Relay behavior at the Perry Nuclear Power Plant during the 1986 earthquake in Leroy, Ohio

The behavior of safety-related relays at the Perry Nuclear Power Plant during the January 31, 1986 magnitude 5.0 Leroy, Ohio earthquake and the seismic response levels to which they were subjected was investigated and documented for further study. The seismic performance of relays is an issue of current interest in the resolution of Unresolved Safety Issue A-46, Seismic Qualification of Equipment in Operating Nuclear Power Plants.'' Relays are a class of equipment, important to the seismic performance of nuclear plants, whose seismic behavior and ruggedness is difficult to quantify. Relays do not have to fail structurally but may operate spuriously by the chatter of their contacts to jeopardize the safety function. The data for this study were provided by the detailed post-earthquake engineering study performed by the Cleveland Electric Illuminating Company and additional investigations performed by the Electric Power Research Institute. All of the energized safety-related systems continued to operate through the event, and none of the safety-related systems in the standby mode experienced any spurious operation. While the Leroy earthquake 2% damped floor response spectra exceeded the safe shutdown earthquake (SSE) design spectra in the frequency range of 18Hz to 30Hz by as much as a factor of aroundmore » three, safety-related relays worked satisfactorily. This was due to the fact that they were seismically qualified at considerably higher levels than the Leroy earthquake. 27 refs., 26 figs., 10 tabs.« less