AbstractIt is found for conditions relative to fusion safety studies that there is a range of initial aerosol masses (up to ≈ 1000 kg) within which the aerosol particle growth dynamics are dominated by Brownian agglomeration. Above this range, the dominant growth mechanism is gravitational agglomeration. Previously, monodisperse aerosol modelling has been reported (W.E. Han, 19th Symposium on Fusion Teechnology, Lisbon, Portugal, 15–20 September, 1996) which enables the accurate prediction of aerosol behaviour up to initial masses of ≈ 1000 kg. Here monodisperse modelling is extended to deal with initial aerosol masses above 1000 kg, enabling the prediction of aerosol transport and the release to the environment in the gravitationally dominated agglomeration regime for hypothetical accidents involving mobilised radionuclides. It is shown that increasing the initial aerosol mass in the Brownian dominated agglomeration regime results in increased release to the environment. However, increases in initial mass in the gravitationally dominated regime soon lead to a maximum in release to the environment; as a result, further increases in initial mass produce smaller releases to the environment.