A method of inspecting, performing maintenance on, or repairing a nuclear reactor may include operatively connecting a fixing device, a first track, an arm including one or more second tracks, and an effector to form an apparatus; inserting the apparatus into the reactor; fixing the apparatus within the reactor; and operating the apparatus. At least one of the one or more second tracks may include at least three track sections. The arm may have a contracted length. The arm may have an expanded length. The expanded length may be greater than two times the contracted length. The first track may include one or more motors configured to move the arm relative to the first track. A method of operating a reactor may include shutting down; inspecting, performing maintenance on, or repairing the reactor; and starting up the reactor.