Abstract: Downcommer coupling apparatus and methods for replacing a core spray line downcommer pipe coupled to a shroud T-box are described. In one embodiment, the coupling apparatus includes a wedge flange, a wedge, a wedge housing, a pipe seal, a cylindrical pipe, an elbow, a lower flange, and a shroud seal. The downcommer pipe is connected to the coupling apparatus by extending the pipe through the wedge flange, the wedge, and the wedge housing. The wedge has a plurality of flexible thinned segments that extend into the wedge housing to secure the downcommer pipe to the wedge housing. Wedge flange bolts extend through the wedge flange, the wedge, and the wedge housing to rigidly secure the downcommer pipe to the coupling apparatus. Dowel bolts extend through the wedge housing and the downcommer pipe to provide vertical and torsional load transfer from the downcommer pipe to the coupling apparatus. The lower flange is configured to receive the shroud T-box.