Unforeseen Events, Resilience and PRA

Woody gave a presentation at the second Resilience Engineering Symposium on November 6th, 2006.  The accompanying article was included in the book, Resilience Engineering: Remaining Sensitive to the Possibilities of Failure, E. Hollnagel, et. al, editors (Ashgate Press), 2007, under the title “Unexampled Events, Resilience, and PRA”.

The words of the presentation have remained the same, but for the changing of “unexampled” to “unforeseen”, and “PRA” to “risk assessment”; the example given in slide #32 has been changed from the Storm King Mountain fire to the hydrogen explosion at Fukushima Daiichi Unit #1.

I have changed the images to reflect the recent events in Japan.

A lovely spring night
suddenly vanished while we
viewed cherry blossoms.
— Basho

March 11, 2011

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“Why isn’t it loaded? Are you afraid of shooting yourself?”
“Of course not. These weapons don’t go off accidentally. You have to do five things in a row before they’ll fire, and an accident can seldom count higher than three … which is a mystery of probability that my intuition tells me is rooted at the very base of physics. No, it’s never loaded because I am a pacifist.”
— Field Marshall Strassnitzky of the First Hussars of the Belvedere during WW I[ref]Helprin, Mark (1991). A Soldier of the Great War, Harcourt and Brace, pg. 546[/ref]

The Ghosts of Risks to Come

The Focus Will be on Well-Tested Systems (WTS)

In the design and operations of a WTS there is a very high degree of reliability of equipment, workers and managers are vigilant in their testing, observations, procedures, training, and operations, with well trained staff, enlightened management, and good operating procedures in place.

Unforeseen Events


And Risk Assessment