Seismic Response Analysis of Small Modular Reactor Containment Based on LRB and FPS Isolation Strategies

Small modular reactor (SMR) refers to a new generation of reactors with a unit power output of less than 300 MW. These reactors utilize innovative technologies for modular design and rapid on-site assembly. The assurance of structural seismic safety becomes a crucial prerequisite for the commercial application of SMR. Traditional seismic resistance theories enhance the strength and stiffness of the structure itself to resist earthquake-induced damage. In contrast, seismic isolation theory employs isolation devices to absorb and dissipate seismic energy, thereby reducing structural deformation and damage and better protecting the internal equipment and piping. To verify the effectiveness of different seismic isolation strategies for SMR under safe shutdown earthquake (SSE) conditions, this study uses the finite element method (FEM) to conduct three-dimensional modeling of the SMR containment structure. Modal analysis is performed to extract the first four modes of vibration and natural frequencies of the structure. Lead rubber bearings (LRB) and friction pendulum systems (FPS) were utilized for the seismic isolation design of the SMR structure, and finite element models of the isolated SMR structures were established. Subsequently, seismic response analyses of the SMR containment structure were conducted. By studying the structural response under SSE and double SSE conditions, the applicability of different seismic isolation strategies for SMR was evaluated. The results show that the natural vibration periods of the SMR containment structure are extended to 2.46 s and 2.53 s based on the LRB and FPS isolation schemes. Under the SSE, the acceleration reduction rates at the peak of the LRB and FPS isolated structures are 74.6% and 63.2%, and the peak horizontal deformation of the containment structure can be reduced by 75.1% and 68.4%. Under the double SSE, the maximum tensile stress peaks of the containment structure can be reduced by 33.5% and 35.8% with the LRB and FPS isolation strategies. In non-isolated structures, tensile damage is mostly concentrated at the connections between the bottom and the side walls. After the damping effect of the isolation devices, no tensile damage was observed in the isolated containment structures, indicating that the LRB and FPS isolation schemes can effectively reduce the seismic response and structural damage of SMR nuclear power plants. This study emphasizes the importance of adopting effective seismic isolation strategies to ensure the seismic resilience of SMR. The LRB and FPS systems, by extending the natural vibration period and reducing the seismic response, offer promising solutions for the seismic protection of SMR. These results provide valuable insights for the design and implementation of seismic isolation in nuclear reactor structures, promoting the safe and reliable operation of SMR in seismically active regions.