- 305 - Loss of the off-site electrical power supplies, and the conventional emergency power supplies, and any other on-site emergency electrical power source The licensee indicates that the loss of the ATPu electrical power supply would not lead to any cliff-edge effect situations. This is because in the event of total loss of the electrical power supplies (off-site, fixed diesel generator sets, batteries), the different networks, including the criticality monitoring and fire detection systems, would no longer be active. This situation would nevertheless not lead to a sudden degradation in the accident sequences. After complete discharging of the batteries, the facility would remain in a static state, all the operations performed in the facility having been stopped. In the event of total loss of the electrical power supplies (external, fixed diesel generator sets, batteries), inspection rounds are scheduled during and outside opening hours. Conclusion on the measures planned to protect the facilities against the risk of loss of the electrical power supplies Insofar as the consequences of the loss of the electrical power supplies would be limited for the ATPu, the licensee does not propose any additional provisions to protect the facilities against this risk. Measures envisaged to reinforce the robustness of the facilities to the loss of the electrical power supplies, and proposed studies Insofar as total loss of the electric power supplies would not be likely to result in situations leading to a cliffedge effect for the ATPu, the licensee does not propose any measures to reinforce the robustness of the facilities to the risk of loss of the electrical power supplies. The foregoing raises no particular comments form ASN, in view of the ongoing decommissioning of the facility. Loss of the cooling systems / heat sink The licensee considered that this subject was not relevant for the ATPu. Effectively, none of the ATPu equipment requires a cooling system. The foregoing raises no particular comments from ASN. 5.3.2. Masurca The ventilation circuits (electric supply and extraction fans) represent the main cooling system of the storage and handling building (BSM). Loss of this system is equivalent to loss of the electrical power supplies. In the event of loss of the electrical power supplies, the licensee indicates that the EDAC (criticality detection and alarm unit) is independent, as it has its own batteries with an autonomy of 8 h. Furthermore, the potential consequences of loss of the electrical power supplies are due to: the stopping of the extraction fans in storeroom MG1, and in the storage compartments in particular. The studies relative to the thermal conditions show that if this "process" extraction ventilation is stopped in the BSM fuel storage areas, the temperature levels reached are not such as to jeopardise the resistance of the cladding of the fissile elements and of the storage compartments themselves. Thus, according to the CEA, loss of cooling of the fuel and storage compartments in fissile material storeroom MG1 would have no impact on the containment of these materials or the sub-criticality of the storage area; the loss of dynamic containment of the BSM, which, given the leakage rates considered in the design, puts the BSM premises in equilibrium with the atmospheric pressure as soon as the extraction ventilation is lost. However, as the integrity of the fuel cladding (1st barrier) is maintained, loss of the second barrier would be of no consequence;
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