• Environmental Analysis Health and Toxicology
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• 제10권1_2호
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• pp.21-35
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• 1995

Risk assessment processes, which include processes for the estimation of human cancer potency using animal bioassay data and calculation of human exposure, entail uncertainties. In the exposure assessment process, exposure scenarios with various assumptions could affect the exposure amount and excess cancer risk. We compared risk estimates among various exposure scenarios of vinyl chloride, trichloroethylene and tetrachloroethylene in tap water. The contaminant concentrations were analyzed from tap water samples in Seoul from 1993 to 1994. The oral and inhalation cancer potencies of the contaminants were estimated using multistage, Weibull, lognormal, and Mantel-Bryan model in TOX-RISK computer software. In the first case, human excess cancer risk was estimated by the US EPA method used to set the MCL(maximum contaminant level). In the second and third case, the risk was estimated for multi-route exposure with and without adopting Monte-Carlo simulation, respectively. In the second case, exposure input parameters and cancer potencies used probability distributions, and in the third case, those values used point estimates(mean, and maximum or 95% upper-bound value). As a result, while the excess cancer risk estimated by US EPA method considering only direct ingestion tended to be underestimated, the risk which was estimated by considering multi-route exposure without Monte-Carlo simulation and then using the maximum or 95% upper-bound value as input parameters tended to be overestimated. In risk assessment for volatile organic compounds, considering multi-route exposure with adopting Monte-Carlo analysis seems to provide the most reasonable estimations.

• 한국안전학회지
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• 제37권2호
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• pp.1-9
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• 2022

Most factories deal with toxic or flammable chemicals in their industrial processes. These hazardous substances pose a risk of leakage due to accidents, such as fire and explosion. In the event of chemical release, massive casualties and property damage can result; hence, quantitative risk prediction and assessment are necessary. Several methods are available for evaluating chemical dispersion in the atmosphere, and most analyses are considered neutral in dispersion models and under far-field wind condition. The foregoing assumption renders a model valid only after a considerable time has elapsed from the moment chemicals are released or dispersed from a source. Hence, an initial dispersion model is required to assess risk quantitatively and predict the extent of damage because the most dangerous locations are those near a leak source. In this study, the dispersion model for initial consequence analysis was developed with three-dimensional unsteady advective diffusion equation. In this expression, instantaneous leakage is assumed as a puff, and wind velocity is considered as a coordinate transform in the solution. To minimize the buoyant force, ethane is used as leaked fuel, and two different diffusion coefficients are introduced. The calculated concentration field with a molecular diffusion coefficient shows a moving circular iso-line in the horizontal plane. The maximum concentration decreases as time progresses and distance increases. In the case of using a coefficient for turbulent diffusion, the dispersion along the wind velocity direction is enhanced, and an elliptic iso-contour line is found. The result yielded by a widely used commercial program, ALOHA, was compared with the end point of the lower explosion limit. In the future, we plan to build a more accurate and general initial risk assessment model by considering the turbulence diffusion and buoyancy effect on dispersion.

• International Journal of Naval Architecture and Ocean Engineering
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• 제11권1호
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• pp.353-363
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• 2019

This paper presents a comprehensive simulation and assessment of gas dispersion above sea from a subsea release using a Computational Fluid Dynamics (CFD) approach. A 3D CFD model is established to evaluate the behavior of flammable gas above sea, and a jack-up drilling platform is included to illustrate the effect of flammable gas cloud on surface vessels. The simulations include a matrix of scenarios for different surface release rates, distances between surface gas pool and offshore platform, and wind speeds. Based on the established model, the development process of flammable gas cloud above sea is predicted, and the dangerous area generated on offshore platform is assessed. Additionally, the effect of some critical factors on flammable gas dispersion behavior is analyzed. The simulations produce some useful outputs including the detailed parameters of flammable gas cloud and the dangerous area on offshore platform, which are expected to give an educational reference for conducting a prior risk assessment and contingency planning.

