1. Approach to natural hazards in French nuclear power plants

French nuclear power plants have been designed according to a defense-in-depth approach, and a series of provisions have been defined [B 3 810] :

• on the one hand, to prevent accidents ;

• secondly, to limit the consequences of accidents that may occur despite the above provisions.

Generally speaking, five levels of defense in depth are currently distinguished for nuclear reactors, with each level designed to limit the consequences of the failure of the previous level or avoid the need to activate the next level.

In this context, the facilities have been protected against hazards of internal origin (fire, flooding due to equipment failure, falling loads, etc.) or external...