- 249 - The potential source term is 99 tonnes of liquid UF6 (coming from seven 48Y containers and five 30B containers). In the event of an SSE + or SSE ++ earthquake, the liquid UF6 would spread in the autoclaves. Given the loss of leak-tightness of the autoclave door inflatable seal in such a scenario, it is possible that 30 tonnes of liquid UF6 could leak from the autoclave into the building. Some of the liquid UF6 would vaporise instantly. This would lead to hydrofluoric acid and uranium hydroxide releases into the environment. The licensee has carried out a study which shows that even without mitigation actions, the radius of the zone of significant hazards for human life is less than the envelope radius of the off-site emergency plan (PPI). Measures envisaged to increase the robustness of the facilities to the seismic risk The Georges Besse I plant On completion of its review of the Georges Besse I plant, ASN considers that the earthquake resistance of the equipment items must be ensured. It will require the licensee to propose measures proportional to the risk of the operations leading up to the shutdown of the facility. For the specific risks associated with the preparation for facility shutdown, then the phases of final shutdown and decommissioning4, ASN will issue the necessary requirements after examining the corresponding authorisation requests. Comurhex On completion of its review of Comurhex, ASN considers that the earthquake resistance of the infrastructures, particularly the fluorine production unit and the risks associated with chlorinated and fluorinated compounds, must be addressed specifically. This facility is currently subject to the regulations governing ICPEs (installations classified on environmental protection grounds). ASN will propose the requirements to the competent Authority. Socatri On completion of its review of Socatri, ASN considers that the earthquake resistance of the infrastructures, particularly the URS building, must be addressed specifically. It will issue requirements on this subject. As a general rule for the Tricastin site as a whole, ASN considers that the earthquake resistance of the emergency management rooms must be addressed specifically. It will issue requirements on this subject. 2.3.2. The La Hague site Design-basis earthquake (DBE) In its complementary safety assessment (CSA) report, the licensee indicated the design-basis spectrum used for each unit (building and equipment), and where applicable the spectrum used for the last periodic safety assessment. Given the year of their construction, many buildings are not subject to earthquake design requirements. Several spectra are thus considered: DBE 1976 for UP2 400, HAO and NPH; DBE 1979 for UP2 800, UP3-A, STE2, ACC, EEVSE, fission product storage areas; DBE 2001 for the last 10-year safety assessment of UP3-A and STE3. 4 Risks not taken into account in the CSA report submitted by the licensee, which in accordance with ASN decision of 5 May 2011, considers the state of the facility on 30 June 2011
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