- 78 - Penly 2 1330 3817 (4117) P4 Reactor 1 : 1990-4 Reactor 2 : 1992-1 Saint Alban 2 1335 3817 (4117) P4 Reactor 1 : 1985-8 Reactor 2 : 1986-6 Saint Laurent 2 915 2785 (2905) CPY (CP2) Reactor 1 : 1981-1 Reactor 2 : 1981-5 Tricastin 4 915 2785 (2905) CPY (CP1) Reactor 1 : 1980-2 Reactor 2 : 1980-7 Reactor 3 : 1980-11 Reactor 4 : 1981-5 (1) Source : Elecnuc, 2011 edition, CEA. (2) the value between parentheses indicates the design value whereas the other value is that stated in the creation authorization decree. 1.1.2 Description of the main safety systems The heat produced by the fission of uranium or plutonium atoms is used to produce steam. The steam is then expanded in a turbine which drives an alternator that generates a 3-phase electric current of 400,000 Volts. After expansion, the steam passes through a condenser where it is cooled on contact with tubes circulating cold water taken from the sea, from a waterway (river) or from an atmospheric cooling system. Each reactor comprises a nuclear island, a conventional island, water intake and discharge infrastructures, and possibly a cooling tower. The nuclear island essentially consists of the nuclear steam supply system comprising the primary system and the systems designed for reactor operation and safety: the chemical and volumetric control (RCV or CVCS), the residual heat removal (RRA or RHRS), safety injection system (RIS or SIS), containment spray system (EAS or CSS), steam generator main feedwater system (ARE or MFMS), electrical, I&C and reactor protection systems. Various support functions are also associated with the nuclear steam supply system: primary waste treatment (TEP or CSTS), boron recovery, feedwater, ventilation and air-conditioning, backup electrical power (diesel generating sets). The fuel storage pool The nuclear island also comprises the main steam system (VVP) that removes the steam to the conventional island, and the building (BK) housing the fuel storage pool. Built adjacent to the reactor building, the BK building is used to store the fuel assemblies before and during the plant unit shutdowns and to cool the spent fuel (a third or a quarter of the fuel is replaced every 12 to 18 months depending on the fuel management strategy). The fuel is kept immersed in a pool filled with the water that acts as a radiological shield. The water in the pool contains about 2500 ppm of boric acid to continue to absorb the neutrons emitted by the nuclei of the fissile elements, but which are too few in number to maintain nuclear fission. Furthermore, each fuel element is placed in a metal compartment whose design and separation distance from the other compartments prevent a critical mass being reached. The fuel pool is cooled by the reactor cavity and spent fuel pool cooling and treatment system (PTR or FPC(P)S). The conventional island equipment includes the turbine, the AC generator and the condenser. Some components of this equipment contribute to reactor safety. The secondary systems belong partly to the nuclear island and partly to the conventional island. The safety of pressurised water reactors is guaranteed by a series of strong, independent, leaktight barriers, for which the safety analysis must demonstrate their effectiveness in normal and accident operating situations. There are three barriers: the fuel cladding (first barrier) the main primary and secondary systems (second barrier) the reactor building containment (third barrier).
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