We present the experience of using the nested modelling technique applied to study of beryllium-7 isotope distribution and lifecycle in the Black Sea. Calculations of water hydrothermodynamics and 7Be transport are performed using the MHI ocean general circulation model for the entire sea basin with a spatial resolution of 1.6 km, as well as for nested water areas off the Southern Coast of Crimea and on the North-Western Shelf with a resolution of about 560 m. Three instances of the MHI model are linked into a single executable and work simultaneously under control of the CMF package, which provides the nesting service to exchange boundary conditions via the cluster interconnect using the Global Arrays library, without involving the disk storage. Modelling of the 7Be transport and lifecycle allows us, starting from the data of its concentrations formed by atmospheric falls, to obtain its 4-dimensional distributions including daily and seasonal variability. The model data are validated relative to ship-based measurements.