Abstract: A nuclear reactor vessel cavity seal plate. An annular support plate is positioned over the cavity between the reactor vessel and the shield structure and seal welded to the shield structure. Inner and outer support rings attached to the annular plate are supported by the existing beams in the annular cavity. A U-shaped flexible annular expansion ring positioned between the annular plate and reactor vessel flange has its inner diameter seal welded to the reactor vessel flange and its outer diameter seal welded to the annular plate. Ports in the annular plate provide access to nuclear instruments below the annular plate. A cover plate is removably attachable to each port to seal the ports. A closable drain is provided in the annular expansion ring. This provides a permanent seal plate that allows flooding of the cavity for refueling with it being necessary to remove only the cover plates for normal reactor operations.

Abstract: A replacement nozzle and method for replacing a nozzle in a pressure vessel. The original nozzle is removed and a weld preparation is machined into the original weld. The vacated nozzle hole is partially drilled out from the interior of the vessel. A weld land sleeve is received in the drilled out portion of the nozzle hole and a replacement nozzle is received in the weld land sleeve. The sleeve and replacement nozzle are welded in place on the inside of the vessel wall.