[en] Pipe whip tests or jet discharge tests have been performed in JAERI, which simulate the instantaneous circumferential guillotine break of primary coolant piping in nuclear power plants. This report summarizes the results of 4 inch pipe whip tests (RUN 5407, 5501, 5504, 5603), under BWR LOCA conditions, which were performed from 1979 to 1981. The test pressure was 6.8 MPa and test temperature 285⁰C. In these tests clearance was kept constant at the value of 100 mm and overhang length were 250 mm, 400 mm, 550 mm and 1000 mm, respectively. The main purpose of these tests was to investigate the effect of overhang length on pipe whip behavior. From the tests results, a shorter overhang length is recommended to minimize the deformation of the pipe and restraints. (author)