In order to estimate the stability of the stress improving effect by water jet peening (WJP) residual stress improvement methods during the long-term operation of nuclear power plants, the residual stress in nickel-based alloy 600 has been studied through the kinetics of hardness reduction behavior in practical operation temperatures. Based on the relationship between the residual stress relaxation and the hardness reduction rates, it has been found that in actual operating condition, when the hardness decr...
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Prediction of Residual Stress Stability Introduced by Water Jet Peening Residual Stress Improvement Method to Ni-based Alloy during Long-Term Operation

In order to compare the stability of the stress improvement effect introduced by laser peening (LP), water jet peening (WJP) and buffing residual stress improvement methods during the long-term operation of nuclear power plants, the hardness in nickel-based alloy 600 has been studied through the kinetics of hardness reduction behavior in practical operation temperatures. The predicted hardness results show that in actual operating condition, the time required to reduce the hardness to 180HV is 1268 years fo...
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Long-Term Stability Comparison of LP, WJP and Buffing Residual Stress Improvement Methods under Actual Operating Condition

In the present study, effect of spurious diagnostics to improvement of safety, and po ssibility of extension in the interval of TBM (Time-Based Maintenance) by introducing CBM (Condition-Based Maintenance) and necessity of TBM were investigated. From these investigations, improvement of safety and reduction of maintenance cost can be seen....
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Study on Best-Mix of CBM and TBM Considering Effect of Spurious Diagnostics Using State Transition Model

１．背景　米国機械学会は、先駆的に原子力発電設備の維持規格制定に取組み、1971年に供用期間中検査を規定したASME Code Section XIを制定している。その後、ASME Code Section XIの1974年版では、検査で発見された欠陥の成長評価と機器の健全性に基づく欠陥評価基準が新たに導入された。この基準は、供用期間中に発見された欠陥については、製造時の許容基準を超えた場合についても健全性を損なわない範囲で許容し、欠陥が存在したまま継続運転可能とするものであり、1960年代に進展した破壊......

Rolling bearing is the most part used in rotating machinery of industrial plant. The condition diagnosis technology of rolling bearing is very important and indispensable for the plant safety and operation stability. The purpose o f this study is to improve the accuracy of the life prediction for a rolling bearing. The paper proposes a searchin g method for the optimum mathematic function for the high accurate prediction by using the genetic algorithms (GA)....
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Life Prediction of Rolling Bearing Using Genetic Algorithm

Abstract : This paper presents a precise condition diagnosis method for a centrifugal pump using sequential fuzzy neural network (SFNN). Firstly, the feature signals of fault states are extracted from the measured vibration signals for the pump condition diagnosis in different frequency regions by statistic filter, symptom parameters (SPs) for distinguishing fault types are defined and calculated by using the feature signals. Secondly, to distinguish the pump state, sequential fuzzy neural network (SFN...
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Precise Diagnosis Method for Centrifugal Pump by Sequential Fuzzy Neural Network

原子力発電プラントの高経年化に伴い発生する経年劣化事象の一つである応力腐食割れ(Stress Corrosion Cracking: SCC)の防止対策として、溶接に伴って発生した引張残留応力を圧縮残留応力に変化させる応力改善が有効である。 本研究では、材料内部の格子欠陥の存在状態を定量的に、かつ、高感度に評価できる陽電子寿命法を採用することにより、応力改善工法の施工により導入された残留応力に密接に関連する格子欠陥や転位によるひずみの存在を調査した。...
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Consideration on Mechanism of Residual Stress Relaxation Behavior of Ni-based Alloy Using Positron Annihilation Lifetime Spectroscopy?

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

In order to determine crack depth in primarily loop recirculation (PLR) piping of boiling water reactors, ultrasonic angle beam testing using time of flight measurement of the diffracted signal from the crack tip, is employed. There are some power stations in Japan having saddle-shaped weld joints at branch connections in PLR piping. If the angle beam testing is applied without considering curvature of saddle-shaped weld joints, unlike weld joints of straight piping, it can be predicted that determine...
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Ultrasonic Depth-sizing Errors of Crack-like Defects in Saddle-shaped Weld Joints