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Fukushima Daiichi Nuclear Accident: A Matter of Unchallenged Basic Assumptions

Abstract of the technical presentation presented at:
International Conference on Human and Organizational Aspects of Assuring Nuclear Safety – Exploring 30 Years of Safety Culture
February 22–26, 2016

Prepared by:
K. Heppell-Masys1, M. Haage2
1Canadian Nuclear Safety Commission
2International Atomic Energy Agency


As part of the International Atomic Energy Agency (IAEA) Fukushima Daiichi Accident Report published in September 2015, a systemic analysis of human and organizational factors, based on the IAEA safety culture assessment methodology, was conducted by 11 international experts to confirm why the accident happened. This accident occurred under the backdrop of the international nuclear community’s progress in nuclear safety, brought about by internationally agreed-upon safety standards, comprehensive review services, and the development of sound regulatory frameworks.

The assumptions on nuclear safety by the main organizational stakeholders involved in the accident at the Fukushima Daiichi nuclear power plant were examined in detail. Through the systemic analysis, it was shown how the actions of these stakeholders were interrelated and interconnected, reinforcing basic assumptions about nuclear safety that prevented adequate preparation for and prevention of the accident on March 11, 2011. These basic assumptions corresponded to the deepest level of safety culture and formed the basis of safety culture from which the stakeholders acted upon — and hence the basis from which decisions and actions were taken well before the March 2011 events. The analysis presented in the report is concluded by two main observations and seven lessons learned, derived from these observations. The presentation will also include further details on these findings.

Analysis conducted as part of The Fukushima Daiichi Accident’, Technical Volume 2 – Safety Assessment report published September 2015, IAEA, Vienna.

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