- 30 - ASN finds that EDF needs to review its calibration procedures and their implementation in order to comply with the requirements of RFS I.3.b. Setting of free field sensor trigger thresholds RFS I.3.b (§ 2.2.2.1) states that the equipment making up the seismic instrumentation must allow measurement of accelerations with a scale range of at least 0.01 g to 1 g. On several sites (Golfech, Civaux, Flamanville, Penly, Tricastin, Paluel), the free field accelerometer is set such that accelerations of less than 0.25 g may not trigger the alarm in the control room. The free field accelerometer is in fact the soil motion reference, independent of the influence of the construction on the site. ASN finds that for all its sites, EDF must verify the alarm settings related to the free field sensor recordings and, as necessary, restore conformity with the requirements of RFS I.3.b. 2.2.4 Event earthquake approach Some functions and equipment require seismic qualification to guarantee complete availability following an earthquake. Moreover, the operation of this equipment must not be affected by equipment that is not seismic classified. As of the second ten-year in-service inspections of the 900 MWe plant series, EDF thus initiated what is known as the "event earthquake" approach, the aim of which is to prevent any damage to an item of equipment important for safety (IPS) by a non-IPS item. This approach applies to all the EDF reactors. This rule guarantees that the IPS equipment remains available after an earthquake occurs. Integration of the national frame of reference and risk analyses The EDF head office departments established rules for integrating this approach (potential hazards and associated countermeasures) into a requirement (operational integration of the event earthquake) that the sites are required to incorporate into their local safety requirements (organisation memos, procedures, training programme, etc.) no later than 6 months after receiving them. Certain sites (Bugey, Chooz for example) are late in integrating the national frame of reference with regard to consideration of the risk of damage to equipment important for safety. This delay concerns the integration of "event earthquake" requirements into the provisions applicable to worksite phases during which temporary equipment such as scaffolding or biological protection is deployed and could constitute potential hazards. The earthquake is therefore not incorporated into the processes used for analysis of the worksite risk (Bugey, Cattenom, Chooz). ASN finds that the event earthquake approach needs to be incorporated into the site procedures as rapidly as possible, in particular for the worksite risks analyses. Implementation of the approach through the field visits The field visits showed that the earthquake event risk merits greater consideration; for example, the inspectors detected the following: Civaux electrical building: several mobile (wheeled) parts of unplugged electrical cabinets were not blocked and, in the event of an earthquake, could strike cabinets containing equipment important for safety; in an area close to the control room at Golfech: presence of several items liable to damage electrical cabinets containing equipment important for safety; Tricastin and Saint-Alban control rooms: presence of a wheeled console (needs to be mobile so that the operating procedures can be more easily moved around, in particular those concerning accident situations) whose wheels were not immobilised and not secured to the ground in front of the control room monitoring equipment and an extinguisher; Saint-Alban control room: computer monitors in the control room liable, in the event of an earthquake, to fall onto the facility control keyboards and pushbuttons. The inspectors did however note the reactivity of the Flamanville site, which took steps regarding the items (repositioning or removal of the drum) liable to constitute a risk for the electricity generating set fuel tanks.
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