EFR

The EFR design has been completed which aimed to encapsulate the combined experience of France, Germany and the UK for liquid metal reactor technology based on pool-type reactors. Although construction is not foreseen in the near future, there is a design now available based on established technology and with realistic cost estimates.

The EFR project was launched in 1988 by the European Fast Reactor Utilities Group (EFRUG) including EdF (France), ENEL (Italy), Nuclear Electric (UK), Bayernwerk, Preussen Elektra and RWE (Germany) and BNFL (UK) and UNESA (Spain) joined later in 1993. Other design and construction companies ‘EFR Associates’ were also involved together with R&D companies to perform supporting experimental and theoretical studies.

The design objectives’ lifetime were for high availability over a lifetime of 40 years. The technology was therefore based as far as possible on proven methods or methods that would be expected to be fully endorsed by appropriate R&D.

The reactor core consists of three radial core zones, with different plutonium contents with the inner, intermediate and outer zones with 207, 108 and 72 fuel assemblies, respectively, in a hexagonal lattice. Surrounding the core are 78 breeder subassemblies. Further, two options for the core design are possible, a homogeneous core and an axially heterogeneous core with axial breeder blankets. There are 24 control and shutdown rods and 9 diverse shutdown rods for fast shutdown.

Each fuel assembly has a bundle of 331 fuel pins and the breeder subassemblies have 169 pins. The fuel and the fertile material consist of pellets of UO2 and (U, Pu)O2, respectively. The control and shutdown rods are each retained in a hexagonal bundle of 37 absorber pins and the diverse shutdown rods each contain 55 absorber pins. These include B4C absorber material.

The reactor and its cooling systems were based on a six circuit sodium coolant design. The reactor unit is an evolution of the Superphenix design. Sodium is circulated through the core region by three primary pumps. The heat is transferred to the secondary sodium loop by six IHXs. Each secondary loop transfers heat to a steam generator unit.

The safety concept is based on the ‘defence-in-depth’ approach. The system is at low pressure and loss of coolant accidents are precluded within the design basis. The prevention is based on enhanced shutdown and removal of decay heat. Decay heat removal is normally via the steam/water plant; there are in addition two diverse decay heat removal systems. An objective is to choose a core height to minimise the sodium voiding positive reactivity effect. Reactor shutdown is assured via two independent and diverse shutdown systems.

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