Earthquakes pose a significant hazard to nuclear power plants as seen from the damage to Fulcushima I Nuclear Power Plant from the magnitude 9.0 Mw Tōhoku earthquake and subsequent tsunami on March 11, 2011. In addition to offering significant advantage in terms of containment structure requirements, favorable hydrogeologic conditions and protection from hostile acts; underground nuclear power plants have at least two important potential advantages compared to an above-ground location during a seismic event. First, the peak acceleration everywhere below the free surface is lower than it is at the surface and second, unlike structures on the surface, these excavations are not ‘free-standing’ but are in the interior of a three-dimensional solid and the reactors can be attached laterally to the wall of the shaft to minimize inertial effects. This results in a more robust seismically resistant design. The dimensions of most excavations in rock are low compared to the dominant wavelengths of a large seismic event and the incident and reflected waves pass across and beyond the excavations with little major change assuming that the excavations are designed to sustain local stress amplifications around the tunnel.

This paper presents numerical simulations comparing the seismic response of a typical modular reactor located on the surface in free standing configuration, to underground configuration, and highlights the benefits of moving nuclear reactors underground.

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