After the seismic category,
we can go to the mechanical classification
of the Defense-in-Depth.
We have four different classes.
The first class includes the Pressure Boundary,
And all those systems components, buildings, that are required
for the reactor to be in safe shutdown
using normal operating systems.
Class 2 includes the Containment Building,
the Pressure Boundary that is not included in Class 1,
the Steam Generators, until safety valves,
and the Residual Heat Removal System,
the Hydrogen Control and Radioactive Releases in Containment.
Class 3 are all those mechanical components
whose failure could lead to radiation emissions,
or which are needed somehow by the safety systems
for the control of the environment radiation levels
or to remove residual heat from the spent fuel pool.
And finally, Class 4, are other systems that would not have
Defense-in-Dept mechanical classification.
Also, we have the electrical classification.
And here we have Class 1E and Class non 1E.
We can say that it constitutes a safety classification
which must have design and maintenance requirements
of electrical equipment and systems that are essential
for a set of different safety functions.
Let's say, reactor emergency shutdown, containment isolation,
reactor core cooling and residual heat removal.
Failure of any of these functions could lead
to a radioactive product release.
And finally, we have the Q list.
The Q list is a list of the equipment that requires quality certification.
In that list we will find that the ECS which are needed
for the prevention and mitigation of Design Basis Accidents,
which can be a risk for the health and safety of the public.
It includes all the emergency systems whose failure could end
in a radiation release close to the limits stated in the 10 CRF 100.
Or are needed for the plant safe shutdown.
Or are needed for residual heat removal.
And we this, we end the Defense-in-Depth classification.