• Korean Journal of Environmental Agriculture
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• v.38 no.1
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• pp.54-60
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• 2019

BACKGROUND: Hydrogen fluoride is one of the 97 accident preparedness substances regulated by the Ministry of Environment (Republic of Korea) and chemical accidents should be managed centrally due to continual occurrence. Especially, hydrogen fluoride has a characteristic of rapid diffusion and very toxic when leaking into the environment. Therefore, it is important to predict the impact range quickly and to evaluate the residual contamination immediately to minimize the human and environmental damages. METHODS AND RESULTS: In order to estimate the accident impact range, the off-site consequence analysis (OCA) was performed to the worst and alternative scenarios. Also, in order to evaluate the residual contamination of hydrogen fluoride in crop, the samples in accident site were collected from 15-divided regions (East direction from accident sites based on the main wind direction), and the concentration was measured by fluoride ($F^-$) ion-selective electrode potentiometer (ISE). As a result of the OCA, the affected distance by the worst scenario was estimated to be >10 km from the accident site and the range by the alternative scenario was estimated to be about 1.9 km. The residual contamination of hydrogen fluoride was highest in the samples near the site of the accident (E-1, 276.82 mg/kg) and tended to decrease as it moved eastward. Meanwhile, the concentrations from SE and NE (4.96~28.98 mg/kg) tended to be lower than the samples near the accident site. As a result, the concentration of hydrogen fluoride was reduced to a low concentration within 2 km from the accident site (<5 mg/kg), and the actual damage range was estimated to be around 2.2 km. Therefore, it is suggested that the results are similar to those of alternative accident scenarios calculated by OCA (about 1.9 km). CONCLUSION: It is difficult to estimate the chemical accident-affecting range/region by the OCA evaluation, because it is not possible to input all physicochemical parameters. However simultaneous measurement of the residual contamination in the environment will be very helpful in determining the diffusion range of actual chemical accident.

• Journal of the Korea Safety Management & Science
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• v.19 no.4
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• pp.133-140
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• 2017

The Ministry of Science, ICT and Future Planning made law for Pre-Hazard Risk Analysis in December 31, 2014 to protect researchers from continuing accidents in laboratory. Conducted before an experiment, Pre-Hazard Risk Analysis finds hazards of the experiment and rules to manage the hazards.So the Pre-Hazard Risk Analysis can support laboratory safety system by prevent accidents in laboratory. Pre-Hazards Risk Analysis is newly created system so that executors need Guidelines to perform this analysis properly. This study is to develop guide tool for Pre-Hazard Risk Analysis by analyzing other risk assessment systems; PSM, Off-site Consequence Assessment, laboratory safety system. Also, this study suggested how to establish database for Pre-Hazard Risk Assessment by analyse KRAS.

• Journal of the Korean Society of Safety
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• v.32 no.6
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• pp.46-53
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• 2017

The risk is expressed as consequence of damage multiplied by likelihood of failure. The installation of a protective system reduces the risk by reducing the likelihood of failure at the facility. Also, the protective system has different effects on the likelihood of failure according to the proof test cycle. However, when assessing risks in the Off-site Risk Assessment (ORA) system, the variation in risk was not reflected according to the proof test cycle of protective system. This study was conducted to examine the need for proof test and the importance of cycle setting by applying periodic proof test of the protective system to ORA. The results showed that the likelihood of failure and the risk increased with longer proof test cycle. The risk of a two-yearly proof test was eight times greater than that of a three-month cycle. From the results, the protective system needs periodic proof test. Untested protective system for a long term cannot be reliable because it is more likely to be failed state when it is called upon to operate. In order to reduce the risk to an acceptable level, it is effective to differently set the proof test cycle according to the priority. This study suggested a more systematic and accurate risk analysis standard than ORA. This standard is expected to enable an acceptable level of risk management by systematically setting the priority and proof test cycle of the protective system. It is also expected to contribute to securing the safety of chemical facilities and at the same time, will lead to the development of the ORA system.

