- 232 - Socatri The feared situations are the dispersal of radioactive and chemical material into the environment. Atmospheric releases would not lead to significant consequences off the site. However, spillage of the STEU (Uranium-containing Effluent Treatment Station) tanks into the alluvial water table and hence into the river Gaffière, would have an impact of a few millisieverts over a year if no protection measures are taken. The following areas of the Socatri site are concerned by the studied accident situations: the uranium-containing material storage areas; Andra's low-level activity long-lived waste (LLW-LL) storage areas; the interim storage areas for waste pending shipment and maintenance equipment for the NPPs; the storage of uranium-containing effluents from the STEU. ASN considers that the identification of the feared situations for Socatri must be supplemented by the inclusion of the flooding and induced effects scenario (criticality risk). TU5 W Given the materials and processes implemented, the only substances present in significant quantity that could be disseminated and present a risk outside the site are the HF and the liquid or gaseous UF6. With regard to the TU5 and W facilities, the operator indicates that the processes involving the largest quantity of dispersible substances (liquid UF6 and HF) are located in the "emission" and "HF storage" areas of the W plant. Fire and explosion have not been retained as risks that could cause a feared situation. For the TU5 and W facilities, ASN considers that the absence of a cliff-edge effect for the fire and explosion scenarios must be substantiated. For the TU5 unit, which is designed to the SSE (safe shutdown earthquake), the feared situation in a typical SSE ++ scenario would be external spillage of uranyl nitrate (16 m3 at 380 g/L), which would have no immediate consequences on the neighbouring populations but would require the implementation of a soil management plan to treat it. The feared situations for the W plant are: for HF storage, the formation of a slick of HF on the ground following loss of retention area integrity and the impossibility of using the oil spreading system (320 t of HF over 1235 m²) in the event of SSE (tanks not built to this design-basis); for the emission building (building used to deice the 48-inch containers and emit UF6 in gaseous phase to the defluoridation ovens), leakage of gaseous UF6 from the containers during emission and heating (57 t of liquid UF6), in case of SSE (area not built to this design-basis); for the hydrogen yard, leakage of H2 with production of ignited jets and H2 explosion, with domino effect leading to the release of HF or UF6 or U3O8 in case of SSE (risk of hose being pulled out). For the storage yards For yard P09 (storage of cubes of depleted U3O8), the feared situation is the dissemination of material outside the building as a result of collapse on containers and damage caused to them. The licensee indicates that the updating of the W plant hazard study will take into account a realistic envelope number of damaged containers, and that this scenario will lead to negligible releases. Finally, the most penalising configurations considered by the licensee are: the leakage of 320 tonnes of HF in the HF storage of the W plant; the leakage of 57 tonnes of liquid UF6 from the ovens in the emission area of the W plant. The licensee has identified the following key SSCs for these feared situations:
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