Vibration optimisation and seismic resistance of a hydraulic power plant

The challenge

How can the safety of critical equipment be guaranteed in the event of an earthquake?

A hydraulic power station used for nuclear fuel storage inter-pool transfer equipment must be capable of withstanding the seismic stresses imposed by its environment. The seismic resistance of this structure is a major issue if damage to key components is to be avoided.

In this context, the objective of the study carried out by Metravib Engineering was to assess the resistance of the hydraulic power plant to seismic loads and to propose solutions for strengthening its most stressed components.

The solution

To address this issue, our teams carried out an in-depth dynamic analysis to assess the resistance of the power plant and propose targeted improvements:

• Finite element modelling using ANSYS: a precise 3D model of the hydraulic power plant was built, incorporating mechanical stresses and the distribution of oil in the reservoir. 
• Modal analysis: this study identified the natural frequencies of the structure and assessed the critical vibration modes in the seismic stress spectrum.
• Seismic spectral calculation: a spectral simulation in the three main directions was used to estimate the dynamic stresses experienced by the hydraulic power station.
• Identification of critical points: the results revealed high stresses on the tank stiffeners (up to 172 MPa) close to the permissible limit. Targeted measures were proposed to reinforce these sensitive areas.

Thanks to this rigorous approach, Metravib Engineering has confirmed that the hydraulic power plant meets the seismic resistance requirements. The integration of localised reinforcements and optimised anchorages have increased the overall robustness of the equipment and ensured a high level of safety in the face of seismic stresses.