- 245 - Measures proposed to reinforce the robustness of the facilities to the seismic risk The ILL has undertaken to solve - during the 2011-2012 winter shutdown, and in any case before the reactor is restarted - the major nonconformities with respect to its previous commitments, notably following the last periodic safety review. Furthermore, in 2008, as part of the continuous improvement in HFR safety, the ILL proposed installing two new safeguard systems, the ultimate reflooding system (CRU) and the seismic depressurisation system (CDS), which is currently in progress. At the end of its complementary safety assessment procedure the ILL undertook to: put in place during the winter 2011-2012 shutdown, the ultimate reflooding system for maintaining the water inventory and therefore core cooling in the event of a breach on portions of the primary cooling system that do not have sufficient margin; put in place for the shutdown of winter 2012-2013, the new safeguard system, the CDS for managing the possible depressurisations of the containment after core meltdown (designed to guarantee its operation in the SSE + σ earthquake). Lastly, the ILL has undertaken to reinforce the equipment identified in its CSA procedure (key SSCs and potential threats to the key SSCs) or to study their reinforcement . ASN requests to reinforce facility robustness ASN considers that the ILL's procedure for evaluating the robustness of the HFR facility to the seismic risk is satisfactory. ASN notes that the licensee has undertaken to bring rapidly into conformity the equipment items requiring reinforcement. ASN also underlines the improvements aiming at installing earthquake-resistant systems to guarantee cooling of the fuel elements and limit releases to the environment. ASN considers that these complementary actions must be carried out. It will issue demands regarding these points to the licensee, some of which will be requirements. 2.3 Nuclear fuel cycle facilities (La Hague, Tricastin, Mélox, FBFC) 2.3.1. Tricastin site Design-basis earthquake For the Tricastin site AREVA presents an assessment of the expected seismic behaviour of the facilities under the SSE resulting from application of RFS 2001-01. It was requested in the examination that this site, which - like the Marcoule site - is situated above the Messinian paleovalley, undergo a specific site effects study to evaluate the seismic ground motion to be considered, as recommended in RFS 2001-01. AREVA retained the following scenarios for the entire Tricastin platform: safe shutdown earthquake (SSE) of magnitude 5.5 (scenario 1); earthquake of magnitude around 6, called SSE + (scenario 2); earthquake of magnitude around 6.5, called SSE ++ (scenario 3); flood corresponding to a water flow rate of 300 m3/s in the siphons supplying the river Gaffière, resulting from extreme climatic conditions or a breach in the embankments of the left bank of the canal (scenario 4); flooding corresponding to a breach of the embankment of the right bank of the canal (scenario 5); SSE ++ earthquake leading to a flood (scenario 6); SSE++ earthquake combined with a fire (scenario 7). Georges Besse I plant Regarding the seismic behaviour of the enrichment cascade, the licensee considers that: the structure of the manifold caissons of plant 120 would remain stable in the SSE with a margin of about 30%; the posts however would crack if the reinforcements were not plasticized;
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