Dispersion and fall out of heavier particles

Nuclear accidents have so far been expected to release gasses and aerosols, but other CBRN events and also nuclear accidents with release of core particles can be expected to also release larger particles to the atmosphere. If not so large and heavy, that they fall to the ground immediately they may like gasses and aerosols be transported more or less far by the wind. The present paper focuses on the growth of plumes of such particles larger and heavier than aerosols and transported by the wind. Implementation in existing decision support puff dispersion programs requires a parameterization of this growth, and two reasonable describing parameterizations have been found, one in the literature, one proposed here, and both are compared to experimental work found in the literature. The parameterization from the literature has been implemented in the dispersion program RIMPUFF, which has subsequently shown that the effect on fall out to a large extent overrules the effect on the dispersion of such particles.