- 152 - usually filled well above the required thresholds, which means that the autonomy is greater. EDF considers this period is sufficiently long to restore the heat sink before the core starts to become exposed. In the primary system open and just-open states, the primary system make-up by the CVCS system is available. Water is supplied from the PTR tank which can be replenished according to the procedures implemented on the initiative of the national crisis team. The primary system closed situation mentioned above therefore encompasses the primary system just-open situation. Case 2: Loss of the heat sink for all the plant units of a site EDF estimates that the plausible time required to restore the heat sink is about three days for riverside sites and one day for seaside sites. Primary system closed states: on the basis of the EFWS and SER water volumes commonly encountered, the feedwater autonomy is greater than the plausible time required to restore the heat sink. Consequently there is no cliff-edge effect and EDF considers that the heat sink will have been restored before the core starts becoming exposed. Primary system just-open state: as the residual power is lower, the primary system closed situation encompasses the primary system just-open situation. Primary system open states: the thermal inertia of the primary system borated water reserve (PTR tank) is used and the vaporisation is compensated by topping up the primary system from the PTR tank. The residual power to remove is also lower than in the primary system closed situation. EDF therefore estimates that in all cases the heat sink will have been restored before the core becomes exposed. To reinforce facility robustness in a whole-site H1 situation, EDF is in the process to re-assess the minimum thresholds of the Technical Specifications (TS) for the SER tanks in order to guarantee the targeted autonomy. Particular case of the EPR: Loss of primary heat sink on a plant unit in state A, B or C38 with primary system closed or just open In an initial condition with a reactor operating at full power, the EFWS tanks will be empty after about 2 days . Replenishing these tanks with water from the JAC39 tanks gives a total water autonomy of 7 more days counting from the loss of the heat sink (i.e. 9 days in all). Damage to the fuel starts about 9 days after the initiating event. The other initial situations are encompassed by the one described above because the residual power to remove is lower. Loss of the primary heat sink on a plant unit in state C, primary system not pressurisable or in state D The study of this accident scenario shows that the core remains covered for several days and long-term removal of the residual power is ensured. For all the plant units of the EPR site: Extending loss of the heat sinks to the entire site changes nothing in the scenario for loss of the heat sink for a single plant unit, as the Flamanville 3 EPR has no equipment in common with the site's plant units 1-2. Given national and international operating experience feedback for coastal sites, the plausible time for restoring the heat sink has been estimated at one day. 38 State A: under power and hot shutdown or intermediate state with all the reactor's automatic protection functions available; some functions may be disabled at low pressure; State B: intermediate shutdown above 120°C, shut down cooling system not connected ; some automatic protection functions may be disabled; State C: intermediate shutdown and cold shutdown with cooling system in operation and primary system closed or able to be closed rapidly; State D : cold shutdown with primary system open 39 JAC : safety-classified fire-fighting water production system.
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