We have seen in the previous unit
why the nuclear power industry is different
from other power facilities.
Especially, why it's important to have extra care in barriers and protections.
Remember the fact that a nuclear power plant
has an amazing amount of energy stored in the reactor core,
enough to have 18 to 24 months of non-stop production.
However, the source of energy is very special.
And when the reactor is shutdown,
the heat production does not stop immediately.
We have to be able to evacuate that heat for extended periods.
And of course, the radioactive materials have to be confined.
So now it's time to see the basic philosophy
behind nuclear safety.
First, we are going to see the beginning
and how nuclear safety started.
And later in this unit, we are going to expand on the concept of risk
that we already saw in the first NOOC.
Risk is a combination of the frequency of an hazard to happen
and the severity that the accident or the hazard could pose,
if you remember from the previous NOOC.
And thanks to risk, we can define a region on a chart
where it is acceptable to operate
having events of different severity and a forbidden area
that could be seen in a representation.
After that, we will see the deterministic analysis,
which are basically safety analysis based on analytical evaluations
of different events which can take place in our reactor
or nuclear power facility.
The idea is to postulate
different transients or physical phenomena
that can happen and predict the outcome for different initiating events.
Those events could be treated using a set of rules.
The result of the analysis has to be qualified
by an acceptance criteria
which are the limits and conditions set by different regulatory bodies.
So using the risks chart and the deterministic analysis,
it's possible to define what we're going to call the deterministic evolve
as an area in the probability severity chart
where the deterministic safety analysis is valid
and passes the acceptance criteria.
Once we have set which are the events that are acceptable to happen,
we have to avoid those ones which are in the forbidden area.
And to do that, we will use a set of barriers and safety levels
that we are going to call defense-in-depth
and that we have seen in the previous unit.
And finally,
we are going to try to preserve the deterministic analysis hypothesis
and we will evolve the deterministic analysis
to a probabilistic analysis in the chapter 7.
This could be a tool to quantify different risk measures.
So now we are going to continue.