Reactor internals are installed in the reactor vessel and are subsequently removed during periodic inspections. To facilitate this process, a gap is maintained between the outlet of the Core Support Barrel (CSB) and the hot-leg nozzle of the Reactor Vessel (RV). However, this gap causes considerable bypass flow, leading to wasted coolant and pump power. This paper presents an improved design of reactor internals to prevent bypass flow and introduces a tool for handling the internals. Advanced computational simulations were used to investigate the tool’s viability. The tool was designed using advanced Finite Element Analysis (FEA) techniques, and its operation was simulated and evaluated with ANSYS Rigid Body Dynamics. The results showed that the CSB can be installed using the insertion tool in a manner that ensures contact with the RV’s interior surface, thereby decreasing the gap and lessening the bypass flow, as well as increasing the structural stiffness of CSB under seismic loads.