Microwave Detection of Circumferential Crack in Piping System of Nuclear Power Plants

In this paper a new method of microwave nondestructive testing based on electromagnetic guided waves is applied to detect circumferential crack in the piping system of nuclear power plants. Microwaves as continues wave are generated by a network analyzer and amplitude of the reflection coefficient is measured by this network. For detection of any type of crack with any orientation in the pipe, suitable mode should be propagated in the inspected pipe. For this purpose a mode converter, which is a transition between rectangular waveguide to circular waveguide is utilized to transform a rectangular TE-modes into the circular TE and TM-modes. To detect circumferential crack, TM01-mode which is the first circular TM-mode, is excited in the mode converter by choosing a proper frequency sweep. Two experiments are performed for detection of crack in straight pipe and piping system including a U-bend. Achieved results are shown the potential of this technique for detection of crack and also to get estimation of crack location.