• Nuclear Engineering and Technology
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• 제47권6호
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• pp.766-775
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• 2015

The integrity assessment of reactor vessel internals should be conducted in the design process to secure the safety of nuclear power plants. Various loads such as self-weight, seismic load, flow-induced load, and preload are applied to the internals. Therefore, the American Society of Mechanical Engineers (ASME) Code, Section III, defines the stress limit for reactor vessel internals. The present study focused on structural response analyses of the upper guide structure upper flange. The distributions of the stress intensity in the flange body were analyzed under various design load cases during normal operation. The allowable stress intensities along the expected sections of stress concentration were derived from the results of the finite element analysis for evaluating the structural integrity of the flange design. Furthermore, seismic analyses of the upper flange were performed to identify dynamic behavior with respect to the seismic and impact input. The mode superposition and full transient methods were used to perform time-history analyses, and the displacement at the lower end of the flange was obtained. The effect of the damping ratio on the response of the flange was also evaluated, and the acceleration was obtained. The results of elastic and seismic analyses in this study will be used as basic information to judge whether a flange design meets the acceptance criteria.

• 한국안전학회지
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• 제33권5호
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• pp.35-41
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• 2018

Chemical accidents generated during maintenance, repair, and normal operation, such as dispersion, fire, and explosions, can cause massive losses like a 2012 hydro fluorine leak in Gumi, South Korea. Since this accident, many researches have studied physical mitigation systems. However, due to the lack of potential costs and time, it is really hard for many companies to install mitigation systems without prior knowledge. Thus, the efficacy of mitigation system should be evaluated. This study assesses a dike design considering the fluid velocity at an open hole when a leakage accident occurs. It is assumed that leakage materials follow a free fall motion. Throughout case studies, a current KOSHA guide for a dike design was evaluated and new guidelines handling various conditions were proposed.

• 대한건축학회논문집:계획계
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• 제34권5호
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• pp.11-20
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• 2018

To prevent illegal building work in advance, regional building safety centers were introduced to perform technical investigations and management. The purpose of this study is to propose the detailed operational directions of the regional building safety center through the analysis on the current status of parameters, such as the operation of designated confirmation and inspection bodies in Japan. We consider the role, building administrative process and establishment criteria of regional building safety centers through the analysis the introduction background and the designation criteria of designated confirmation and inspection bodies. In establishing the center's professional manpower qualifications, we refer to the criteria for the professional qualifications of the designated confirmation and inspection bodies. In addition, the calculation method of required manpower of verification inspectors in Japan was used as a reference in setting the scale of regional professional manpower. Finally, we propose the detailed operational directions of the regional building safety center such as (1)roles of the center, (2)establishing management plan of the center, (3)work scope (4)scale of the professional manpower, (5)qualification of the professional manpower, and (6)funds.

• Nuclear Engineering and Technology
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• 제52권12호
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• pp.2812-2820
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• 2020

House load operation (HLO) occurs when the generator supplies power to the house load without triggering reactor trips during grid disturbances. In Korea, the HLO capability of optimized power reactor 1000 (OPR1000) plants has prevented several reactor trips. Operational experiences demonstrate the difference in the reactor trip incidence due to grid disturbances between OPR1000 plants and Westinghouse plants in Korea, attributable to the availability of the HLO capability. However, probabilistic safety assessments (PSAs) for OPR1000 plants have not considered their specific design features in the initiating event analyses. In an at-power PSA, the HLO capability can affect the initiating event frequencies of general transients (GTRN) and loss of offsite power (LOOP), resulting from transients within the grid system. The initiating event frequencies of GTRN and LOOP for an OPR1000 plant are reduced by 17.7% and 78.7%, respectively, compared to the Korean industry-average initiating event frequencies, and its core damage frequency from internal events is reduced by 15.2%. The explicit consideration of the HLO capability in initiating event analyses makes significant changes in the risk contributions of the initiating events. Consequently, for more realistic at-power PSAs in Korea, we recommend incorporating plant-specific HLO-related design features when estimating initiating event frequencies.

• 한국산업융합학회 논문집
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• 제23권5호
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• pp.789-798
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• 2020

This paper considers the development of the dynamic analysis model and simulation-based operation safety estimation of A-Frame to be applied to the test evaluation support vessel for real sea test. The support vessel will be manufactured by modifying the existing offshore support vessel. Also, development and installation of various sensors and supporting facilities for test evaluation are under preparation. Among these facilities, A-Frame is an equipment that transfers marine equipment from ship deck to the sea floor, and is being designed to transfer up to 50 ton class equipment. However, the A-Frame is a moving equipment using hydraulic cylinders. When the 50 ton equipment is attached and transferred to A-Frame, the buckling of cylinders may occur or A-Frame becomes inoperable due to the influence of huge inertia. For this reason, safety verification should be performed using dynamic analysis techniques that can take into account huge inertia forces in the design of A-Frame. Therefore, in this study, A-Frame and ship behavior were modeled using dynamic analysis method, and the applied loads of various equipment including hydraulic cylinder of A-Frame was measured and the operation safety review was performed.

