In one aspect, the present disclosure is directed to a rotor blade for a turbomachine. The rotor blade includes an airfoil defining at least one cooling passage. The rotor blade also includes a tip shroud coupled to the airfoil. The tip shroud and the airfoil define a core fluidly coupled to the cooling passage. A maximum radial depth of the core is at least six times greater than a minimum hydraulic diameter of a largest cooling passage of the at least one cooling passage.