Paris (AFP)

The shutdown of the Fessenheim plant, a "historic event" in the words of Minister Elisabeth Borne, heralds a long process of dismantling, which has already seen many precedents abroad.

A "historic" stop?

This closure seals the vast nuclear equipment program decided by Paris in the context of the oil shock and launched in 1977 with the start-up of Fessenheim.

"Yes, it is historic: it was the shutdown of the first two reactors which were the start of the French fleet," underlines Thierry Charles, deputy director of the Institute for Radiation Protection and Nuclear Safety (IRSN).

The most nuclearised country in the world, France has decided to reduce the share of the atom in its electrical production, from 72% today to 50% by 2035.

In France, the last closure was back to the Superphénix breeder, in 1997. Previously, it was the Chooz A reactor (Ardennes), operating under pressurized water like Fessenheim but more "small" (300 megawatts electric and not 900 MWe ), which had been arrested in 1991 and is still being dismantled.

Why close a power plant?

Many countries have closed reactors for energy, political or economic reasons.

According to the International Atomic Energy Agency, by the end of 2017, 614 electric power reactors had been put into service worldwide, including 342 pressurized water (REP) and 115 boiling water (REB), launched for the essential in the years 1970 to 1990. Today, 50 REP and 40 REB are closed.

Germany, after the Fukushima accident in 2011, has given itself until 2022 to exit nuclear power.

Switzerland has decided to do the same, while maintaining certain sites for the time being. In December, after 47 years of service, the Mühleberg power station was disconnected from the grid due to the high cost of its maintenance.

Also in December, Sweden closed a reactor, for economic reasons, after 43 years, while planning to keep the atom.

In the United States, the administration admits that reactors can go to 80 years, but some close before, generally for reasons of profitability, notes the IRSN.

In France, EDF had initially envisaged lifetimes of 40 years, before expressing the wish, in 2009, that they be extended. Tricastin was the first, in 2019, to undergo the 40-year security visit.

How long should you allow for disassembly?

In Fessenheim, once shutdown, a maneuver regularly performed for maintenance, EDF plans a five-year preparatory phase during which the fuel must be removed, cooled in the pool and then evacuated to the La Hague plant basin .

At the same time, it will have to constitute a thick file to obtain the decommissioning decree, by 2025. A tedious step because involving technical examinations and risk studies, inventory of equipment, etc.

"The operator must justify all of the operations, from start to finish, and demonstrate that displays can protect operators and the environment," said Charles, of IRSN.

Once approved, dismantling can begin, for approximately 15 years.

"Given the international experience, 20 years in total it is consistent," said Mr. Charles.

Then there will be the painful question of waste.

In Fessenheim, out of 380,000 tonnes of waste planned by EDF, 18,400 tonnes should be radioactive, including 200 tonnes (400 m3) highly radioactive intended to be buried in a deep geological layer (Cigeo project planned in the Meuse).

After Fessenheim, whose turn is it?

To drop to 50% nuclear, 12 more reactors will have to close by 2035.

How often? France's energy roadmap project foresees two in 2027-28, or even two in 2025-26 depending on current demand.

"EDF will have to organize all the sites to be able to manage them. We must be certain that the industry around will be able to respond," stresses Mr. Charles. "The positive side is that the Fessenheim shutdown, which will serve as the seed, will allow the industrial fabric to get used to, and having a vision of the shutdown dates will facilitate the workload plan".

EDF has proposed to the government to study the shutdown of "pairs of reactors" at the Blayais, Bugey, Chinon, Cruas, Dampierre, Gravelines and Tricastin sites. Sites that each have at least four, the idea being to avoid the closure of entire plants.

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