AbstractAnalysis of potential consequences of hypothetical accidents in fusion power plants involves models designed to study transport of aerosols, and their possible release into the atmosphere following a LOCA. Calculations of released material have been based on assessed values of leak rates across containment volumes and to the surroundings. This paper describes the gas–solid model and computer code Activation Release and Transport (ART), which has been developed to determine releases of mobilised particulates and the associated leak rates, based on the description of a flow of particles through small channels across a barrier. The source of particulates in the primary chamber is obtained using the mobilisation code APMOB. Results of example calculations show that for typical anticipated chamber conditions the flow through the channels is initially compressible and choked. Also, the deposition of aerosol particles onto the channel walls may, depending on particulate size distribution and number density conditions, block the channels and prevent further transport of material. Flow through the system causes variable deposition of particles and changes their distribution. The model allows for any particle distribution to be treated and improves calculation of leakages by solving the system of continuity of mass, momentum and energy equations allowing for compressibility effects.