Complementarity
Diversity
Redundancy
EPR™ Robustness
to Extreme Hazards
More Than 7 Days
of Autonomy
Safe by Design
The EPR™ reactor achieves by design the highest safety level.
Both the probability and the consequences of severe
accidents are drastically reduced as compared to previous
generations of reactors.
CE TO MAJOR HA
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TAN
RD
SIS
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R
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C
F
O
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CA
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ROBUS
T
AL DAMAGE
NT
NVIRONME
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In particular, The EPR™ reactor is highly resistant to:
• External threats (large commercial airplane crash, explosion, …)
• Extreme external hazards (earthquake, external flooding, …)
• Internal hazards (fire, flooding, …)
It also features successive layers of defense and provides protected power
sources and water reserves to cope with extreme situations.
PREVENTION O
S
Improved Resistance to External Hazards
Diverse, Robust and Redundant Safety Systems
Diverse, robust and redundant safety systems fulfil essential safety functions of reactivity control, core cooling
and confinement of radioactive substances to achieve the highest safety standards.
• Reliable and proven technology benefiting from decades of operations in France and Germany
• Diversity and redundancy of safety systems, including power supply and water resources
• Separation and physical protection of qualified and testable safety systems
• Improved digital I&C
Double-shell
containment
Airplane crash protection
Ready for the Unexpected
The design of the EPR™ safety systems is developed based
on a deterministic approach complemented with probabilistic
safety assessments; complex combination of events and extreme
events have been taken into account in the design bases. In case
of severe accident, dedicated features, such as the core catcher,
ensure no long-term impact on the surroundings.
Core catcher
Safety design Validated by European Post-Fukushima Stress Tests
“The safety systems of [the EPR™ reactor] OL3 are well designed to tolerate external events by applying
adequate physical separation and protection against dynamic loads. Earthquakes and flooding are included in
the design to ensure safety functions to a high level of confidence”. STUK, Finnish Safety Authority
“The different systems which are needed to handle accidents, including severe accidents, are able to remain
operable against the design basis earthquake and flooding event.[…] The enhanced design ensures already
an improved robustness with respect to the severe accident. In particular, this reactor has integrated, from
the onset, specific design features to handle core melt situations and combination of hazards.” ASN, French
Safety Authority.
EPR™ Timeline in Case of Extreme Hazards
Power
ratio:
p=
100 %
Postulated
Initiating
Event (
):
Immediate Shutdown
of the Reactor –
Actuation of the
Emergency Systems
p<
5%
Automatic trip occurs when the control rods drop
within seconds
Nuclear Chain Reaction is Stopped
Decay heat immediately reduced to a few percent of initial level
Emergency Power Supply Starts Automatically
Emergency cooling systems ensure the removal of decay heat
to prevent fuel damage
Extreme
external
hazards
such as
earthquake
or flooding
Robust, Protected and Redundant Safeguard Systems
Safeguard function comprises four separate, protected and redundant
trains, located in four dedicated safeguard buildings (1, 2, 3, 4).
Hazards in one building would not affect another building.
Each safety train is capable of performing 100% of the plant safety
functions on its own.
Emergency Power Supply
Starts Automatically
Robustness
of the EPR™
buildings and
equipment
ensure that
there is no
consequence
beyond Loss
of Offsite
Power (LOOP)
and Loss of
Ultimate Heat
Sink (LUHS)
Each train is supplied with an
Emergency Diesel Generator
(EDG). Each EDG is
designed to provide each
100% of the needed power
to supply safety systems.
Systematic Application
of Functional Diversity
All diesel generators are safety class.
They are housed in two, geographically
separated and protected buildings
2 SBO diesel generators
2
1
3
4
4 Emergency
diesel generators
Diversity and redundancy are further reinforced with two additional
station blackout diesel generators (SBO DG) using different
technologies from the main diesel generators to prevent from
common cause failures.
Heat Control in the Fuel Pool
The Spent Fuel Pool (SFP) is located in a separate building, protected
against extreme hazards similary to the Reactor Building.
The Fuel Pool Cooling System (FPCS) removes the heat.
It is composed of two redundant, safety-related cooling trains in
the Fuel Building and a third one located in the Safeguard Buildings.
