Context and research themes
The safety of any nuclear installation (reactor, plant, storage, research centre) must be ensured, even in the event of an earthquake on the site. These requirements mean that seismic risk must be incorporated in the design calculations for installations, and therefore, in the first instance, the characteristics of the earthquakes liable to occur on the sites where they are located must be evaluated.
Berssin has the following missions:
- To carry out assessments of the seismic hazard for basic nuclear installations (power reactors, laboratories and plants, surface storage sites, etc.). These assessments are performed in the context of technical support to the Nuclear Safety Authority (ASN).
- To perform research in geology, geophysics, and seismology in order to evaluate the seismic hazard. This work is also used as a basis for the updating of regulations.
- Berssin participates in the revision of national and international regulations in the field of seismic hazard for nuclear installations. Berssin also provides technical support to the Ministry of Ecology, Energy, Sustainable Development, and Land Use Planning (Meddat), particularly for the revision of the regulations applicable to standard buildings and facilities classified for environmental protection.
Evaluation of seismic risk, whatever the installation concerned (nuclear or not), requires:
- The geological sources liable to produce earthquakes (active faults) to be identified and located,
- The size (magnitude) of potential earthquakes to be estimated,
- An estimate of the soil displacement expected on the site in the event of earthquake, taking into account the nature of the soils under the installation (site effects).
To improve the knowledge and practices associated with each of these stages, BERSSIN conducts studies, generally in collaboration with national or international scientific bodies.
Identification of active faults
The characterization of the activity of a fault (i.e. its potential to generate an earthquake) or the discovery of new active faults in France is necessary to serve as a basis, confirm or improve evaluations of the seismic hazard. This work combines different approaches (study of anomalies in the morphology using numerical field models and Spot photos, field geological studies, and creation of trenches to find traces of paleoseismic events). This type of project is currently conducted by Berssin on the Vuache fault (Jura), which is most notably responsible for the earthquake that caused damage in Annecy in 1996.
This type of project is also studied as an active fault in a context of moderate deformation. A network of seismological stations and two GPS stations are operational around the fault.
Study of site effects
These effects of amplification of the seismic movement in the sedimentary basins are capable of significantly modifying the local seismic hazard. Following the drilling of a deep borehole at the instigation of the IRSN in 1999, the Grenoble Basin has become the French test site for the observation of these site effects in deep valleys: various teams are participating in this research.
Berssin also works on this topic in areas of seismic activity: