Optimization of placement of continuous air monitors in a radiological facility

Abstract

Airborne radioactive materials are encountered in the atmosphere of any radiological facility. Their concentration is affected by the ventilation system and/or air purification system and by the processes of the facility. Continuous air monitors (CAMs) are installed in these workplaces during both routine and non-routine operations to monitor the ambient air quality in terms of concentration of airborne radioactive aerosols and trigger interventions. The location for these monitors is typically determined by rules of thumb like direction of maximum air flow. The aerodynamic behaviour of aerosols does not follow the behaviour of air streamlines and this poses a question on the appropriateness of selection of location of CAMs. Addressing this issue, we used a computational fluid dynamics model coupled to aerosol dynamics code to calculate a parameter termed as CAM placement parameter (CPP) that estimates the relative merit of positioning the CAMs in a radiological facility. Our method involved simulation of dispersing aerosol particles in a typical geometry of such a facility. The results imply that inclusion of aerosol microphysical processes (coagulation, gravitational settling, turbophoresis, thermophoresis etc) in the flow dynamics can help to determine the CPP in workplace environment and therefore minimize the occupational exposure.