A liquid-metal fast breeder reactor (LMFBR) differs from a light water reactor in that it has a much lower internal pressure and a significantly higher operating temperature. These divergent design conditions lead to a special design concept and require specific efforts in fabrication and installation. Important features in design, analyses, fabrication, and installation of LMFBR thin-walled piping systems had to be developed or standards had to be modified. They were accomplished in the KKW Kalkar project. All final checks, including leak tests and pressure tests of the primary and secondary systems, have met the requirements. The installation of the KKW Kalkar pipeworks was finished with the filling of sodium into the last main system in April 1985.