[en] Aiming at optimization of maintenance of nuclear fusion reactors, we propose a new concept of maintenance that components including defects under control can be kept in use without replacement of them. For the purpose, a life-cycle simulation of fatigue crack behavior was carried out, taking an example of the ITER vacuum vessel. The simulation shows that there is no possibility that virtual defects penetrate the vessel, which implies no inspection is required based on the present concept. (author)

[en] The remote field eddy current testing (RFECT) is usually used for inspection of ferromagnetic small tubes with inner coils. The aim of this study is to clarify the precise characteristics of RFECT for inspection of flat plates with pancake coils, which has rarely appeared in the literature. The study performed by actual experiments and computations based on electromagnetic analysis to evaluate the capability of RFECT to detect a defect and estimate the shape of a defect. This paper introduces some of the results obtained from these experiments and computations for a simple probe configuration having only one excitation and one pick-up coils. The results shows even this simple configuration enables RFECT to detect local wall thinning and roughly estimate its shape. (author)

[en] A main impediment to optimization of the plant maintenance is the fact that we can not predict when and how troubles are introduced in a plant. Having regard to the point, the authors propose a 'virtual system' concept for prevention and prediction of accidents in plants. The virtual system is a system constructed in computers and it evaluates responses to various loads of the object system. The authors introduce the resistance to loads and the testing availability as key parameters characterizing object sub-systems and place their evaluation as the first step of construction of the virtual system. (author)

[en] The authors have proposed a novel eddy current testing (ECT) probe for thick-walled plates. A basic concept of the probe is that a couple of differential pick-up coils is arranged between two exciting coils carrying currents opposite to each other. This arrangement allows strong eddy currents opposite to scan surfaces and the weak decay of eddy currents in the thickness direction. In this study, the present probe was applied to ECT of welding area. For the purpose, experiments were carried out using INCONEL718 specimen with thickness of 7.0mm and SUS304 specimen with thickness of 8.0mm. Both specimens have welded parts with beads. The present probe successfully detected the defect although a conventional pancake probe did not, which supports for the robustness of the probe against noises of welded parts. (author)

[en] Advance of eddy current testing (ECT) simulation by development of computer technologies is abstracted. Numerical simulation is discussed by operation speed, desktop PC (Intel chips) over time and progress of numerical simulation of ECT by scale of the problem, forward problem, analytical methods, and nondestructive inspection structure. ECT numerical analytical method simulated the detected cracks at the first stage and then reconstructed the cracks. The method is able to simulate the correct length of cracks and depth within 20% error. A genetic programming (GP) method is expected to solve the multi cracks problems. Comparison the signals of EDM crack in ferromagnetic A533B plate by conventional method and the fast simulator, reconstructed results of EDM cracks in a 20 mm thick plate, and length of detected cracks are shown. (S.Y.)

[en] The authors have proposed EMAT (Electromagnetic Acoustic Transducer) and EC (Eddy Current) dual probe which provides sizing with high reliability based on the complementarity between eddy current testing and ultrasonic testing. In the previous work, the feasibility of EMAT/EC dual probe was verified through experiment using austenitic stainless steel plates with thinning defects. This paper discusses the feasibility of monitoring in high temperature environment using the EMAT/EC dual probe. For the purpose, EMAT/EC dual probe for high temperature is designed and fabricated, and the basic performance is investigated in high temperature environment. (author)

[en] The remote field eddy current testing (RFECT) is usually used for inspection of ferromagnetic small tubes with inner coils. The aim of this study is to clarify the precise characteristics of RFECT for inspection of flat plates with pancake coils, which has rarely appeared in the literature. The study was performed by actual experiments and computations based on electromagnetic analysis to evaluate the capability of RFECT to detect a defect and estimate the shape of a defect. This paper introduces some of the results obtained from these computations for a simple probe configuration having only one excitation and one pick-up coils. The results shows even this simple configuration enables RFECT to detect local wall thinning and roughly estimate its shape. (author)

[en] This paper shows phase characteristics of crack indications obtained with a 48-channel ECT system, and proposes a method to reduce noise and extract crack indications from detection signals of this ECT system based on these phase characteristics. Because this ECT system performs two kinds of scanning patterns: U-scan and T-scan, and obtains two sets of signal distributions for one scanning area simultaneously, the proposed method uses a two-stage process that includes so-called a main filter and a sub filter. While the main filter uses the phase information of the same scanning pattern by which the target signals are obtained, the sub filter uses the phase information of the other scanning pattern for the target signals. Using these two filters imposes more strict conditions on extracting crack indications so as to reduce more noise. The results of a round robin test shows that this filtering method is effective to extract crack indications from the background of complicated noises. (author)

[en] We propose a new method for measuring flux flow resistivity, and name it the 'pulse-excited vibration method'. This method is capable of evaluating effective flux flow resistivity, which is important to analyze the properties of superconducting bulk materials in a transient mode. In this paper, we describe the pulse-excited vibration method in detail, and estimate the flux flow resistivity of a superconducting bulk sample based on our model. Furthermore, the validity of this method was verified successfully by applying the measurement process to a superconducting tape. (author)

[en] Eddy current testing (ECT) has been widely used for the non-destructive testing of metal structures. ECT has high capability of detecting surface breaking cracks and length sizing in nuclear power plants. However, it is known there is the error in the evaluation of the depth of the crack. Martensitic phase occurs due to the stress of crack in the vicinity of the crack and oxide layer of crack surface can affect the evaluation of crack depth. In this study, we assess the influence that impact these factors have on the sizing depth. Specifically, fatigue crack of different depths is introduced on the specimen of SUS316 by the four-point bending and an oxide film is progressed by heat treatment to evaluate the effect of the sizing. Further, martensitic phase in the vicinity of cracks is removed by heat treatment for reverse magnetic martensite to evaluate the effect on the sizing. (author)