• Nuclear Engineering and Technology
• /
• v.41 no.6
• /
• pp.849-858
• /
• 2009

Risk caused by safety-critical instrumentation and control (I&C) systems considerably affects overall plant risk. As digitalization of safety-critical systems in nuclear power plants progresses, a risk model of a digitalized safety system is required and must be included in a plant safety model in order to assess this risk effect on the plant. Unique features of a digital system cause some challenges in risk modeling. This article aims at providing an overview of the issues related to the development of a static fault-tree-based risk model. We categorize the complicated issues of digital system probabilistic risk assessment (PRA) into four groups based on their characteristics: hardware module issues, software issues, system issues, and safety function issues. Quantification of the effect of these issues dominates the quality of a developed risk model. Recent research activities for addressing various issues, such as the modeling framework of a software-based system, the software failure probability and the fault coverage of a self monitoring mechanism, are discussed. Although these issues are interrelated and affect each other, the categorized and systematic approach suggested here will provide a proper insight for analyzing risk from a digital system.

• Nuclear Engineering and Technology
• /
• v.55 no.3
• /
• pp.981-988
• /
• 2023

A seismic event caused an accident at the Fukushima Nuclear Power Plant, which further resulted in simultaneous accidents at several units. Consequently, this incident has aroused great interest in the safety of nuclear power plants worldwide. A reasonable safety evaluation of such an external event should appropriately consider the correlation between SSCs (structures, systems, and components) and the probability of failure. However, a probabilistic safety assessment in current nuclear industries is performed conservatively, assuming that the failure correlation between SSCs is independent or completely dependent. This is an extreme assumption; a reasonable risk can be calculated, or risk-based decision-making can be conducted only when the appropriate failure correlation between SSCs is considered. Thus, this study analyzed the effect of the failure correlation of SSCs on the safety of the system to realize rational safety assessment and decision-making. Consequently, the impact on the system differs according to the size of the failure probability of the SSCs and the AND and OR conditions.

• The Transactions of The Korean Institute of Electrical Engineers
• /
• v.57 no.12
• /
• pp.2308-2312
• /
• 2008

As power plant facilities are being deteriorated, their safety is getting more important, and more routine surveillance is being required. For this purpose, this paper presents an indoor localization system for field robot system which performs the surveillance of power plant facilities instead of human workers from the viewpoint of the workers' safety and work efficiency.

• Journal of the Korea Institute of Building Construction
• /
• v.15 no.2
• /
• pp.227-235
• /
• 2015

For last decade, the number of foreign workers in all industries has been increased continuously. In the construction industry, the number of foreign workers has also increased as 80,000 persons in 2010. According to the increase of foreign workers at domestic construction sites, the frequency of construction disasters has increased as well. The safety education can be a effective solution to decrease the construction disaster. So, it is necessary to develop the appropriate education system for foreign workers. Therefore, the objective of this study is to propose a safety education model for foreign workers and to develop the prototype system. In a result of that, a new safety education model and prototype system was constructed based on the method of E-learning. The system can support for foreign workers in domestic construction sites to understand the safety education easily. And, it can also assist the safety manager to educate and manage the foreign workers efficiently.

• Journal of the Korean Institute of Gas
• /
• v.8 no.4 s.25
• /
• pp.55-61
• /
• 2004

This paper provided a counter measures against the troubles and accidents that are likely to take place in the power plant using hydrogen gas as a coolant for the cooling system of the generator. Because of the extremely wide flammability limits of hydrogen in comparison to the other flammable gases, the safety measures against the hydrogen accidents is very important to ensure the normal operation of electric-power facility. This study's purpose was a presentation of standard model of safety management of hydrogen equipments in the coal firing power plant such as following items: 1) providing the technical prevention manual of the hydrogen explosions and hydrogen fires occurring in the cooling system of power generator; 2) the selection of explosion-proof equipments in terms of the risk level of operating environment; 3) the establishment of regulations and counter measures, such as the incorporation of gas leakage alarm device, for preventing the accidents from arising, 4) the establishment of safety management system to ensure the normal operation of the power plant.

• Transactions of the Korean Society of Pressure Vessels and Piping
• /
• v.8 no.1
• /
• pp.25-32
• /
• 2012

Korea Hydro & Nuclear Power Co. (KHNP) has developed and implemented the maintenance effectiveness monitoring (MR) programs for the operating nuclear power plants. The MR program is developed by reflecting design characteristics of the operating nuclear power plants to monitor the plant performance for improving the safety and reliability. Recently, KHNP has built a new nuclear power plant, and developed the MR program to establish the advanced maintenance system by reflecting unique design characteristics based on the OPR1000 standard model. So, the MR program developed in this study has another characteristics in comparison with the OPR1000 standard model, and we will verify the suitability of the MR program through evaluating initial performance of the plant. The safety and reliability of the new plant will be improved by developing and implementing the MR program.

• Journal of the Korea Safety Management & Science
• /
• v.16 no.4
• /
• pp.417-426
• /
• 2014

Plant management have a greatest influence on the corporate variety of tasks such as production, quality, environment. So, various performance indices for plant management are operating. But plant management tasks can be carried out effectively, so that all of how to organize and efficiently manage indicators is lacking real condition In this paper, improved profitability, cost savings by applying the concept for the performance assessment, plant management services, such as the key indices for performance according to the objectives of the firm. Dashboard for plant management work using me to develop a system that manage.

• Journal of the Korean Society of Safety
• /
• v.7 no.2
• /
• pp.14-23
• /
• 1992

A methodology for developing an object description system based on functional-structure of chemical plant is proposed. A knowledge base for chemical plant fault diagnosis is also organized in a generic fashion using the heuristic knowledge of human operators. A plant can be seen as a hierarchical set of subsystems. Each subsystem is called a SCOPE. The state of the plant and the behavior of each subsystem is managed by the SCOPES. A computer-based system based on thls methodology and knowledge base has been developed and applied to the subprocess of ethylene plant to evaluate the effectiveness of the methodology.

• Nuclear Engineering and Technology
• /
• v.44 no.3
• /
• pp.343-354
• /
• 2012

Primary water stress corrosion cracking (PWSCC) is a major safety concern in the nuclear power industry worldwide. PWSCC is known to initiate only in the condition in which sufficiently high tensile stress is applied to alloy 600 tube material or alloy 82/182 weld material in pressurized water reactor operating environments. However, it is still uncertain how much tensile stress is re-quired to generate PWSCC or what causes such high tensile stress. This study was performed to pre-dict the magnitude of weld residual stress and operating stress and compare it with previous experi-mental results for PWSCC initiation. For the study, a pressurizer safety nozzle was selected because it is reported to be vulnerable to PWSCC in overseas plants. The assessment was conducted by nu-merical analysis. Before performing stress analysis for plant conditions, a preliminary mock-up ana-lysis was done. The result of the preliminary analysis was validated by residual stress measurement in the mock-up. After verification of the analysis methodology, an analysis under plant conditions was conducted. The analysis results show that the stress level is not high enough to initiate PWSCC. If a plant is properly welded and operated, PWSCC is not likely to occur in the pressurizer safety nozzle.

• Transactions of the Korean Society of Mechanical Engineers B
• /
• v.35 no.3
• /
• pp.287-291
• /
• 2011

We solve the simple physical model for liquid pool spreading with vaporization semi-analytically for the first time, using perturbation techniques. The results are compared with those obtained using numerical methods. We use the evaporation rate per unit area as a perturbation parameter, and first-order solutions are obtained for continuous and instantaneous release. The two solutions are nearly identical with respect to the pool radius. The pool volumes are nearly the same at the early stage of the spread and then start to diverge.