- 83 - the fire-fighting water systems; the instrumentation & control system and the electrical systems. 1.2 The main differences between nuclear power plant installations In spite of the standardizing of the French nuclear reactor fleet, a number of technological innovations have been introduced as the design and construction of nuclear reactors have progressed. Compared with the CP0 series reactors of the Bugey and Fessenhiem NPPs, the CPY series has a different building design, an intermediate cooling system between the system that sprays the containment in the event of an accident and that containing the water from the heat sink, and provides for greater management flexibility. Significant changes with respect to the CPY series have been made in the design of the circuits and systems protecting the core of the 1300 MWe reactors (plant series P4 and P4) and the design of the buildings accommodating the installation. The increased power has resulted in a primary system with four steam generators (SG) offering a greater cooling capacity than on the 900 MWe reactors, which have three SGs. Furthermore, the reactor containment has a double concrete wall instead of a single concrete wall with a steel sealing liner as is the case with the 900 MWe reactors. The P4 series reactors display a few differences with respect to the P4, notably the fuel building and the design of certain systems. The N4 series reactors differ from the preceding reactors more particularly in the design of the SGs which are more compact, the design of the primary pumps, and the control room computerisation. A 1650 MWe EPR-type pressurised water reactor is under construction at the Flamanville NPP, which already has two 1300 MWe reactors. Furthermore, ASN is currently examining an application from EDF to create another EPR PWR on the Penly site. The EPR reactors under construction at Flamanville (Flamanville 3, BNI 167), and planned at Penly (Penly 3), are four-loop reactors with a unit electrical output of about 1 650 MWe. Compared with the existing power reactors operating in France, they are characterized by the fact that severe accident scenarios are integrated from the design stage. Based on the principle of a quadrupling (4 trains) of the safeguard systems (with a few exceptions) and, in addition to the presence of an aircraft crash-resistant shell (protecting the reactor building, the fuel building and two buildings housing two engineered safeguard trains) to counter external hazards, the EPR incorporates, for example: prevention measures, in particular: o to prevent high-pressure core meltdown accidents ; o to enhance the reliability of the on-site electric power supplies by adding two diversified diesel generator sets (ultimate backup); o to protect the water supply of the safeguard systems cooling the reactor core and containment; o by installing the IRWST (in-containment refuelling water storage tank) directly in the reactor building; o by having an alternate heat sink based on the "reversed" use of the sea discharge channel, to take in water from the sea; mitigation measures such as a corium collector under the reactor vessel in the reactor building, or having a double-walled containment with a metallic internal sealing liner in the reactor building. For the spent fuel pools of the 900 MWe CP0 and CPY series reactors, the fuel assemblies will be placed in storage rack compartments. These storage racks are made from a corrosion-resistant material not specifically designed to absorb neutrons, sub-criticality being guaranteed by the geometric arrangement of the assemblies. The fuel pools of the CP0 series reactors have 313 compartments, while the CPY series have 382. To load the spent fuel assemblies into the transportation container, the container must be placed in the loading pool, a dedicated location that communicates with the fuel storage pool.
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