- 52 - must be demonstrated in flood accident conditions. Finally, the licensee shall ensure that its drainage networks are kept in good condition. Tricastin site Concerning the Tricastin site, protective structures have been built along the Gaffière river upstream, at the site and downstream, to prevent the risk of flooding by a high water level potentially capable of occurring every 500 years. These works were performed following the "flooding" advisory committee meeting of 2007. Their purpose is to protect all the facilities, except for the Socatri establishment and the Tricastin operational hot unit (BCOT). The inspections highlighted that there was no inspection, testing and maintenance programme for these new structures. In the event of off-site flooding, some premises of the Socatri and Eurodif establishments would need to be protected by the installation of cofferdams, but there is also no programme of periodic checks and maintenance for this equipment or of its seating surfaces. Moreover, to the south of the site, in the event of large-scale flooding, the water could enter the Socatri facilities, in particular the fissile materials storage building. In the inspection follow-up letter ASN asked the licensee to check whether tie-down would be affected if the building were flooded. This tie-down would help prevent the criticality risk. For the entire site, the inspectors revealed that particular attention would be needed on the upkeep and monitoring of the rainwater networks, which must guarantee the water drainage capacity in the event of heavy rainfall. An up-to-date drawing showing the locations of the rainwater drains and a servicing plan for these drains were requested. To conclude, for the facilities examined, protection against the risk of off-site flooding would seem to be provided through compliance with the safety frame of reference in force. Periodic inspection, maintenance and testing programmes will need to be drawn up, with appropriate intervals, and will have to be followed. Nuclear fuel fabrication facilities (Mélox, FBFC) Concerning Mélox, for reasons related to prevention of the criticality risk, Pu oxide in the form of powder or solid can only be used in areas without water. This constraint includes fire-fighting measures. As of 1985, COGEMA aligned the design principles of the Melox plant with the provisions adopted for the NPPs (RFS I.2.e): safety maximum thousand year flood CMM (increased by 15%) and the proposed location of "sensitive" buildings on the high ground of the site chosen. The safety study (safety report index B August 2005) thus selected 4 scenarios: rising groundwater, torrential rain (Cévennes mountains storm phenomenon), flooding of the Rhone river, Rhone embankment burst in the event of an earthquake. With regard to the first two points, flood risk prevention is based on construction measures and the quality of construction. The Mélox facility, on the higher part of the site (+40 NGF), places the plant out of reach of the Rhone flood safety margin level CMS (+37.5 NGF), the effects of this high water on the outflow channel and the consequences of an embankment burst. The site analysis enclosed with the preliminary safety analysis report (February 1988), the design options and the resulting choices, are a robust package which has never been called into question since the plant was commissioned (February 1995). The points at which information arrives from the outside are the general surveillance post (PSG) and the nuclear materials protection post (PMN). This information is transmitted to the shift supervisors. Finally, Mélox can receive the support of the AREVA flooding referral agent. There are also agreements between Mélox and various points of contact: Météo France, CNR, CEA, in particular the FLS and the civil security services, the dam operators and the office of the préfet of the Gard. Mélox also maintains close ties with the departmental fire and emergency service (SDIS). For the Marcoule sector, CEA at Marcoule is responsible for keeping a watch and has thus installed and operates the necessary monitoring resources. Mélox however has its own weather station but does not have its own system for monitoring the level of the Rhone river or the groundwater.
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