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Normal Accident Theory 

I just learned a new phrase, “ingestion pathway zone.”  This is Nuclear Regulatory Commission (NRC) speak for “you’re in trouble” if the Vermont Yankee Nuclear Power Plant, thirty-nine miles from my home in Northampton, MA, has a Fukushima moment. Around the valley, our fine Hadley Loam - a premimum farm soil classification – will glow, and the government will confiscate food harvested from these coffee black fields. Locavores would go extinct.  But who would want to live here anyway?

There are 104 aging nuclear power plants in the United States.  As of June 2011, the NRC was asked to extend the life of 66 US reactors for another 20 years.  It said yes to all of them.  While we were listening to reports from Japan about spent fuel rods melting in pools of water and hydrogen explosions threatening to rupture concrete containment vessels, the NRC was signing a new lease on life for our own Vermont Yankee Plant. The same General Electric boiling water reactor design the commentators were lamenting at Fukushima.

The skeptic in me looks to corporate greed, political dealing, and hedonistic self-interest to explain their willingness to risk the lives and properties of well over a million people.  The psychologist in me looks to the way we humans think – or don’t.  Consider Yale sociologist Charles Perrow’s Normal Accident Theory:

Normal accidents in complex technological systems are caused by multiple small failures that interact fatally in ways that designers and engineers can’t see.  The accidents can’t be stopped because they are initially incomprehensible to the operators of the systems.  

It is hard for the human mind to comprehend the multiplier effect in highly complex systems.  Small, ordinary problems in isolation to one another tend to be forgivable.  But in combination their dangers can expand exponentially, until the next minor mishap tips the calculus toward catastrophe.  Moreover, when danger arises we want to reverse engineer the problem.  Complex systems do not play by such rules - by the time a nuclear chain reaction has started, you can’t go back. 

There are hints of Normal Accident Theory lurking in the NRC’s Vermont Yankee 4Q/2011 Plant Inspection Findings.  Five events warranted reporting.   Consider some examples. (1) For a brief period a vague control-wiring diagram compromised the reactor’s cooling ability.  (2) Following the wrong instructions led to the inadvertent tripping of the emergency diesel generator fuel rack.  (3) The maintenance and planning folks did not speak to the engineers resulting in the use of the wrong gasket for the flange of a High Pressure Coolant Injection System.  A bad diagram, misunderstanding directions, and poor communication are all common aggravations.  But imagine these events happening in symphony, at a nuclear power plant, thirty-nine miles from home. 

To learn more about local efforts to decommission Vermont Yankee, see the Safe and Green Campaign at or the SAGE Alliance.


Reader Comments (1)

I just discovered your wonderful blog. Lots and lots of fascinating, inspiring and useful information. And, in this case, chilling. But ah, so beautifully written. I look forward to reading more. Keep those fingers tapping!

April 23, 2012 | Unregistered CommenterJayne Pearl

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