Abstract: A machine for dismantling, unloading and transferring to a disposal facility, nuclear reactor structure and/or components, which have been irradiated during operation of the reactor. The machine includes in one example a gantry mounted on a rigid, undismantled part of the reactor such as rails on the refuelling level of the reactor, a carriage angularly movable on the gantry, a platform movable linearly on the carriage, a mast on and axially movable relative to the platform, a manipulator mounted on the mast for angular and linear movement relative thereto, a variety of tools selectively mountable on the manipulator for effecting dismantling of reactor structure and/or components, and hoist means movable along a beam rotatable about the reactor center line and alignable with other beams to allow transfer of the hoist means from one beam to another. Alternative arrangements for varying the elevation of the mast are also disclosed.