Replacement of the feedwater piping system in the reactor building outside the containment at Philippsburg I nuclear power station

Abstract

At Philippsburg/Nuclear Power Station the replacement of the feedwater lines (WB35) from their point of entry into the reactor building up to the first external isolation valve of each line brought the quality level of the whole of the feedwater pipe system in the reactor building with basic safety requirements. The design of the new piping was based on a state-of-the-art concept in the mechanical and fluid-dynamics behavior. The extensive analyses focused on the optimization of the closing behavior of the third damped check valves and the integrity analysis of the RPV nozzle. The integrity analysis was performed on the basis of a postulated reliably detectable defect, using the plastic limit load method with the specified yield strength as yield stress. The planning period for preparation of the licensing and approval documents lasted approximately 30 months, following a preliminary concept phase. Replacement was performed in 43 days.