Indigenous development and performance evaluation of BARC aerodynamic size separator (BASS)

Commercially available cascade impactors, commonly used for aerodynamic size separation of aerosol particles, are based on the principle of inertial impaction. As of now, these instruments are imported at a cost of several lakhs of rupees; hence an effort has been made to develop an aerodynamic particle sizer indigenously in BARC. This unit, referred to as BARC Aerodynamic Size Separator (BASS), separates aerosols into seven size classes ranging from 0.53 mu m to 10 mu m and operates at a flow rate of 45 Ipm. Intercomparison studies between the standard Andersen Mark-II (Grasbey Andersen Inc.) impactor and BASS using nebulizer generated aerosols have consistently shown excellent performance by BASS in all respects. In particular, BASS yielded the parameters of polydisperse aerosols quite accurately. Experiments to evaluate the individual stage cut-off diameters show that these are within 8% of their designed value for all stages except the higher two stages which indicate about 30% lower values than the designed ones. The replotting of all the mass distribution data using the experimental cut-off diameters showed perfect lognormal fits, thereby indicating that these diameters are closer to the true stage cut-off diameters for BASS. The studies show that BASS will be suitable for determining the particle size distributions in the context of the radiological safety programmes of DAE. Being indigenous in design, it may be fabricated on a commercial scale at a cost far less than that of the imported units. Such a venture will greatly help several national programmes on atmospheric pollution being carried out by many laboratories and institutions across the country.