Seismic isolation of small modular reactors using metamaterials

Abstract

Adaptation of metamaterials at micro- to nanometer scales to metastructures at much larger scales offers a new alternative for seismic isolation systems. These new isolation systems, known as periodic foundations, function both as a structural foundation to support gravitational weight of the superstructure and also as a seismic isolator to isolate the superstructure from incoming seismic waves. Here we describe the application of periodic foundations for the seismic protection of nuclear power plants, in particular small modular reactors (SMR). For this purpose, a large-scale shake table test on a one-dimensional (1D) periodic foundation supporting an SMR building model was conducted. The 1D periodic foundation was designed and fabricated using reinforced concrete and synthetic rubber (polyurethane) materials. The 1D periodic foundation structural system was tested under various input waves, which include white noise, stepped sine and seismic waves in the horizontal and vertical directions as well as in the torsional mode. The shake table test results show that the 1D periodic foundation can reduce the acceleration response (transmissibility) of the SMR building up to 90%. In addition, the periodic foundation-isolated structure also exhibited smaller displacement than the non-isolated SMR building. This study indicates that the challenge faced in developing metastructures can be overcome and the periodic foundations can be applied to isolating vibration response of engineering structures.

A Review of Research on Seismic Metamaterials

“…[61] They further optimized the periodic metafoundation in 2019, [62] as shown in Figure 7. In 2018, Witarto et al applied alternating materials layer periodic foundation to the seismic protection of the small modular reactor and conducted a large-scale shake table test, [63] as shown in Figure 8. Casablanca et al proposed a composite foundation based on local resonance and dual-stiffness structure, [64] as shown in Figure 9, and tested on the laboratory scale.…”

“…[62] Copyright 2019, John Wiley and Sons Ltd. Reproduced with permission. [63] Copyright 2018, American Institute of Physics. Figure 9.…”

“…However, considering that the seismic protection objects are large buildings, there are still a lot of studies using the Bragg scattering mechanism to design largesized SMs for low-frequency and long-wavelength seismic waves. [9,10,[17][18][19][20]40,50,63] For example, Brule et al introduced SMs composed of vertically drilled holes in the soil. A self-stabilizing hole with a diameter of 0.32 m, a center distance of 1.73 m, and a depth of 5 m was adopted to conduct field tests on a 50 Hz source with a corresponding wavelength of 1.56 m. [9,10] The experiment and simulation results consistently showed that it could improve the energy distribution of seismic waves, which is identical to the bandgap shown in the dispersion curve, as shown in Figure 11.…”

“…[17,18] Geng et al, Bao et al, and Witarto et al studied the wave attenuation capacity of 1D alternating material layer SMs. [40,50,63] Chen et al studied the SMs of concrete piles and pointed out that wave attenuation in homogeneous soil is caused by destructive interference, namely, Bragg scattering, by the result of uniformly distributed concrete piles. [48]…”

“…[61,62] Witarto et al pointed out that structures housing sensitive equipment (such as nuclear power plants) should experience very little vibrations and therefore maintain the safety of nuclear facilities. They further developed a new vibration isolation system, which can overcome the shortcomings of conventional isolation systems to isolate vertical earthquakes, and designed a scaled model for small modular reactors, [63] as shown in Figure 17.…”