A model based on the RETRAN code was developed for analyzing the turbine trip tests performed at the Peach Bottom Atomic Power Station Unit 2, near the end of the second fuel cycle. Special features of the model include a detailed nodal description of the steam lines and the steam bypass system as needed to properly describe pressure wave phenomena caused by stop valve closure during the early phase of the transient, and dynamic effects associated with operation of the bypass. Furthermore, it is shown that the power excursion, deliberately enhanced by delayed scram, is strongly influenced by the nature of the pressure wave as it appears in the core region and by direct moderator heating effects. Good agreement between measured transients and most calculated counterparts makes this effort an important contribution toward qualification of RETRAN for this class of transients.