Elastic-plastic response of a piping system due to simulated double-ended guillotine break events

In the design criteria for nuclear power plant components of light water reactors of the Federal Republic of Germany (FRG) a double-ended guillotine break of a feedwater line outside the reactor containment is postulated ( Fig. 1 ) /1/. In case of a blowdown induced by a double-ended guillotine break in a boiling water reactor the feedwater check valves (SRV) serve the purpose of closing so quickly that the consequences of the accident are limited. The blowdown first produces a pressure relief wave within the piping followed by high pressure peaks (water hammer effect) as a result of the quick closure of the check valve. The differential pressures in the individual pipe sections, especially in front of and behind the pipe bends, give rise to fluid dynamic forces in the piping which load the structure considerably. To show the load bearing and plasticizing capacity of high ductile pipework materials nowadays used in reactor technology /2/, three blowdown tests were performed at the decommissioned Heiβdampfreaktor (HDR) near Franfurt. The experiments reported in this paper are part of Phase II of the HDR Safety Program which is sponsored by the Ministry of Research and Technology of the Federal Republic of Germany /3, 4/. These