1,721,040 research outputs found
Error analysis in improved motor control center method for stem thrust estimation of motor-operated valves in nuclear power plants
No full textAn error analysis for improved motor control center (MCC) method that estimates the stem thrust of motor-operated valve (MOV) is suggested in this work. This method focuses on providing an alternative means for the periodic performance verification test with relatively lower error than the conventional MCC-based method. For evaluating the overall error of the improved MCC method, the errors are classified into two categories: the biased error and the random error. The biased error consists of the mean of the relative error between measured and estimated torque and that of the stem factor. The random error comes from the statistical analysis of the measured torque, stem factor, and motor electric data. The experiment result shows that this method has a reasonably lower error than the MCC-based method. Therefore, this method can be applied to the periodic verification test of valves with relatively low margins
Estimation of the flow profile correction factor of a transit-time ultrasonic flow meter for the feedwater flow measurement in a nuclear power plant
No full textA new method to estimate the flow profile correction factor (FPCF) for a transit-time ultrasonic flow meter (UFM) having a diametral transducer configuration is introduced in this work. For the adaptation of a diametral UFM for a feedwater measurement, the optimized flow profile correction factor is obtained through experiments and a simulation in actual flow conditions. The log function curve fitting is performed on a combined data set; the velocity ratio of UFM reading versus standard fluid measurement at low flow velocity, UFM reading versus standard fluid measurement at medium flow velocity, and UFM reading versus clean Venturi measurement at high flow velocity. Through an uncertainty analysis, the uncertainty of the FPCF is calculated. The resultant uncertainty of the new FPCF is 0.335%. This value is approximately half the value presented by UFM manufacturers. By adaptation of a diametral UFM with the new FPCF proposed in this work, feedwater flow measurement in nuclear power plants (NPPs) can be easily performed at lower cost than either chordal or cross-correlation UFM
An improved method for reactor coolant pump abnormality monitoring using power line signal analysis
No full textAn improved method to detect the reactor coolant pump (RCP) abnormality is suggested in this work. The monitoring parameters that are acquired from power line signal analysis are motor torque, motor speed and characteristic harmonic frequencies. The combination of Wigner-Ville Distribution (WVD) and feature area matrix comparison method is used for abnormality diagnosis. For validation of the proposed method, the test was performed during cool-down phase and heat-up phase in nuclear power plant (NPP) by cross-comparison with RCP vibration monitoring system (VMS). Using pump internal inspection results, the diagnosis prediction is verified. (c) 2005 Elsevier B.V. All rights reserved
Application of an integrated power line signal analysis methodology to the detection of major rotating machine abnormalities in nuclear power plants
No full textAn integrated and improved method to detect and identify the abnormality of motor driven rotating machinery in nuclear power plants (NPPs) using power line signal analysis is suggested in this work. The primary goal of this work is to improve the motor current signature analysis (MCSA) method that has been used as an alternative or supplement of the conventional vibration monitoring system (VMS). Through this work, the integrated system using both modulated flux density model (MFDM) and rotating flux model (RFM) is proposed. The MFDM is based on the fact that the major mechanical vibration of rotating machines can be normalized to the motor air-gap eccentricity and the modulation of air-gap flux density. Therefore, if the major defect such as bearing defect or the shaft deformation is present, it is identifiable through the power line signal resulting from the modulated magnetic density. Moreover, the broken rotor bar state or rotor eccentricity due to electrical imbalance can be analyzed using the RFM. The other important feature of this system is an automated abnormality detection and diagnosis algorithm. It is possible to diagnose the abnormality without relying on experts in NPPs. The verification is done through varying load/torque test experiment as well as via computer simulation in this work. The experimental results show that they are in good agreement with the simulated results. (C) 2004 Elsevier B.V. All rights reserved
Algorithm automation for nuclear power plant Loose Parts Monitoring System
No full textLoose Parts Monitoring signals in the control room of the nuclear power plant come in through multiple channels and are presented as graphs on the display devices. It involves a lengthy and complicated process to determine the size, mass, speed, and impact location of the loose part when the signals are collected and processed. In this work, a simple and efficient model for determining the impact location of the loose part using the Least-Sum-of-Square-Errors (LSSEs) method combined with iteration has been developed based on the phase distortion of the impact signal envelopes. The signal peak point shifts to the right on the time axis when the sensor is located farther away from the impact location. This method provides a good estimation of the impact location and can be used as an alternative to existing calculations based on other attributes of the impacting signal. To automate the backend portion of the LPMS algorithm, interpolation was used for compensating the impact attenuation effect and log-log regression was also employed to determine the impacting part size and impact velocity, and the result turned out to be well in line with the manual calculations. The automated algorithm will improve the efficiency of the LPMS software. (C) 2003 Published by Elsevier B.V
New base-soluble positive-working photosensitive polyimides having o-nitrobenzyl ester group
No full textA new positive-working polyimide having photosensitive o-nitrobenzyl ester group as side substituent, poly(1,4-phenyleneoxy-1,4-phenylene-3,6-di[4-(o-nitrobenzyloxy)carbonylphenyl]pyromellit imide] (ODA-PI-Nb), was prepared and its aqueous alkali-developability and photosensitivity were investigated. ODA-PI-Nb was synthesized by the esterification reaction of poly[1,4-phenyleneoxy-1.4-phenylene-3,6-di(4-carboxylphenyl)pyromellit imide] (ODA-PI) with o-nitrobenzyl bromide in the presence of triethylamine (Et3N). ODA-PI-Nb obtained was characterized by FT-IR and H-1-NMR spectroscopy. The degree of esterification reaction was found from H-1-NMR absorption of CH2 proton to be over 95mol%. Upon photo-irradiation ODA-PI-Nb transformed to the freely aqueous alkali-soluble ODA-PI under formation of o-nitrosobenzaldehyde. The thickness loss of thin ODA-PI-Nb films upon post-baking at 400 degrees C was in the 10-15% range. ODA-PI-Nb showed positive-tone behavior in characteristic sensitivity curve and positive patterns were obtained using a typical lithographic process using aqueous tetramethylammonium hydroxide developer. The patterns with excellent resolution were observed and evaluated by optical microscopy and scanning electron microscopy. Copyright (c) 2005 John Wiley & Sons, Ltd
Concept Selection of NPP Construction Delay Risk Assessment Methodology Using Systems Engineering Approach
No full textConstruction industry faces a lot of inherent uncertainties and issues and the construction phase of nuclear power project is not free from this risk. This paper investigates promising methodologies to be used on nuclear power plant (NPP) construction schedule delay risk assessment by using entry level systems engineering approach. This study contains how the initial concept for the risk assessment methodology has been developed. In this point of view, this work structured on three main phases: needs analysis (NA), concept exploration (CE), and concept definition (CD) through systems engineering (SE) approach. Traditionally, the SE process is applied to technical development programs but this study opens up a new avenue that SE can also be successfully applied to the development and optimization of the risk assessment model. This study provides a rational and systematic process for developing and selecting the best risk assessment model. This paper selects analytic hierarchy process (AHP) method to assess NPP construction schedule delay risk for international project. As conclusion, the proposed concept and selected method can discriminate successfully and clearly among schedule delay risk assessment methods.
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
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