Thermo-fluid-dynamic Evaluation of a Microsystem to Analyse Radioactive Solutions

It has become common place to use micro-electromechanical system (MEMS) to evaluate the chemical properties of solutions. However, such microchips have not yet been applied to analyse radioactive solutions, for the purpose of nuclear safeguards, in the nuclear reprocessing industry. Implementing MEMS in this area results in a reduced volume of the sample to be analysed. This brings about a reduction in radiation and many advantages over conventional methods. The radioactive solution is sucked into through a microchannel (300 x 300 µm) in this chip; the solution will release heat due to radioactive decay. The flow and heat characteristics of microchannels have been observed to deviate from conventional and well established theory. This work initially evaluates these differences with an in-depth literature study examining the reasons for these differences. The microscopic effect of the electrical double layer (EDL) is focused on. These investigations on the validity of the traditional macroscopic models allowed application of classical theories within a well defined validity range and the adaptation of these theories to suit microscopic models. It was concluded that the EDL was the most influential on the flow. FEMLAB 3 (COMSOL AB 2004) was then utilised to model the microchip for both fluid dynamics and thermodynamics. Subsequent thermal stresses were also investigated. From this study conditions on the released heat were derived that guarantee no deformation of the chip and no temperature shift for the absorptiometry measurements.

JANSSENS-MAENHOUT Greet;  MATTHEWS Rowan Mary;  HOWELL John; 

2008-09-15

COMSOL Co.

JRC31672

http://www.it.comsol.com/conference2006/2005_presentations.php,    https://publications.jrc.ec.europa.eu/repository/handle/JRC31672,