• 시스템엔지니어링학술지
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• 제11권1호
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• pp.1-7
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• 2015

The purpose of this paper is to present the results of reengineering of the YGN 3&4 (Yonggwang Nuclear Power Plant, Units 3&4) SDS (Safety Depressurization System) retrofit design and to make recommendations for the improvement in design and design procedure implementing the Systems Engineering (SE) process. YGN 3&4 is a basic model for OPR1000 (the Korean standard 1000 MWe plant). The basic model, herein, represents the reference plant for the OPR1000 development. In the middle of the YGN 3&4 construction, the Korean Nuclear Regulatory Body requested a retrofit of this plant with a means to rapidly depressurize the plant in conformance with a severe accident mitigation requirement. For the reengineering of the SDS in YGN 3&4, V-model and functional and physical architectures have been developed. A SE decision making method has been used for the selection of SDS valves. Finally, recommendations have been made to improve OPR1000 design for the improved operation and enhanced safety.

• 한국철도학회:학술대회논문집
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• 한국철도학회 2004년도 춘계학술대회 논문집
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• pp.206-212
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• 2004

This paper is application of System Assurance(SA) for the rolling stock. As railway systems become more complex, design teams are increasingly under pressure to deliver, design solutions, which integrate both technical and Systems Assurance(SA). Systems Assurance is the application of management methods and analysis techniques to ensure that a design meets Reliability, Availability, Maintainability and Safety (RAMS) criteria. It should be clearly understood that the intent of System Assurance is not just to provide analytical techniques as a metric on performance, but more importantly it should provide a management tool with which to co-ordinate and assure the whole design. System Assurance encompasses the ongoing requirement to consider safety, and RAM through each stage of a Project, from feasibility study through to commissioning and operation. If System Assurance is undertaken properly at feasibility study at the design stages of a Project, the benefits of such analyses can be significant in identifying potential problems early enough for action to be taken before manufacture or installation. At commissioning, RAMS demonstration activities are undertaken to validate the predictive and analytical techniques undertaken during the design.

• International Journal of CAD/CAM
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• 제6권1호
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• pp.29-40
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• 2006

The paper presents an optimization system which integrates a parametric design tool, 3D diffraction-radiation analysis and hydrodynamic performance assessment based on short and long term wave statistics. Controlled by formal optimization strategies the system is able to design offshore structure hulls with superior seakeeping qualities. The parametric modeling tool enables the designer to specify the geometric characteristics of the design from displacement over principal dimensions down to local shape properties. The computer generates the hull form and passes it on to the hydrodynamic analysis, which computes response amplitude operators (RAOs) for forces and motions. Combining the RAOs with short and long-term wave statistics provides a realistic assessment of the quality of the design. The optimization algorithm changes selected shape parameters in order to minimize forces and motions, thus increasing availability and safety of the system. Constraints ensure that only feasible designs with sufficient stability in operation and survival condition are generated. As an example the optimization study of a semisubmersible is discussed. It illustrates how offshore structures can be optimized for a specific target area of operation.

• 한국항해항만학회지
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• 제41권5호
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• pp.277-286
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• 2017

IMO introduced e-Navigation concept to improve the efficiency of ship operation, port operation, and ship navigation technology. IMO proposed sixteen MSPs (Maritime Service Portfolio) applicable to the ships and onshore in case of e-Navigation implementation. In order to meet the demands of the international society, the system implementation work for the Korean e-Navigation has been specified. The Korean e-Navigation system has five service categories: the S2 service category, which is a ship anomaly monitoring service, is a service that classifies emergency levels according to the degree of abnormal condition when a ship has an abnormality in ship operation, and provides guidance for emergency situations. The navigation safety module is a sub-module of the S2 service that determines the emergency level in case of navigation equipment malfunctioning, engine or steering gear failure during navigation. It provides emergency response guidance based on emergency level to the abnormal ship. If an abnormal condition occurs during the ship operation, first, the ship shall determine the emergency level, according to the degree of abnormality of the ship. Second, an emergency response guidance is generated based on the determined emergency level, and the guidance is transmitted to the ship, which helps the navigators prevent accidents and not to spread. In this study, the operational concept for the implementation of the Korean e-Navigation system is designed and the concept is focused on the navigation safety module of S2 service.

• Nuclear Engineering and Technology
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• 제32권4호
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• pp.316-327
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• 2000

The Emergency Core Cooling System in current nuclear power plants typically has a considerable number of complex functions and largely cumbersome operator interfaces. Functions for initiation, switch-over between various phases of operation, interlocks, monitoring, and alarming are usually performed by relays and analog comparator logic which are difficult to maintain and test. To improve problems of an analog based ECC (Emergency Core Cooling) System, the trip computer for ECCS based on Dynamic Safety System (DSS) is implemented. The DSS is a computer based reactor protection system that has fail-safe nature and performs a dynamic self-testing. The most important feature of the DSS is the introduction of test signal that send the system into a tripped state. The test signals are interleaved with the plant signals to produce an output which switches between a tripped and health state. The dynamic operation is a key feature of the failsafe design of the system. In this work, a possible implementation of the DSS using PLC is presented for a CANDU Reactor. ECC System of the CANDU Reactor is selected as the reference system.