Electromagnetic acoustic transducer (EMAT) is suited to monitoring because of its non-contacting nature. However, a standard EMAT tends to give overestimating results because the estimated thickness is associated with the average of varying thickness over an area under the coil of EMAT. To solve this problem, Point-Focusing EMAT (PF EMAT), which concentrates ultrasonic waves at a certain point, was applied to thickness gauging. This study evaluates the focusing property of PF EMAT and its applicability to l...
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Evaluation of Point Focusing EMAT using ultrasonic wave visualization system and finite element analysis

The electromagnetic acoustic resonance (EMAR) method with an electromagnetic acoustic transducer (EMAT) is proposed for pipe wall thinning measurement in the previous study. In this study, the Cepstrum method is proposed to process the data obtained by an EMAR method, and it is compared with the previous autocorrelation function (ACF), superposition of nth compression (SNC), multiplication of nth compression (MNC) methods. The Cepstrum method can evaluate the thickness range of the specimen under EMAT. Also...
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Piping System, Risk Management based on Wall Thinning Monitoring and Prediction Data Processing Methods of Pipe Wall Thinning Measurement by Electromagnetic Acoustic Resonance (EMAR)

Electromagnetic acoustic transducer (EMAT) generates ultrasonic wave without direct contact with the specimen. This feature allows EMAT to be used under higher temperature environment compared with piezoelectric transducer, which means EMAT has a potential to be applied to monitoring of the piping system of operating power plants. However, the conventional EMAT may read thicker than the actual thickness of the pipe wall in the case of degraded pipes with rough surface. This is because the reflected signal i...
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Development of point focusing electromagnetic acoustic transducer for accurate pipe wall thinning measurement

This paper proposed the evaluation of rebar corrosion in reinforced concrete by an electromagnetic pulse-induced acoustic testing method. A strong pulsed electromagnetic force is applied to the specimen, and the rebars will generate the elastic waves. The difference in the bonding force between the rebars and concrete depending on rust is evaluated based on the intensity and waveform variation of elastic waves. In this study, the rusted and un- rusted rebar specimens are prepared, and the AE sensor is place...
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Evaluation of Rebar Corrosion in Reinforced Concrete using Electromagnetic Pulse-induced Acoustic Testing Method

This paper discusses the feasibility of characterization of graphite morphology in gray cast irons based on electromagnetic method. For the pur pose, gray cast iron with different graphite morphology was systematically evaluated. In order to discuss electromagnetic property of gray cast iron with different graphite morphology, conductivity and permeability were measured. It was found that both conductivity and permeability mai nly depend on graphite morphology. It was shown that the graphite morphology of ...
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Characterization of graphite morphology of gray cast irons using electromagnetic method

In the decommissioning measures of Fukushima Daiichi Nuclear Power plant (1F), it is important to ensure the thermal stability of the reactor and the whole system by the cooling system in order to prevent criticality of fuel and fuel debris. However, wall thinning is concerned due to the corrosion in the piping of the cooling system. In order to maintain the safety of the system, it is necessary to manage the piping thinning. In this study, the EMAT thickness monitoring system, which can measure thickne...
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Application of monitoring system using electromagnetic acoustic transducers for wall thickness measurement to Fukushima Daiichi nuclear power plant Unit 4 spent fuel pool cooling piping

In this study, we propose a novel EMAT-ECT multi sensor aiming at advanced structural health monitoring. For the purpose, proto-type EMAT-ECT multi-sensor was developed and their functions both as ECT and EMAT prove were evaluated. Experimental results of pulse ECT using the EMAT-ECT multi-sensor showed that the pr oposed sensor has a capability of detection and sizing of flaws. Experimental results of EMAT evaluation using the EMAT-ECT multi-sensor showed that ultrasoni c wave was transmitted by EMAT-ECT ...
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Development of novel EMAT-ECT multi-sensor and verification of its feasibility

The electromagnetic acoustic resonance (EMAR) method provides accurate and stable evaluation in high temperature environment, and it is an effective tool for online monitoring. In this study, the EMAR method and the superposition of the nth compression (SNC) for data processing are applied to online monitoring of pipe wall thinning, and the accuracy and reliability of the measurements are demonstrated through field tests using a large-scale corrosion test loop at high temperature. To measure the thic...
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Online Monitoring of Pipe Wall Thinning with Electromagnetic Acoustic Resonance Method

Electromagnetic acoustic transducer (EMAT) provides non-contacting measurements and is often applied to monitoring in gh temperature environment. One of drawbacks of EMAT is its low sensitivity and S/N ratio. One way to overcome the uwback is to introduce an Electromagnetic acoustic resonance meth od (EMAR); it has a high capability of evaluating ckness or ultrasonic velocity, and it is applied to the measurement of thickness, elastic constants, damping propertiesso on. Since the principle of the method is...
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Measurement and Evaluation of Pipe Wall Thinning by Electromagnetic Acoustic Resonance

In this study, we developed a method to measure pipe wall thinning by electromagnetic acoustic resonance method (EMAR) which is one of electromagnetic ultrasonic method. The EMAR can evaluate the thickness of piping with high accuracy. In addition, we propose a method to obtain the resonance frequency with high accuracy when the thickness reduction progresses and the SN ratio decreases. We applied the technology to PWR and BWR pipings and examined its applicability....
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Wall thickness measurement of piping using electromagnetic acoustic resonance method and its application to nuclear reactor cooling system