Problems of radiation situation assessment and prediction in environment around NPP of Ukraine in the case of nuclear emergency

The review of countermeasures efficiency is executed, which were conducted after the largest communal nuclear accidents at nuclear enterprises and power stations. It is showed that countermeasures efficiency is determined by a readiness to the realization of protective measures in a before-accident period above all. The basic ways of increase of their timeliness and efficiency are described, including creation of the computer decision support systems for emergency management, development and improvement of mod is of radionuclide migration in environment, determination of radiation-hygienic status of territories around nuclear dangerous objects.