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Perrochet, Pierre
Nom
Perrochet, Pierre
Affiliation principale
Fonction
Professeur ordinaire
Email
pierre.perrochet@unine.ch
Identifiants
RĂ©sultat de la recherche
Voici les éléments 1 - 8 sur 8
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- PublicationMétadonnées seulementReservoir theory, groundwater transit time distributions, and lumped parameter models(1999)
;Etcheverry, David - PublicationMétadonnées seulementError propagation in the Newton-based solution control of unsaturated flow(: Int Assoc Hydrological Sciences, 1999)
;Diersch, Hans-Jörg; ;Stauffer, Fritz ;Kinzelbach, Wolfgang ;Kovar, KarelHoehn, EduardThe Newton method represents the numerical core of the primary variable switching technique (PVST) which has been shown to be superior to conventional approaches in both unsaturated flow and multiphase flow modelling. In the context of PVST, empirically controlled strategies in time are rather common, where the Newton convergence is attempted for a possibly large step size. This technique is known as the target-based full Newton (TBFN) time stepping strategy. In comparison to adaptive techniques satisfying a predefined discretization error, the TBFN results can be inaccurate in spite of the convergence achieved in the Newton method. The present paper aims to analyse the cause of discrepancies in simulating unsaturated flows. This is done by comparison of analytical solutions which are based on exponential constitutive laws. - PublicationMétadonnées seulementRadionuclide release and transport from nuclear underground tests performed at Mururoa and Fangataufa - predictions under uncertaintyIn the context of a study by the International Geomechanical Commission (IGC) and the International Atomic Energy Agency (IAEA) on the effects of nuclear tests at the: atolls of Mururoa and Fangataufa, release to the biosphere is estimated for 35 radionuclides originating from 147 nuclear underground tests. Based on a qualitatively characterised hydrogeological situation of atolls and relatively scarce site-specific data, a model chain was developed to conservatively estimate the radionuclide fluxes via groundwater, from their sources, the explosion cavities. towards the biosphere, the ocean or lagoon. Finite element hydro-thermal modelling was used to describe water flow. Parameters were calibrated by a very few measured pre-test temperature profiles in bore holes. The impact of the tests on groundwater flow and mechanical impact on rock was considered. Estimates were made to quantify spatial extensions and temporal evolution of impact by using measurements on refilling rate of the cavities. Tests were categorised according to their specific yield and location although detailed data were missing. A base case parameter set was defined for the hydraulic conditions and for the initial radionuclide inventory of individual tests. Models were used to describe the concentration of radionuclides in the cavities as a function of time. Radionuclide transport from the cavities to the biosphere was represented by two different approaches: a double porosity model for the fractured volcanic rock and a single porosity model for the overlaying, highly porous carbonates. Results consist of conservative estimates on radionuclide release into the environment, or concentration in the lagoon or ocean water. Their sensitivity was investigated using different models and parameters. A few measured data (concentrations in a few cavities, in the deep carbonates and in the lagoons for selected radionuclides, such as H-3, C-14, Cl-36, Sr-90, I-129, Cs-137(239), Pu-240 and Am-241) were available for a comparison with the calculations. In view of the lack and uncertainty of site-specific data, the agreement is of acceptable quality. (C) 2001 Elsevier Science B.V. All rights reserved.
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