Les cahiers de l'ASN #03 - 10 years after Fukushima

A BUNKER FOR THE CRISIS UNIT A new crisis management centre, capable of withstanding extreme hazards, will be created on each NPP. It will enable the local crews to provide long-termmanagement of a major nuclear crisis. The first one was commissioned in 2020 in Flamanville. EDF aims to complete the construction of these centres in 2026 for all its NPPs in service. An operational hardened safety core The “hardened safety core” is a significant and specifically French step forward , which should enable the essential safety functions of the reactors and spent fuel pools to be guaranteed in the event of an extreme hazard greater than that considered in the design of the NPP: earthquake, flooding (including very heavy rain), wind, lightning, hail and tornadoes. This “hardened safety core”, the aim of which is to prevent an accident with fuel melt and to mitigate large-scale releases and long-term effects in the environment, will be implemented as part of the safety improvements linked to continued operation of the 900 MWe and 1300 MWe reactors beyond 40 years and of the 1450 MWe reactors beyond 30 years. Some of this equipment is already in place, such as the ultimate backup generating set. MORE WATER FOR THE POOL Additional means for cooling and topping up the spent fuel pool water will be installed. This will consist of fixed equipment (pipes and connection systems outside the fuel building) and mobile equipment brought in and deployed on the site by the FARN* (pump and heat exchanger, electricity generating set, system for pumping water from the river or sea). ... and tomorrow A COLD SHOWER FOR A MOLTEN CORE New ultimate cooling systems for the containment and for stabilisation of the corium* in the event of core melt will be added. The challenge is to be able to evacuate the heat from a damaged reactor outside the containment, notably by means of a new heat exchanger. In addition, corium (magma of molten fuels and reactor components) could melt through the reactor vessel. Changes will be made so that the corium can spread and then be covered with water and cooled. These provisions will significantly mitigate releases of radioactivity into the air and into the groundwater in the event of an accident with core melt. 10 years after Fukushima, what safety improvements for nuclear facilities in France? • 13