Design earthquakes for ITER in Europe at Cadarache. Comparison of the semi-empirical methods used according to the French regulation and the seismic probabilistic assessment of the site

Input requirements and assumptions for ITER consider that an infrequent, severe earthquake (called SL-2) which, although unlikely to occur during the lifetime of the facility, is assessed to demonstrate adequate protection of the public. This earthquake is assumed to have a return period of 10,000 years. An investment protection level or inspection level (where all Structures, Systems and Components are safe) with a peak ground acceleration (pga) at 0.5 m/s2 is also considered. As a basis, orders of magnitude of consequences, if no countermeasures were taken, are given. The European site proposed for ITER is situated in the South of France, 40 km North-East of Aix-en-Provence, in a low to moderate seismic area according to the Global Seismic Hazard Map (GSHAP Group 1999). The-tokamak building would be implemented on good bedrock made of limestone with a shear wave velocity of over 1,300 m/s. Four aspects are discussed: regulation, implementation of this regulation for the proposed site (site geology, tectonic, seismo-tectonic), a probabilistic seismic hazard assessment of the site has been performed using a methodology which considers uncertainties (this work has been developed by the team which had contributed to large parts of the GSHAP map study), finally the fulfillment of the requirements and assumptions are discussed, according to IAEA guides for instance. As a conclusion of the studies the main characteristics of the Cadarache European site are discussed: as a reference the standardized 475 year mean return period hazard (i.e. 10 % of chance to occur in 50 years); 10,000 year return period in accordance with the ITER assumption. Preliminary studies have shown that the European site proposal will ensure a low level of project risk with respect to the seismic hazard. (authors)