- 269 - 3.3 Nuclear fuel cycle facilities (La Hague, Tricastin, Mélox, FBFC) 3.3.1 Tricastin site Design AREVA indicates that the site flood protection level is set at 51.1 m NGFO (French orthometric datum system). The Georges Besse I plant The floor of the BNI is situated at level 49.50 m NGFO. No equipment items containing radioactive materials are installed below the 53.50 m NGFO level. Only the UF6 containers could be reached by a flood. Comurhex The land covered by the Comhurex facility is situated at an elevation equal to or higher than 51 m NGFO, the buildings having a slightly higher elevation and the retention areas being protected against rainwater runoff by low walls. The environmental consequences of a flood are therefore limited to leaching of the soils, representing about 900 grammes of uranium. The minimum elevation of the floors of Comurhex II is 51.40 m NGFO, which guarantees that the facility is kept out of water. Socatri The licensee's file presents no particular information on the consequences of a flood on the facility. Nevertheless, previous studies (safety review, safety options file of the TRIDENT project) show that the facility is floodable with respect to the current frame of reference. An increased 100-year return storm could create a flash flood of about 20 cm height and loss of certain electrical power supplies and information feedback (the minimum elevation of the effluent treatment stations is 47.70 m NGFO). This aspects is studied in the ongoing periodic safety review. TU5 W The sensitive areas that could be impacted by a flood are: "HF storage" area of the W facility "emission" area of the W facility "HF storage" area The risk considered by the licensee in the event of flooding is the lifting of tanks. The licensee indicates that the design of the HF storage tanks is based on two different principles: Storage SHF1: The tanks are installed on concrete blocks placed in retention tanks protected by a low surrounding wall. In this case, above a filling factor of 71% (the licensee states that the tanks are either empty or filled to more than 75%), the tanks cannot be lifted by the water, whatever the height it reaches. Lifting an empty tank has no impact. Storage SHF2: The tanks are anchored on a concrete foundation, placed in retention tanks, protected by a low surrounding wall. In this case the anchoring of the tanks totally excludes the risk of them being lifted by the water, whatever the height it reaches. "Emission" zone The risk considered by the licensee in the event of flooding is the lifting of the containers and the pulling out of pipes. The containers of solid-phase UF6 are placed on handling trolleys whose low point is 96 cm above the unit floor. They are connected to drying ovens by needle valves situated 2 m above the ground. The first manual
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