The Development of Impact Analysis Methodology for CEDM Missile of APR1400

The paper deals with the impact analysis methodology for control element drive mechanism (CEDM) missile of advanced Power Reactor 1400 (APR1400). The methodology includes the development of jet expansion models to develop the missile velocity as well as the missile impact analysis itself and the application of Fauske model to obtain jet velocity in two-phase critical flow. The CEDM missile is produced by jet thrust when the reactor vessel nozzle breaks during Safe-Shutdown-Earthquake (SSE) and/or dynamic events of accidental condition. Jet velocity from the nozzle exit should be determined before the determination of missile velocity. The jet provides the kinetic energy pushing up a missile. In previously operating plants, the jet was assumed to occur in a single-phase flow so that it may result in overly conservative velocities to design missile barriers. In order to determine the jet velocity, the jet is characterized in two-phase critical flow, and Fauske slip equilibrium model is applied to the jet. Furthermore it is important to determine the missile velocity from the jet impingement to be applied in the missile impact analysis as an input loading. Various jet expansion models are suggested in calculating the missile velocities herein, where consideration is given to various jet expansion and jet impingement on an object. With the missile velocities using the models, the nonlinear CEDM missile impact analysis is performed to investigate structural responses of the missile shield with the Integrated Head Assembly (IHA) of APR1400. Because the missile shield is tied to the inside of IHA with a complicate manner, it is important to analyze and evaluate the missile impact behaviors to demonstrate the structural adequacy of the missile shield as well as IHA. Comparisons of the analysis results are influential to the design evaluation in case of using missile velocities by different flow models, wherein the jet is assumed to occur in single-phase flow or two-phase flow.