Now we are going to see an example that happened
in Davis-Besse Nuclear Power Station in March 2002.
Then, plant staff discovered that the borated water
that any PWR or pressurized water reactor uses as a reactor coolant,
had been leaking for a long time
through the control drive mechanism
that is over the reactor vessel head.
This borated water is highly corrosive.
So during a extended period, that water was leaking
through the cracked control rod drive mechanism
and started to corrode and eat
through more than approximately 15 cm
of carbon steel of the reactor pressure vessel head
over an area of roughly a football ball.
So this significant reactor head wastage on the interior of the reactor vessel
left just 9.5 mm of stainless steel cladding holding back
the high-pressure, approximately 0.17 MPa,
of the reactor coolant.
This means that a breach most likely would produce
a huger locker or a loss of coolant accident
in which the reactor coolant would have jetted
into the reactors containment and result
in emergency safety procedures entering
to protect from core damage or meltdown.
So they had to go to an extended shut down.
And obviously they had to fix, repair all the reactor vessel head
and do an investigation.
During this investigation there were many concerns
that came to light.
The first one was that a number of management and leadership themes
identified by INPO, that is an American Organization
made or operated by all the power plants.
As I have said, a number of management and leadership themes
identified by INPO in 1998
at six other plants that had experienced extended shutdowns
were evident at the Davis-Besse
during the years leading to the extended shutdown.
And here we can include the overconfidence
from part of the employees and management.
Also the isolationism and a failure to fully use
all the available industry data.
Also they had defensiveness and a reluctance to be self-critical.
The issue is that there were some clues that something was happening there,
but they were overconfident on their safety performance.
Also, usually, nuclear industry is very isolatious.
So we don't, or before, they didn't talk too much
between different facilities in order to improve safety.
And finally and most important,
they had the production priority.
When we are in a nuclear facility
we have to weight between safety and economical benefit.
So when we are producing, we are making profit,
if we stop our plant and shutdown the reactor,
then, we are not making profit. That time that we are not working
is time that we are losing money.
So they were taking all their priority on producing energy,
allowing equipment problems to linger while plant stayed online.
It was or it is interesting to see what Peter Burg
that was chairman and chief executive officer of FirstEnergy,
that is the electric company owner of Davis-Besse, said.
Basically he said: "Signs that should have indicated
that there was a problem were there,
because they were there, they saw many things,
but they preferred to ignore it, not because they wanted,
but because they were overconfident on their performance.
But they were not simply pieced together.
The most important lesson that has been reinforced
during this process is that nothing is more important
than an uncompromising focus on safety.
The highest levels of productivity are meaningless
if they are not achieved through safe operations.
Davis-Besse changed our mind in industry.
And we started to focus more and more on safety.
There was any huge incident, but it could have happened.
Let's see a couple of pictures.
In the first picture you can see
all the red rusty boric acid deposits
that formed on the vessel flange.
On the middle upper left
or in the middle upper picture,
we can see all the erosion hole
within a diagram.
You can see those 150 mm thick carbon reactor head,
hole, caused by the persistent leak of borated water
on the bottom right.
And finally, the hole in the vessel head.
So, whenever you think of safety,
it is important to remember Davis-Besse example.
Because they were making things bad,
when they have several clues
that would have helped them to avoid all their problems.