The mechanisms involved in the formation and transport of aerosols that might be present during possible fusion reactor accidents were investigated. A cascade impactor was used to collect particles formed by oxidation and volatilization of a tungsten alloy containing 1% rhenium, an activation product of tungsten. The alloy was tested at 800, 1000 and 1200°C in flowing air and at 800°C in steam. The quantities, size distributions, and chemical compositions of the particles were determined using a variety of analytical methods. Comparisons were then made with calculations of the vapor release rate, the aerosol nucleation, and the transport of aerosol to the impactor.