Nuclear Technology / Volume 160 / Number 2 / November 2007 / Pages 187-204
Technical Paper / Reactor Safety
Nuclear aerosols formed during nuclear reactor accidents or explosions evolve via natural transport processes as well as under the influence of engineered safety features. These aerosols can be hazardous and may pose risk to the public if released into the environment. Computations of their evolution, movement, and distribution involve the study of various processes such as coagulation, deposition, condensation, evaporation, etc., and are influenced by factors such as particle shape, charge, radioactivity, and spatial inhomogeneity. These many processes and factors make the numerical study of nuclear aerosol evolution computationally very complicated. The Direct Simulation Monte Carlo (DSMC) technique was developed to elucidate the role of various phenomena that influence the evolution of nuclear aerosols. This will allow, then, for an assessment of the limitations of other methods used at present. Coagulation, deposition, and source reinforcement processes for a multicomponent, aerosol dynamics problem have been explored. As a simple verification, the DSMC results were compared with analytical results for a single-component aerosol dynamics problem with coagulation and deposition processes. In addition, the DSMC results were compared against those obtained using the sectional method for several multicomponent test problems with the same component densities. It is clear from the present results that the assumption of a single mean density is not appropriate in such problems because of the complicated effect of component densities on the aerosol processes.