• 환경영향평가
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• 제22권1호
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• pp.89-97
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• 2013

RADCONS Ver. 1.0 (RADiological CONSequence Assessment Program) was developed for radiological risk assessment in this study. A Gaussian plume model was used to analyze the fate and transport of radionuclides released into the air in case of accidents. Both single meterological data and time series meterological data can be used in RADCONS. To assess the radiological risk of the early phase after an accident, ED (Effective Dose) estimated by both deterministic and probabilistic approaches are presented. These EDs by deterministic and probabilistic will be helpful to efficient decision making for decision makers. External doses from deposited materials by time are presented for quantifying the effects of mid and late phases of an accident. A radiological risk assessment was conducted using RADCONS for an accident scenario of 1 Ci of Cs-137. The maximum of ED for radii of 1,000 meters from the accident point was 8.51E-4 mSv. After Monte-Carlo simulation, considering the uncertainty of the breathing rate and dispersion parameters, the average ED was 8.49E-4, and the 95 percentile was 1.10E-3. A data base of the dose coefficients and a sampling module of the meteorological data will be modified to improve the user's convenience in the next version.

• Journal of Radiation Protection and Research
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• 제41권4호
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• pp.368-372
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• 2016

Background: Methodologies for a series of radiological consequence assessments show a distinctive difference according to the design principles of the original nuclear suppliers and their technical standards to be imposed. This is due to the uncertainties of the accidental source term, radionuclide behavior in the environment, and subsequent radiological dose. Both types of PWR and PHWR are operated in Korea. However, technical standards for evaluating atmospheric dispersion have been enacted based on the U.S. NRC's positions regardless of the reactor types. For this reason, it might cause a controversy between the licensor and licensee of a nuclear power plant. Materials and Methods: It was modelled under the framework of the NRC Regulatory Guide 1.145 for light-water reactors, reflecting the features of heavy-water reactors as specified in the Canadian National Standard and the modelling features in MACCS2, such as atmospheric diffusion coefficient, ground deposition, surface roughness, radioactive plume depletion, and exposure from ground deposition. Results and Discussion: An integrated accident consequence assessment code, ACCESS (Accident Consequence Assessment Code for Evaluating Site Suitability), was developed by taking into account the unique regulatory positions for reactor types under the framework of the current Korean technical standards. Field tracer experiments and hand calculations have been carried out for validation and verification of the models. Conclusion: The modelling approaches of ACCESS and its features are introduced, and its applicative results for a hypothetical accidental scenario are comprehensively discussed. In an applicative study, the predicted results by the light-water reactor assessment model were higher than those by other models in terms of total doses.

• Nuclear Engineering and Technology
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• 제36권1호
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• pp.24-35
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• 2004

In order to analyze the hydrogen distribution during a severe accident in the APR1400 containment, GASFLOW II was used. For the APR1400 NPP, a hydrogen mitigation system is considered from the design stage, but a fully time-dependent, three-dimensional analysis has not been performed yet. In this study GASFLOW code II is used for the three-dimensional analysis. The first step to analysis involving hydrogen behavior in a full containment with the GASLOW code is to generate a realistic geometry model, which includes nodalization and modeling of the internal structures such as walls, ceilings and equipment. Geometry modeling of the APR1400 is conducted using GUI program by overlapping the containment cut drawings in a graphical file format on the mesh view. The total number of mesh cells generated is 49,476. And the calculated free volume of the APR1400 containment by GASFLOW is almost the same as the value from the GOTHIC modeling. A hypothetical SB-LOCA scenario beyond design base accident was selected to analyze the hydrogen behavior with the hydrogen mitigation system. The source of hydrogen and steam for the GASFLOW II analysis is obtained from a MAAP calculation. Combustion pressure and temperature load possibilities within the compartments used in the GOTHIC analysis are studied based on the Sigma-Lambda criteria. Finally the effectiveness of HMS installed in the APR1400 containment is evaluated from the point of severe accident management

• 해양환경안전학회지
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• 제23권6호
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• pp.661-668
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• 2017

본 연구의 목적은 혼산 화물의 폭발사고에 대한 화학반응 경로를 분석하는데 있다. 분석에는 사건-가지분석기법을 적용한 구조적인 시나리오를 이용하였다. 구조적인 시나리오는 재결서에 기록된 혼산 화물 사고의 내용에서 다양한 화학반응 경로를 추정하여 구축하였다. 분석에는 화학 이론에 의거한 정성적 분석과 화학 반응식을 이용한 정량적 분석 및 설문조사를 통한 확률적 분석 등 세 가지 방법을 혼합 적용하였다. 분석결과, 사고 발생의 주요 경로는 진한 황산과 물이 반응하여 폭발하는 경로, 혼산과 금속이 반응하여 폭발하는 경로, 특수한 물질과 합성하여 폭발하는 경로 등 세 가지로 나타났다. 이 결과는 재결서에 기록된 경로와 유사함을 알았고, 이를 통해서 본 연구에서 제안한 화학물질의 경로분석 기법이 타당함을 알았다. 본 연구에서 제안한 방법은 다양한 화학물질 사고의 화학반응 경로 추정에 적용 가능할 것으로 기대된다.

• 한국가스학회지
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• 제26권4호
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• pp.36-40
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• 2022

최근 산업계에서 가장 큰 화두는 산업안전보건관리에 대한 영역이다. 도시가스는 인화성 가스로 화재 및 폭발의 위험이 크기 때문에 중대 산업 및 시민 재해를 예방하기 위해 많은 노력이 요구된다. 본 연구에서는 도시가스 안전관리의 일환으로 Consequence Analysis를 통해 도시가스 누출에 의한 폭발사고 발생 시 피해 범위 및 정도를 정량적으로 예측하고자 하였다. 그 결과 압력, 기상상황 등 다양한 누출조건에 따라 분석결과 값에 차이를 보였다. 본 연구를 통해 도시가스 안전관리업무 수행 시 도시가스 누출에 의한 사고의 시나리오를 마련하여 보다 효과적인 사고예방과 비상조치계획을 마련하는데 활용할 예정이다.

