• Nuclear Engineering and Technology
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• v.50 no.8
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• pp.1217-1233
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• 2018

Following a surge of interest in multi-unit risk in the last few years, many recent studies have suggested methods for multi-unit probabilistic safety assessment (MUPSA) and addressed several related aspects. Most of the existing studies though focused on two-unit nuclear power plant (NPP) sites or used rather simplified probabilistic safety assessment (PSA) models to demonstrate the proposed approaches. When considering an NPP site with three or more units, some approaches are inapplicable or yield very conservative results. Since the number of such sites is increasing, there is a strong need to develop and validate practical approaches to the related MUPSA. This article provides several detailed approaches that are applicable to multi-unit Level 1 PSA for sites with up to six or more reactor units. To validate the approaches, a multi-unit Level 1 PSA model is developed and the site core damage frequency is estimated for each of four representative multi-unit initiators, as well as for the case of a simultaneous occurrence of independent single-unit initiators in multiple units. For this purpose, an NPP site with six identical OPR-1000 units is considered, with full-scale Level 1 PSA models for a specific OPR-1000 plant used as the base single-unit models.

• Journal of the Korean Society of Propulsion Engineers
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• v.2 no.2
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• pp.74-82
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• 1998

Combined cycle power plant is a system where a gas turbine or a steam turbine is used to produce shaft power to drive a generator for producing electrical power and the steam from the HRSG is expanded in a steam turbine for additional shaft power. The temperature of the exhaust gases from a gas turbine ranges from $400{\sim}650^{\circ}C$, and can be used effectively in a heat recovery steam generator to produce steam. Combined cycle can be classed as a topping and bottoming cycle. The first cycle, to which most of the heat is supplied, is a Brayton gas turbine cycle. The wasted heat it produces is then utilized in a second process which operates at a lower temperature level is a steam turbine cycle. The combined gas and steam turbine power plant have been widely accepted because, first, each separate system has already proven themselves in power plants as an independent cycle, therefore, the development costs are low. Secondly, using the air as a working medium, the operation is relatively non- problematic and inexpensive and can be used in gas turbines at an elevated temperature level over $1000^{\circ}C$. The steam process uses water, which is likewise inexpensive and widely available, but better suited for the medium and low temperature ranges. It therefore, is quite reasonable to use the steam process for the bottoming cycle. Recently gas turbine attained inlet temperature that make it possible to design a highly efficient combined cycle. In the present study, performance analysis of a 3 pressured combined cycle power plant is carried out to investigate the influence of topping cycle to combined cycle performance. Present calculation is compared with acceptance performance test data from SeoInchon combined cycle power plant. Present results is expected to shed some light to design and manufacture 150~200MW class heavy duty gas turbine whose conceptual design is already being undertaken.

• Plant Journal
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• v.9 no.1
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• pp.50-57
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• 2013

This study investigates the risks that can occur during the development stage of IPP project in developing countries. In case that ECA and MLA cannot participate due to poor credit rating of the country, the diversification of power purchaser in marginal states can be a great help to reduce both market risk and country risk at the same time. In case of thermal power plants and combined cycle power plants, the effect of performance degradation as time passed will be considered and expected profit of sponsors should be maintained. Recently, developing countries are expanding IPP projects to reduce the financing cost and Korean power companies are positively participating in IPP projects. Accordingly, the loss of Korean companies should be minimized by risk management through the risk mitigation methods of this study.

• Journal of Drive and Control
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• v.16 no.2
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• pp.30-35
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• 2019

EPPR (Electro-hydraulic Proportional Pressure Reducing) valves are pressure control valves. In this study, an independent metering valve (IMV), which is a combination of a spool valve opened and closed with the help of an EPPR valve, was discussed. The overall performance of the valve (IMV) was obtained by the respective modeling and simulation of the system. The valve investigated in this study is to be used for independent metering of hydraulic excavator actuator e.g. boom, arm, bucket etc. To design the model, continuity equations and force balance equations were used. The set of differential equations were then simulated in Simulink using ODE45 option in the configuration toolbox. The valve has to be able to control the flow rate going in and out of the cylinder separately, which is why the particular configuration was needed and selected.

• Nuclear Engineering and Technology
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• v.41 no.9
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• pp.1181-1190
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• 2009

Knowing more about the Local Power Density (LPD) at the hottest part of a nuclear reactor core can provide more important information than knowledge of the LPD at any other position. The LPD at the hottest part needs to be estimated accurately in order to prevent the fuel rod from melting in a nuclear reactor. Support Vector Machines (SVMs) have successfully been applied in classification and regression problems. Therefore, in this paper, the power peaking factor, which is defined as the highest LPD to the average power density in a reactor core, was estimated by SVMs which use numerous measured signals of the reactor coolant system. The SVM models were developed by using a training data set and validated by an independent test data set. The SVM models' uncertainty was analyzed by using 100 sampled training data sets and verification data sets. The prediction intervals were very small, which means that the predicted values were very accurate. The predicted values were then applied to the first fuel cycle of the Yonggwang Nuclear Power Plant Unit 3. The root mean squared error was approximately 0.15%, which is accurate enough for use in LPD monitoring and for core protection that uses LPD estimation.

