• 한국안전학회지
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• 제33권1호
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• pp.135-141
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• 2018

Rotary that causes traffic delays and safety issues by high-speed entry vehicles is currently being improved to roundabout. The operational difference between rotary and roundabout can cause driver's confusion and traffic accident. The purpose of this study is to develop the accident rate models which explain the factors related to the accidents by land use and intersection type. The main results are as follows. First, the null hypotheses that the type of land use and two intersections do not affect the accident rate are rejected. Second, the conflicting factors such as the number of crosswalk and bicycle lane should be carefully considered to reduce traffic accident at rotary. In the case of roundabout, greater than 3.5 m in circulatory lane width and two circulatory lane are analyzed to be important to prevent the accidents. Finally, the commercial and mixed areas are evaluated to be weak to traffic accidents than residential area.

• 한국안전학회지
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• 제34권1호
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• pp.45-52
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• 2019

Accident analysis models were developed to improve the construction site safety and case studies was conducted. In 2016, 86% of fatality accidents occurred due to simple unsafe acts. Structure related accidents are less frequent than the non structure related causes, but the number of casualties per accident is two times higher than non structure one. In the view of risk perception, efforts should be given to reduce accidents caused by low frequency - high consequence structure related causes. In case of structure related accident, structural safety inspection and management (including quality), ground condition management / inspection technology, and provision of risk information delivery system in case of non structure related accident were proposed as a solution. In analysis of relationship between safety related stakeholder, the main problem were the lack of knowledge of controller and player, loss of control due to duplicated controls, lack of communication system of risk information, and relative position error of controller and player.

• 한국안전학회지
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• 제36권4호
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• pp.62-70
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• 2021

Representative systematic accident analysis methods proposed so far include AcciMap, STAMP, and FRAM. This study used these three techniques to analyze a fire accident case that occurred during routine manufacturing work in a domestic chemical plant and compared the results. The methods used different approaches to identify the cause of the accident, but they all highlighted similar causal factors. In addition to technical issues, the three accident analysis methods identified factors related to safety education, risk assessment, and the operation of the process safety management system, as well as management philosophy and company culture as problems. The AcciMap and STAMP models play complementary roles because they use hierarchical structures, while FRAM is more effective in analyses centered on human and organizational functions than in technical analyses.

• Nuclear Engineering and Technology
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• 제54권1호
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• pp.138-151
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• 2022

Cladding ballooning and rupture are the important phenomena at the early stage of a severe accident. Most severe accident analysis codes determine the cladding rupture based on simple parameter models. In this paper, a FRTMB module was developed using the thermal-mechanical model to analyze the fuel mechanical behavior. The purpose is to judge the cladding rupture with the severe accident analysis code. The FRTMB module was integrated into the self-developed severe accident analysis code ISAA to simulate the PHEBUS FPT3 experiment. The predicted rupture time and temperature of the cladding were basically consistent with the measured values, which verified the correctness and effectiveness of the FRTMB module. The results showed that the rising of gas pressure in the fuel rod and high temperature led to cladding ballooning. Consequently, the cladding hoop strain exceeded the strain limit, and the cladding burst. The developed FRTMB module can be applied not only to rod-type fuel, but also to plate-type fuel and other types of reactor fuel rods. Moreover, the FRTMB module can improve the channel blockage model of ISAA code and make contributions to analyzing the effect of clad ballooning on transient and subsequent parts of core degradation.

• Nuclear Engineering and Technology
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• 제38권6호
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• pp.535-550
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• 2006

The objectives of this paper are twofold to summarize the new findings and confirmed results from the Phebus FPT-1 experimental data and to report useful information to MELCOR users regarding the better use of MELCOR. For the core damage behavior, the early stage of a melt progression was predicted well; however, the late phase models, concerned with fuel dissolution, oxide cladding failure, fuel slumping, rubble debris heat up, effects of burn-up fuel, and so on, still showed limitations in MELCOR. For the fission product behavior, the comparison showed unexpected phenomena, various limitations, unresolved issues, and even absence of models. The issues summarized in this study have revealed the main areas where our endeavors need to be intensified in order to improve our understanding of severe accident phenomena. From the analysis of the Phebus FPT-1 test results, not only new core damage features, such as foaming or core expansion, but also possible new fission product release patterns due to effects from a high burn-up fuel have raised alternative challenging phenomena that should be solved in the next severe accident research phase.

• 한국압력기기공학회 논문집
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• 제13권1호
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• pp.61-68
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• 2017

Reactor pressure vessel (RPV) under severe accident conditions accompanied by core melting is exposed to direct high-temperature thermal loads. Understanding the creep behavior of the material is one of the most important factors for evaluating the structural integrity at these conditions. While damage evaluation studies have been conducted on critical structures of nuclear power plants through finite element (FE) analyses considering creep behavior, for accurate creep damage evaluation, constitutive equations considered in the FE analyses may have different results depending on the time hardening and strain hardening models as well as the tertiary creep consideration. The purpose of this study is to evaluate the creep damage under severe accident conditions by using FE method for a representative domestic RPV material, SA508 Gr.3. The effect of material hardening models and constitutive equations which are the main variables were also investigated.

