Improvement of microfluidic tools for kinetic data measurement

The development and modeling chemical processes require the acquisition of many thermodynamic and kinetic data . Conventional methods for measuring these data generally involve significant amounts of reagents. In particular for the reactive crystallisation, where the stochastic nature of nucleation requires the realization of a large number of experiments . The subject is to continue the work already done on the development of a dedicated chip to measure rapid nucleation kinetics . Firstly , the validity of kinetic measurements obtained by microfluidics technique will be evaluated and optimized based on well known and non- radioactive chemical systems . The microfluidic tool will then be used to study the sensitivity of these reactions to various operating parameters ( supersaturation , impurities , additives, etc. . ), before considering its transposition to nuclear processes such as decontamination of radioactive effluents. Finally, a new chip design could be proposed for the measurement of kinetics of liquid-liquid extraction , in connection with the development of new hydrometallurgical processes.

Development of a compact XRF for online analysis dedicated to process monitoring.

X-ray fluorescence (XRF) spectrometry is a well-known analytical technique for elemental analysis in an industrial context. In a simplified way, this technique is based on the measurement of X-radiation characteristics that are emitted by the atoms rearranging their electron cloud following an external stimulus. This is a non-destructive measurement relevant for the determination of chemical elements within liquid and solid mixture. In the 90s, the work conducted by the CEA has shown the relevance of XRF for the measurement of heavy elements using L-edge, (U, Pu, Am, Np, Cm, Pb) as well as lighter ones (Zr, Mo, Sr) using K-edge. Low detection limits (few mg/l) have been reached and the method has been implemented industrially for monitoring several processes (for instance at La Hague plant). However, operating a XRF requires heavy and cumbersome equipment, especially a nitrogen-cooled detector and a large X-Ray generator.
Recently the technology has been significantly improved on two key issues:
• The X-rays sources, which were miniaturized,
• The detectors thanks to new type of semiconductor of small volumes, operating at room temperature with a convenient spectral resolution (CdZnTe crystals for instance).
In this framework, the proposed subject concerns new R&D studies on potentialities offered by these improvements, regarding two application fields:
• On-line monitoring in reprocessing process.
• Screening of the contaminant in the polluted soils before remediation in a decommissioning context