Modeling of a centrifuge device and validation of the efficiency estimate by comparison with experimental data

International audienceIn the nuclear industry and specifically in the context of nuclear spent fuel reprocessing, the function of a centrifuge is to stop the particles that were not dissolved by the nitric dissolution step. Those particles are not desirable in the liquid-liquid extraction devices responsible for recovering the noble materials. The high level of radioactivity of the involved materials usually makes impossible the basic measurements required for a better knowledge and optimization of the devices.In this context, the laboratory of chemical engineering and instrumentation of CEA Marcoule undertook a numerical modelling of centrifuges supported by experimental studies. Data acquisitions were performed on a CEPA LS laboratory scale centrifuge produced by the CEPA Company.Experimental studies gave access to the efficiency of the apparatus under operating conditions ranging from industrial conditions to so-called degraded conditions. Two types of powder were used for this study TiO$_2$ powders representative of the insoluble particles of the industrial process and a PMMA powder selected for its ease of measurement by standard laser granulometers.The numerical model, implemented in OpenFoam, handles three-phase-flows involving gas, water and particles. It is based on the combination of a Volume Of Fluid (VOF) solver with a lagrangian particle tracking solver using the Multi-Phase-Particle-In-Cell (MPPIC) method. The bowl rotation was modelled by the Multi-Reference-Frames2 (MRF) method.Comparison of the calculations with the experimental data validates the model for TiO$_2$ particle diameters greater than 0.5 $\mu$ for centrifugal accelerations ranging from 600 to 2000g and feed rates ranging from 21 to 42L/h. Below these sizes, the numerical model underestimates the efficiency of the laboratory centrifuge. Regarding the PMMA powder, the model showed the same trends as the experimental observations which indicated a poor efficiency of the centrifuge even at 2000g. The numerical model has been validated under operating conditions comparable to industrial conditions and can now be used as a tool to assist the industrial centrifuge management

Modeling of a centrifuge device and its validation by comparison with experimental data of the efficiency estimates

International audienceIn the nuclear industry and specifically in the context of nuclear spent fuel reprocessing, the function of a centrifuge is to stop the particles that were not dissolved by the nitric dissolution step. Those particles are not desirable in the liquid-liquid extraction devices responsible for recovering the noble materials. The high level of radioactivity of the involved materials usually makes impossible the basic measurements required for a better knowledge and optimization of the devices.In this context, the laboratory of chemical engineering and instrumentation of CEA Marcoule undertook a numerical modelling of centrifuges supported by experimental studies. Data acquisitions were performed on a CEPA LS laboratory scale centrifuge produced by the CEPA Company.Experimental studies gave access to the efficiency of the apparatus under operating conditions ranging from industrial conditions to so-called degraded conditions. Two types of powder were used for this study TiO2 powders representative of the insoluble particles of the industrial process and a PMMA powder selected for its ease of measurement by standard laser granulometers.The numerical model, implemented in OpenFoam, handles three-phase-flows involving gas, water and particles. It is based on the combination of a Volume Of Fluid3 (VOF) solver with a lagrangian particle tracking solver using the Multi-Phase-Particle-In-Cell1 (MPPIC) method. The bowl rotation was modelled by the Multi-Reference-Frames2 (MRF) method.Comparison of the calculations with the experimental data validates the model for TiO2 particle diameters greater than 0.5 and#956;m for centrifugal accelerations ranging from 600 to 2000g and feed rates ranging from 21 to 42L/h. Below these sizes, the numerical model underestimates the efficiency of the laboratory centrifuge. Regarding the PMMA powder, the model showed the same trends as the experimental observations which indicated a poor efficiency of the centrifuge even at 2000g.The numerical model has been validated under operating conditions comparable to industrial conditions and can now be used as a tool to assist the industrial centrifuge management

Relevance of CFD in the development of separation processes

International audienc

New roadmap for the design and optimization of chemical engineering equipment for the reprocessing of nuclear fuel an increased contribution of CFD.

International audienc

Relevance of CFD in the development of separation processes

International audienc

Use of synchronised PIV to measure a pulsed flow velocity field in a discs and doughnuts column

The study presented here deals with the pulsed flow in a discs and doughnuts column. We aim for the understanding of the hydrodynamic properties of the one-phase flow. We experimentaly investigate the pulsation intensity effects on flow structure. Velocity fields from the PIV process reveal that the use of pulsation intensity (Amplitude x Frequency) can only be limited to qualitative analysis. No obvious tendency of the flow structure and intensity could be linked to it. Moreover, an unexpected eddy stemming from the lack of centenring of the packings appeared in the measured velocity fields, highlighting the asymmetry of the flow

Study of irradiated and non-irradiated MOX fuel reprocessing

International audienceAn important RandD program on reprocessing of MOX nuclear fuels is on-going at the French Alternative Energies and Atomic Energy Commission. This program covers both experiments on real nuclear fuels with different characteristics and modelling developments. It is lead in support of Orano's industrial project of a future polyvalent dissolution unit at La Hague facility called TCP (French acronym for specific fuel treatment) workshop [1].Plutonium-rich fuels being hard to dissolve, a specific dissolution process has been designed for the TCP unit. In the UOX standard reprocessing flowsheet, the sheared nuclear fuel is dissolved in a nitric acid solution. In the case of MOx fuel, hulls and undissolved particles possibly obtained after this dissolution step still contain significant quantities of plutonium which have to be recovered. That's why a complementary oxidizing dissolution step is added by using silver ion. In the presence of silver ions, the plutonium dissolution is enhanced by the modification of its oxidation state from IV to VI. This promising process is studied in order to optimize the operating parameters, with analysis performed on both liquid and solid phases. The process gas treatment is also investigated in particular regarding the release of gaseous ruthenium. The RandD program aims to validate the efficiency of the TCP dissolution process on different kinds of MOX fuels sodium fast reactor (SFR) fuels and light water reactor fuels (LWR) of different Pu contents, burnups, claddings and manufacturing methods. All the experiments are performed at laboratory scale in the Atalante facility