ROBUSTNESS OF AN ORIGINALLY NON-SEISMIC DESIGNED PIPING SYSTEM

摘要

In the 1990s in German nuclear power plants (NPPs) a system for filtered venting has been designed and upgraded under consideration of operational aspects. This system has not been designed for the earthquake load case. After the Fukushima accident the German Reactor Safety Commission (RSK) drafted recommendations regarding the robustness of the German nuclear power plants. According to this, German NPP-operators have to show that the piping and components of the filtered venting system have a sufficient resistance against earthquake and that the system still has the integrity after earthquake load case. Germany is characterized by low seismicity. Particularly for the E.ON Kernkraft GmbH (EKK)-operated nuclear power plants, the design intensity for the sites is below the intensity of I < 6.5. Because of this low intensity the robustness of the system of the filtered venting was assessed by engineering practice. This means the assessment included a combination of assessment criteria for verification by experience based considerations: Inspection walk down Review of the documentation European Macroseismic Scale 98 Observations of earthquakes in Germany International experiences regarding originally non-seismic designed piping systems under seismic action Comparison of originally non-seismic designed system-areas with the originally seismic-designed system-areas of the same nuclear power plant Comparison of the structure with the application guidelines PAR Reviewing the design calculation of the system for operating loads (positive reviewed by the authorities) By considering all the above listed criteria it can be assumed that the piping and components of the filtered venting system in EKK owned NPPs resist the design earthquake and are still integer after the earthquake.