Temporary and Long Term Design Provisions Taken on the French NPP Fleet to Cope with Extended Station Black out in case of Rare and Severe External Events

Following the events at Fukushima, the Institute for Radiological Protection and Nuclear Safety (IRSN) has been strongly involved in a series of reviews related to the robustness of French nuclear power plants in case of 'rare and severe' external hazards. These reviews included in particular the 'stress tests' performed in 2011 as required by the European Commission. Those reviews, and the proposal made by EDF to reinforce NPPs robustness in such situation, led to the introduction of the concept of a hardened safety core (HSC) to avoid massive releases and prolonged effects in the environment in case of rare and severe natural hazards. This concept will be explained in the paper and the new specific electrical equipment as well as the interfaces with the existing electrical distribution required to implement this HSC will be explained. As the detailed design, manufacturing and installation of the HSC in all NPP sites will take several years, temporary measures have been adopted. This paper will also present the electrical sources and the distribution related to those temporary measures. The specific situation of the new built EPR reactor in Flamanville is also addressed. Lastly, in complement to the above on-site design provisions, a Nuclear Rapid Response Force has been set up by EDF to bring off-site support to French NPPs in case of emergency. The paper will describe the type of electrical equipment to be delivered and the principle for distributing the electrical power to the required loads. (authors)