RESISTANCE TO EXTREME HAZARDS AND ROBUSTNESS OF THE COOLING FUNCTION

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EPR reactor: safety robustness (3D animation)

AREVA's EPR reactor satisfies the most stringent safety standards. This means: An EPR unit would remain intact even in the event of an extreme impact. This animation demonstrates how the robustness of the EPR safety concept is ensured.

  • Fuel building

    The fuel pool is located outside the Reactor Building in a separate building, protected by a double concrete shield, to simplify access for fuel handling during plant operation and handling of fuel casks.

    The fuel pool allows to store spent fuel until it can be transported outside the plant giving a large flexibility and autonomy to the operator for spent fuel management.

    The fuel pool is also designed with two redundant cooling systems backed up by a third diverse one.

  • Reliability through redundancy

    Safety trains

    The EPR™ reactor features 4 separate safety subsystems called "safety trains” located in 4 different “Divisions". The safety trains are designed for quadruple redundancy, in terms of their mechanical and electrical parts as well as their supporting instrumentation and control (I&C) systems. As a result, each safety train is capable of performing 100% of the plant’s safety functions on its own.

    Each safety building of an EPR™ reactor includes one train of:

    • a system for injecting water into the reactor vessel in case of a loss of coolant
    • the steam generator emergency feedwater system
    • the electrical and instrumentation & control (I&C) systems

    The 4 safety trains also enable online maintenance (maintenance that can be performed without shutting down the plant). This renders more timely preventive maintenance that is independent from scheduled outages, thus boosting the safety systems’ reliability.

    Emergency power back-up

    In case of external power disruption, the EPR™ reactor can continue to autonomously and safely operate disconnected from the grid while powering all house loads thanks to its capacity to accept a generator load rejection from 100% power or less without a reactor turbine trip.

    However, in case of station black out in addition to external power disruption, the EPR™ reactor benefits from on-site emergency power supply systems, located in protected and physically separated buildings. Each of the four emergency diesel generators (one dedicated to each safety subsystem) can power the safeguard divisions for 72 hours.

    This set of emergency diesel generators is back-up by a diverse power supply system which is manufactured and designed by different suppliers prevents from a common cause failure.

    These two redundant SBO (Station Black-out) generators can supply power for 24 hours. In addition, a set of batteries located in the reactor building can power critical equipment for 12 hours.

    With power still available, the cooling is provided by any of the safeguard divisions.

    Fuel building

    The fuel pool is located outside the Reactor Building in a separate building, protected by a double concrete shield, to simplify access for fuel handling during plant operation and handling of fuel casks.

    The fuel pool allows to store spent fuel until it can be transported outside the plant giving a large flexibility and autonomy to the operator for spent fuel management.

    The fuel pool is also designed with two redundant cooling systems backed up by a third diverse one.

  • Cooling water inventory

    A larger on site cooling water inventory

    In addition to the cooling chain used during normal operation, each of the four safety systems can cool the core through two sub-systems:

    • The Emergency Feedwater Systems (EFWS) can cool through the steam generator secondary system and rely on four water tanks (total capacity: 1,600 m3), one in each of the four safeguard buildings. Those tanks can be further refilled by the 2,600 m3 fire-fighting tank or others on site water reserves.
    • The Safety Injection System (SIS) cools the core directly relying first on borated water inventory made of four pressurized accumulator water tanks (total capacity: 200 m3) and a large tank placed at the bottom of the reactor building, the In-containment Refueling Water Storage Tank the IRWST) of 1,800 m3.

    The large volumes of protected fuel and water reserves available on site can ensure the cooling functions for more than 7 days before the operator needs to replenish from external sources.

    If after more than 7 days grid power and access to the cooling source (e.g. river) has not been recovered, the operators can supply fuel and water from mobile means to continue decay heat removal.

  • Reducing human error

    Reducing human error with a state-of-the-art I&C system

    The control room runs on a fully digital I&C system, which has been shown to be more reliable than its analogue-based predecessors.

    The control room’s instrumentation & control (I&C) system enables the operators to monitor and operate the entire plant.

    Equipped with the latest digital technology, the system centralizes all operating data and features a user-friendly human-machine interface. Operators have full control over important parameters for plant operation and access to real-time summary data. Specially designed access way and ventilation systems ensure the control room’s accessibility in an emergency while a reinforced concrete helps protect it from external attack. And if the control room ever becomes inaccessible, the plant can be operated from a remote shutdown station.

    The digital I&C system reduces the occurrence of human errors in operation and maintenance because it:

    • is easier to maintain,
    • provides instructions in the case of an abnormal situation,
    • minimizes the possibility of failures remaining undetected.

    The EPR™ I&C architecture fulfills defense in depth and diversity international requirements, it considers simplicity and robustness as key aspects, relies on several lines of defense and defines the minimum of I&C systems (automation part) to process related functions.

EPR™ Reactor - Robustness to Extreme Hazards