Enhancing safety: improving seismic risk assessments

CERN is located in a particularly complex geological setting, which also happens to be prone to earthquakes. Seismic events of a certain magnitude have the potential to inflict substantial damage or lead to equipment failure, which naturally poses a risk to both personnel and assets.

Complex research infrastructures like CERN often boast unique technologies and equipment hidden deep underground. This presents a unique set of challenges, since there are currently no regulations covering either the structural systems or the subterranean infrastructure, resulting in a lack of established procedures for conducting seismic risk assessments. Regarding radiation shielding in particular, the prevailing approach frequently involves using high-density blocks to achieve the required level of shielding, an exceptional solution that is not regulated by European or Swiss norms.

To bridge this gap and identify feasible solutions, CERN's HSE unit and SCE and BE departments have been carrying out dedicated research for the last three years, in collaboration with the Swiss Federal Institute of Technology Lausanne (EPFL), the California Institute of Technology (Caltech), the University of Montpellier and the European Centre for Training and Research in Earthquake Engineering (EUCENTRE). Together, they have performed full-scale seismic tests on a large shaking table at EUCENTRE to observe the dynamic behaviour of stacked concrete blocks. The numerical models were calibrated using the test data, enabling the simulation of the seismic behaviour of real block configurations at CERN. This research provides the basis for a novel methodology for the seismic risk assessment of this kind of structure, which is currently applied as a routine activity in areas such as the PS, SPS and LHC complex. Furthermore, the research has resulted in a clear procedure for calibrating the numerical models, as well as a methodology and risk assessment process that will be applied to future block configurations in new experiments and facilities to be built at CERN.

The collaboration was recently awarded the "Best Paper Award 2023" by the Engineering Structures journal for the paper entitled "Shaking table tests for seismic stability of stacked concrete blocks used for radiation shielding". According to Marco Andreini, senior structural engineer in the HSE-OHS group, "this award recognises the significance and impact of our work, not only for CERN but also for other similar complex infrastructures around the world."

Looking ahead, it is hoped that this novel approach can be used by other large research infrastructures and beyond.