Electromigration experiments for studying transport parameters and sorption of cesium and strontium on intact crystalline rock

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http://hdl.handle.net/10138/250555

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Puukko , E , Lehto , J , Lindberg , A & Voutilainen , M 2018 , ' Electromigration experiments for studying transport parameters and sorption of cesium and strontium on intact crystalline rock ' , Journal of Contaminant Hydrology , vol. 217 , pp. 1-7 . https://doi.org/10.1016/j.jconhyd.2018.08.010

Title: Electromigration experiments for studying transport parameters and sorption of cesium and strontium on intact crystalline rock
Author: Puukko, Esa; Lehto, Jukka; Lindberg, Antero; Voutilainen, Mikko
Contributor: University of Helsinki, Ion exchange for nuclear waste treatment and for recycling
University of Helsinki, Department of Chemistry
University of Helsinki, Geological disposal of spent nuclear fuel
Date: 2018-10
Language: eng
Number of pages: 7
Belongs to series: Journal of Contaminant Hydrology
ISSN: 0169-7722
URI: http://hdl.handle.net/10138/250555
Abstract: This study aims to determine upscaling factors for the radionuclides' distribution coefficients (Kd) on crushed rocks to intact rock for the safety analysis of radionuclide migration from spent nuclear fuel in bedrock towards biosphere. Here we report the distribution coefficients for intact rock determined by electromigration sorption experiments and compare the results with those from recently performed batch sorption experiments. In total 34 rock samples, representing three typical rock types from Olkiluoto Finland, were studied in order to determine distribution coefficients, effective diffusion coefficients and porosities using the electromigration sorption experiments, formation factor experiments and porosity measurement. The parameters determined represent the three main parameters of geosphere used in the safety assessment of spent nuclear fuel disposal. The distribution coefficients of cesium and strontium on intact rock varied between (0.12–26.2) × 10−3 m3/kg and (1.4–13.3) × 10−3 m3/kg, respectively, whereas recent results for crushed rock varied between (2–57) × 10−3 m3/kg and (17–40) × 10−3 m3/kg, respectively. This implies that crushing increases the distribution coefficient significantly and upscaling factors from 3 to 33 were determined for scaling the distribution coefficients of crushed rock to ones of intact rock. The determined distribution coefficients of cesium and strontium for intact rock can be directly applied in the safety assessment whereas the upscaling factors can be used to convert distribution coefficients determined for crushed rock into ones for intact rock. Based on the results for porosities and effective diffusion coefficients it was concluded that they do not seem to correlate with sorption parameters. However, an alteration state, heterogeneity and mineral content seem to be important factors affecting the distribution coefficients and upscaling factors.
Subject: Electromigration
Sorption
Distribution coefficient
Formation factor
Effective diffusion coefficient
Porosity
POROSITY
GRANITE
COEFFICIENTS
SAMPLES
IN-SITU
116 Chemical sciences
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