- 155 - spent fuel pool remains well above the top of the fuel assemblies. There is no risk of reaching the feared situation (exposure of the fuel assemblies). Depending on the residual power in the pool, the autonomy is estimated to be at least one month, a duration that is amply compatible with an external intervention. With a whole site affected: The site's autonomy with respect to situations of heat sink loss associated with natural external hazards was verified during the third 10-year inspection of the 900 MW plant units. The target is to have several days' autonomy. The equipment and water reserves available are: the SED system and all the SED tanks; the JPI and JPP systems. Operator management of the situation for each plant unit is identical to the preceding case, as the JPI and SED systems remain available. Kinetics of the phenomenon The JPP system guarantees permanent topping up of the spent fuel pool. There is no risk of reaching the feared situation (exposure of the fuel assemblies). Throughout this period where make up is guaranteed, the level of water in the spent fuel pool remains well above the top of the fuel assemblies. Conclusion for one site As the SED and JPI systems remain available and make-up continues if the heat sink is lost, the fuel assemblies will not become exposed in an H1 situation affecting the entire site. If the JPP is affected (for example in case of heat sink clogging), only the SED system will be able to make up the spent fuel pool in the BK building. In this case the time before the fuel becomes exposed is estimated at a few days in the states where the residual power in the spent fuel pool (APR and RCD states) is at maximum level, and about one week in the other less penalising cases. For the EPR: Loss of the primary heat sink leads to the loss of the CCWS/ESWS trains, and therefore loss of cooling of the two main PTR trains. In states C with the primary system not pressurisable, D, and potentially part of state E45, two EVU trains are required to manage the situation of the boiler. In this case the spent fuel pool is no longer cooled. Topping up with water by a JAC pump aligned on one of the two JAC tanks (1000 m3 and 2600 m3) prevents the exposure of the fuel assemblies. Making up by the JAC enables the water level in the spent fuel pool to be maintained for: about four days with the JAC tank of 1000 m3; more than 10 days with the JAC tank of 2600 m3. The time before the fuel assemblies in the storage rack become exposed is about 18 days, which is compatible with an external intervention. In the other states, the third PTR train, cooled by EVU/SRU, can be started with alignment on the diversified heat sink (outfall structure) in the event of loss of the primary heat sink, to ensure the cooling of the spent fuel pool. 44 JPP: Fire-fighting water production system 45 State "E" of the EPR: Cold shutdown with reactor cavity full for reloading.
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