Influence of nuclear island on seismic acceleration response on soft rock sites

As the site resources of nuclear power plant are getting increasingly scarce day by day, soft rock sites will be gradually used for nuclear power plant construction. In this paper, a three-dimensional finite element model for the nuclear island structure on soft rock site (based on the horizontal layered soft rock site) was established using the ABAQUS finite element software by adopting the modified Davidenkov constitutive model with configuration of viscoelastic artificial boundary and consideration of the embedding effect. This model was used to simulate the nonlinear characteristics of the soft rock site and comparatively analyse the influence of the nuclear island on the seismic acceleration response of soft rock site. The results show that the nuclear island increases the peak acceleration of the soft rock site. As the input ground motion increases, the ground surface peak acceleration increases accordingly, but due to the nonlinear effect of the soft rock site, the acceleration amplification factor shows a decreasing trend. Under the far-field ground motion, the ground surface acceleration increases significantly and may cause a strong potential destruction to the nuclear island. A non-free field (with a nuclear island) moves the ground surface acceleration response spectrum slightly toward the long-period direction. Under the near-field ground motion enriched with high-frequency components, the ground surface peak acceleration response spectrum caused by the nuclear island shows an increasing trend. Our research conclusions can provide useful reference for both the site selection and aseismic design of nuclear power plants.