- 25 - rules to be applied to prevent the effects associated with earthquakes. EDF also applies RFS I.3.b relative to seismic instrumentation. Stakes An earthquake can have simultaneous effects on several parts of a nuclear facility and its environment. It can cause an event initiating an accident, while disabling the safeguard systems designed to deal with this initiating event. It can have more wide-ranging effects on the facility and its environment, such as an outbreak of fire or the loss of electrical power to the facility. The design principle adopted is that the plant must be designed to be restored to and maintained in safe shutdown conditions after an earthquake corresponding to a hazard level at least equivalent to that of the safe shutdown earthquake (SSE). The equipment, systems and structures, to which behaviour and performance requirements are allocated (integrity, functional capability, operability). Consideration must also be given to the possible failure of elements having no safety role but which, in the event of an earthquake, could constitute a hazard for systems contributing to safety from the seismic risk viewpoint. Inspection frame of reference EDF describes the results of its evaluations and the resulting protection measures in each of its safety reports, which are periodically assessed by ASN through the periodic safety reviews conducted on the facilities. The sites also rely on operational documents, to anticipate and manage an earthquake situation. This for example includes reports of periodic tests or maintenance performed on the instrumentation used by the sites in the event of an earthquake. The purpose of the inspections on this topic was to check the conformity of the facilities with this frame of reference. These inspections in particular involved field visits and exercises to assess the effectiveness of the organisation put into place by EDF. 2.2.2 Organisation During the course of the inspections, particular attention was given to analysing the effectiveness of the planned organisational arrangements in the aftermath of an earthquake. For the purposes of this analysis, the inspectors used the organisation memos in effect, the breakdown of responsibilities and the training plans for the on-site and external respondents. An exercise simulating the occurrence of an earthquake was also performed on virtually all the sites inspected, to check that the measures stipulated in the memos are possible and are performed correctly in good time. Seismic frame of reference ASN considered it satisfactory that certain sites have a seismic coordinator. However, the inspectors observed that several sites had not appointed this person (with a list of duties, training qualifications, responsibilities) and provided no evidence of any training on this point. Post-seismic operating documents Inconsistencies were found in certain operational documents used in the event of an earthquake (for example, inconsistent flowchart and procedure text, inversion of the numbering of the 3-axis accelerometers on the EAU4 rack, in particular at Flamanville). A number of instructions also fail to indicate how to respond to unavailability of one of the measurements (for example, at Chooz in the event of a failure of the accelerometer on the floor of the reactor 1 building fuel pit floor). Finally, certain operating documents do not meet quality standards (validation date, handwritten annotations, etc.). Section 2.3 of RFS I.3.b ("Operation of seismic instrumentation") states that: "if the earthquake level corresponding to a spectrum with an amplitude half the design response spectrum for the site is exceeded by any of the measurements, the licensee shall immediately go to the shutdown state considered, for each unit, to be the safest". The procedure on certain sites concerning what to do in the case of an earthquake 4 EAU rack: Containment instrumentation system for seismic monitoring and measurement
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