Areva EPR

■ SAFETY
Greater provision for the risk arising
from internal and external hazards
The choices taken for the installation of the safeguard systems and
the civil works minimize the risks arising from the various hazards
(earthquake, flooding, fire, aircraft crash).
The safeguard systems are designed on the basis of a quadruple
redundancy, both for the mechanical and electrical portions and for
the I & C. This means that each system is made up of four subsystems,
or “trains”, each one capable by itself of fulfilling the whole
of the safeguard function. The four redundant trains are physically
separated from each other and geographically shared among four
independent divisions (buildings).
1
1
2
1
Each division includes:
• for borated water safety injection into the reactor vessel in case
of loss of coolant accident, a low-head injection system and
its cooling loop, together with a medium-head injection system,
•a steam generator emergency feedwater system,
• the electrical systems and I & C linked to these systems.
The building housing the reactor, the building in which the spent fuel
is interim-stored, and the four buildings corresponding to the four
divisions of the safeguard systems, are given special protection
against externally-generated hazards such as earthquakes and
explosions.
This protection is further strengthened against an airplane crash.
The reactor building is covered with a double concrete shell: an
outer shell made of 1.30 m thick reinforced concrete and an inner
shell made of pre-stressed concrete and also 1.30 m thick which is
internally covered with a 6 mm thick metallic liner. The thickness and
the reinforcement of the outer shell on its own have sufficient
strength to absorb the impact of a military or large commercial
aircraft. The double concrete wall protection is extended to the fuel
building, two of the four buildings dedicated to the safeguard
systems, the main control room and the remote shutdown station
which would be used in a state of emergency.
The other two buildings dedicated to the safeguard systems, those
which are not protected by the double wall, are remote from each
other and separated by the reactor building, which shelters them
from simultaneous damage. In this way, should an aircraft crash
occur, at least three of the four divisions of the safeguard systems
would be preserved.
The choices regarding the equipment
and systems, in order to reduce the risk
of an abnormal situation deteriorating
into an accident
Elimination of the risk of a large
reactor coolant pipe break
The reactor coolant system design, the use of forged pipes and
components, construction with high mechanical performance
materials, combined with the measures taken to detect leaks at the
earliest time and to promote in-service inspections, practically rule out
any risk of large pipe rupture.
1
The major safety systems comprise four sub-systems or trains, each capable
of performing the entire safety function on its own. There is one train in each
of the four safeguard buildings (1) surrounding the reactor building (2) to prevent
common-mode failure of the trains.
† A set of quadruple redundant
safeguard systems, with independent
and geographically separated trains,
minimize consequences of potential
internal and external hazards.
† This protection is even reinforced
against the airplane crash risk by
the strong double concrete shell
implemented to shelter the EPR.
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1
3
2
The outer shell (5) covers the
reactor building (2), the spent
fuel building (3) and two of the
four safeguard buildings (1).
The other two safeguard
buildings are separated
geographically.
4
5
The reactor containment building has two walls: an inner
prestressed concrete housing (4) internally covered with a metallic liner
and an outer reinforced concrete shell (5), both 1.30 m thick.
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