The sinaps french research project first lessons of an integrated seismic risk assessment for nuclear plants safety
Résumé
Whatever the level of seismicity of a country, the seismic risk has to be assessed and accounted in the frame of
nuclear plant safety, from its design, during its operational as well as dismantling phases. The seismic risk assessment
combines the seismic hazard and the seismic vulnerability of the civil engineering and equipment estimates. Acceptable
methods to perform seismic risk analyses are guided by international references, such as the Safety Guides and
Requirements published by the International Atomic Energy Agency (IAEA) but also by national documents. The current
methodologies used in France to assess the seismic hazard are firstly the scenario-based approach proposed in the French
Fundamental Safety Rule (RFS 2001-01), and secondly the ASN/2/01 Guide providing design rules of nuclear civil
engineering structures. These references were respectively updated by the Nuclear Safety Authority in 2001 and 2006. Since
then, the 2011 Tohoku earthquake that triggered a huge tsunami caused the severe accident at the Fukushima Daïchi nuclear
plant. The analysis of the observations demonstrated that the seismic and tsunami hazards were underestimated for this
region. Consequently worldwide nuclear operators were asked by their authority to perform “stress tests” to estimate their
plant capacity sustaining extreme seismic loadings. In this framework, an 5 years research project called SINAPS@
(Earthquake and Nuclear Installations: Ensuring and Sustaining Safety) is on-going in France. SINAPS@ brings together a
multidisciplinary community of researchers and engineers, funding also 12 Ph.D. and 19 post-doctoral researchers.
SINAPS@ aims at conducting a continuous analysis of completeness and gaps in data bases (all data types, from geology,
seismology, site characterization and materials), of the reliability or deficiency of models available to describe physical
phenomena (prediction of seismic motion, site effects, soil and structure interaction, linear and nonlinear wave propagation,
materials constitutive laws in nonlinear domain), and of the relevance or weakness of methodologies used to performed
seismic risk assessment. This critical analysis conducted confronting methods, either deterministic or probabilistic, and
available data to the international state of the art systematically addresses the uncertainties issue, should improve the
seismic margins assessment. The present contribution will expose the first lessons learned from SINAPS@ few 18 months
before its end.
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