Analytical and experimental evaluations of the blowdown thrust forces

An instantaneous pipe rupture is considered to be one of the hypothetical accidents in the light water reactor. To evaluate the dynamic responses of the pipe-restraint system under the LOCA conditions, the time hystories of the blowdown thrust force must be clarified both experimentally and analytically. The studies of pipe rupture accidents concerning both the jet discharge and the pipe whipping have been performed at the Japan Atomic Energy Research Institute (JAERI). This paper presents the experimental and analytical studies of the blowdown thrust forces. It comprises the evaluations of the time-dependent and the maximum blowdown thrust forces, and those influences by the break area and the break mode. The tests were carried out under the PWR or the BWR LOCA conditions using a 4-inch or 6-inch diameter pipe. The blow-down thrust forces were analytically evaluated both by the momentum equation, and by the thermal-hydraulic quantities which were obtained from the analysis by the RELAP4/MOD5 code. (orig./RW)