A simulation on seismic failure of piping system in NPP with some testing data

This paper deals with a simulation method of failure process of major piping systems in NPP under seismic conditions. One of the authors has been working on the study of the possibility of DEGB (Double Ended Guilotine Break) piping failure during destructive earthquake conditions for fifteen years. He pointed out that the ratcheting phenomenon is very significant for a large diameter piping system failure, especially, as a cause of DEGB[ 1 ]. But it should be assumed the seismic induced strain larger than 1% dynamic strain cycle to produce ratcheting phenomenon. This paper briefly reviewed the causes of such over-strain based on his previous papers[ 1 ][ 2 ], and then they introduce new results of the simulation program of failure process as a whole piping system including its supporting devices. Most of piping failure would occure by failure of supporting systems. Based on this assumption, the failure test of several snubbers was made, and the parameters of their fragility were estimated by test data and existing failure reports[ 3 ].