• Journal of the Earthquake Engineering Society of Korea
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• v.23 no.3
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• pp.191-199
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• 2019

To calculate proper seismic design load and seismic design category, the exact site class for construction site is required. At present, the average shear-wave velocity for multi-layer soil deposits is calculated by the sum of shear-wave velocities without considering of vertical relationship of the strata. In this study, the transfer function for the multi-layered soil deposits was reviewed on the basis of the wave propagation theory. Also, the transfer function was accurately verified by the finite element model and the eigenvalue analysis. Three methods for site period estimation were evaluated. The sum of shear-wave velocities underestimated the average shear-wave velocities of 526 strata with large deviations. The equation of Mexican code overestimated the average shear-wave velocities. The equation of Japanese code well estimated the average shear-wave velocities with small deviation.

• Nuclear Engineering and Technology
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• v.53 no.10
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• pp.3247-3255
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• 2021

As Probabilistic Safety Assessments (PSAs) are thoroughly conducted for the Site Operating States (SOSs) for a single unit, multi-unit Probabilistic Safety Assessments (MUPSAs) are ongoing worldwide to address new technical challenges or issues. In South Korea, the determination of the site operating states for a single site requires a logical approach with reasonable assumptions due to the fact that there are 4-8 operating units for each site. This paper suggests a simulation model that gives a reasonable expectation of the site operation states using the Monte-Carlo method as a stochastic approach and deterministic aspects such as operational policies. Statistical hypothesis tests were conducted so that the reliance of the simulation results can be guaranteed. In this study, 7 units of the Kori site were analysed as a case study. The result shows that the fraction of full power for all 7 units is nearly 0.45. For situations when more than two units are not in operation, the highest fraction combination was obtained for Plant Operation State (POS) 8, which is the stage of inspection and repairment. By entering various site operation scenarios, the simulation model can be used for the analysis of other site operation states.

• New & Renewable Energy
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• v.19 no.2
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• pp.40-58
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• 2023

Several offshore wind power conflicts occur due to the problems in which the site selection process led by private operators is improperly managed. To review the institutional improvement measures that solve this problem, domestic and foreign institutions and operational cases were comparatively analyzed, focusing on key actors from the multi-level governance perspective. First, the status of the site selection process in the Republic of Korea, major issues in stakeholder conflicts, and discussions on the planned site system-related laws (draft) were reviewed. Next, the site selection process and relevant cases in Germany, the Netherlands, and Japan were analyzed. In all these countries, site selection is done by the central government. In Germany and the Netherlands, maritime-related ministries establish overall offshore wind power site plans and conduct strategic environmental assessments for these plans. Futhermore, in the process of determining each individual site, extensive site investigation including environmental assessments are conducted. This aspect needs to be supplemented in the discussion on the direction of institutional improvement in the Republic of Korea.

• Journal of the Korean Society of Safety
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• v.33 no.6
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• pp.144-156
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• 2018

Level 3 Probabilistic Safety Assessment (PSA) is performed for the risk assessment that calculates radioactive material dispersion to the environment. This risk assessment is performed with a tool of MELCOR Accident Consequence Code System (MACCS2 or WinMACCS). For the off-site consequence analysis of multi-unit nuclear power plant (NPP) accident, the single location (Center Of Mass, COM) method has been usually adopted with the assumption that all the NPPs in the nuclear site are located at the same COM point. It was well known that this COM calculation can lead to underestimated or overestimated radionuclide concentration. In order to overcome this underestimation or overestimation of radionuclide concentrations in the COM method, Multiple Location (ML) method was developed in this study. The radionuclide concentrations for the individual NPPs are separately calculated, and they are summed at every location in the nuclear site by the post-processing of radionuclide concentrations that is based on two-dimensional Gaussian Plume equations. In order to demonstrate the efficiency of the ML method, radionuclide concentrations were calculated for the six-unit NPP site, radionuclide concentrations of the ML method were compared with those by COM method. This comparison was performed for conditions of constant weather, yearly weather in Korea, and four seasons, and the results were discussed. This new ML method (1) improves accuracy of radionuclide concentrations when multi-unit NPP accident occurs, (2) calculates realistic atmospheric dispersion of radionuclides under various weather conditions, and finally (3) supports off-site emergency plan optimization. It is recommended that this new method be applied to the risk assessment of multi-unit NPP accident. This new method drastically improves the accuracy of radionuclide concentrations at the locations adjacent to or very close to NPPs. This ML method has a great strength over the COM method when people live near nuclear site, since it provides accurate radionuclide concentrations or radiation doses.

