[en] The strategy of protective measures and the system of intervention levels are considered. It makes it possible to limit the region where post-accident measures must be taken. The concept of 'safe living' for life and surface contamination concept are discussed. The measurement results of a surface contamination are pointed out in the maps for series settlements of the 30 km zone. The features of severe accidents to nuclear power plants are that damage is caused not only by destruction and downtime of power installations, but also by radioactive contamination of the environment. Therefore, the term 'severe accident' is accepted to mean an accident with an off-site impact, which requires to perform large-scale and expensive work on elimination of the consequences of the accident. The whole off-site damage due to the Chernobyl accident is caused exclusively by contamination, as no destruction was observed beyond the site. As a result of the Chernobyl accident the greatest short-term releases of radioactive materials to the atmosphere occurred from a single source. Four elements from all the materials released from the core have determined the short-term and long-term radiological situation in the affected areas. These are iodine, cesium, strontium and plutonium. Moreover, in the releases there were highly - radioactive fragments of fuel (hot particles). 7 figs