Introduction  In order to improve heat exchange efficiency, the condensate pipelines, main water supply pipelines drain pipelines and partial extraction pipelines of nuclear power plants are all coated outside the pipelines. At present, the test methods of ferromagnetic pipelines are mainly conventional ultrasound and ultrasonic guided waves. These test methods are limited by the detection environment and preconditions, which increase the difficulty of test. In order to improve the test efficiency of pipelines with insulation layer, we shall enrich technical methods, shorten maintenance period and improve economic benefit of nuclear power plant.

  Method  This paper mainly studied the feasibility and reliability of pulsed eddy current testing method under low frequency electromagnetic interference in nuclear power plant, and used the measured and calculated values of the induced voltage to establish the optimal parameter inversion problem. In combination with the coupling relationship between the parameters and based on the time-domain analytical solution of the pipeline pulsed eddy current field, the paper established the specific relationship between the measured value and the calculated value of the induced voltage, and established the optimization parameter inversion problem. In combination with the coupling relationship between the parameters, the paper proposed a pulsed eddy current detection method for in-service operation and maintenance of insulated pipes in nuclear power plants.

  Result  Using the pulsed eddy current detection method for the relative wall thickness of ferromagnetic pipelines proposed in this paper, in-service sample pipelines of nuclear power plant are tested and the testing result is compared with conventional ultrasonic testing. The error of the two testing results is about 5%.

  Conclusion  The testing results of impulse eddy current testing are reliable and it is suitable for non-destructive testing and evaluation of nuclear power plant ferromagnetic pipeline wall thickness corrosion thinning.