CRUAS 2019 International Benchmark on a Seismic Base Isolated NPP Which Experienced a Real Earthquake

Ibrahim Bitar (1) , Emmanuel Viallet (2) , Maria Lancieri (3) , Benjamin Richard (1) , Adrien Guilloux (4)

1 IRSN/PSN-EXP/SES/LMAPS - Laboratoire de Modélisation et d’Analyse de la Performance des Structures
2 EDF - EDF
3 IRSN/PSE-ENV/SCAN/BERSSIN - Bureau d'évaluation des risques sismiques pour la sûreté des installations
4 EDF Labs

Cruas PWR Nuclear Power Plant was designed at the end of the 70’s. At that time, due to the seismic hazard evaluation at the site and considering the standard design of the French 900 MW NPP series, the decision was made to build the plant on seismic base isolation. Even though the technology used (laminated steel-neoprene anti-seismic bearings) was already well-known and widely used in conventional structures, issues were raised to apply this technology in a nuclear context, including definition of values for design characteristics (stiffness and damping especially), prediction of ageing (for long term operation), assessment of the behaviour in case of fire and actual improvement of the seismic response of the buildings including floor response spectra. These issues were initially addressed through appropriate design studies and qualification actions and complemented by a specific maintenance programs. This technology can now be considered as controlled for nuclear projects; however, it is still an open question within the international community and only a few NPP have been built with seismic base isolation. The lack of feedback from actual earthquakes recorded on such facilities remains an open issue (especially related to in-structure response). Nevertheless, new designs such as SMRs, Jules Horowitz research reactor (located in Cadarache site, France) or ITER are willing to apply this type of technology for both safety and competitiveness of nuclear industry. On November 11, 2019, a 4.9 magnitude (Mw) earthquake occurred at approximately 15 km from Cruas NPP (called Le-Teil earthquake). The peak ground acceleration values recorded in free-field are between 0.02 and 0.05g (in three directions for two monitoring stations); according to operational procedures, the in-structure response was also recorded. In addition, post-earthquake walkdowns were performed to collect in situ data on various SSCs. In this context, the objective of this paper is to present the main content of a new international benchmark under the umbrella of OECD/NEA that will start in early 2023 and run till 2024 in order to assess the adequacy of engineering practices to compute in-structure seismic response especially for this specific NPP isolated seismic base and to share experience among the larger community. More precisely, the benchmark will include two main phases: (i) characterisation of the seismic ground motion at Cruas site and (ii) assessment of the seismic response of Cruas base-isolated NPP. The lessons learned and consensus reached will be shared and discussed during an open restitution workshop. The content of each phase will be exposed during the presentation as well as the provisional schedule. Representatives interested in joining this challenging project will be invited to express their intention.

Domaines: Sciences de l'ingénieur [physics]

Ibrahim Bitar, Emmanuel Viallet, Maria Lancieri, Benjamin Richard, Adrien Guilloux. CRUAS 2019 International Benchmark on a Seismic Base Isolated NPP Which Experienced a Real Earthquake. 26th International Conference on Structural Mechanics in Reactor Technology SMIRT, Jul 2022, Berlin/Potsdam, Germany. ⟨hal-03738264⟩