A waste disposal system (30) with a waste receiver (32) for receiving pharmaceutical waste material. A locking assembly (34) is secured to a fixed surface and actuated from a locked configuration to an unlocked configuration. A lock cylinder of the locking assembly may extend forward of a front wall (44) of a receiver body (36) of the waste receiver to engage a locking feature of a cover (82) in the locked configuration. A cover retention feature (124) may prevent axial decoupling of the cover from the receiver body. The receiver body may be formed from two shells (62,64). A reaction agent (150) is positioned within the container volume and spaced apart from a bottom wall of the receiver body. The reaction agent may be positioned within the container volume between the lock passageway (94) and/or a solid receiver volume, and opposing sidewalls of the receiver body. A support may maintain the position of the reaction agent within the container volume.