Study on prevention of airborne radioactivity diffusion of underground nuclear power plants

The general principle for the prevention of the airborne radioactivity diffusion in underground nuclear power plants is put forward. The engineering measures to prevent the radioactivity diffusion in the underground nuclear power plant are studied with the emphasis on the engineering measures under severe accidents. The pressure relief system for containment and reactor building cavern under severe accidents which vents and filters the airborne radioactivity according to the different conditions in severe accidents was proposed. By these engineering measures, the airborne radioactivity in severe accidents in underground nuclear power plants is more effectively prevented and controlled, and it is possible to achieve the practical elimination of the accident sequences that may lead to radioactive release by design. (authors)