Microtomography-based Inter-Granular Network for the simulation of radionuclide diffusion and sorption in a granitic rock

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http://hdl.handle.net/10138/313034

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Iraola , A , Trinchero , P , Voutilainen , M , Gylling , B , Selroos , J-O , Molinero , J , Svensson , U , Bosbach , D & Deissmann , G 2017 , ' Microtomography-based Inter-Granular Network for the simulation of radionuclide diffusion and sorption in a granitic rock ' , Journal of Contaminant Hydrology , vol. 207 , pp. 8-16 . https://doi.org/10.1016/j.jconhyd.2017.10.003

Title: Microtomography-based Inter-Granular Network for the simulation of radionuclide diffusion and sorption in a granitic rock
Author: Iraola, Aitor; Trinchero, Paolo; Voutilainen, Mikko; Gylling, Bjorn; Selroos, Jan-Olof; Molinero, Jorge; Svensson, Urban; Bosbach, Dirk; Deissmann, Guido
Contributor: University of Helsinki, Department of Chemistry
Date: 2017-12
Language: eng
Number of pages: 9
Belongs to series: Journal of Contaminant Hydrology
ISSN: 0169-7722
URI: http://hdl.handle.net/10138/313034
Abstract: Field investigation studies, conducted in the context of safety analyses of deep geological repositories for nuclear waste, have pointed out that in fractured crystalline rocks sorbing radionuclides can diffuse surprisingly long distances deep into the intact rock matrix; i.e. much longer distances than those predicted by reactive transport models based on a homogeneous description of the properties of the rock matrix. Here, we focus on cesium diffusion and use detailed micro characterisation data, based on micro computed tomography, along with a grain-scale Inter-Granular Network model, to offer a plausible explanation for the anomalously long cesium penetration profiles observed in these in-situ experiments. The sparse distribution of chemically reactive grains (i.e. grains belonging to sorbing mineral phases) is shown to have a strong control on the diffusive patterns of sorbing radionuclides. The computed penetration profiles of cesium agree well with an analytical model based on two parallel diffusive pathways. This agreement, along with visual inspection of the spatial distribution of cesium concentration, indicates that for sorbing radionuclides the medium indeed behaves as a composite system, with most of the mass being retained close to the injection boundary and a non-negligible part diffusing faster along preferential diffusive pathways.
Subject: Grain-scale model
Diffusion experiment
Anomalously long cesium penetration
Heterogeneity of sorption sites
CRYSTALLINE ROCKS
1171 Geosciences
114 Physical sciences
116 Chemical sciences
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