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Bouillard, N.
Universite de Provence, 13 - Marseille (France); CEA Saclay, Dept. Modelisation de Systemes et Structures, Service Fluides Numeriques Modelisation et Etudes, Lab. de Modelisation des Transferts en Milieux Solides, 91 - Gif sur Yvette (France)2006
Universite de Provence, 13 - Marseille (France); CEA Saclay, Dept. Modelisation de Systemes et Structures, Service Fluides Numeriques Modelisation et Etudes, Lab. de Modelisation des Transferts en Milieux Solides, 91 - Gif sur Yvette (France)2006
AbstractAbstract
[en] When a radioactive waste is stored in deep geological disposals, it is expected that the waste package will be damaged under water action (concrete leaching, iron corrosion). Then, to understand these damaging processes, chemical reactions and solutes transport are modelled. Numerical simulations of reactive transport can be done sequentially by the coupling of several codes. This is the case of the software platform ALLIANCES which is developed jointly with CEA, ANDRA and EDF. Stiff reactions like precipitation-dissolution are crucial for the radioactive waste storage applications, but standard sequential iterative approaches like Picard's fail in solving rapidly reactive transport simulations with such stiff reactions. In the first part of this work, we focus on a simplified precipitation and dissolution process: a system made up with one solid species and two aqueous species moving by diffusion is studied mathematically. It is assumed that a precipitation dissolution reaction occurs in between them, and it is modelled by a discontinuous kinetics law of unknown sign. By using monotonicity properties, the convergence of a finite volume scheme on admissible mesh is proved. Existence of a weak solution is obtained as a by-product of the convergence of the scheme. The second part is dedicated to coupling algorithms which improve Picard's method and can be easily used in an existing coupling code. By extending previous works, we propose a general and adaptable framework to solve nonlinear systems. Indeed by selecting special options, we can either recover well known methods, like nonlinear conjugate gradient methods, or design specific method. This algorithm has two main steps, a preconditioning one and an acceleration one. This algorithm is tested on several examples, some of them being rather academical and others being more realistic. We test it on the 'three species model'' example. Other reactive transport simulations use an external chemical code CHESS. For a realistic case of Uraninite leaching, accelerated Picard methods divide the CPU cost of standard Picard's by three and the number of iteration by five. (author)
Original Title
Developpement de methodes numeriques pour le transport reactif
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Secondary Subject
Source
Dec 2006; 239 p; [115 refs.]; These mathematiques
Record Type
Report
Literature Type
Thesis/Dissertation
Report Number
Country of publication
BUILDING MATERIALS, CALCULATION METHODS, DISSOLUTION, FUNCTIONS, KINETICS, MANAGEMENT, MATERIALS, MATHEMATICAL LOGIC, MATHEMATICAL SOLUTIONS, MAXIMUM-LIKELIHOOD FIT, MINERALS, NUMERICAL SOLUTION, OPTIMIZATION, OXIDE MINERALS, RADIOACTIVE MATERIALS, RADIOACTIVE MINERALS, RADIOACTIVE WASTE MANAGEMENT, REACTION KINETICS, SEPARATION PROCESSES, SIMULATION, URANIUM MINERALS, WASTE DISPOSAL, WASTE MANAGEMENT
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