- 296 - Conclusion on the measures planned to protect the facilities against the risk of loss of the electrical power supplies According to the operator, the robustness of the electrical power supply is ensured by: the multiplicity of the power supply sources (redundant trains or off-site sources (RTE), multiple independent on-site sources); the multiplicity of the mutually interconnectable physical routing paths; the performance of preventive maintenance and periodic and regular inspections; the robustness of the backup diesel generator sets in the event of an earthquake. ASN considers that loss of the electrical power supplies on the La Hague site must not lead to a reduction in process safety (ventilations, pool cooling, FP tanks, etc.). Consequently this loss must be compensated by the implementation of robust manual reinjection means or passive protection means. This demand will be issued as a requirement. Loss of the cooling systems Feared situations in the event of loss of the cooling system Loss of the cooling systems could lead to a rise in the temperature of the stored high thermal power solutions (FP tanks) and the water in the pools. Design measures to prevent loss of the ultimate cooling system / heat sink The BNIs in operation are permanently cooled by: the systems associated with the NPH, C, D and E pools (each pool has its own cooling circuits); the cooling unit of the T2 unit supplying the units of the UP3-A plant (units T1, T2 and T7); the CNRS cooling unit supplying the units of the UP2-800 plant (units R1, R2 and R7). Although cooling of the UP2-400 plant facilities does not appear in the CSA report, the CRS3 cooling plant cools the units of the UP2-400 plant and the SPF4 unit of BNI 117. The cooling systems comprise: an "internal" loop specific to each unit, consisting of a demineralised water circuit; an "external" loop consisting of a demineralised water circuit allowing cooling of the internal loop via a system of "water/water" heat exchangers and removal of thermal power to the exterior via a system of cooling tower-type "water/air" heat exchangers. These systems include "active" equipment items such as motor-driven pumps that require electrical power to function. In a degraded situation, depending on the equipment items: their operation is ensured by one of the various electrical power sources presented in the preceding paragraph (particularly the backup electrical power supply: diesel generator sets), their design allows operation in "passive" mode, following the thermosiphon principle, as is the case with the "Nymphéas" heat exchangers of the pools and the cooling towers. The key components of these cooling systems are designed and verified to be able to withstand potential external hazards and in particular a design-basis earthquake exceeding the seismic hazard. Conclusion on the measures planned to protect the facilities against the risk of loss of the ultimate cooling system The licensee considers that the degree of equipment redundancy and the earthquake robustness study are sufficient to conclude that the cooling systems of the pools and the SPF5 and SPF6 units (cases that were studied) have good overall robustness. According to the licensee, the conclusions can be transposed to the
RkJQdWJsaXNoZXIy NjQ0NzU=