Cesium and Niobium transport through poorly cemented sandstone from Krasnoyarsk-26 (Russian Federation): From Batch to T
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Cesium and Niobium transport through poorly cemented sandstone from Krasnoyarsk-26 (Russian Federation): From Batch to Transport experiments Ignasi Casas1, Javier Giménez1, Joan M. Merino1, Emilio Arasanz1, Joan de Pablo1,2, Josep Torras2 and Miquel Rovira1,2 1 Chemical Engineering Department, UPC, 08028 Barcelona, Spain 2 Waste Management Laboratory, CTM-UPC, 08240 Manresa, Spain ABSTRACT We have studied the sorption of Cs and Nb onto poorly cemented sandstone (drillcore from ∼ 250 m depth) from the radioactive waste disposal site at Krasnoyarsk-26 (Russian Federation). Results were evaluated in terms of KD-values and Langmuir isotherms. These values have been used to model the transport of Cs and Nb through a sandstone column using the RETRASO code (REactive TRAnsport of Solutes), which is able to simulate simultaneously groundwater flow, heat transport and multicomponent reactive solute. Good agreement between experimental data and modeling has been achieved for both elements. Cs transport has been modeled using rapid sorption equilibrium, while for Nb a kinetically controlled transport has been considered. The results obtained in this work have been used to predict the 1D transport of Cs and Nb taking into account some parameters of the hydrogeology of Krasnoyarsk-26. INTRODUCTION The European Commission Fifth Framework BORIS project ran from November 2000 to July 2002. The overall goal of BORIS was to use data and samples from the Russian borehole injection sites for liquid radioactive waste at Krasnoyarsk-26 and Tomsk-7 to further understanding of the chemical behavior and migration of radionuclides in the geological environment. A subsidiary goal has been to archive historical data from the sites, thereby ensuring its preservation. At the Russian sites, the migration behavior of many radionuclides, and the effectiveness of clay layers in isolating radionuclides, can be studied in a natural groundwater system at repository depths. The project has sought to use this information to build scientific and societal confidence in radioactive waste disposal safety assessments and the deep disposal concept. In this work, we focus on a study of the sorption behavior of radionuclides at the Krasnoyarsk-26 site on the eastern side of the Yenisey River, about 50 km northeast of the city of Krasnoyarsk. The geological structure comprises an erosional syncline filled with an interbedded mixed sequence of weakly-cemented, permeable Jurassic sandstones and relatively impermeable clays. The principal aquifer horizons in the Jurassic sediments comprise sandstones with multiple clay interbeds, and are named Horizon I and Horizon II, located within the disposal site at depths of 370-465 m and 180-280 m respectively. A detailed description of the site can be found in [1]. These horizons were selected as reservoir formations for waste disposal. Since the mid-1960s, liquid HLW and ILW have been injected into Horizon I, and liquid LLW into Horizon II. At Krasnoyarsk-26, the total waste injected comprises 6.1 million m3 having
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