By using the FCVS technology, we had started to develop a high decontamination air cleaning system to remove multi-nuclides for radiation protection to conduct decommissioning the Fukushima NPP. High efficiency multi-nuclide aerosol filters for radiation protection during a process of cutting core debris has been developing at Hokkaido University. A plasma cutter, laser cutter, wire cutter, drilling machine, etc., will be used and will generate aerosols. Therefore, the air cleaning system should be needed f...
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Development of a high efficiency multi-nuclide aerosol filters for radiation protection during a process of cutting core debris (4) Improvement for Wet-Type Filter

This study investigated the influence of probe types on the detection capability of eddy current testing technique against the flaws on F82H steel. Three surface slits were fabricated in F82H specimens with a thickness of 10 mm. The slit depth is 0.5, 1, and 3 mm. The slits were detected by pancake probe, vertical pancake probe, uniform probe, and plus point probe. The signal to noise ratio of used probes was calculated and compared. The greatest signal to noise ratio was plus point probe, followed in order...
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Influence of probe types on detection capability of eddy current testing to blanket cooling tube of fusion prototype reactor

A core machine in the present state of the fusion energy development is ITER. In the next step, of which the goal is net electric power generation with an acceptable availability, the core machine is a DEMO reactor and the plan towards it is drawn up by the committee of the MEXT. The action plan towards the DEMO is composed of 12 issues and two issues of them are related to the maintenance technology. In this paper, we are briefly reviewing those issues in the action plan....
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Action Plan towards Establishment of Maintenance Technology for Fusion Reactors

Maintenance engineers who are involved in activities of maintenance for industrial plants like nuclear power plants need an adequate understanding about maintenance activities PDCA and are required to develop guidelines for improving actual maintenance activities by bringing together their own knowledge and maintenance data. This paper reports a summary of the current status of consideration concerning the optimization of overhaul inspection intervals for components by a working group under the JSM maintena...
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Consideration concerning the optimization of the overhaul inspection cycle for components

AI application examples in the field of nuclear power maintenance in the United States (US) and Europe were investigated from publicly available information. Various tools and software utilizing digital technology such as IoT and AI are being developed by manufacturers and IT vendors, and their application has begun in some nuclear power stations in Europe and the US. AI technology is being applied to power generation, transmission and distribution facilities including nuclear power plants in the US and Eur...
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Application of AI technology in the Maintenance at Western Nuclear Power Plants

In May 2011, at Hamaoka-5, the main condenser thin tube was damaged and seawater intruded to the reactor facility. It was purified to a level where corrosion did not occur by replacing the intruding water. However a few years later, the leak occurred from the stainless steel welded joint. It is presumed that the cause is that crevice corrosion was caused by the welded part of stainless steel with high corrosion sensitivity, the inflow of chloride ions, and the crud deposits. And in this study, we aim to elu...
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Elucidating the corrosion of the stainless steel welded joint caused by seawater intrusion at Hamaoka-5

This paper proposes a neural network to achieve automated data analysis target. A neural network, which is commonly used as an artificial intelligence technology, possesses excellent feature recognition and logistic regression ability, which are very important to implement automated data analysis. In this paper, the principle and characteristics of the neural network are presented. A neural network is established to discern the depth and length of slits automatically, and it is verified whether the ANN can ...
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Feasibility study of neural network technology applied to advanced eddy current testing -Depth and length sizing of defects using neural networks-

In the previous study, we proposed an eddy current magnetic signature method as a way to evaluate the residual strain of low carbon steels. However, the dependence of the pearlite content which affects magnetic properties of steel on the eddy current magnetic signature has not been discussed yet. In this study, to evaluate the effect of the pearlite content on the eddy current magnetic signature, two kinds of low carbon steels with different pearlite contents are investigated. The specimens with different r...
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Evaluation of residual strain of low carbon steels with various pearlite contents by eddy current magnetic signature method

In this study, we focus on the eddy current testing (ECT) as a method to investigate the hydrogen embrittlement mechanism of austenitic stainless steels which are widely used in hydrogen components. ECT is applied to hydrogen-charged austenitic stainless steel AISI 304 specimens with different amounts of residual strain. Permeability values of the specimens are estimated by comparing the signals obtained by the ECT experiment and the results of the electromagnetic field analysis, and the phase transformatio...
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Evaluation of Phase Transition of Austenitic Stainless Steel due in Hydrogen Embrittlement by Eddy Current Magnetic Signature Method

Eddy Current Testing (ECT) is widely used for non-destructive testing in the industrial fields. Furthermore, ECT is expected to be used not only for evaluating the integrity of products, but also in the field of fundamental research, such as the mechanism study of hydrogen assisted fatigue crack growth since ECT can evaluate electromagnetic properties. However, the low spatial resolution of ECT is an issue for such applications. To improve the resolution of ECT system, a magneto-optic (MO) element is applie...
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Development and Evaluation of Eddy Current Probe Using Magneto-Optical Effect