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The Role of Colloids in the Transport of Radionuclides in Geological Media

Objective

The main objective of this programme is to understand how colloids could influence the migration behaviour of radionuclides in geological formations. This is being achieved firstly, by identifying the retention mechanisms of colloids and pseudocolloids to mineral surfaces by static and dynamic experiments, and secondly by investigating the formation of pseudocolloids. These studies will provide an insight into retention mechanisms and there upon validate retardation parameters used in transport models, which will be developed to predict colloid transport under conditions relevant to geological disposals. Moreover, this research is focused on model systems (surfaces, colloids) selected from studies carried out on the El Berrocal site (Spain).
The main objective of this program is to understand how colloids could influence the migration behaviour of radionuclides in geological formations. This is being achieved firstly by identifying the retention mechanisms of colloids and pseudocolloids (association of radionuclides with colloids) to mineral surfaces by static and dynamic experiments, and secondly by investigating the formation of pseudocolloids. These studies will provide an insight into retention mechanisms and there upon validate retardation parameters used in transport models.

Characterization of natural colloids has been achieved through scanning electron microscopy after concentration by ultrafiltration for the determination of composition and size distribution of colloids, and also through photon correlation spectroscopy for the colloid size distribution.
The sorption mechanisms of cations onto fine particle suspensions (model colloidal particles such as silica and muscovite mica) and on mineral monoliths (silica, muscovite mica) as a macroscopic equivalent to particle surfaces has been investigated in order to identify processes occurring between particles and cations.
The effect of organics coatings on the transport of cations has also been studied. A novel procedure has been developed to coat well defined packing particles (silica) with humic substances.
Work has also involved the identification of data needed for the modelling of colloid transport into porous media.
Work programme:

B.1. Colloid properties
B.1.1 Colloid characterization
B.1.2 Application to a site
B.2 Sorption mechanisms
B.2.1 Association of radioelements with colloids
B.2.2 Interaction of colloids and pseudocolloids on mineral surfaces
B.3 Transport mechanisms
B.3.1 Transport experiments in model systems without organic coatings
B.3.2 Transport experiments in model systems with organic coatings
B.4 Modelling

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Funding Scheme

CSC - Cost-sharing contracts

Coordinator

Commissariat à l'Energie Atomique (CEA)
EU contribution
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Address
Centre d'Études de Cadarache Sere-Ders
13108 Saint-Paul-lez-Durance
France

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Last update: 9 January 1996

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Permalink: https://cordis.europa.eu/project/id/FI2W0097

European Union, 2024