessory minerals such as apatite. In analogy to this, a similar behavior might be expected from actinides such as Am and Cm, which would in the case of a leaking salt nuclear waste repository probably be immobilized when phosphate minerals are present in the backfill material.
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This book provides incentives for further development of sustainable fuel cycles through a novel and interdisciplinary approach to an Earth science-related topic. The main focus is on geochemical concepts in immobilizing, isolating or neutralizing waste derived from energy production and consumption. The book also addresses the issue of using some types of energy-derived waste as alternative raw materials. Moreover, it highlights research on how certain wastes can be used for energy production, an increasingly important aspect of modern integrated waste management strategies. The main objectives are to: (a) identify the most serious environmental problems related to various types of power generation and associated waste accumulation; (b) present strategies, based on natural analogue materials, for the immobilization of toxic and radioactive waste components through mineralogical barriers; (c) discuss modern procedures for reuse of waste or certain waste components; and (d) review the importance of geochemical modelling in describing and predicting the interaction between waste and the environment.