Computational Modeling and Experimental Characterization of Indoor Aerosol Transport

Abstract

When a hazardous aerosol or gas is inadvertently or deliberately released in an occupied facility, the airborne material presents a hazard to people. Inadvertent accidents and exposures continue to occur in Los Alamos and other nuclear facilities despite state-of-art engineering and administrative controls, and heightened diligence. Despite the obvious need in occupational settings and for homeland defense, the body of research in hazardous aerosol dispersion and control in large, complex, ventilated enclosures is extremely limited.The science governing generation, transport, inhalation, and detection of airborne hazards is lacking and must be developed to where it can be used by engineers or safety professionals in the prediction of worker exposure, in the prevention of accidents, or in the mitigation of terrorist actions.In this study, a commercial computational fluid dynamics (CFD) code, CFX5.4, and experiments were used to assess flow field characteristics, and to investigate aerosol release and transport in a large, ventilated workroom in a facility at Savannah River Site. Steady state CFD results illustrating a complex, ventilation-induced, flow field with vortices, velocity gradients, and quiet zones are presented, as are timedependent CFD and experimental aerosol dispersion results. The comparison of response times between CFD and experimental results was favorable.It is believed that future applications of CFD and experiments can have a favorable impact on the design of ventilation (HVAC) systems and worker safety with consideration to facility costs. Ultimately, statistical methods will be used in conjunction with CFD calculations to determine the optimal number and location of detectors, as well as optimal egress routes in event of a release.

Optimization of placement of continuous air monitors in a radiological facility

“…Dispersion of aerosols in large room was found to be advection-dominated as opposed to diffusiondominated (Konecni et al 2002). This shortcoming results due to the lack of coupling of aerosol dynamics with CFD framework.…”

“…Haim et al (2000) showed that the computer simulation to estimate the air ow patterns in nuclear workplace can be very useful in decision making of the appropriate location of air samplers. Konecni et al (2000) in their study using computational uid dynamics (CFD) indicated that a strategy based on quantitative parameters are superior to the more traditional strategy of placing CAMs in front of potential release points or near to the exhaust points. In their study of a granite processing plant (Dieguez-Elizondo et al…”

“…Disparate strategies towards the optimized placement of CAMs were adopted in literatures. A concentration ratio adapted as dose fraction (DF) was employed as the CAM placement parameter for a workroom with a set of glove boxes by Konecni et al (2000). Study performed in plutonium handing facilities by Whicker et al (1997), a matrix based on the lag time (time de ning the gap between the start of release and the trigger of alarm in monitor), maximum concentration and average concentration was devised for CAM placement location optimization.…”