- 236 - Other facilities ATPu The licensee has identified the release of plutonium outside the site as being a feared situation. This situation could arise in the event of partial or total collapse of the building further to an earthquake. The licensee has defined the following as key SSCs: the civil engineering structure of the ATPu, the anchoring devices of the glove boxes and other equipment forming the primary containment system, and the seismic detection system and automatic cut-off of electrical power supplies and water infeeds. The aim of this automatic cut-off, which occurs in the event of acceleration of 0.65 m.s-2 or 0.065 g, is to limit the indirect effects of the earthquake, notably fire and internal flooding. Loss of these "key SSCs" would lead to the dissemination of a larger quantity of radioactive material than that considered in the on-site emergency plan (PUI), which could lead to pollution of the water table. ASN considers that the identification of feared situations for the ATPu is satisfactory. Masurca The CEA takes a feared situation for the facility corresponding to partial or total collapse of the handling and storage building (BSM) containing the nuclear material. This situation could potentially be aggravated by a criticality accident or a sodium fire. Thus, the key equipment items identified by the CEA are the civil engineering of the BSM and the material storage systems in store MG1 (storage compartments, boxes, etc). The CEA considers the overhead travelling stacking crane in store MG1 as a potential hazard for the key equipment. ASN considers that the identification of the feared situations for Masurca is satisfactory. 1.4 ASN's overall assessment of the identification of the feared situations ASN considers on the whole that the feared situations have been satisfactorily identified in the initial approach, even if they require supplementing for AREVA's La Hague site to particularly integrate combined accident situations. After this feared situation identification exercise, ASN considers that the licensees must focus on defining a hard core of reinforced material and organisational provisions. The idea is to give these facilities means for coping with: combination of natural phenomena of an exceptional scale, greater than the phenomena considered in the design or the periodic safety review of the facilities; severe accidents, particularly very long-duration loss of electrical power supplies or cooling functions that could affect all the facilities on a given site. ASN will thus instruct the licensees to establish a "hard core" of robust material and organisational provisions, reinforced if necessary, to guarantee the operability of the structures and equipment necessary for controlling the fundamental safety functions in these exceptional situations. These provisions must ensure an ultimate protection of the facilities, with the following three objectives: prevent or mitigate a severe accident; limit massive releases in an uncontrollable accident scenario; enable the licensee to fulfil the emergency management duties incumbent upon it. ASN will ask the licensees to submit to it for approval the requirements applicable to this hard core, which must be defined adopting fixed margins that are significantly higher than the current frame of reference.
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