Title: Group presentation:
1Group presentation
- Normal Accident at Three Mile Island
- by Charles Perrow
2The accident at Three Mile Island
- The Three Mile Island (TMI) Unit 2 nuclear plant
near Harrisburg, Pennsylvania, on March 28, 1979. - The most serious nuclear power plant accident to
date. - TMI is an example of the accident potential of
complex systems. - Next the accident
3The plant
Maintenance of complex systems have big room for
errors. In retrospective operators conceded that
someone didnt open the valves.
This is actually the one indicator thats
wrong. Misinterpretation of a situation or an
order. If your action results in an expected
result, you validate your action as successful.
This is not always right. In fact, if the result,
in your eyes, are correct and they do not
correspond to the result happening in the real
world, your actions may lead to disaster.
Pressure increases Pressure decreases
4The plant
- A new shift supervisor arrives and discovers the
open valve - Situation improves temporarily
5 Again the operators presumed that instruments
were malfunctioning, and quickly dismissed the
sudden pressure surge in the containment
building. Only one man guessed that the surge
was caused by an explosion, but didnt warn
others that they might expect another
The plant
- The fuel rods have become so hot that they begin
reacting with the water, producing hydrogen - Pockets of hydrogen gas emerge inside the core,
which then explode thirty-three hours after the
accident began
6Essentials (1)
- Lesson In complex systems any part of the system
might be interacting with other parts in an
unanticipated ways. - In this case where several indicators gave the
operators different information the operators
assumed the indicators were wrong, because they
didnt expect this complex scenario.
7Essentials (2)
- Would better organization help, or money and
resources for better people and equipment? - According to Charles Perrow No.