Response to water hammer of Loop No. 1, including the pressurizer cold injection piping, at the Temelin NPP, Units 1 and 2

Within the Leak Before Break analysis of the primary circuit pipeline system, it is necessary to demonstrate the resistance of the pipe system to water hammers, i.e., various high-frequency hydrodynamic events of the type of collapse of an air or steam crack (unexpected impact shock) and of an abrupt halt of a moving liquid column or vice versa (expected impact shock). The demonstration consists in analyzing the stability of a postulated circumferential pass-through crack and its fatigue growth and comparing the results with the requirements of applicable standards. The publication describes an analysis of the primary circuit of the Temelin NPP, Units 1 and 2, Loop No. 1, i.e. the 850 mm i.d. main circulation loop along with the associated pressurizer cold injection piping. Abrupt seizure of the main circulation pump rotor caused by a seismic event was chosen as the initiating event. It is shown that the water hammer can be neglected against the seismic effect. The results are generalized for Loops No. 2 through 4. (P.A.). 9 tabs., 11 figs., 5 refs