- 101 - Earthquake-induced explosion risk: Application of the SSE design requirement to the hydrogen systems and inclusion of the "event earthquake" approach for lines carrying hydrogen in the nuclear island, is in progress on the N4 plant series, and is scheduled: between 2009 and 2019 for the 900 MWe rectors, between 2015 and 2023 for the reactors of the 1,300 MWe plant series. ASN will ask EDF to speed up application of the SSE design requirement to hydrogen systems and the implementation of the "event earthquake" approach for lines carrying hydrogen. The hydrogen presence detectors and the shut-off valves situated outside the reactor building are not covered by seismic strength requirements. ASN will be asking EDF to guarantee the ability of this equipment to withstand a SSE and to supplement the forthcoming safety requirements. ASN considers that management of the explosion risk, for these lines, also entails correct application of a maintenance programme and ensuring that there are no nonconformities. 2.1.3 Conformity of facilities with existing safety requirements The conformity of nuclear facilities with the safety requirements that are applicable to them is a key component of their safety and their robustness to accident initiators or hazards. For ASN, this conformity must be continuously managed and be based on a systematic search for possible nonconformities, which must be dealt with in a way commensurate with the safety stakes. The detection, notification and processing of nonconformities are now the subject of ASN requirements defined in the order of 10th August 198411 and in the general operating rules for nuclear power plants which, for example, specify the time within which the reactors must be shut down according to the importance of the nonconformity. These nonconformities may be the result of errors in the initial design, the construction, modifications made during the course of operation or during maintenance operations, but also following reassessments of the safety requirements stipulated by ASN during the periodic safety reviews. They may for example concern equipment whose ability to resist an earthquake to be withstood by the facilities is not be guaranteed. EDF's general organisation for guaranteeing conformity The review of the seismic conformity of the equipment, conducted by the licensee and checked by ASN, comprises a number of complementary parts: the detection of nonconformities, particularly concerning maintenance and scheduled periodic tests, examination of unit conformity (ECOT) and the complementary investigation programme (PIC), performed as part of the periodic safety reviews, incorporation of international operating experience feedback, performance of specific studies or inspections dedicated to evaluating the seismic robustness of the facilities (robustness diagnosis, implementation of the Seismic Margin Evaluation-SMA method, etc.). The basis of this examination is the updated safety requirements, both for the hazard and for justification of the seismic strength of equipment and structures. The conformity evaluation of the equipment and structures is an opportunity for a regular review, based on specific checks and studies, of the adequacy of their initial design. ASN considers this organisation to be pertinent. Processing of seismic nonconformities: Seismic-classified equipment undergoes maintenance in accordance with the maintenance programmes, as do the anchors and supports. 11 Order of 10th August 1984 concerning the quality of design, construction and operation of basic nuclear installations.
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