The CA (Control Assembly) of PGSFR (Prototype Gen-IV Sodium-cooled Fast Reactor) has a CRA (Control Rod Assembly) with an inner duct and control rod. During an emergency situation, the CRA falls into the duct of the CA for a rapid shut-down. The drop time and impact velocity of the CRA are important parameters with respect to the reactivity insertion time and the structural integrity of the CRA. The objective of this study was to investigate the dynamic behavior and integrity of the CRA owing to a drop. In General, dynamic behavior analysis in fluids using CFD commercial code such as CFX and FLUENT. However, it is not suitable for parameter study of damping system design of control assembly because commercial code requires a lot of resource. So, KAERI developed the in-house code called HEXCON that predict dynamic behaviors (drop elevation, velocity and acceleration) of CRA. Shape of the damper and CRA was modified by considering the results of HEXCON. The impact analysis of the modified model under normal/abnormal drop conditions was performed to evaluate structural integrity using the commercial FEM code LS-DYNA. Results of the drop impact analysis demonstrated that the CRA maintained structural integrity, and could be safely inserted into the flow hole of the damper under abnormal conditions.