taken the initiative and studied the plans and diagrams of the network in anticipation of venting, investigators asked Yoshida about when he had proposed this
solution. He said that he had only considered venting when he had sufficient data to
confirm that there was excess pressure in the chamber. The priority was therefore to
obtain information on the key parameters indicating the state of the reactor [2].
The Commission was also surprised that operators had not considered the possibility of a hydrogen leak from the tank to the containment vessel into damaged pipes,
although it was known that core fusion can produce large amounts of hydrogen. The
Director said he had been aware that, if the core was damaged, hydrogen was produced; notwithstanding, he felt that it would remain confined within the vessel and he
had focused on the threat of a container explosion, given the high pressure that had
been observed. He stated, “the top of the reactor building is covered and ventilation
panels are arranged on the side. We had not even imagined that these panels were
closed and that hydrogen and oxygen had accumulated. We focused on the containment vessel. […] We were prisoners of our a priori assumptions” [2] (our translation). Moreover, the entire international nuclear community was unaware of this
scenario (Ibid.). It was only several hours after the explosion, following an investigation of the destroyed buildings, that operators concluded that the accumulation of
hydrogen was probably the cause. They then studied the measures that needed to be
taken in order to prevent a similar scenario at the plant’s other reactors.
At dawn on 15 March, although Reactors 1 and 3 had already exploded, operators felt a strong jolt and heard a loud noise, which they could not immediately
identify the source of; at the same time they noted damage to the building of
Reactor 4 and that the pressure in the containment vessel of Reactor 2 had fallen to
zero [5]. Although they gave little credibility to the reading from the pressure
indicator and, on a scientific level, the hypothesis that Reactor 2 had exploded was
not consistent with the available information, Yoshida considered the noise to be
the most important factor and ordered an evacuation.
These examples suggest that the criteria for decision making, the relevance of
the decision and the resources available to the decision maker were deficient, to the
extent that they hindered the management of the accident. According to Yoshida
himself, “it was total confusion. And that was in this atmosphere that it was
necessary to give orders. So I recognize that it was not done in a logical and
considered order” [2] (our translation). However, identifying potential derivations
from logical reasoning and understanding the circumstances presupposes that the
processes at work can be formalized.
3 Testing Decision Models Using the Fukushima Daiichi
Accident
A classical approach in management science is to model decision-making in four
phases. After collecting the information necessary to diagnose the problem, the
decision maker formulates potential ways to resolve it, based on a necessarily
172
S. Travadel
solution. He said that he had only considered venting when he had sufficient data to
confirm that there was excess pressure in the chamber. The priority was therefore to
obtain information on the key parameters indicating the state of the reactor [2].
The Commission was also surprised that operators had not considered the possibility of a hydrogen leak from the tank to the containment vessel into damaged pipes,
although it was known that core fusion can produce large amounts of hydrogen. The
Director said he had been aware that, if the core was damaged, hydrogen was produced; notwithstanding, he felt that it would remain confined within the vessel and he
had focused on the threat of a container explosion, given the high pressure that had
been observed. He stated, “the top of the reactor building is covered and ventilation
panels are arranged on the side. We had not even imagined that these panels were
closed and that hydrogen and oxygen had accumulated. We focused on the containment vessel. […] We were prisoners of our a priori assumptions” [2] (our translation). Moreover, the entire international nuclear community was unaware of this
scenario (Ibid.). It was only several hours after the explosion, following an investigation of the destroyed buildings, that operators concluded that the accumulation of
hydrogen was probably the cause. They then studied the measures that needed to be
taken in order to prevent a similar scenario at the plant’s other reactors.
At dawn on 15 March, although Reactors 1 and 3 had already exploded, operators felt a strong jolt and heard a loud noise, which they could not immediately
identify the source of; at the same time they noted damage to the building of
Reactor 4 and that the pressure in the containment vessel of Reactor 2 had fallen to
zero [5]. Although they gave little credibility to the reading from the pressure
indicator and, on a scientific level, the hypothesis that Reactor 2 had exploded was
not consistent with the available information, Yoshida considered the noise to be
the most important factor and ordered an evacuation.
These examples suggest that the criteria for decision making, the relevance of
the decision and the resources available to the decision maker were deficient, to the
extent that they hindered the management of the accident. According to Yoshida
himself, “it was total confusion. And that was in this atmosphere that it was
necessary to give orders. So I recognize that it was not done in a logical and
considered order” [2] (our translation). However, identifying potential derivations
from logical reasoning and understanding the circumstances presupposes that the
processes at work can be formalized.
3 Testing Decision Models Using the Fukushima Daiichi
Accident
A classical approach in management science is to model decision-making in four
phases. After collecting the information necessary to diagnose the problem, the
decision maker formulates potential ways to resolve it, based on a necessarily
172
S. Travadel