ANDRA is the French National Agency for Radioactive Waste Management and is in charge of long-term management of all radioactive waste, under the supervision of the Ministry of Ecology, Energy, Sustain- able Development and the Sea (formerly the Ministry of Industry and the Ministry of Environment), and the Ministry of Research. Andra is involved in (i) a R&D mission, in order to propose long-term safety solutions for all kinds of radioactive wastes, including long-term storage, in particular studies about the deep geological repository project for high/intermediate level long lived wastes; (ii) an industrial mission concerning, on one hand, waste acceptance criteria and control and, on the other hand, sitting, construc- tion, operation, closure and monitoring of repositories; (iii) an information mission, through the regular publication of the national inventory of radioactive materials and waste. This mission includes as well an active policy of dialogue with stakeholders both at national and local level.
The Performance Assessment Department from Research and Development Division is the entity involved in the C2S@Exa. The department is responsible of the phenomenological description and performance/safety assessment of the integrated disposal repositories and their geological environments. It provides phe- nomenological and conceptual description of the behavior of each repository and geological component during operating and post-closure periods, in space and time (thermal, chemical, mechanical, hydraulic- gas, radionuclide/toxic release and transfer), including uncertainties analysis. The objective is to achieve a relevant, traceable and justified data base on multiphysic understanding at all space and time scales, in order (i) to develop safety assessment of repositories, (ii) to contribute to choices of design concept, (iii) to contribute to monitor the repositories and their environments, and (iv) to contribute to define step by step operating of the repositories. To assess the objective, the department and its subcontractors set up and perform many numerical simulations, involving efficient and robust methods and tools, and sound link with characterization data. The department also supports definition, development, choice and implementation of relevant simulation tools for all agency activities.
In the field of phenomenological description and performance/safety assessment, ANDRA has to perform many numerical simulations, in particular to quantify flow and solute transfer in saturated or unsaturated porous media, from the waste package to the human being, and through the repository and geological environment. Simulations have to take into account many physical processes, applied to different components (from the waste packages to the geological media) and material (clay, concrete, iron, glass, etc.) on very large time (up to one million years) and scale (from centimeter to tens of kilometers.
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Modeling context of radioactive wave management
Simulations are based on a large data set derived from an intensive characterization program. They are thus complex because they require a detailed geometry, with contrasts of parameters to manage, and applied to physical processes, with couplings, and non-linear equations. Up to now, in order to fulfill good understanding of the global system with previous peculiarities, and to get knowledge and information with both reasonable time and good accuracy, many simplifications are made, whose levels depend on the efficiency of available numerical methods and tools. Two levels of simulations are thus carried out:
- Complex physicochemical processes, involving strong couplings (such as chemical-transport, 2 phase-flow with radionuclide transfer, thermo-hydro-mechanics problems) but solved on small systems with grids up to many thousands of elements.
- Simplified physicochemical processes (leak coupling) consisting of modifying in space and time hydraulic and solute transfer parameters, but solved on big systems with grids of many millions of elements. Global system is splitted into embedded compartments whose scales are bigger and bigger.
For each application, ANDRA has been considering the use of HPC facilities for several years, through the development or new or use of existing methods and tools that would lead to improve the level of representation, in terms of geometry and/or physical processes. Thus, ANDRA is particularly interested in specific methods such as domain decomposition (space and time), parallel solvers, efficient preconditionners and solvers that would allow to take into account many millions of elements.
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Radioactive waste management scenario based on simplified
physicochemical processes