- 264 - The roof is angled to prevent water accumulating on the buildings; it has downpipes conveying storm water to the drainage system, an overflow guaranteeing water discharge if the pipe gets blocked, and a sealed coating. Roof-mounted equipment items are situated at height and the ventilation openings are protected against infiltrations. The ventilation penetrations are raised above the roof slab; In the connecting galleries, the fluid pipe and electric cable penetrations with the UN are raised above the ground surface of these galleries and sealed to prevent infiltrations. The Nuclear Materials Building (BMN) gallery has a gradient and a low wall perpendicular to the gallery allowing water to flow towards the BMR building which has a retention capacity of 200 m3. The BAGs are equipped with coamings and sumps. The upper slab of the BAGs and BMN, which acts as a roof, is on a gradient and has overhangs with a drip groove. With regard to water ingress into the safeguard auxiliary buildings (BAS) A and B, these buildings are raised and at different elevations on platforms with gradients that direct the runoff water towards the storm water drainage systems. The floors of the BAS buildings are raised by between 0.1 and 0.6 m with respect to the external finished ground surface. The diesel tanks supplying the backup generators are installed in pits protected by concrete slabs that prevent water infiltration. Lastly, the CEA underlines that no drainage channel can create a communication between the two BAS buildings (geographical separation): the storm water drainage channels of BAS A discharge to the Eastern edge of the site; the storm water drainage channels of BAS B discharge to the Western edge of the site; Regarding water ingress by water table rise and exceptional storm water infiltration, the UN is protected against flooding by: the sealing of the internal surface of the UN basemat (-3 m level) and of the primary bunkers; the lower basemat of the UN which supports the paraseismic supports designed to withstand the uplift in an accidental rise of the water table; the reinforcement of the excavations (passive nailing of the bedrock, pneumatically placed reinforced concrete walls, bored drains and barbicans); the UN drainage system, which is independent of the storm water drainage system, collects the water table rise water and rain infiltation water and discharges it to the Ravin de la Bête. As regards the buildings other than the UN, some are situated at higher elevations than the 100-year water table rises (BAS B and BAG B), and are therefore protected against water ingress. The other buildings have peripheral drainage systems capable of draining to the storm water drainage system an envelope value equivalent to a 100-year water table rise. Regarding the operating measures for alerting to the imminence of a flood and mitigate its consequences, the ground water level is periodically checked by the piezometers situated near the facility. The frequency of these inspections can be increased according to the evolution of the water table level. Flood detectors carried over to the control room alert the operator to the infiltration of water in the buildings BAS A and B, BAG A and B, and the lower basemat of the UN. Conformity of the facilities to the current frame of reference The CEA specifies that the storm water drainage system is inspected periodically and cleaned as required to remove any material that could block the channels. Periodic inspection rounds are carried out in the lower basemat to check the condition of the system draining the water to the Ravin de la Bête. Cleaning is carried out if necessary. If a flood significantly higher than a 100-year flood were to cause water ingress in the lower basemat, the following measures would be taken: inspection of the condition of the structures and mechanical parts of the inter-basemat space; inspection of the condition of the foundation basemat.
RkJQdWJsaXNoZXIy NjQ0NzU=