DEM’N’MELT Process : Optimisation of operating conditions by modelling
Within the framework of the PROVIDENCE project (Plan Relance, France), the DEM'N'MELT process was developed with the aim of marketing a solution for the treatment and conditioning of high and medium level waste to sites operators undergoing dismantling or remediation, in France and abroad. In this context, studies have been undertaken to optimise the operating conditions of the process.
The candidate will have to take in charge the software used in our Laboratory (Fluent, Workbench, SpaceClaim, Meshing), to appropriate the existing models. These models will have to evolve to :
o take into account additional measurements to calibrate the model
o study the sensitivity of the system to the physical properties of the glass
o optimise furnace operation and manage the feed capacity according to the filling level
o add agitation to the glass bath.
The candidate will be able to rely on the skills of the LDPV Laboratory, both experimentally and in modelling.
Modelling and evaluation of the future e-CO2 refinery
In the context of achieving carbon neutrality by 2050, the CEA has initiated a project in 2021 to assess the relevance of coupling a nuclear power system with a direct atmospheric carbon capture device (DAC) thanks to the use of the system's waste heat.
As a member of a team of about twenty experts(energy system evaluation, techno-economic engineering, energy system modeling, optimization and computer programming), you will participate in a research project on the modeling and evaluation of a CO2 refinery dedicated to the production of Jet Fuel fed by a nuclear reactor and coupled with an atmospheric CO2 capture process.
Agglomerate breakage model and homogenisation by DEM simulations: Calibration with tomographic micro-compressions in X ray beam line Soleil
Context:
The reference ceramic fabrication process involves three main stages: grinding, pressing, and sintering. Pellet compaction during pressing relies on three main densification steps rearrangements by motion, compaction by strain, and agglomerate fractures by compression. This research project aims to explore the influence of the pressing step on the microstructure behavior during the sintering process. The study focuses on a powder composed of agglomerates with a microstructure based on a homogeneous mix of TiO2-Y2O3, TiO2 for surrogate UO2 and Y2O3 for surrogate PuO2. Each agglomerate consists of unbreakable elementary particles included in breakable aggregates, synthesized using the Cryogenic Granulation Synthesis Process (CGSP) [1].
Recent investigations at the Anatomix X-ray beam line in the synchrotron Soleil [2] have validated the results of tomographic micro-compressions, aligning with Kendall's theory, Fig 1. The experiments involved one-way cyclic micro-compression tests on agglomerates subjected to a simple load and unload cycle until breakage. Tomographic post-treatments provided insights into porosities, crack initiation, and propagation. Several DEM simulation studies have also been used to explore agglomerate behavior under dynamic or quasi-static loading with and without breakage, however without fully calibrating the breakage model [3], [4], [5].
Application of the Hybrid-High-Order (HHO) method for the treatment of non-local effects in crystal plasticity via a micromorph approach
Describing the behavior of materials at the crystalline scale is the subject of much academic research, and is of growing interest in industrial R&D studies. Classically, this description is based on behavior laws describing the local evolution of the material's microstructural state: (visco-)plastic deformation, dislocation density, etc.
The main driving force behind this evolution is resolved shear stress, the projection of the stress tensor on the slip systems.
The formalism of these local constitutive equations (as opposed to non-local constitutive
equations discussed hereafter) is now well established, whether we are considering
infinitesimal or finite transformations, and benefits from special support within the MFront code generator. Thanks to MFront, those constitutive equations can be used in various mechanical solvers at CEA (Manta, Cast3M , Europlexus , AMITEX_FFTP ) and EDF
(code_aster, Manta, Europlexus ).
However, the use of local constitutive equations does not allow to account for many effects.
The aim of the post-doc is to develop a robust numerical strategy for reliably solving
structural problems using non-local crystal plasticity laws, and guaranteeing the
transferability of the constitutive equations between the CEA and EDF codes.
Development and characterization of concentrator photovoltaic (CPV) receivers for high-efficiency CPV modules
Concentrator photovoltaics (CPV) arises as a promising technology capable of economically justify the use of highly efficient (and highly expensive) monolithically stacked multijunction solar cells (MJSC). CPV takes advantage of low-cost optical elements, such as mirrors or lenses, to capture the sunlight and concentrate it into small-size cells, exchanging solar cell surface by optical elements. This technology, which is at an industrial stage, uses state-of-the-art triple junction (3J) solar cells with efficiencies up to 45%.
The postdoc position here proposed will deal with novel architectures of CPV receivers conceived from high-efficiency MJSC that will be integrated in next-generation CPV modules. The research engineer will also need to learn how to characterize these systems, for which he/she will use the tools available at the CPV Lab at INES (CEA). Novel characterization techniques may also be required.
The candidate must have a M.S. in Physics or Engineer with specialization on solid state physics, electronics, electrical engineering, mechatronics or similar. He/she must be a PhD, preferably in the field of photovoltaics and particularly on CPV. Good language skills and laboratory experience are required.
Robust path-following solvers for the simulation of reinforced concrete structures
Path-following procedures are generally employed for describing unstable structural responses characterized by ``snap-backs'' and/or ``snap-troughs''. In these formulations, the evolution of the external actions (forces/displacements) is updated throughout the deformation process to fulfill a given criterion. Adapting the external loading during the calculation to control the evolution of the material non-linearities is helpful to obtain a solution and/or to reduce the number of iterations to convergence. This second aspect is of paramount importance, especially for large calculations (at the structural scale). Different path-following formulations were proposed in the literature. Unfortunately, an objective criterion for choosing one formulation over another for the simulation of reinforced concrete (RC) structures (in the presence of different and complex dissipation mechanisms) still needs to be made available. The proposed work will focus on the formulation of path-following algorithms adapted to simulate RC structures.
Production of green hydrogen and ammonia from offshore energy
This subject is dedicated to the high potential of offshore wind power in the high seas, where it seems extremely complicated and expensive to install an electric transmission to a continental grid. In addition, the IMO, a United Nation agency that is responsible for environmental impacts of ships, adopted ambitious targets to reduce greenhouse gas (GHG) emissions from marine shipping. The IMO plan regulates carbon dioxide (CO2 ) emissions from ships and requires shipping companies to halve their GHG emissions by 2050 (compared to 2008 levels).
Different ways are being explored in order to identify the best low-carbon fuel that will be able to power new marine propulsion systems without GHC emissions (and others polluants like Sox, Nox…).
Hydrogen combined with a fuel cell is a good option for small application (fishing boat…). However, issues associated with hydrogen storage and distribution (low energy density) are currently a barrier for its implementation for large and massive marine application which drivess 80–90% global trade, moving over 10 billion tonnes of containers, solid and liquid bulk cargo across the world’s oceans annually.
Hence, other indirect storage media are currently being considered. Of these, ammonia is a carbon free carrier which offers high energy density. First studies and demonstration projects show that it could be used as a fuel coupled with a new generation of high-temperature fuel cells (SOFC) or internal combustion engines.
This project focuses on the green ammonia production on a high seas platform including an offshore wind farm that use renewable electricity to first generate hydrogen from water (via electrolysis) and nitrogen from air and then combine both in a Haber-Bosch process to synthesize ammonia. The objective is to develop modeling tools (Modelica / Dymola environment) in order to build, simulate and optimize "wind to ammonia" systems and energy management solutions to minimize the production cost of ammonia.