Common Cause at Daiichi Fukushima

28/04/2011 — Leave a comment

Fukushima NPP March 17 (Image Source: )

There are few purely technical problems…

The Washington Post has discovered that concerns about the vulnerability of the Daiichi Fukushima plant to potential Tsunami events were brushed aside at a review of nuclear plant safety conducted in the aftermath of the Kobe earthquake. Yet at other plants the Japanese National Institute of Advanced Industrial Science and Technology (NISA) had directed the panel of engineers and geologists to consider tsunami events.

However for the study of the Daiichi Fukushima site the NISA panel was instructed to focus on earthquake risk because Tsunami’s were thought to be unlikely. Presumably because of this judgement a tsunami expert was not called to work on the study panel.

At a review of the panel’s report by a larger working group concerns raised by Yukinomo Okamura a seismologist over the failure to consider the risk of tsunami, based on historical records of the 869 AD major tsunami, were brushed aside by the TEPCO representative as being ‘historical’.

… Research results are out, but there is no mention of that [tsunami] here, and I would like to ask why…
Yukinomo Okamura
NISA seismologist
Transcript of working group meeting

According to a transcript obtained by the Washington Post debate on the issue was ended by a NISA official promising further followup  on the issue. But instead the working group’s report affirming the adequacy of existing safeguards was approved unchanged at the next meeting.

Unfortunately while the plant successfully withstood the seismic even the plants flood walls were over topped by the subsequent tsunami which then flooded the site knocking out emergency generators.

While there are obvious lessons to be learned here about the design of standby systems for nuclear plant, see Peter Ladkins discussion on his Abnormal Distribution blog for example, what interests me is the group dynamics leading up-to the collective decision (and collective failure by doing so) to accept the Daiichi safety study ‘as is’.

In the behaviour of the NISA staff and TEPCO staff we can see symptoms of a collective view or ‘groupthink‘ that denied the possibility of a hazard to the plant from a tsunami event.

As I noted in a preceding post on the psychology of Groupthink this effect can impact upon risk assessments in three ways, in downplaying risks, accentuating confirmatory bias and reducing the likelihood of developing contingency plans.

In this case Groupthink appears to have led to the risk of a major tsunami raised by Yukinomo Okamura being down played and ignored in the final report, despite there being no valid reason to do so and every reason to open the initial scoping assumption of the study up to critical review.

As Irving Janis has pointed out, such behaviour is highly likely when a flawed organisation context is coupled to a challenging decision task.

In this case a highly homogenous group (comprising engineers and scientists) working to a ‘directed’ outcome all within a culture that values conformity and dislikes uncertainty have to deal with high consequence low probability risk decision on nuclear safety. Groupthink reinforced the organisational malaise of complacency which in turn resulted in a failure to make the changes necessary to the relevant design standards for the plant.

I should note that the japanese engineers and scientists are not alone in this sort of behaviour, see the report by the AIA on the risks of jet engine rotor bursts as another example of making assumptions of safety that cannot be based upon credible statistical evidence.

Perhaps in managing the safety of technological systems we should guard against the occurrence of psychological ‘common cause failure’ within our soft organisational systems, as much as we guard against its occurrence within our hard technological systems.

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