• Nuclear Engineering and Technology
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• v.41 no.3
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• pp.225-236
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• 2009

This study has identified human performance research issues associated with the implementation of new technology in nuclear power plants (NPPs). To identify the research issues, current industry developments and trends were evaluated in the areas of reactor technology, instrumentation and control technology, human-system integration technology, and human factors engineering (HFE) methods and tools. The issues were prioritized into four categories based on evaluations provided by 14 independent subject matter experts representing vendors, utilities, research organizations and regulators. Twenty issues were categorized into the top priority category. The study also identifies the priority of each issue and the rationale for those in the top priority category. The top priority issues were then organized into research program areas of: New Concepts of Operation using Multi-agent Teams, Human-system Interface Design, Complexity Issues in Advanced Systems, Operating Experience of New and Modernized Plants, and HFE Methods and Tools. The results can serve as input to the development of a long-term strategy and plan for addressing human performance in these areas to support the safe operation of new NPPs.

• Nuclear Engineering and Technology
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• v.53 no.8
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• pp.2753-2760
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• 2021

This paper proposes using sodium-cooled fast reactor technologies for use in hydrogen vapor methane (SMR) modification. Using three independent energy rings in the Russian BN-600 fast reactor, steam is generated in one of the steam-generating cycles with a pressure of 13.1 MPa and a temperature of 505 ℃. The reactor's second energy cycles can increase the gas-steam mixture's temperature to the required amount for efficient correction. The 620 ton/hr 540 ℃ steam generated in this cycle is sufficient to supply a high-temperature synthesis current source (700 ℃), which raises the steam-gas mixture's temperature in the reactor. The proposed technology provides a high rate of hydrogen production (approximately 144.5 ton/hr of standard H₂), also up to 25% of the original natural gas, in line with existing SMR technology for preparing and heating steam and gas mixtures will be saved. Also, exergy analysis results show that the plant's efficiency reaches 78.5% using HTR heat for combined hydrogen and power generation.

• Nuclear Engineering and Technology
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• v.55 no.8
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• pp.2897-2904
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• 2023

The Standardized Plant Analysis Risk-Human Reliability Analysis (SPAR-H) method is a widely used method in human reliability analysis (HRA). Performance shaping factors (PSFs) refer to the factors that may influence human performance and are used to adjust nominal human error probabilities (HEPs) in SPAR-H. However, the PSFs are assumed to be independent, which is unrealistic and can lead to unreasonable estimation of HEPs. In this paper, a new method is proposed to handle the dependencies among PSFs in SPAR-H to obtain more reasonable results. Firstly, the dependencies among PSFs are analyzed by using decision-making trial and evaluation laboratory (DEMATEL) method. Then, PSFs are assigned different weights according to their dependent relationships. Finally, multipliers of PSFs are modified based on the relative weights of PSFs. A case study is illustrated that the proposed method is effective in handling the dependent PSFs in SPAR-H, where the duplicate calculations of the dependent part can be reduced. The proposed method can deal with a more general situation that PSFs are dependent, and can provide more reasonable results.

• Journal of Power Electronics
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• v.14 no.1
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• pp.74-81
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• 2014

In this study, a brain emotional learning-based intelligent controller (BELBIC) is developed for the speed control of an interior permanent magnet synchronous motor (IPMSM). A novel and simple model of the IPMSM drive structure is established with the intelligent control system, which controls motor speed accurately without the use of any conventional PI controllers and is independent of motor parameters. This study is conducted in both real time and simulation with a new control plant for a laboratory 3 ph, 3.8 Nm IPMSM digital signal processor (DSP)-based drive system. This DSP-based drive system is then compared with conventional BELBIC and an optimized conventional PI controller. Results show that the proposed method performs better than the other controllers and exhibits excellent control characteristics, such as fast response, simple implementation, and robustness with respect to disturbances and manufacturing imperfections.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.63 no.6
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• pp.752-757
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• 2014

This paper attempts to evaluate the impact of power plant penetration on constraints of a transmission network and proposes a methodology based on risk level, which can evaluate the condition of the network and facilities intuitionally. Furthermore, based on this methodology, RLII(Risk Level Improvement Index) is proposed in order to establish comprehensive TNEP(Transmission Network Expansion Planning) from a viewpoint of ISO(Independent System Operator). In order to verify the proposed methods in this paper, real power systems in Incheon and Shiheung areas, south Korea are applied to the case study.