This paper proposes backpropagation neural network models which are based on artificial intelligence technology to detect the defect signals and to discern the measurements of defects according to the eddy current testing (ECT) results even under the probe lift-off and probe wobble noise effects. In this paper, a stainless plate with three different depth slits is tested by ECT to collect defect signals. And during the scanning process, the noise which is mentioned above is added. All the collected data are...
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Detection and sizing of defects in eddy current testing using artificial neural network

Flow Acceleration Corrosion (FAC) is one of the mechanisms of pipe wall thinning in power plants. The wall thinning caused by FAC is usually found between 90 ℃ and 230 ℃ with a peak at about 150 ℃. However, FAC has been reported at temperatures below this range. This study evaluated the effect of DO and Cr content on wall thinning rate at 50 ℃. Raman spectroscopy was performed to identify the constituent species of the oxide film. FAC rate was seen to decrease by increasing Cr content. In terms of DO, wall ...
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Combined Effect of Cr content and Dissolved Oxygen Concentration on Wall Thinning Rate by Low Temperature FAC

It is important for maintenance of nuclear power station facilities in the future to promote mathematical techniques which support judgement to modify maintenance practices, such as maintenance tasks, maintenance implementation timing, and so on. Mathematical Maintenance Working Group, which has been established by Maintenance Standardization Committee since July 6, 2018, is investigating application examples of such mathematical techniques in maintenance planning as influence evaluation of changing maint...
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Investigation on application examples of mathematical techniques to support judgement to modify maintenance practices

It is necessary to improve not only plant system but also human system for maintenance to optimize maintenance for industrial plants like nuclear power plants. Codes and standards for design and construction of plant system have been already well developed. On the contrary, standardization of documents relating to human system including maintenance implementation plan, field work procedures etc. have poorly developed. So we have established the special committee in Japan Society of Maintenology to standardi...
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Necessity and Direction of Consideration of Maintenance Standardization

There are three technologies for facility maintenance, i.e. inspection, aging degradation evaluation and corrective measure. It was discussed that it was important to develop them systematically to be able to cope with any situation which occurs in industrial plants....
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Study on the Position and Role of Corrective Measures in Plant Maintenance

Electromagnetic acoustic resonance (EMAR) method is useful for measuring thickness of pipe. But in the case of thickness changing complicatedly in part of pipe wall thinning for various factor, accurate thickness measurement is difficult. In this study, thickness of specimens of pipe corroded under various conditions is evaluated by EMAR. The error of thickness evaluation is investigated in view of maximum value of spectrum and roughness and curvature of pipe. As a result, it is suggested that signal streng...
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Evaluation of pipe wall thinning with electromagnetic acoustic resonance method considering effects of roughness and curvature of inner surface.

In this study, the generalized failure mechanism knowledge (GFMK) derived from trouble cases in the Rokkasho reprocessing plant has been applied to an mechanical subsystem in the same plant in order to examine its general applicability. This study confirms that the GFMK can be applied to the subsystem of a pool water cooling system and that a potential failure mechanism can be successfully derived. The efficacy of the derived knowledge regarding this failure mechanism was evaluated by referring to maintenan...
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Application of the structured representation of trouble cases in reprocessing plant

The purpose in this research is to verify whether risk recognition can be explained not only by the subjective evaluation methods but also by the objective evaluation based on autonomic nervous activity. In the present study, a fundamental method to realize objective risk recognition evaluation has been proposed using heartbeat data in the safety education at experiential training facilities. Based on the results obtained in this research, it has been confirmed that risk-taking behavior characteristics can ...
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Evaluation of risk sensitivity and risk taking behavior based on objective measurements

This study performed finite element simulations to evaluate the applicability of a low-frequency eddy current nondestructive testing method for the detection of corrosions appearing in a double tank used in a reprocessing plant using a large diameter coil attached to the bottom of the tank. The simulations modeled the tank as an axisymmetric one, and evaluated the effect of various parameters such as frequency, coil radius and the gap between the inner and the outer vessels. The results of the simulations c...
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Finite Element Evaluation of the Low Frequency Electromagnetic Method using a Large Exciter Coil for Monitoring the Corrosion of Double Tank in a Reprocessing Plant

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(3) Improvement for Wet-Type Filter