Phénix was one of the first prototype sodium-cooled fast reactors of its size. It stopped generating power in March 2009, but continued operation until October for end-of-life tests, before being shutdown for future decommissioning. The plant will be dismantled over the next fifteen years.

Although it is no longer generating power, Phénix still has an important role to play in the future development of fast reactors. Capitalising on and analysing the operating feedback from Phénix forms a major part of the current research towards next generation sodium fast reactors, currently being carried out by CEA, Areva and EDF.


Phénix is a pool-type (integrated) reactor with a power of 583MWt (250MWe). But from 1993 it operated on a power rating of 350MWt (140MWe).

The main vessel is 11.8m in diameter and holds around 800t of primary sodium.

The core is made up of an array of hexagonal MOX fuel assemblies with a width across flats of 127mm and length of 4.3m. Each assembly contains 217 pins. Reactor control was initially ensured by six control rods, with an additional rod added in 1996 at the centre of the core.

Six intermediate heat exchangers are connected in pairs to three secondary loops (each containing 140t of sodium) to remove the heat generated by the core. The secondary loops transfer the heat to the steam generators, which are held inside a casing strong enough to withstand a sodium leak involving a sodium-water reaction.


As well as being an experimental reactor carrying out irradiation programmes over the years, Phénix has also been an industrial demonstrator.

First, it validated the use of sodium for a power reactor. For example, since its restart in 2003, its availability rate has been between 69% and 85%.

Second, in the 1980s, reprocessing of irradiated rods was carried out and fuel cycle was closed several times. The fuel reached specific burn-up rates of more than 100GWd/t and almost 150GWd/t for some experimental assemblies, three times greater than the project values. Also a significant breeding rate was demonstrated: 16% more plutonium than the initial quantity was manufactured.

From 2003 onwards, Phénix carried out transmutation experiments, demonstrating the potential of this system to transmute minor actinides and long-lived fission products.


Phénix was part of the ambitious fast neutron reactor development programme in 1960s France, following on from Rapsodie, the small experimental reactor.

A detailed design for the 250MWe prototype was produced in 1967. In 1969 the French Atomic Energy Commission (CEA) and EDF signed an agreement to jointly build and operate the power plant, each contributing 80% and 20%, respectively. Construction work started in October 1968, the reactor went critical on 31 August 1973 and was commissioned for service on 14 July 1974.

From 1974 to 1990, the reactor far exceeded its objectives. A few incidents, including leaks in the intermediate heat exchangers, sodium leakage and sodium-water reactions in the steam generators, were successfully overcome to continue operation.

Phénix faced some more major problems at the start of the 1990s. It suffered variations in core reactivity on four occasions, which required three years of investigation. The power plant started up again in 1994.

The service life had to be extended and a programme to upgrade the safety of the power plant was undertaken in the late 1990s. This required major work, which lasted six years and was a great source of learning.

The reactor returned to normal operation in 2003 and the irradiation programme was completed successfully.

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