A rotor wheel assembly has a rotor wheel including a plurality of dovetail slots. The rotor wheel assembly includes a bucket closure assembly having a leading auxiliary bucket with a dovetail coupled to a dovetail slot and an integral cover having a back side edge oriented at a first angle relative to the rotor wheel rotation axis. The bucket closure assembly includes a closure bucket having a dovetail coupled to a dovetail slot and an integral cover having a front side and a back side edge, where the back side edge is oriented to a second angle and the front side edge is parallel to the back side edge of the leading auxiliary bucket. The bucket closure assembly includes a trailing auxiliary bucket having a dovetail coupled to a dovetail slot and an integral cover having a front side edge parallel to the back side edge of the closure bucket.