Test and Analysis Research on Seismic Structural Integrity of Nuclear Power Piping

摘要

Current seismic design codes are very conservative in dealing with occasional seismic load for design of nuclear power piping system, which leads to application of large numbers of dampers, hangers and supports, and results in high cost for manufacture, installation, in-service inspection and repair of the nuclear power piping system. Based on current seismic design code and dynamic characteristics of piping system in nuclear power plant, three kinds of test specimens were tested for bearing vibrational or seismic limit loads, with both straight pipe and bend pipe tested on electromagnetic shake table and a typical large size 3D complex piping system tested in a 6m><6m seismic shake table. Leakage occurs in tests for straight pipes and bends, obvious plastic deformation remains in large size piping system. After the tests, finite element models for different tested specimens were made and results of nominal stress and cumulative fatigue factors were obtained with loads input originating from tests measurement data. Based on test and calculation results as well as relevant code items in RCC-M ,ASME and Chinese seismic design codes, it is suggested that damping ratio shall have a value of 5% for piping structure which has a frequency lower than 20Hz. It's also suggested that allowable stresses shall be remained unchanged while bending moments due to dynamic loads shall be reduced 50% in seismic analysis of piping system.