In order to understand the scope and complexity of the event, an interdisciplinary analysis team was formed at ENSI. Its members include (for example) experts in the fields of people and organisation, radiation protection, electrical engineering, mechanical engineering, materials technology and system technology.
Some initial and provisional explanations as to why the design defects came about and why the accident progressed in such a catastrophic manner are presented by the Swiss Federal Nuclear Safety Inspectorate (ENSI) in a three-part report which examines the circumstances before, during and after the accident.
Today, ENSI is presenting the second part: Analysis Fukushima 11032011 (People and Organisation)
What at first sight appeared to be a technical plant failure triggered by natural events very soon proved to be a complex event in which human and organisational aspects are of crucial importance.
For instance, it has to be assumed that the on-site staff had no accurate knowledge of the actual situation and the condition of the plant for considerable periods of time. This led to incorrect assessments of the situation, at least on a temporary basis.
The first incorrect assessment was probably made just a few minutes after the earthquake, following the issue by the Japanese meteorological agency of a first tsunami warning about a wave of at least three metres in height (“major tsunami”).
Based on this warning, which did not allow a forecast of the true extent of the expected tsunami, it is likely that no special technical precautionary measures were regarded as necessary at Fukushima Dai-ichi, nor were there seen to be any grounds for particular concern. The consequences of this error would prove to be grave.
Analysis shows that the human factor plays a key part not only in preventing an accident but also in bringing it under control. The organisations of operators and authorities in which people work must take account of human factors by means of appropriate structures and procedures, and with the help of a suitable safety culture. And they must be able to cope with the unexpected.
- Part 2 of the ENSI report on Fukushima can be downloaded here: Analysis Fukushima 11032011 (People and Organisation)
- A commentary by Rosa Sardella, Head of the Japan Team at ENSI, is also available: “It is the people who make the decisions.” (in german)
- NZZ interview with Hans Wanner: “Improving emergency plans for nuclear power plant incidents.” (in german)