Analytical Modeling of Control Rod Drop Behavior

摘要

In a PWR the RCCA drop behavior is mainly influenced by hydraulic resistance and friction forces between the RCCA and its surroundings, CRDM, control rod guide assembly and fuel assembly. A coupled structure-dynamic and hydraulic analystical model is developed for evaluation of the RCCA drop behavior down to dashpot. In the hydraulic models the hydraulic resistance on the RCCA drop behavior down to dashpot. In the hydraulic models the hydraulic resistance on the RCCA in the CRDM and fuel assembly are evalauted by means of well-known laws of hydraulic resistance (2). Simultaneously the mechanical friction forces between the RCCA and its surroundings are estimated with a structure-dynamic model. The equation of motion of the RCCA drop is then solved by an explicit time history integration method. This model can be used for study of the RCCA drop behavior during a seismic event or by a fixed fuel assembly bow shape.