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Geochemical Modelling of the Alteration of a Granitic Rock Around a Repository for Spent Nuclear Fuel

Published online by Cambridge University Press:  28 February 2011

Bertrand Fritz ,
Marie Kam  and
Yves Tardy
Bertrand Fritz
Affiliation:
Centre de Sédimentologie et de Géochimie de la Surface (CNRS), 1, rue Blessig - F 67084 STRASBOURG Cedex - France
Marie Kam
Affiliation:
Centre de Sédimentologie et de Géochimie de la Surface (CNRS), 1, rue Blessig - F 67084 STRASBOURG Cedex - France
Yves Tardy
Affiliation:
Institut de Géologie, 1, rue Blessig - F 67084 STRASBOURG Cedex - France
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Abstract

The alteration of a granitic rock around a repository for spent nuclear fuel has been simulated considering the geothermal effect through an increase of temperature. The results of the simulation were considered in terms of mass transfers and their volumic consequences. The dissolution of primary minerals by alteration tends to increase the porous volume due to fissures and cracks, while the precipitation of secondary minerals and particularly here calcite and clay minerals will tend to decrease the porosity by sealing the cracks. The results of the simulations show that an increase of temperature from 10 to 100°C will favour the alteration of the granitic rock by the solutions circulating today in the rock. This rock is characterized by a very low fissure porosity and the water velocity is consequently particularly low. These conditions favour intense water-rock interactions and the water-rock system will probably reach the stability field of secondary clay minerals predicted by the calculations: the porosity will decrease. A combination of these thermodynamic mass balance calculations and hydrodynamic considerations, with a kinetic approach of mineral dissolutions gives a first attempt to calibrate the modelling in the time scale.

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 50: Symposium STOCKHOLM – Scientific Basis for Nuclear Waste Management IX , 1985 , 517
Copyright
Copyright © Materials Research Society 1985

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