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A nondestructive testing device, consisting of a scanner and signal processing circuits was developed to detect cracks in turbine disk roots. The scanner consists of a longitudinal feeder and a fir-tree-shaped sensor probe. The feeder inserted the sensor probe along the grooves of the turbine blade attachment. Meanwhile, permanent magnets were placed in opposite direction, to generate a closed magnetic field between the magnetic sensors located on the crests of the sensor probe. The fatigue crack in the turbine disk root occurred in the circumferential direction of the turbine. As a result, magnetic flux leakage was caused by disturbing the flow of closed magnetic field by permanent magnets. The magnetic flux leakage was measured by a magnetic sensor. The effectiveness of the proposed device has been verified using artificial defects introduced into the turbine disk roots by electric discharge machining. [ABSTRACT FROM AUTHOR]

Nondestructive examination and evaluation system for high pressure feed water heat exchanger tubes in nuclear power plant was developed. Differential-type bobbin coils made of copper wire are placed on both sides of GMR sensors arranged in a ring shape. If alternating current (AC) is applied to the bobbin coils, then an inductive current is occurred in circumferential direction of the tube to be examined. Under these conditions, eddy currents are generated around the defect. Because the time-varying magnetic field is distorted by eddy current that is generated around the defect, the shapes and dimensions of defect can be quantitatively evaluated with cylindrical arrayed GMR sensors. The result was verified by the artificial defects fabricated in a small diameter heat exchanger tube. [ABSTRACT FROM AUTHOR]

A moisture separator reheater (MSR) system is installed between the high-pressure and low-pressure steam turbines in a nuclear power plant to increase the heat efficiency of the power plant. Erosion and corrosion of the MSR tubes have threatened the long-term operation of nuclear power plants. Thus a partial saturation eddy current testing (PSECT) method using a bobbin-type integrated Hall sensor array (BIHaS) was proposed in our previous study and it showed good results compared with a conventional PSECT. This paper presents a novel signal processing technique to improve detectability and measurability of electromagnetic testing method using a BIHaS through mitigating the inherent vibration signal noise between the BIHaS and ferritic stainless steel tubes. [ABSTRACT FROM AUTHOR]