Testing of waste containers under open field conditions is a component part of the research program that is being carried out at SIA “Radon”for more than 20 years to understand the long-term behaviour of radioactive waste forms and waste packages. This paper presents the preliminary results of these ongoing studies. We used a typical NPP operational waste, containing 137Cs, 134Cs, and 60Co as the dominant radioactive constituents. Bituminized and vitrified waste samples with 30–50 wt.% waste loading were prepared. Combined effects of climatic factors on corrosion behaviour of carbon steel containers were estimated using gravimetric and chemical analyses. The observations suggest that uniform corrosion of containers prevails under open field conditions. The upper limits for the lifetime of containers were derived from calculations based on the model of atmospheric steel corrosion. Estimated lifetime values range from 300 to 600 years for carbon steel containers with the wall thickness of 2 mm containing vitrified waste, and from 450 to 500 years for containers with the wall thickness of 2.5 mm that were used for bituminized waste. However, following the most conservative method, pitting corrosion may cause container integrity failure after 60 to 90 years of exposure.