• Proceedings of the KSME Conference
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• 2003.04a
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• pp.610-616
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• 2003

Recently, the common concern of nuclear power industry in the development of technology mitigating and preventing the aging of steam generator tubes prevails, because the trends of steam generator flaws at Uljin unit #1,2 and KSNP(Korea Standard Nuclear Power Plant) impose a burden on the operation of nuclear power plant. While the regulatory agency is demanding the establishment of the advanced general performance maintenance system, the steam generator management program adapting advanced technology is being developed which may comply with EPRI PWR SG Guidelines based on NEI 97-06 ‘ General Guidelines including all the maintenance aspects consist of the tube integrity assessment criteria, repair limit, allowable leakage level, water chemistry will be composed in order to obtain the approval of regulatory agency and be applied to Nuclear power plant early 2005. This presentation is to introduce maintenance state including SG tube degradation and main contents of advanced SG management program being developed, and futhermore update present and future plan, and estimate the alternation after the completion.

• Journal of Institute of Control, Robotics and Systems
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• v.10 no.12
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• pp.1217-1222
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• 2004

This paper describes the development of tele-robotic interface for the hot-line maintenance robot system. One of main issues in designing human-robot interface for the hot-line maintenance robot system is to plan the control procedure for each part of the robotic system. Another issue is that the actual degree of freedom (DOF) in the hot-line maintenance robot system is much greater than that of available control devices such as joysticks and gloves in the remote-cabin. For this purpose, a virtual simulator, which includes the virtual hot-line maintenance robot system and the environment, is developed in the 3D environment using CAD data. It is assumed that the control operation is done in the remote cabin and the overall work process is observed using the main-camera with 2 DOFs. For the input device, two joysticks, one pedal, two data gloves, and a Head Mounted Display (HMD) with tracker sensor were used. The interface is developed for each control mode. Designed human-interface system is operated using high-level control commands which are intuitive and easy to understand without any special training.

• Proceedings of the KSR Conference
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• 2004.10a
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• pp.1303-1308
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• 2004

This paper proposes a reduction method for the mis-operation analysis of the DC High Speed Circuit Breaker(HSCB) in electric railway substation system. The analysis method is based on present condition of operation which is a method for accuracy level up. There is reason to operation of HSCB that it is mis-operation of fault detection relay(50F), operation of ground fault relay(64P), and trouble of electric car. A countermeasure is relay resetting through field test, induction of GTOCB(Gate Turn Off Thyristor Circuit Breaker), HSVCB(High Speed Vacuum Circuit Breaker), coordination with electric car. The results presented in the paper can be used as a reference for maintenance free in electric railway substation system.

• Journal of the Korean Society of Safety
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• v.11 no.2
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• pp.52-59
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• 1996

This paper presents a new approach for assessing the dynamic reliability in a complex system such as a nuclear power plant. The method is applied to a dynamic analysis of the potential accident sequences which may occur during mid-loop operation. Mid-loop operation is defined as an operation to make RCS water level below the top of the flow area of the hot legs at the junction with the reactor vessel for repairs and maintenance of steam generators and reactor coolant pumps for a specific time. The Idea behind this approach consists of both the use of the concept of the performance achievement/requirement correlation and of a dynamic event tree generation method. The assessment of the system reliability depends on the determination of both the required performance distribution and the achieved performance distribution. The quantified correlation between requirement and achievement represents a comparison between two competing variables. It is demonstrated that this method is easily applicable and flexible in that it can be applied to any kind of dynamic reliability problem.

• Journal of the Korean Society of Safety
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• v.27 no.4
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• pp.115-120
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• 2012

In order to establish preventive maintenance standards through analysis & reliability prediction of about 60,000pcs of 20kindsof relays and contractors used for Seoul subway trains, several life prediction methodologies were applied. Firstly, Occurrence, Severity, Detection were defined and predicted by applying operation characteristic of EMU to the number of actions of relays & contactors which the manufacturers generally offer as the life cycle data. Secondly, failure distribution and average life of parts were analyzed through interpretation of field data based on a lot of experience which had built up in the field for a long time. Finally, using the 217PLUS standard as a reliability prediction program, comparative analysis of use reliability and inherent reliability was done through reliability prediction at the part level and system level.

