- 282 - As regards the Pascal pond (2 500 m3), the licensee considers that any leaks would tend to flow southward without having any significant impact on the site. The CEA also presents envelope scenarios for rupture of all the water systems inside the reactor and handling buildings, leading to maximum water depths of 5 cm and 10 cm. Two pipe rupture cases in the peripheral buildings were also studied, one concerning the link with the water tower, the other with the Rhône. The operator concluded that there was no cliff-edge effect regarding the flooding of the buildings. In this context the CEA proposed the following improvement measures in its complementary safety assessment report: Study the creation in the reactor building of a preferential flow path channelling water towards the basemat recesses and avoiding contact with the sodium equipment; Seal an opening giving access to sodium tank situated at the reactor building low point; Establish an instruction for shutting down the raw water pumps further to an earthquake. ASN considers that the licensee's proposals to reinforce the Phénix facility's robustness to the risks presented by other extreme phenomena (meteorological phenomena and combined earthquake and flooding) are acceptable. ASN may give them formal request status (some are already concerned by the flooding aspect). 4.2.2. Reactor operated by the ILL The worst-case flood would result from failure of the Monteynard dam, which is totally independent of, and unaffected by, even extreme meteorological conditions. This paragraph is therefore not applicable to the HFR once the case of a flood further to failure of the most penalizing dam - the Monteynard dam - has been taken into account and used as the design basis (see "flood" section). 4.3 Facilities in the nuclear fuel cycle (La Hague, Tricastin, Mélox, FBFC) 4.3.1 Tricastin site All the facilities on the Tricastin site, with the exception of Comurhex, were designed in accordance with the Snow and Wind 65 (NV 65) rules. According to the licensee, no extreme snowfall, wind or temperature events would lead to a more severe accident than those mentioned before. Furthermore, the kinetics of these events would be sufficiently slow to allow the facilities to be placed in safe condition. AREVA has also undertaken to consider in its analysis of extreme meteorological phenomena due for submittal in the 1st quarter 2013, the consequences of exceptional wind speeds defined on the basis of local experience feedback, evaluating all the related effects (negative pressure, resistance of chimney stacks, etc.) and the impact of any induced projectiles on the key SSCs. TU5 W The risk associated with tornadoes or very strong winds lies in possible "missile" effects that could damage sensitive structures where there is an explosion risk. In this case it concerns the hydrogen storage yard and racks of the W facility which, given its location, could cause two types of accident: hydrogen leak creating a cloud of hydrogen gas which subsequently explodes; hydrogen leak with production of an ignited jet that heats a nearby gas tank causing it to explode. The licensee considers that neither of these two scenarios is likely to cause a severe accident, therefore it does not envisage implementing additional measures. ASN considers that, given AREVA's commitment to study the effects of very strong winds, the procedure its has adopted is satisfactory. ASN may ask the licensee for targeted reinforcements, depending on the results of this study.
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