Mechanical Engineering Journal (Oct 2019)
Feasibility study of full-scale elastic-plastic seismic response analysis of nuclear power plant
Abstract
A finite element elastic-plastic seismic response analysis using a full-scale integrated model of Unit 1 of the Fukushima-Daiichi Nuclear Power Plant, which was subjected to the 2011 off the Pacific coast of Tohoku Earthquake, is performed using the K computer in order to obtain both the global and local responses more precisely. The purpose of the present study is to investigate the computational performance and show the feasibility of such an analysis. The high-fidelity finite element mesh for the plant used in the present study was generated using tetrahedral elements in a previous study by Yoshimura et al. (2019a) for the pressure vessel, the containment vessel, the suppression chamber, the vent pipes, a number of supports, and the reactor building. The mesh with linear elements has approximately 200 million DOFs. The elastoplasticity is taken into account for only the steel used in the pressure and containment vessels. However, the material for the reactor building is assumed to be elastic. The dynamic response during 55 s is solved successfully, although yielding occurs at very few points. The total elapsed time for analysis is approximately 14.2 days using 1,032 nodes of the K computer. If the nonlinearity increases, the computation time may be increased by three to four times due to the increase in the number of Newton-Raphson iteration steps. Even in this case, the computation time can be estimated to be less than two months, which means that an elastic-plastic seismic response analysis of the plant using the high-fidelity finite element mesh is feasible. An elastic-plastic seismic response analysis using a quadratic element model with approximately 1.5 billion DOFs is also successfully conducted for 12 time steps (0.12 s) using 4,128 nodes of the K computer.
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