Critical review on what factors affected the evolution of the Fukushima accident
OHSUGA Yasuhiko1, YOSHIDA Tamiya2, and SAKUDA Hiroshi3
1. Symbio Community Forum, Tanaka-Ohi-Cho 49, Sakyo-ku, Kyoto, 606-8202 Japan (ohsuga_y@yahoo.co.jp)
2. Symbio Community Forum, Tanaka-Ohi-Cho 49, Sakyo-ku, Kyoto, 606-8202 Japan (ijns@nike.eonet.ne.jp)
3. Institute of Nuclear Safety System, Inc., 64 Sata, Mihama-cho, Fukui 919-1205 Japan (sakuda@inss.co.jp)
Abstract: This paper focuses on why the Fukushima disaster caused such different outcomes at the Fukushima Daiichi nuclear power station (NPS) and the Fukushima Daini NPS, although both NPSs were hit by the largest tsunami in Japanese historical records and are located only 10 km apart. First, the authors’ study classifies the progression of the Fukushima accident into four phases: Phase I (between earthquake occurrence and tsunami inundation), Phase II (after tsunami inundation), Phase III (efforts at restoration) and Phase IV (recovery from harsh conditions), in order to clarify the difference in the accident progression in each unit of both NPSs.
The course of the accident’s evolution at each unit is compared to derive the differences of mechanical and human factors which affected the accident’s progression. Second, the differences of both factors are reviewed from resilience engineering perspectives to know what factors are important to improve the safety of nuclear power plants. As the conclusions of this critical review, it can be said that: (i) the system, structures and components of NPS are systematically designed, manufactured and maintained to perform the intended functions for expected events, however they have limitations to cope with unexpected events, and (ii) the plant personnel can respond to such situations successfully by changing their approach flexibly in a number of ways.
Keyword: Fukushima accident; resilience engineering; nuclear power plant safety; human factors |