Decay Heat Removed
Through Steam Generators
p<
0.6 %
Decay Heat is Continuously
Removed Through Steam
Generators to Prevent Fuel
Damage and Related
Consequences.
Each steam generator has the full decay heat removal
capacity. The large volume of water of the steam
generators provides an increased safety margin.
EFW Tanks
4 x 400 m3
The Emergency Feedwater System (EFWS)
provides water to the steam generators when the
dedicated cooling sources are unavailable.
Heat removal is ensured through
natural circulation
The EFWS water reserves consist of four 400 m3 water tanks, housed in each of the separate
and protected safeguard buildings.
Each Emergency Feedwater Tanks Provide Sufficient Water
Inventory for 24 Hours
Before Refill with On-site Reserve
Close Monitoring of the Fuel Pool Conditions
•Temperature and water levels of the fuel pool are
continuously monitored.
•The Fuel Pool Cooling System (FCPS) maintains the water
temperature at the required level by removing decay heat
from the spent fuel assemblies.
p<
0.3 %
At least 7 Days of Autonomy
for Decay Heat Removal
Continuous Refill of EFW Tanks with On-site
Water Reserves
EFW Tanks
4 x 400 m3
On site
water
reserves
On-site Water and Fuel reserves Provide Full Autonomy for
a Minimum of 7 Days
The large volumes of water available on-site of an EPR™ reactor can ensure
the cooling functions for a minimum of 7 days before the operator needs to get water from
external sources.
Existing connections and lines provide the possibility to feed the EFW tanks with alternate onsite water reserves including the seismic-resistant fire fighting tank (2,600 m3).
Fuel storage capacities or EDG and SBO diesels are designed according to
client’s requirements, so that they can provide sufficient time to enable external re-supply.
Standard capacity is 3 days for each EDG and 1 day for each SBO Diesel.
Fuel standard capacity on site is more than 12 days in total.
Redundant and Diverse Cooling Functions of the Fuel Pool
The FPCS can also supply external water to the pools. A steam exhaust system removes steam from the fuel po
In case of fuel pool evaporation, water make-up is possible by taking credit either from the on-site supply reserv
Possibility to Supply
Fuel and Water
from Off-site Souces
Extension of the Site
Autonomy by Mobile Means
After 7 days, if off-site power and ultimate heat
sink have not been restored, the operators
can supply fuel and water from mobile means
to continue decay heat removal.
Restoration of
Off-site Power and
Normal Cooling
Restart
of Normal
Operations
Full Integrity
of the Three
Protective Barriers
is Ensured.
When off-site power and
ultimate heat sink are restored,
the operator can prepare the
restart of normal operations.
Multiple points are available to connect mobile
means.
ool hall after filtration.
ves, or by external water supply.
3
2
1
EFW
Tanks
4x
400 m3
1 – Fuel cladding
2 – Reactor coolant boundary
3 – Reactor containment
Cooling and Water
Make-up are Ensured,
Up to the Restart
of Normal Operations
A Determininistic Approach to Mitigate
Severe Potential Consequences
Prevention of Hydrogen
Detonation
In the unlikely event of hydrogen release,
passive autocatalytic hydrogen recombiners
installed inside the containment can keep the
average concentration below the threshold risk
of a detonation. Their location and number are
precisely defined to ensure that any destructive
phenomena endangering the containment
are excluded.
Corium Retention
Core Catcher
Even in the extremely unlikely event of a core melt accident
that may result in a breach of the reactor pressure vessel,
the molten core and radioactive products will remain
confined inside a specifically designed core catcher
whose long-term integrity would be maintained.
The design prevents interaction between the corium and
the cooling fluid to prevent steam explosion.
Containment Heat
Removal
Long-term integrity of the containment in a severe
accident is achieved through a dedicated dual-train
spray system with heat exchangers and dedicated heat
sink to fulfil this cooling function.
Double Shell Containment
In the event of a core melt leading to vessel failure, the
containment building remains undamaged and leak-tight.
• a metal liner internally covers the pre-stressed concrete
inner shell,
• the inter-space between the inner and outer shells is
maintained at a slightly negative pressure to enable leaks
from the inner containment to be collected.
However Low the Risk of a Severe Accident,
the EPR™ Design Ensures Long-term Integrity of the
Containment and prevention of environmental damages.
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