Experimental determination of the dynamic shape factor of the primary sodium peroxide aerosol

Abstract A hypothetical accident in a fast breeder reactor could cause aerosols to be generated in a sodium fire. The computer codes relating to the modelization of these accidents make it necessary to use various input parameters, among which is the dynamic shape factor κ of the aerosols produced. This study concerns the shape factor of sodium peroxide; the divergence of the values of this parameter given in the literature justifies the usefulness of our work. We have tried to use the simplest method possible for this experiment. The dynamic shape factor is proportional to the ratio of the equivalent volume diameter to the aerodynamic diameter for a given particle. Therefore, these two quantities must be determined. A centrifuge enables classification of the particles as a function of their aerodynamic diameter; the equivalent volume diameter of the particle thus selected can then be determined by assessing the mass (neutron activation) and the number (electron microscope) on the same sample of particles. Our results show that the dynamic shape factor of the sodium peroxide submicronic particles generated by a fire is nearly 1 and that the values of this parameter increase with the size of the particles.