Possibility and extent of reactor accidents

The basic design objective for nuclear power plants is to aim at preventing accident situations which might lead to major releases of radioactive substances into the environment. The approach is based on multilevel defence-in-depth safety philosophy relying among others on redundant protection systems, multiple release barriers and several independent engineered safety features. For the utmost unlikely situation where all technical and procedural precautions fail, the emergency preparedness measures both inside and outside of the plant are planned to provide the last resort to mitigate the off-site consequences due to major releases. (orig.)