Control rod drive exchanger having monitoring device

Since the state of an exchanger for exchanging control rod drives was not indicated, an operator could not easily judge whether they were in a proper state or not. Then in the present invention, actual operation of an uncouple rod is detected by a magnet disposed in the uncouple rod and a limit switch disposed in an index tube. Detected signals are inputted as input signals together with plant operation state signals and then subjected to mathematical processing. Thus, the operation state is shown in a state display section to accurately judge the state of the operation. Accordingly, since the state monitoring function for the control rod drive exchanger can be improved, and a failed portion during the uncoupling operation can be found in an early stage, damages to control rods and control rod drives caused by operator's misoperation can be prevented and operator's burdens can also be moderated. (N.H.)