Now let's say that we have an installation
dedicated to drilling oil wells
that has eight different protection barriers to avoid accidents.
Do you think it would be extremely safe?
In the next video, we will show you an example of this.
The case of Deepwater Horizon platform
where its accident in the Gulf of Mexico
involved the failure of eight different barriers.
Precisely, knowing that there are so many barriers,
but not knowing the reason for their existence,
may lead people to think that they can live
when some of them failed.
To understand what we mean now,
we are going to remind you or speak again about the barrier model.
James Reason set the hypothesis that, in most cases,
an accident can be traced back to one or more failure domains.
The failure domains are four different "domains" or categories.
Let's say organizational influences,
supervision, precondition and specific acts.
So he postulated that an organization's defense against challenges
can be seen like a set of barriers, but not exactly like a castle.
But rather, they look like Swiss cheese slices
with holes on them.
The holes are moving,
are changing the size, growing and shrinking, constantly.
Which means that that at any moment it could produced
an accident or a failure when those holes align themselves
allowing what James Reason defined as:
"A trajectory of accident opportunity".
That means that a challenge in form of a hazard
can pass through all the different slices
and produce an accident or failure.
So why do we use barriers?
With barriers we try to avoid that the hazards become damages.
What are our hazards in nuclear industry?
Obviously, the radiation and the damage, the dose that we can receive
or be exposed to.
In our industry, we will have a set of engineering barriers
that are safeguards,
and some physical barriers as fuel cladding,
reactor vessel and the containment.
If you want to remind them, you have all of them in the 4th NOOC.
And finally, organization barriers
which include the training, the procedures, the quality of our job
and especially, the organizational culture.
All of them can have holes and, in fact, they have holes.
As the model says, there are active and latent failures.
They are included in the Swiss cheese model.
The active failures are the ones
that can be directly related to an accident.
For example:
To have a not properly aligned safeguards safety injection system.
And latent failures that can be either for longer time,
such as boron leaking,
producing corrosion on the reactor vessel
or months or even years.
So now, please, watch the following video
and we can continue differentiating characteristics
from nuclear power plants.