• 한국가스학회지
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• 제26권3호
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• pp.10-20
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• 2022

지난 10년간 국내 화학물질 사고의 약 21%가 운송 차량에 의해 발생하였으며 그중 암모니아는 국내 화학물질 관련 사고 672건 중 82건으로 가장 많은 사고가 발생한 화학물질이다. 따라서 본 연구에서는 어선과 운송 차량 간 암모니아 이적 작업 중 누출사고가 발생할 경우의 계절별 대안 시나리오와 최악의 시나리오를 가정하였고 인구밀도 자료와 기상 특성을 토대로 ALOHA와 프로빗 분석, Python의 Folium 모듈을 통해 피해 범위와 그 영향을 해석하였다. 대안 시나리오에서 복사열의 경우 겨울철 2도 화상이 우려되는 범위가 41m, 최고 복사열이 5.01kW/m²로 가장 높았으며 과압의 경우 피해 최저기준보다 낮은 6.56kPa를 보여 압력에 의한 영향이 적은 것을 파악하였다. 그리고 독성 피해의 경우 여름철 EPPG-2 끝점이 5.0km로 복사열과 과압의 피해 영향보다 넓은 범위를 보였고, 독성 사망률에 대한 프로빗 분석 결과 인구밀도가 높은 항만과 관광지역에서 95~100%의 사망률을 확인하였다.

• Nuclear Engineering and Technology
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• 제49권2호
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• pp.442-449
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• 2017

Risk management of the Fukushima Daiichi Nuclear Power Station decommissioning is a great challenge. In the present study, a risk management framework has been developed for the decommissioning work. It is applied to fuel assembly retrieval from Unit 3 spent fuel pool. Whole retrieval work is divided into three phases: preparation, retrieval, and transportation and storage. First of all, the end point has been established and the success path has been developed. Then, possible threats, which are internal/external and technical/societal/management, are identified and selected. "What can go wrong?" is a question about the failure scenario. The likelihoods and consequences for each scenario are roughly estimated. The whole decommissioning project will continue for several decades, i.e., long-term perspective is important. What should be emphasized is that we do not always have enough knowledge and experience of this kind. It is expected that the decommissioning can make steady and good progress in support of the proposed risk management framework. Thus, risk assessment and management are required, and the process needs to be updated in accordance with the most recent information and knowledge on the decommissioning works.

• 한국안전학회지
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• 제27권3호
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• pp.117-124
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• 2012

There have been recently introduced new types of urban metro vehicles called LRT (Light Rail Transit) running on elevated guideway such as Uijeongbu VAL(which stands for V$\acute{e}$hicule Automatique L$\acute{e}$ger: Automatic Light Rail Vehicle) system, Yong-In LIM(Linear Induction Motor) system, Incheon international airport MAGLEV(Magnetic Levitated Vehicle) system and Daegu monorail system. Most of accidents by the vehicles are bound to happen on elevated guideway. Therefore, it is of vital importance to analyze hazards related to vehicles running on elevated guideway and study emergency evacuation scenarios applicable in case of accidents on elevated guideway so as to secure the safety of the new types of urban metro vehicles. In this study, FTA(Fault Tree Analysis) model was developed to identify all possible hazards, and all possible evacuation scenarios were studied. It was also confirmed that each hazard can be corresponded to one or more evacuation scenarios. This result shows that passengers can be evacuated according to one of the scenarios identified in this study in case of an accident of "Train Stranded on Elevated Guideway".

• 한국가스학회지
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• 제21권3호
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• pp.9-16
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• 2017

위험물을 취급하는 사업장에서 인근에 미치는 영향을 평가할 때 독성물질의 누출은 가장 관심있는 분야중의 하나이다. 대표적인 시설로서 염산 생산시설을 선정하여 공정정보로부터 사고 시나리오를 선정하고 독성물질 누출시 사업장외로 영향을 미치는 사고 시나리오를 선정하여 환경부의 지침에 따라서 평가하였다. ALOHA를 활용하여서 최악의 사고 시나리오를 비롯한 사고 시나리오를 평가하였으며 이들의 사고시 피해완화대책도 살펴보았다. 평가결과 염산생산시설은 현재의 안전조치가 충분하여서 추가의 개선대책이 필요하지 않은 것으로 판명되었다.

• Nuclear Engineering and Technology
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• 제51권1호
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• pp.104-115
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• 2019

Since the Fukushima Daiichi accident, there has been an emphasis on the risk resulting from multi-unit accidents. Human reliability analysis (HRA) is one of the important issues in multi-unit probabilistic safety assessment (MUPSA). Hence, there is a need to properly identify all the human and organizational factors relevant to a multi-unit incident scenario in a nuclear power plant (NPP). This study identifies and categorizes the human and organizational factors relevant to a multi-unit incident scenario of NPPs based on a review of relevant literature. These factors are then analyzed to ascertain all possible unit-to-unit interactions that need to be considered in the multi-unit HRA and the pattern of interactions. The human and organizational factors are classified into five categories: organization, work device, task, performance shaping factors, and environmental factors. The identification and classification of these factors will significantly contribute to the development of adequate strategies and guidelines for managing multi-unit accidents. This study is a necessary initial step in developing an effective HRA method for multiple NPP units in a site.