[en] The paper presents the experimental and theoretical results from investigating the effects occurring during the cooling of HLW glass melts in canisters. It was intented to produce monolithic HLW glass blocks by controlled cooling. The experimental and numerical tools are specified and the results of measurements are compared with computed data. The influence of lining, isolation materials and crack systems in glass blocks on the heat transfer were modelled. Temperature calculations were performed for heat producing HLW glass blocks and the computed center-line temperature were analysed for various canister diameters and various conditions of interim storage. The calculations were performed by means of the finite element programs ADINA/ADINAT. For stress calculations only those volume elements were considered having temperatures below the transition temperature. A thermoelastical material model was applied. Model calculations were also performed for radioactive glass products with a thermal power of 17 W/l. The development of mechanical stresses depending on variations of heat flow from the canister surface and on change of thermal power by the radioactive decay were studied. Temperatures and arising stresses of vitrified waste forms in canister having 0.30 m and 0.43 m diameter respectively, were compared. (orig.)