On site vibration test of PWR nuclear power plant reactor coolant loop

The main object of this vibration test being carried out in 1984 due to large exciting force is to examine the critical damping value of PWR Reactor Coolant Loop (RCL) system of actual nuclear power plant. The test was conducted on Kansai Electric Power Takahama station No. 4 Unit on site and 5 ton capacity hydraulic exciter was mounted directly on the secondary side manhole plate located at the enough higher location of the typical steam generator. After finished that test, specific hydraulic snubber which is just same type for steam generator support was also tested in laboratory to investigate the vibrational characteristics itself. These tests were reviewed technically and it was concluded that the conventional design value for damping in Japan was a very conservative one and new reasonable damping ratio, 3%, was recommended for RCL seismic design