• Proceedings of the KSR Conference
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• 2008.11b
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• pp.275-280
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• 2008

Recently the railway safety is very important issue in Korea because there are lots of changes like the separation of operation and facility of national rail network, the inauguration of high speed train and Daegu subway fire accident. Railway safety management system is based on risk assessment of rolling stocks, electrical system, signaling, operation & maintenance and human element. With this process, railway risk will be reduced as low as reasonably acceptable level. Through risk assessment on accident data, this study predicted the current risk level of railway electrical system and presented the proper safety ensuring measures.

• Journal of Korean Society of Industrial and Systems Engineering
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• v.42 no.4
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• pp.145-152
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• 2019

All machines deteriorate in performance over time. The phenomenon that causes such performance degradation is called deterioration. Due to the deterioration, the process mean of the machine shifts, process variance increases due to the expansion of separate interval, and the failure rate of the machine increases. The maintenance model is a matter of determining the timing of preventive maintenance that minimizes the total cost per wear between the relation to the increasing production cost and the decreasing maintenance cost. The essential requirement of this model is that the preventive maintenance cost is less than the failure maintenance cost. In the process mean shift model, determining the resetting timing due to increasing production costs is the same as the maintenance model. In determining the timing of machine adjustments, there are two differences between the models. First, the process mean shift model excludes failure from the model. This model is limited to the period during the operation of the machine. Second, in the maintenance model, the production cost is set as a general function of the operating time. But in the process mean shift model, the production cost is set as a probability functions associated with the product. In the production system, the maintenance cost of the equipment and the production cost due to the non-confirming items and the quality loss cost are always occurring simultaneously. So it is reasonable that the failure and process mean shift should be dealt with at the same time in determining the maintenance time. This study proposes a model that integrates both of them. In order to reflect the actual production system more accurately, this integrated model includes the items of process variance function and the loss function according to wear level.

• Journal of Korean Society of Environmental Engineers
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• v.31 no.5
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• pp.325-331
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• 2009

This study was performed to evaluate characteristics of algal occurrence in Lake Paldang. Chlorophyll a concentration was highest during spring, based on weekly measurements from 2006 to 2008, which revealed a different trend compared to the data before 2000 that showed the highest level during summer. Total algae cell quantity was also highest during spring, based on monthly data. Overall, Bacillariophyceae was dominant and represented 87% of total algae cells and occupation was more significant during spring and winter. Cyanophyceae was dominant during summer. 2-MIB and geosmin originating in algae which caused odor problems was high in July 2008, and more research on the relationship between algae and production of odor causing material is needed.

• Journal of Environmental Science International
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• v.21 no.9
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• pp.1069-1078
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• 2012

This study was performed to evaluate the asbestos exposure levels and to calculate excess lifetime cacer risks(ELCRs) in asbestos-containing buildings for maintenance and management. The range of airborne asbestos concentration of 33 buildings was 0.0018 ~ 0.0126 f/cc and one site exceeded indoor air-quality recommended limit 0.01 f/cc. And ELCRs based on US EPA IRIS(Integrated risk information system) model are 1.5E-06 ~ 3.9E-05 levels, and there was no site showed 1.0E-04 (one person per million) level or more, and 11 sites showed 1.0E-05 (one person per 100,000 people) level or more. To prevent the release of asbestos fibers, it needs operation and maintenance of asbestos-containing building materials, and there are some methods such as removal, repairment, enclosure and encapsulation. In conclusion, a risk-based air action level for asbestos in air is an appropriate metric for asbestos-containing building management.

• Journal of the Society of Disaster Information
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• v.10 no.2
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• pp.282-286
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• 2014

This study is to present an improvement of physical security system operation by survey on the install and operation of physical security system of 90 facilities. The level of CCTV operation is higher than Access Control system and Intrusion Detection System. But the level of maintenance and management of physical security system is low. The rate of install of X-ray Inspection device show the concern on material detection, although the rate is low. The level of install and operation for the Integration of physical security system is low, so integration of security personnel and security system is necessary for the effective operation. For reinforcement of access control management, security gate and preparing of some obstacles are required with RFID.