Mid‐height seismic isolation of equipment in nuclear power plants

Abstract An innovative seismic isolation solution for designers of safety‐class equipment in advanced nuclear power plants is introduced. The test specimen was a tall, slender, carbon steel vessel that could represent a reactor vessel, steam generator, or a heat exchanger in a nuclear power plant: 240 inches tall, outer diameter of 60 inches, and wall thickness of 1 inch. The vessel was supported by three radial mounts at its mid‐height, near its center of gravity, on a steel frame. The vessel was subjected to three‐component ground motions using a 6DOF earthquake simulator. The specimen was filled with water for testing to indirectly account for the fluid and internal equipment present inside a prototype vessel. Three configurations were tested: non‐isolated, isolated using single Friction Pendulum (SFP) bearings, and isolated using triple Friction Pendulum (TFP) bearings. The test results demonstrate that mid‐height seismic isolation is practical and enables a significant reduction in horizontal spectral accelerations. These outcomes are not specific to the spherical sliding bearings used in the experiments but are broadly applicable to mid‐height, seismically isolated equipment.