The defence-in-depth safety concept: Comparison between the Fukushima Daiichi units and German nuclear power units

The accident at the Japanese nuclear power plant Fukushima Daiichi, caused by the devastating tsunami on March 11, 2011 has raised questions worldwide about the safety of nuclear power plants. The affected plants belong to the oldest generation of NPPs built in Japan. The paper describes and evaluates the key features of the event sequence and actions taken at the affected plants. The safety reserves of German plants, compared to Fukushima, are also addressed.