Discussion on station blackout

Safety of nuclear power plants could be assured with a 'defense-in-depth' approach with multiple systems. Considering effects of the Great East Japan Earthquake on nuclear power plants according to 'defense-in-depth' approach, power supply would be indispensable in any case. It would be important to consider countermeasures against loss of all ac power (station blackout), loss of all ac power system and loss of all power and others corresponding to probability of occurrence and risk. Even with small amount of power capacity some time would be earned before damage progressed. It would be surely important to reduce risk of nuclear power plant with arranging events and evaluate them from a bird eye viewpoint. (T. Tanaka)