- 158 - ASN will ask EDF to supplement its demonstration with a temperature sensitivity study of the equipment items required to manage a whole-site H1 situation and which are situated in areas that are no longer cooled. This study must be carried out considering a representative duration of utilisation of these equipment items in the event of a lasting H1 situation and considering that the entire site may be affected. More specifically for the spent fuel pools: ASN observes that the availability of water from the fire-fighting network to make up the spent fuel pools is not guaranteed in the event of an earthquake. In a situation of total loss of the electrical power supplies, this system will not function. EDF proposes an ultimate backup make-up means specific to each plant unit, which will draw water from the water table or large-capacity ponds using a stand-alone motor-driven pump or an electric pump backed by the ultimate backup diesel generator (DUS). EDF specifies that the study of this ultimate make-up means is planned for the end of 2012. ASN considers that the proposed improvements, which meet the CSA specifications, must be implemented. It will issue a requirement on this subject. More specifically for the EPR: The cooling system of the EPR reactor spent fuel pool has a third cooling train. The heat sink of this third train is independent and should therefore remain functional if the heat sink common to the main two cooling trains is lost. In all the reactor operating ranges, the spent fuel pool can be made up by the fire-fighting system. This firefighting system is also used when necessary to replenish the tanks of the auxiliary feedwater supply to the steam generators. It must therefore be available in all the reactor operating ranges. In the framework of Flamanville 3 EPR commissioning examination, ASN will ask EDF to present its maintenance and management strategy for the systems shared between the spent fuel pool and the reactor (such as the fire-fighting water system) in order to minimise their temporary unavailability. Capacity of the site to manage an accident involving heat sink loss: Managing an H1 situation involves many actions, some in the control room but above all locally. EDF provides little information on how they are performed, given the ambient conditions in the premises, their accessibility, and the human resources available to implement them on all the plant units. Furthermore, means evaluated in an H1 situation are planned to be used by EDF as part of the complementary measures to prevent severe accidents. ASN considers that EDF must back up its conclusions regarding the capability of the NPPs to manage a degraded situation (H1 or H3) on several plant units simultaneously, including when a plant unit suffers a severe accident. If necessary, EDF will define additional provisions for the management of this situation. ASN will issue a requirement on this subject. These requests are applicable to the reactors in service and to the EPR. 5.2.4 Measures envisaged to increase the robustness of the facilities with respect to loss of the ultimate cooling system / heat sink ASN asked EDF to "indicate what measures could be envisaged to prevent or delay the onset of these cliff-edge effects, to improve the site's autonomy and increase the robustness of the facility (design change, change in procedures, organisational arrangements, etc.)." For the reactors in service, EDF proposes measures to increase the time lapses before the core becomes exposed. EDF proposes increasing the on-site water reserves (to supply the feedwater system, the primary cooling system and the spent fuel pool) as a complement to the FARN, which will then take over.
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