THE ULTIMATE STRENGTH OF CYLINDRICAL LIQUID STORAGE TANKS UNDER EARTHQUAKES: SEISMIC CAPACITY TEST OF TANKS USED IN PWR PLANTS(PART2 : STATIC POST-BUCKLING STRENGTH TESTS)

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 previous study, by conducting the dynamic and static buckling tests with aluminum alloy, it was confirmed that static buckling test represents dynamic buckling and post-buckling behavior in terms of energy absorption capacity. In this study, static buckling tests with actual material were performed in order to evaluate the ultimate strength of real tanks. Although the buckling mode did not differ among materials, tests with actual materials (steel, stainless steel) resulted higher seismic capacity compared to the aluminum alloy, and inner water leakage occurred from the cracks initiated at the secondary buckling on the EFB section.