Effects of thermal history and segregation on the susceptibility of stress corrosion cracking (SCC) in the heat-affected zone (HAZ) of an alloy 182-A533B dissimilar weld joint in high temperature, oxygenated water doped with SO4 2- and Cl- was evaluated by creviced bent beam test. Results indicate that step cooling and the addition of Cl- promoted SCC propagation and reactivation in HAZ. It is also suggested that compositional changes induced by welding and step cooling, especially the segregation of ph...
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Correlation between phosphorus segregation and stress corrosion cracking susceptibility in the heat affected zone of an A533B-A182 dissimilar weld joint

Grain boundary (GB) segregation of phosphorus and alloying elements in the heat-affected zone (HAZ) of an Alloy182- A533B dissimilar weld joint used in nuclear reactor pressure vessels was studied quantitatively by three-dimensional atom probe tomography. Non-equilibrium segregation occurred during welding and post-weld heat treatment, leading to remarkable enrichment of P, C, Mn and Mo at GBs, of which the levels were all microstructure- dependent. After step cooling, P and Mn showed further increase ...
英字タイトル:
Effects of thermal history and microstructure on grain boundary segregation in the heat-affected zone of an Alloy182-A533B dissimilar weld joint

In power plant, the operator monitors measured values of many installed sensors for operation and maintenance. Since the number that can be visually confirmed is limited, we have proposed two-stage autoencoder for anomaly detection. The latest version was developed to suppress false positives due to spurious correlations in training data, and its effectiveness was shown using simulation data. In this paper, the anomaly detection performance is shown using the operational data of an actual power plant. As a ...
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Performance Evaluation of the Anomaly Detection by Two-Stage Autoencoder using Power Plant Data

Abstract Most of low speed rotating equipments includes large important equipments, and an equipment stoppage caused by damage of rolling element bearing brings significant losses to a plant. This paper relates to a diagnostic method of rolling element bearing in low speed rotating equipment of 100 rpm or less, and proposes a method to diagnose using AE envelope waveform of a 100 k to 1 MHz frequency region. Abnormal ity diagnosis wasafter envelope processing in addition to amplification of AE waveform. Fu...
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Diagnosis of Low Speed Rolling Element Bearing by AE Method.

1．背景および概要沸騰水型原子炉（BWR）プラントにおける応力腐食割れ（SCC）の発生事例は、1974年に米国で原子炉一次系のステンレス鋼配管に確認され、国内においても、多くの事例が確認されている。炉心シュラウドについては、1990年にスイスで、1993年には米国、翌年には東京電力福島第一２号機で も確認された。本稿では、国内BWRプラントにおけるSCC対策と して実機に適用された工法と評価について述べる。2．原子炉内大型構造物の取替2-1） 概 要1994年に福島第一２号機シュラウド中間リング溶接 部（......

Abstract: Since more and more bridges built several decades ago in Japan have become aged and dangerous, the non-destructive evaluation of those bridges is really an urgent problem. CT system with portable 3.95MeV linacs for bridge inspection is considered to work on-site, considering the law of Japanese radiation protection allows using linacs up to 4MeV outside radiation controlled area. The system would confirm the internal steel si tuation of bridges and analyze structural strain and stress with 3D mod...
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On-Site Bridge Inspection with Partial CT by 3.95Mev X-Band Linac Source

In domestic nuclear power plants, ultrasonic testing is performed as an in-service inspection for piping accor ding to JSME code. Using automated UT equipments and UT analysis system, confirmation of repeatability for UT data, automated extraction and detailed evaluation are performed. Furthermore, automated reporting function ma kes reduction of hours of work. In this report, the outline and advantage of UT analysis system are described....
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Upgrading of UT Evaluation Technique Applying UT Analysis System

Microstructural state of metallic materials can be expressed by the system free energy, and the estimation of the system free energy is useful for the damage analysis of the materials. In this study, change in the system free energy of 9Cr heat resistant ferritic steels is estimated with cre ep time on the basis of Thermo-Calc calculation as well as a series of experiments such as X ray diffraction analysis, chemical analysis using ext racted residues, etc., and the change with creep time is expressed quan...
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Change in the system free energy of 9Cr heat resistant ferritic steels with creep time

Tsuruga Power Station Unit 2 (1,160 MW, PWR) has been operated since February 1987, and has long term maintenance experience for the past 29-years. Tsuruga Unit 2 is the first plant which applied prestressed concrete vessel (PCCV) in Japan. In-service inspection has been applied to PCCV, and it has been maintained good condition in spite of long term operation. Before the passing of 30 years from the start of operation, a technical evaluation of degradation of the PCCV due to aging needs to be performe...
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Maintenance experience and Plant Life Management for Prestressed Concrete Containment Vessel of Tsuruga Power Station Unit 2

Muon tomography has recently been put to practical use for nondestructive testing of shipping container. But it can’t be used in a high dose environment(～1mSv/h) without shielding. So, we are developing high dose tolerant muon track measurement system using spark chamber technology. In this paper, the result of simulation is described. We found that it is necessary to use 10cm-square scintillation counters and its pulse width is in 300ns. We confirmed this design is achievable to use in high dose rate(...
英字タイトル:
High dose tolerant nondestructive testing using muon tomography