Abstract: The invention concerns a method comprising measurement on a fuel channel (14) of fuel assemblies (8) for nuclear boiling water reactors. The method comprises that: the measurement is done by the use of a non-destructive inductive eddy current measurement method, the measurement is done on a fuel channel (14) which has been used at least a certain time during operation in the core of a nuclear boiling water reactor, the measurement is done when the fuel channel (14) is located in water, the measurement is done on different places on the fuel channel (14), wherein through the method at least the hydride content of the fuel channel (14) at said places is determined. The method can be used in order to find out how shadow corrosion from a neighboring control rod influences the properties of the fuel channel (14).

Abstract: The invention concerns a system suited for carrying out eddy current measurements on components for nuclear reactors when these components are located in water. The system comprises a control unit, a measurement probe and a first cable suited to constitute at least a part of the connection between the control unit and the measurement probe. The system also comprises a switching unit, suited to be located in water and arranged to be connected with said first cable, and to be connected with the measurement probe. The switching unit has a switching device which can assume at least a first and a second state. In the first state, the first cable is connected with the measurement probe. In the second state, the first cable is not connected with the measurement probe. The invention also concerns the use of the system.