Cementation is currently the preferred method for conditioning a large number of nuclear wastes. Developing a conditioning process requires to master the mixing and blending phases, which will condition the proper dispersion of the waste in the cement matrix and the performance of the final material.
The LNPA is proposing a thesis on the modeling and simulation of the mixing process (mixing of dry fillers, water, waste simulants representative of nuclear waste deposits) to meet the following objectives:
- Simulate the flow of cementitious paste in the mixer and experimentally verify the results obtained
- Optimize process parameters to improve waste dispersion quality
- Predict coating feasibility based on the characteristics of the waste to be conditioned
- Validate transfer from laboratory to industrial scale
A CFD approach is considered: the aim is to describe the evolution of the free surface of the flow, to highlight specific modes such as recirculation and trajectory bifurcation, and finally to describe particle transport with and without coupling to rheology. The simulation results will be evaluated by cross-checking with tests carried out on a conical mixer. This thesis will therefore be the first step in setting up a predictive sizing tool for a cement mixing process applied to the conditioning of nuclear waste.
The candidate, with a background in materials engineering, mechanical engineering or process engineering, will gain experimental experience in process instrumentation and exploitation of results, as well as experience in numerical fluid mechanics and process modelling.