• 한국토양비료학회지
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• 제43권5호
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• pp.674-683
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• 2010

본 연구에서는 폐광산 주변 농경지 용도의 경작 적합성을 판단하고자 토양의 위해성을 정량적으로 측정할 수 있는 과학적 방법인 한국, 미국 및 영국의 위해성평가를 이용하였다. 예비위해성평가를 통하여 선택한 DM, MG 및 KS광산을 위해성평가 대상 지역으로 선택하여 토양 및 농작물 시료를 채취하였다. 이후 토양과 농작물 시료 중 중금속 분석을 통하여 위해성 평가 및 농경지 적합성 판단을 위한 변수를 확보하였다. 토양 중 중금속 분석결과, 환경부 보고서에 수록된 수치보다 토양 중 중금속의 함량이 낮은 것을 확인하였으며, 대상 광산지역 모두에서 토양 중 Cd의 함량이 토양 환경보전법의 1 지역 토양오염우려기준을 초과하고 있는 것을 확인 할 수 있었다. S3와 S6지역은 As함량이 각각 1 지역의 대책기준과 우려기준을 초과하였다. 농작물 내 중금속 농도는 작물의 중금속 한계 농도를 근거로 DM광산주변에서 재배되고 있는 고추, 콩, 옥수수에서 Zn의 경우에만 오염식물의 범위로 판단되었으며, 이 외의 중금속 함량은 Kabata-pendias and Pendias의 일반적으로 오염되지 않은 식물의 배경농도 범위에 비교하여 안전한 수준을 보였다. 위해성평가 결과에 따르면 한국과 미국의 위해 성평가 모델의 경우, MG광산과 KS광산에서 농작물 내 Pb에 의한 인체 위해성이 나타날 것으로 예상되었고, 영국의 모델에서는 조사 전 지역에서 농작물의 Pb에 의한 독성이 나타날 것으로 예상되었다. 이 후 위해성평가 모델을 통한 토양 중 중금속의 오염기준을 한국의 정화목표치과 영국의 토양지침값으로 도출하고, 현재 토양 중 중금속 농도와 비교하였다. 그 결과 현재 토양 중 중금속의 농도가 영국의 토양지침값을 초과하여 MG광산, DM광산 및 KS광산지역에서 농경지 용도로 토지를 사용하는 데 문제가 있을 것으로 판단되었고, 오염물질에 대한 대책이 필요함을 알 수 있었다.

• 한국환경보건학회지
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• 제44권5호
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• pp.460-467
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• 2018

Objectives: The objectives of this study are to estimate the inhalation exposure level of benzene for workers using Tier 1 exposure models ECETOC TRA (European Center for Ecotoxicology and Toxicology of Chemicals Target Risk Assessment) and Stoffenmanager, and to investigate their reliability for exposure assessment in K-REACH. Methods: Two exposure scenarios, 'manufacture of benzene' and 'use as solvents,' were developed for assessment of workers' exposure to benzene. The Process Category (PROC) for ECETOC TRA was collected from the European Chemical Agency (ECHA) registration dossier, and the Activity for Stoffenmanager was converted from PROC using translation of exposure models (TREXMO). The information related to exposure, such as working duration, Respiratory Protective Equipment (RPE), Local Exhaust Ventilation (LEV), and Risk Management Measure (RMM) were classified into high, medium, and low exposure conditions. The risk was determined by the ratio of the estimated exposure and occupational exposure limits of benzene. Results: Under high exposure conditions, the worker exposure level calculated from all PROCs and Activities exceeded the risk level, with the exception of PROC 1 and Activity 1. In the medium exposure condition, PROC 8a, 8b, and 9 and Activity 3, 7, and 8 all exceeded the risk, whereas in the low condition, all PROCs and Activities were determined to be safe. As a result, action corresponding with the low exposure condition is required to reduce the risk of exposure among workers in workplaces where benzene is manufactured or used as a solvent. In addition, the predicted exposure levels derived from the exposure models were lower than measured levels. The exposure levels estimated from Stoffenmanager were more conservative than those from ECETOC TRA. Conclusions: This study demonstrates the feasibility of exposure models for exposure assessment through the example of occupational inhalation exposure assessment for benzene. For more active utilization of exposure models in K-REACH, the exact application of collected information and accurate interpretation of obtained results are necessary.

• 한국가스학회지
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• 제22권6호
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• pp.40-43
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• 2018

압력안전밸브의 열림고장과 닫힘고장은 서로 부분적으로 종속되어있다. 본 연구에서는 마르코프 프로세스 모델과 Weibull 분포 모델을 이용하여 두 가지 고장에 대한 신뢰성 모델을 구축하는 방법을 제안한다. 압력안전 밸브 모델은 알려진 열림고장 모델, 유도된 닫힘고장 모델, 최근 보고된 점검결과를 재현하는 동시고장 모델로부터 얻어진다. 제안된 방법은 부분적으로 종속된 다중 고장상태를 갖는 다양한 시스템의 정량적 위험성 평가로 확대 적용할 수 있을 것으로 기대된다.

