A system for refueling a nuclear reactor, comprising: a lower reactor vessel comprising a plurality of fuel rods and a plurality of control rods disposed therein, the lower reactor vessel further comprising an upper flange; an upper reactor vessel comprising a steam generator and pressurizer disposed therein, the upper reactor vessel further comprising a lower flange that matingly engages the upper flange of the lower reactor vessel; and a transporter surrounding an outer surface of the upper reactor vessel, wherein the transporter is configured to selectively engage the upper reactor vessel and separately selectively translate the upper reactor vessel vertically toward and away from the lower reactor vessel, and the transporter is configured to selectively translate the upper reactor vessel horizontally toward or away from vertical alignment with the lower reactor vessel; wherein the transporter comprises a collar surrounding the outer surface of the upper reactor vessel, the collar comprises first and second set of rollers that are disposed upon respective first and second horizontal tracks (202, 204), wherein the upper reactor vessel comprises an upper flange disposed concentrically around the outer surface thereof, wherein the upper flange of the upper reactor vessel is disposed below the pressurizer, wherein one or more lifts are fixed with respect to the collar and are movable to selectively engage the upper flange of the upper reactor vessel to urge the upper reactor vessel vertically with respect to the lower reactor vessel when the transporter translates vertically, and wherein the one or more lifts comprise rigid flanges that are selectively translatable laterally toward and away from registry with the upper flange. a lower reactor vessel comprising a plurality of fuel rods and a plurality of control rods disposed therein, the lower reactor vessel further comprising an upper flange; an upper reactor vessel comprising a steam generator and pressurizer disposed therein, the upper reactor vessel further comprising a lower flange that matingly engages the upper flange of the lower reactor vessel; and a transporter surrounding an outer surface of the upper reactor vessel, wherein the transporter is configured to selectively engage the upper reactor vessel and separately selectively translate the upper reactor vessel vertically toward and away from the lower reactor vessel, and the transporter is configured to selectively translate the upper reactor vessel horizontally toward or away from vertical alignment with the lower reactor vessel; wherein the transporter comprises a collar surrounding the outer surface of the upper reactor vessel, the collar comprises first and second set of rollers that are disposed upon respective first and second horizontal tracks (202, 204), wherein the upper reactor vessel comprises an upper flange disposed concentrically around the outer surface thereof, wherein the upper flange of the upper reactor vessel is disposed below the pressurizer, wherein one or more lifts are fixed with respect to the collar and are movable to selectively engage the upper flange of the upper reactor vessel to urge the upper reactor vessel vertically with respect to the lower reactor vessel when the transporter translates vertically, and wherein the one or more lifts comprise rigid flanges that are selectively translatable laterally toward and away from registry with the upper flange.