- 291 - The CEA indicates that the Ultimate Situation Measurement Acquisition System (SAMU) delivers sufficient information on the condition of the primary cooling system to different places in the facility, particularly further to accident situations adversely affecting transmission of this information to the control room, or loss of the control room, such as: a large sodium fire in the Reactor building; an earthquake that has destroyed the Reactor Building / Supervision-Office Building connecting passageway; loss of the control room; loss of the data logger distribution frame (RCM). The SAMU can be consulted via: a transportable consultation computer in the fall-back room, three transportable computers installed: o in the control room; o in the emergency room in the Supervision-Office Building; o in the handling building at level + 0.0 m. The CEA specifies that the processing unit, the racks and the frames supporting these equipment items are earthquake resistant. All the system connections and power supplies are made in earthquake-resistant cableways specific to the SAMU system. It is possible to obtain different types of information concerning the "relevant" measurements further to reactor shutdown at each of the SAMU consultation stations, particularly information relating to core reactivity, primary sodium temperature, condition of the ultimate backup system, etc. The SAMU is connected to a set of battery-backed busbars supplied by the ultimate backup diesel generators DE or DW in the event of a general loss of power. It also has an independent battery power supply with an autonomy of 6 hours. Consequently, the CEA considers in its CSA report that total loss of the electrical power supply would not lead to a cliff-edge effect. The electrical power supplies do nevertheless play a role in the monitoring of the condition of the facility in degraded situations (earthquake, flood in particular) The licensee's analysis of the risk of loss of electrical power supplies for the Phénix facility raises no particular remarks from ASN. ASN does nevertheless consider it necessary to conduct a complementary study to verify that freezing of the sodium does not jeopardize the integrity of the reactor vessel and the spent fuel storage drum. The CEA has undertaken to consolidate the analysis concluding that there is no risk of a cliff-edge effect if the sodium in the vessel and drum freezes. ASN will take this commitment up in a formal request. Loss of the cooling systems / heat sink In view of the state of the facility, which is in the decommissioning preparation phase, and the low residual power level of the fuel assemblies, the operator identifies no risk of a cliff-edge effect in the event of loss of equipment cooling or loss of the heat sinks. Combined loss of the electrical power supplies and the heat sink The CEA considers that loss of the electrical power supplies combined with loss of the heat sink would not lead to a cliff-edge effect given the state of facility. These conclusions regarding the loss-of-cooling-source risk for the Phénix facility raise no remarks from ASN.
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