Safety of the French Nuclear Power Plants after the Accident of Fukushima

French nuclear power plants are designed to withstand a variety of natural hazards: earthquakes, floods, snow, wind, extreme temperatures, etc. At the design stage, the characteristics of hazards likely to affect plant safety are determined (intensity for earthquakes, kinetics of water rise and associated level for floods, speed and force for winds, etc.); these characteristics obviously depend on the site where the plant is located. This information is then used to design the facilities, i.e. to implement measures to ensure that the equipment required for plant safety remains available and operational in the event of an attack.

The hazards considered and their characteristics have been reassessed several times since the initial design of French nuclear power plants, during periodic safety reviews or following events that have occurred in France (extreme cold in 1985-1987, partial flooding of the Blayais power plant at the end of 1999, heat waves in 2003 and 2006).

The Fukushima accident, which occurred in Japan on March 11, 2011, served as a reminder that the occurrence of natural hazards that exceed the characteristics used to design the facilities cannot be completely ruled out, and that such hazards can affect all the measures put in place to prevent accidents and limit the consequences of an accident that occurs despite the preventive measures in place. The Tohoku earthquake, for example, triggered a tsunami whose height exceeded that of the protective dikes in place: the water that invaded the buildings led to the loss of power supplies, and then progressively to the loss of cooling systems for the reactor cores and spent fuel deactivation pools. These successive losses led to core meltdowns in three of the six boiling water reactors built on the site, and a deterioration in the safety of the spent fuel assembly storage pools. This accident led to significant radioactive releases into the environment, both atmospherically and in liquid form into the sea.

Following this accident, French nuclear operators carried out additional safety assessments (SSAs) to assess the behavior of their facilities in extreme situations such as those that occurred in Japan on March 11, 2011.

In conclusion, although the ability of French nuclear power plants to cope with plausible hazards was confirmed, it was deemed useful to implement additional measures to reinforce their protection against extreme natural hazards and reduce the risk of radioactive releases in the event of a sustained loss of power supplies or cooling sources.

Assessments of this type have also been carried out elsewhere in the world, particularly in Europe and in the major nuclearized countries. They have also led to existing design provisions...