• Nuclear Engineering and Technology
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• 제54권8호
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• pp.2941-2959
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• 2022

The fire brigade non-suppression probability model is a major factor that should be considered in evaluating fire-induced risk through fire probabilistic risk assessment (PRA), and also uncertainty is a critical consideration in support of risk-informed performance-based (RIPB) fire protection decision-making. This study developed an optimal integrated probabilistic fire brigade non-suppression model considering uncertainty of parameters based on the Bayesian Markov Chain Monte Carlo (MCMC) approach on electrical fire which is one of the most risk significant contributors. The result shows that the log-normal probability model with a location parameter (µ) of 2.063 and a scale parameter (σ) of 1.879 is best fitting to the actual fire experience data. It gives optimal model adequacy performance with Bayesian information criterion (BIC) of -1601.766, residual sum of squares (RSS) of 2.51E-04, and mean squared error (MSE) of 2.08E-06. This optimal log-normal model shows the better performance of the model adequacy than the exponential probability model suggested in the current fire PRA methodology, with a decrease of 17.3% in BIC, 85.3% in RSS, and 85.3% in MSE. The outcomes of this study are expected to contribute to the improvement and securement of fire PRA realism in the support of decision-making for RIPB fire protection programs.

• 한국컴퓨터정보학회논문지
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• 제20권3호
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• pp.9-17
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• 2015

본 논문에서는 자동차 기능안전 표준인 ISO 26262에서 요구하는 위험원 분석 및 위험 평가에서 온톨로지와 추론 규칙을 적용하는 방법을 제안한다. 위험원 분석 및 위험 평가는 일반적으로 수작업으로 수행되어 많은 노력이 소요되고 오류가 발생하기 쉬우며 일관성과 정확성이 부족한 문제점이 있다. 이러한 문제를 해결하기 위해서 본 논문에서는 위험원을 온톨로지로 표현하고, 평가를 위한 온톨로지 규칙을 정의하여 자동화하고 일관성 및 정확성 문제를 개선한다. 본 제안 방법을 검증하기 위해서 ESCL(electronic steering column lock) 시스템에 적용하였다. 온톨로지 규칙 적용 결과를 DL(Description Logics) Query를 실행하여 제대로 동작하는지 확인하였으며, 이를 통해 위험 평가 시에 발생할 수 있는 오류를 파악할 수 있었다.

• 한국항공운항학회지
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• 제18권3호
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• pp.34-41
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• 2010

'Aviation Safety' is the state in which the risk of harm to persons or of property damage is reduced to, and maintained at or below, an acceptable level through a continuing process of hazard identification and risk management in the aviation field. 'Risk' is the assessed potential for adverse consequences resulting from a hazard and 'Risk assessment' involves consideration of both the frequency and the severity of any adverse consequence. This study focused on the risk frequency about a case airport which does not meet the 'Runway end safety area' requirement of ICAO SARPs and Korea standards and used 'RSA risk model' for estimating the risk frequency. As results of this study, risk frequency of the runway end safety areas in the case airport is higher than that of 'Runway end safety area' requirement of ICAO SARPs and Korea standards, which means that alternatives for risk frequency mitigation to a level as low as reasonably practicable is required in the case airport. The optimum solution analysed from this study is to impose restriction of aircraft operation when the runway condition is poor(icing condition) and also it snows in the case airport.

• 한국항공운항학회지
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• 제23권2호
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• pp.1-6
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• 2015

The RSA is intended to prevent the following five types of events from becoming an accident: landing overruns, landing undershoots, landing veer-offs, takeoff overruns and takeoff veer-offs. The improved models are based on evidence from worldwide accidents and incidents that occurred during the past 27 years. The analysis utilizes historical data from the specific airport and allows the user to take into consideration specific operational conditions to which movements are subject, as well as the actual or planned RSA conditions in terms of dimensions, configuration, type of terrain, and boundaries defined by existing obstacles. This paper shows how to apply the improved models for Risk Assessment of Runway Safety Areas (Airport cooperative research program(ACRP) Report 50) into an airport and the outcome differences between the old models based on ACRP report 3-Analysis of aircraft overrun and undershoots for runway safety areas and the new models from ACRP report 50 in the specific airport.