• Nuclear Engineering and Technology
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• v.50 no.8
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• pp.1246-1254
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• 2018

The importance of performing Level 3 probabilistic safety assessments (PSA) along with a general interest in assessing multi-unit risk has been sharply increasing after the Fukushima Daiichi nuclear power plant (NPP) accident. However, relatively few studies on multi-unit Level 3 PSA have been performed to date, reflecting limited scenarios of multi-unit accidents with higher priority. The major difficulty to carry out a multi-unit Level 3 PSA lies in the exponentially increasing number of multi-unit accident combinations, as different source terms can be released from each NPP unit; indeed, building consequence models for the astronomical number of accident scenarios is simply impractical. In this study, a new approach has been developed that employs the look-up table method to cover every multi-unit accident scenario. Consequence results for each scenario can be found on the table, established with a practical amount of effort, and can be matched to the frequency of the scenario. Preliminary application to a six-unit NPP site was carried out, where it was found that the difference between full-coverage and cut-off cases could be considerably high and therefore influence the total risk. Additional studies should be performed to fine tune the details and overcome the limitations of the approach.

• Proceedings of the Korean Operations and Management Science Society Conference
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• 1993.04a
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• pp.36-45
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• 1993

This paper presents a model and a heuristic procedure to design production planning and transportation scheduling systems of critical items, components and products on the basis of material requirement planning concept and transportation planning model. These systems are stemmed from a multi-site multi-product production company in a international economic zone. An example is provided to validate the heuristic procedure developed.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2015.11a
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• pp.76-77
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• 2015

In construction industry, management of construction factors such as cost, schedule, quality and safety is the most important key for delivering successful projects. According to the Smart Market Report, a magazine specialized in construction industry, recently said 'Off-site Prefabrication' is a significant trend related with construction productivity in global construction industry. It is a kind of practice shift from On-site to Off-site. A lot of general contractors in oversea have been using 'Multi-trade MEP Ceiling Rack Prefabrication' method for getting benefits such as decreased cost & schedule and increased labor productivity. Thus, in this paper, critical management factors at each phase from design to installation was derived by researching case studies. Forwardly, it can be a basic guideline for applying Multi-trade MEP Ceiling Rack Prefabrication in Korea construction industry.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2016.05a
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• pp.113-114
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• 2016

This paper proposes a technical requirements analysis of implementation of multi-trade prefabrication. Recently, there has been a rise in the use of prefabrication to minimize on-site work for time reduction to increase productivity. Prefabrication technique is evolved into multi-trade prefabrication combining other trades from single-trade prefabrication. For implementation of new technique, not only itself but complementary techniques have to be prepared. In this paper, MEP corridor rack, a major item of multi-trade prefabrication, was implemented in the test bed and its process was analyzed to find out technical requirements. As a result, comparatively high level of IT technique was required for efficient use of multi-trade prefabrication in design, lifting and construction phase. In design phase, component level of BIM library was needed for manufacturing; and in lifting phase, BIM-based site logistics process was required. Also in construction phase, laser scanning was implemented for gathering shape and geometry of the wall and slab that were attached to multi-trade prefabrication module.

• Nuclear Engineering and Technology
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• v.50 no.8
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• pp.1255-1265
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• 2018

The need for a PSA (Probabilistic Safety Assessment) for a multi-unit at a site is growing after the Fukushima accident. Many countries have been studying issues regarding a multi-unit PSA. One of these issues is the problem of many combinations of accident sequences in a multi-unit PSA. This paper deals with the methodology and software to quantify a PSA scenarios for a multi-unit site. Two approaches are developed to quantify a multi-unit PSA. One is to use a minimal cut set approach, and the other is to use a Monte Carlo approach.

• Nuclear Engineering and Technology
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• v.52 no.5
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• pp.975-983
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• 2020

Since the Fukushima Daiichi accident in 2011, concerns for the safety of multi-unit Nuclear Power Plant (NPP) sites have risen. This is because more than 70% of NPP sites are multi-unit sites that have two or more NPP units and a multi-unit accident occurred for the first time. After this accident, Probability Safety Assessment (PSA) has been considered in many countries as one of the tools to quantitatively assess the safety for multi-unit NPP sites. One of the biggest concerns for a multi-unit accident such as Fukushima is that the consequences (health and economic) will be significantly higher than in the case of a single-unit accident. However, many studies on multi-unit PSA have focused on Level 1 & 2 PSA, and there are many challenges in terms of public acceptance due to various speculations without an engineering background. In this study, two kinds of multi-unit Level 3 PSA for multi-unit site have been carried out. The first case was the estimation of multi-unit risk with conservative assumptions to investigate the margin between multi-unit risk and QHO, and the other was to identify the effect of time delays in releases between NPP units on the same site. Through these two kinds of assessments, we aimed at investigating the level of multi-unit risk and understanding the characteristics of risk in a multiunit context.