According to one aspect of the invention, a turbine assembly includes a rotor wheel and a circumferential slot formed in the rotor wheel, the circumferential slot including a uniform cross-section shape for a circumference of the rotor wheel. The assembly also includes a first ring member positioned in the circumferential slot, the first ring member being configured to prevent radial movement of a dovetail attachment when positioned in the circumferential slot, wherein the dovetail attachment is part of a turbine blade.