How the Fukushima Daiichi Accident
Changed (or not) the Nuclear Safety
Fundamentals?
Kazuo Furuta and Taro Kanno
Abstract In this chapter, the fundamentals of nuclear safety that the Fukushima
Daiichi accident did and did not change will be discussed. While the most basic
strategy of defense-in-depth principle is still valid, some problems have emerged
after Fukushima, preparedness for all-hazards and multiple disasters, and importance of the administration of emergency response. From this observation,
enhancing the resilience of nuclear systems is a critical issue after Fukushima. The
safety enhancement measures considered in nuclear facilities will be reviewed
referring to the elementary characteristics of systems resilience, and a new framework will be proposed for dealing with unsafe events, where unsafe events are
classified into three categories.
Keywords Defense-in-depth Á Residual risk Á Beyond design-basis Á Resilience Á
Category 2 events
1 Introduction
After the Great East Japan Earthquake (Tohoku Earthquake) and the Fukushima
Daiichi accident (Fukushima), people used a word “unanticipated” for describing
the disaster. It is true that the up-to-date seismology at the time of disaster could not
foresee that such a huge earthquake and tsunami can ever occur in the area, and the
main cause of the accident was insufficient preparedness of the plants against
tsunamis [1]. It seems an improper remedial action, however, just reevaluating the
risk of tsunamis more precisely and increasing the height of seawalls. It seems
wrong also to think that the fundamentals of nuclear safety has broken down and it
should be replaced with another one. Having reviewed the experiences of the
K. Furuta (&) Á T. Kanno
School of Engineering, The University of Tokyo, Tokyo, Japan
e-mail: furuta@rerc.t.u-tokyo.ac.jp
© The Author(s) 2017
J. Ahn et al. (eds.), Resilience: A New Paradigm of Nuclear Safety,
DOI 10.1007/978-3-319-58768-4_3
35
Changed (or not) the Nuclear Safety
Fundamentals?
Kazuo Furuta and Taro Kanno
Abstract In this chapter, the fundamentals of nuclear safety that the Fukushima
Daiichi accident did and did not change will be discussed. While the most basic
strategy of defense-in-depth principle is still valid, some problems have emerged
after Fukushima, preparedness for all-hazards and multiple disasters, and importance of the administration of emergency response. From this observation,
enhancing the resilience of nuclear systems is a critical issue after Fukushima. The
safety enhancement measures considered in nuclear facilities will be reviewed
referring to the elementary characteristics of systems resilience, and a new framework will be proposed for dealing with unsafe events, where unsafe events are
classified into three categories.
Keywords Defense-in-depth Á Residual risk Á Beyond design-basis Á Resilience Á
Category 2 events
1 Introduction
After the Great East Japan Earthquake (Tohoku Earthquake) and the Fukushima
Daiichi accident (Fukushima), people used a word “unanticipated” for describing
the disaster. It is true that the up-to-date seismology at the time of disaster could not
foresee that such a huge earthquake and tsunami can ever occur in the area, and the
main cause of the accident was insufficient preparedness of the plants against
tsunamis [1]. It seems an improper remedial action, however, just reevaluating the
risk of tsunamis more precisely and increasing the height of seawalls. It seems
wrong also to think that the fundamentals of nuclear safety has broken down and it
should be replaced with another one. Having reviewed the experiences of the
K. Furuta (&) Á T. Kanno
School of Engineering, The University of Tokyo, Tokyo, Japan
e-mail: furuta@rerc.t.u-tokyo.ac.jp
© The Author(s) 2017
J. Ahn et al. (eds.), Resilience: A New Paradigm of Nuclear Safety,
DOI 10.1007/978-3-319-58768-4_3
35