The accident at TEPCO's Fukushima-Daiichi Nuclear Power Station: What went wrong and what lessons are universal?

摘要

After a short summary of the nuclear accident at the Fukushima Daiichi Nuclear Power Station, this paper discusses "what went wrong" by illustrating the problems of the specific layers of defense-in-depth (basic strategy for assuring nuclear safety) and "what lessons are universal." Breaches in the multiple layers of defense were particularly significant in respective protection (a) against natural disasters (first layer of defense) as well as (b) against severe conditions, specifically in this case, a complete loss of AC/DC power and isolation from the primary heat sink (fourth layer of defense). Confusion in crisis management by the government and insufficient implementation of offsitc emergency plans revealed problems in the fifth layer of defense. By taking into consideration managerial and safety culture that might have relevance to this accident, in the author's view, universal lessons are as follows: a) Resilience: the need to enhance organizational capabilities to respond, monitor, anticipate, and learn in changing conditions, especially to prepare for the unexpected. This includes increasing distance to cliff edge by knowing where it exists and how to increase safety margin. b) Responsibility: the operator is primarily responsible for safety, and the government is responsible for protecting public health and environment. For both, their right decisions are supported by competence, knowledge, and an understanding of the technology, as well as humble attitudes toward the limitations of what we know and what we can learn from others. c) Social license to operate: the need to avoid, as much as possible regardless of its probability of occurrence, the reasonably anticipated environmental impact (such as land contamination), as well as to build public confidence/trust and a renewed liability scheme.