• 한국안전학회지
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• 제37권6호
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• pp.128-135
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• 2022

The comparative evaluation of occupational accident fatality rates (OAFRs) of different countries is complicated owing to the differences in their level of socio-economic development. However, such evaluation is necessary to assess the national occupational safety and health system of a country. This study proposes a statistical method to compare the OAFRs of countries taking into consideration the difference in their level of socio-economic development. We first collected data on the socio-economic indicators and OAFRs of 11 countries over a 30-year period. Next, based on literature survey and statistical correlation analysis, we selected the significant independent variables and built multiple linear regression models to predict OAFR. We also determined the groups of countries having heterogeneous relationships between the independent variables and OAFRs, which are represented by the regression models. The proposed method is demonstrated by comparing the OAFR of Korea with the OAFRs of 10 other developed countries.

• Nuclear Engineering and Technology
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• 제56권4호
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• pp.1310-1319
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• 2024

The reactor cavity cooling system (RCCS) is a passive reactor safety system commonly present in the designs of High-Temperature Gas-cooled Reactors (HTGR) that removes heat from the reactor pressure vessel by means of natural convection and radiation. It is one of the factors responsible for ensuring that the reactor does not melt down under any plausible accident scenario. For the simulation of accident scenarios, which are transient phenomena unfolding over a span of up to several days, intermediate fidelity methods and system codes must be employed to limit the models' execution time. These models can quantify radiation heat transfer well, but heat transfer caused by natural convection must be quantified with the use of correlations for the heat transfer coefficient. It is difficult to obtain reliable correlations for HTGR RCCS heat transfer coefficients experimentally due to such a system's size. They could, however, be obtained from high-fidelity steady-state simulations of RCCSs. The Rayleigh number in RCCSs is too high for using a Direct Numerical Simulation (DNS) technique; thus, a Reynolds-Averaged Navier-Stokes (RANS) approach must be employed. There are many RANS models, each performing best under different geometry and fluid flow conditions. To find the most suitable one for simulating an RCCS, the RANS models need to be validated. This work benchmarks various RANS models against three experiments performed on the HTTR RCCS Mockup by the Japanese Atomic Energy Agency (JAEA) in 1993. This facility is a 1/6 scale model of a vessel cooling system (VCS) for the High Temperature Engineering Test Reactor (HTTR), which is operated by JAEA. Multiple RANS models were evaluated on a simplified 2d-axisymmetric geometry. They were found to reproduce the experimental temperature profiles with errors of up to 22% for the lowest temperature benchmark and 15% for the higher temperature benchmarks. The results highlight that the pragmatic turbulence models need to be validated for high Rayleigh natural convection-driven flows and improved accordingly, more publicly available experimental data of RCCS resembling experiments is needed and indicate that a 2d-axisymmetric geometry approximation is likely insufficient to capture all the relevant phenomena in RCCS simulations.

• 대한안전경영과학회:학술대회논문집
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• 대한안전경영과학회 2003년도 추계학술대회
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• pp.75-80
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• 2003

The objectives of this study is to achieved by the use of the conceptual approach and accident data bases to develop statistical accident analysis, effectiveness values, comparison analysis of statistical models to determine which variables are significantly related to accidents, human factor, and hazard factor analysis, all of which were used in the railroad crossing. The result from this approach applicable to the railroad crossing where systematic safety management criteria have been considered.

• 대한교통학회지
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• 제30권2호
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• pp.101-116
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• 2012

사고예측모형은 장래 계획 노선이나 다른 노선에 적용되어 사고를 예측하거나 안전개선사업 및 교통정책의 평가 등에 활용된다. 본 연구에서는 고속도로 본선에 대해 이러한 용도로 활용될 수 있는 사고예측모형을 구축하고자 한다. 또한 자료 구축이 용이한 변수를 선정하여 모형을 쉽게 활용할 수 있도록 하는 것을 기본 목표로 하였다. 모형은 종속변수를 사고건수와 사상자발생사고건수로 하여 사고모형과 사상자발생사고모형을 각각 구축하였다. 모형에 적용된 확률구조는 음이항 분포와 포아송 분포이며, 추정에 의해 적합한 모형을 선별하였다. 국내 고속도로중 주요한 9개 노선을 선정하였고, 시간적으로는 2003~2007년까지 5개년도 자료를 활용하였다. 모형의 설명변수는 교통류 특성을 나타내는 교통량 등의 예측 가능한 변수와 기하구조 요인 등을 적용하였다. 최우추정법에 의한 추정 결과 사고모형의 경우 구간길이, 일교통량, 버스비율, 곡선구간수가 유의한 변수로 추정되었으며 사상자발생사고모형에서는 구간 길이와 일교통량, 버스비율이 유의한 변수로 추정되었다. 모형의 공간적 시간적 전이 가능성을 확인하기 위해 우도비 검정을 수행한 결과, 사고모형은 6차로 이상이나 4차로의 교통류 및 기하구조 특성을 가지는 도로로의 전이가 가능하였다, 반면 사상자발생 사고모형은 모든 도로와 시간대로의 전이가 가능하여, 모형의 활용도가 높게 나타났다. 결과적으로 본 연구에서 구축된 모형은 다른 노선과 장래 계획, 정책 평가 등에 다양하게 활용될 수 있을 것이다.