Abstract For the last couple of years, issue of defects in Alloy 600 weld lowered the capacity factor of nuclear power plants. To apply newly developed repair technique, like temper-bead welding that has not been prescribed in technical standards, it is necessary to evaluate its technical applicability to the requirement. In the previous cases, this process has been completed by issuance of no action letter for specific area and condition, utilizing implementation process, such as confirm testing by J...
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Study on implementing newly developed repair welding technique within a limited time frame for nuclear power plant

Many anchor bolts have been used for fixing many components in nuclear power plant (NPP), securing safety against seismic ev ents. Some methods have been developed to detect crack-like defects in bolts which may occur after seismic events. On the ot her hand, assuming long term use of NPP, a method to detect bolt thinning was thought to be needed. In this study, by using bolt specimens with an artificially grinded portion, a new method to detect thinning and to measure its depth was developed....
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Development of inspection method for thinned bolts by PA-UT

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......

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

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