The Fukushima Daiichi NPP accident serves as a case study for various disciplines within nuclear sciences. Researchers worldwide in health physics, radio-ecology, severe accident analysis, and human and organisational factors have investigated the progression of the accidents and their consequences. The WGOE is focused on the lessons learned from operating experiences, and the Fukushima Daiichi NPP accident is an extremely important source for deriving generic lessons. The main goal of the operating experience feedback is to prevent such accidents. Therefore, this report analyses whether and why this accident could not be prevented. To understand the role operating experience could play in identifying plant vulnerabilities and minimizing the potential of severe accidents leading to significant public health consequences, the identification of the initiating events and the barriers that failed during the Fukushima Daiichi NPP accident is necessary.
The report focusses on the initiators and event sequences. A root cause analysis has not been performed. The answer to the question “Why it was not prevented?” is not part of this report.