4 Resilience in the Field of Nuclear Safety Engineering
The term “resilience” is understood among nuclear engineers as a concept for
enhancing nuclear safety. It is, however, used to describe a wide range of perspectives. Consensus is required about the meaning and the role of the term in the
field of nuclear safety engineering. In this chapter, the role of resilience is discussed
from the viewpoint of enhancing nuclear safety.
The concept of resilience is considered important when dealing with risk under
large uncertainty as discussed above. The concept of resilience is not introduced
when risk is simply regarded as the possibility that something untoward may
happen, but when it is regarded as something whose occurrence is rare but inevitable, to be managed when it in fact does occur. In such case, the importance of
understanding the characteristics of the scenario when the risk becomes obvious is
more emphasized, including the temporal sequence. Conventionally, as discussed
heretofore, defense in depth is fundamental to nuclear safety, and was gradually
refined to include lessons learned from the Three Mile Island accident as well as the
Chernobyl accident. Resilience is considered to be a concept that can further refine
and enhance the concept of defense in depth.
4.1 Resilience Engineering for Possible Future Nuclear
Accident
Resilience can be defined as the ability to prepare for and plan for, absorb, recover
from, or more successfully adapt to actual or potential adverse events [10]. In this
sense, resilience is a concept that is relevant in the context of emergencies, such as
nuclear accidents. Figure 3 schematically shows the accident sequence with respect
to time, from occurrence to conclusion of nuclear accidents, all of which are in the
scope of resilience engineering. The vertical axis of the figure shows the function,
i.e. malfunction of barrier in each level of defense in depth, while the horizontal
axis represents time. The temporal sequence to deal with abnormal and accidental
conditions until recovery, e.g., accident management, off-site emergency response,
decontamination and decommissioning, is illustrated in the figure.
To protect both the public and the workers, defense in depth is a widely accepted
approach combining both prevention of incidents and accidents, and mitigation of
their consequences, as discussed above. The safety barriers and procedures installed
based on the concept of defense in depth are to prepare for, mitigate and respond to
the accident, which are within the scope of resilience engineering.
In other words, from the viewpoint of nuclear safety engineering, resilience is a
concept that expands the concept of defense in depth by enlarging the scope of
nuclear safety engineering from only preventing accidents and mitigating consequences to responding to and recovering from accidents in the medium and long
term.
Challenges for Nuclear Safety from the Viewpoint …
75
The term “resilience” is understood among nuclear engineers as a concept for
enhancing nuclear safety. It is, however, used to describe a wide range of perspectives. Consensus is required about the meaning and the role of the term in the
field of nuclear safety engineering. In this chapter, the role of resilience is discussed
from the viewpoint of enhancing nuclear safety.
The concept of resilience is considered important when dealing with risk under
large uncertainty as discussed above. The concept of resilience is not introduced
when risk is simply regarded as the possibility that something untoward may
happen, but when it is regarded as something whose occurrence is rare but inevitable, to be managed when it in fact does occur. In such case, the importance of
understanding the characteristics of the scenario when the risk becomes obvious is
more emphasized, including the temporal sequence. Conventionally, as discussed
heretofore, defense in depth is fundamental to nuclear safety, and was gradually
refined to include lessons learned from the Three Mile Island accident as well as the
Chernobyl accident. Resilience is considered to be a concept that can further refine
and enhance the concept of defense in depth.
4.1 Resilience Engineering for Possible Future Nuclear
Accident
Resilience can be defined as the ability to prepare for and plan for, absorb, recover
from, or more successfully adapt to actual or potential adverse events [10]. In this
sense, resilience is a concept that is relevant in the context of emergencies, such as
nuclear accidents. Figure 3 schematically shows the accident sequence with respect
to time, from occurrence to conclusion of nuclear accidents, all of which are in the
scope of resilience engineering. The vertical axis of the figure shows the function,
i.e. malfunction of barrier in each level of defense in depth, while the horizontal
axis represents time. The temporal sequence to deal with abnormal and accidental
conditions until recovery, e.g., accident management, off-site emergency response,
decontamination and decommissioning, is illustrated in the figure.
To protect both the public and the workers, defense in depth is a widely accepted
approach combining both prevention of incidents and accidents, and mitigation of
their consequences, as discussed above. The safety barriers and procedures installed
based on the concept of defense in depth are to prepare for, mitigate and respond to
the accident, which are within the scope of resilience engineering.
In other words, from the viewpoint of nuclear safety engineering, resilience is a
concept that expands the concept of defense in depth by enlarging the scope of
nuclear safety engineering from only preventing accidents and mitigating consequences to responding to and recovering from accidents in the medium and long
term.
Challenges for Nuclear Safety from the Viewpoint …
75