Seismic Performance of Fuel Lines Connected to Emergency Diesel Generator Considering Isolation Device

Applying isolation devices to nuclear power plant equipment can improve the equipment’s seismic safety. When the equipment is connected to piping, however, its seismic safety can rather be decreased due to the increase in the relative displacement of the connected pipes. An emergency diesel generator (EDG) supplies power when a generator and an external power source in a nuclear power plant do not operate. Isolation devices can be installed to improve EDG’s seismic safety. The seismic safety of EDG is generally evaluated considering only EDG and the isolation device. Since the piping connected to EDG is responsible for fuel supply and cooling, however, the seismic safety of EDG must be evaluated considering the piping as well. In this study, seismic fragility analyses were conducted according to the modeling of isolation devices for EDG equipped with the isolation device and the piping connected to EDG. Seismic response analyses were performed considering the fuel line in EDG to which the seismic isolation devices were applied, and seismic fragility curves were estimated based on the results of the seismic response analysis. The research results showed that the piping connected to EDG could be damaged earlier than EDG, indicating that proper piping system design and seismic safety assessment are required to apply isolation devices to EDG.