THE ULTIMATE STRENGTH OF CYLINDRICAL LIQUID STORAGE TANKS UNDER EARTHQUAKES: SEISMIC CAPACITY TEST OF TANKS USED IN PWR PLANTS(PART1: EVALUATION METHOD VERIFICATION TEST)

摘要

Since 2002, Japan Nuclear Energy Safety Organization (JNES) has been carrying out seismic capacity tests for several types of equipment which significantly contribute to core damage frequency. The primary purpose of this study is to acquire the seismic capacity data of thin walled cylindrical liquid storage tanks in nuclear power plants and to establish an evaluation procedure of the ultimate strength.As for the refueling water storage tank and the condensate storage tank which are used in PWR plants, elephant-foot bulge (EFB) is the typical buckling behavior of those tanks and the primary failure mode to be focused on. In the study, dynamic buckling tests were performed using scaled models of tanks. The input seismic acceleration was increased until the tanks reached the ultimate state at which internal water leaked from a crack on the sidewall. In addition, static buckling tests were performed in order to compare to the dynamic buckling tests and numerical simulation results. In the dynamic and static buckling tests, EFB occurred and internal water leaked at the EFB cross-section. Incremental deformation growth observed in the static buckling test was simulated by FEM, and analysis results showed a practically sufficient consistency in terms of out-of-plane displacement and local strain.