• Journal of the Korean Institute of Gas
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• v.20 no.6
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• pp.1-8
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• 2016

Gu-mi hydrogen fluoride leak accident in 2012 was amplified social anxiety for chemical accidents. To relieve these anxieties Off-site Risk Assessment was introduced in 2015. Off-site Risk Assessment is targeted at most chemicals, and most of the high-pressure-toxic gases which are mainly used in high-tech industries such as semi conductor, display, Photovoltaic panels industry are included in the substance of the Off-site Risk Assessment. Since Korean companies occupy a high market share in high-tech industries, high pressure-toxic domestic gas consumption is constantly increasing. Accordingly, it is expected to increase the possibility of accidents. In accordance with the circumstances, this study was to conducted Consequence Analysis(CA) about high pressure-toxic gases those are high demand in domestic. CA was used for ALOHA developed by US EPA & US NOAA and the CA result of Arsine was the largest at 4,700 m. CA results are expected to be utilized for determining the effective Safety distances when high pressure-toxic gas leak.

• Journal of Korean Society of Environmental Engineers
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• v.39 no.2
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• pp.74-81
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• 2017

An off-site consequence analysis is used to calculate the risks when hazardous chemicals that is being used on-site has been exposed off-site; the biggest factor that impacts the risk is the risks of accident scenarios. This study seeks to calculate risks according to accident scenarios by applying OGP/LOPA risk calculating methods for similar facilities, calculate risk reduction ratio by inspecting applicable IPL for incidents, and propose an appropriate risk standard for different risk calculating methods. Considering all applicable IPL when estimating the safety improvement of accident scenarios, the risk of OGP is 8.05E-04 and the risk of LOPA is 1.00E-04, According to the case of IPL, the risk is 1.34E-02. The optimal risk level for accident scenarios using LOPA was $10^{-2}$, but the appropriate risk criteria for accident scenarios in foreign similar studies were $10^{-3}{\sim}10^{-4}$, the risk of a scenario can be determined at an unacceptable level. When OGP is applied, it is analyzed as acceptable level, but in case of applying LOPA, all applicable IPL should be applied in order to satisfy the acceptable risk level. Compared to OGP, the risk is high when LOPA is applied. Therefore, the acceptable risk level should be set differently for each risk method.

• Journal of the Korean Society of Safety
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• v.32 no.5
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• pp.168-178
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• 2017

In order to prevent major and chemical accidents, some of the plants which would like to install and operate hazard chemicals handling facilities must submit Off-site Consequence Analysis due to recent arisen leak accidents since 2015. A lot of chemical industrials choose gas detectors as mitigation equipment to early detect gas vapor. The way of placement of gas detectors has two methods; Code-based Design(CBD) and Performance-based Design. The CBD has principles for gas detectors to be installed with consideration for the place that is expected to accumulate gas, and the leak locations according to legal standards and technical guidelines, and has a possibility to be unable to detect by these rules to locate gas detectors by vapor density information. The PBD has two methods; a Geographic Method and Scenario based Method. The Scenario-based Method has been suggested to make up for the Geographic Coverage Method. This Scenario-based Method draw the best optimum placement of gas detectors by considering leak locations, leak speed information, leak directions and etc. However, the domestic placement guidelines just refers to the CBD. Therefore, this study is to compare existing placement location of gas detectors by the domestic CBD with placement locations, coverages and the number of gas detectors in accordance with the Scenario-based Method. Also this study has measures for early detecting interest of Vapor Cloud and suitable placement of gas detectors to prevent chemical accidents. The Phast software was selected to simulate vapor cloud dispersion to predict the consequence. There are two cases; an accident hole size of leak(8 mm) from API which is the highst accident hole size less than 24.5 mm, and a normal leak hole size from KOSHA Guide (1.8 mm). Detect3D was also selected to locate gas detectors efficiently and compare CBD results and PBD results. Currently, domestic methods of gas detectors do not consider any risk, but just depend on domestic code methods which lead to placement of gas detectors not to make personnels recognize tolerable or intolerable risks. The results of the Scenario-based Method, however, analyze the leak estimated range by simulating leak dispersion, and then it is able to tell tolerable risks. Thus it is considered that individuals will be able to place gas detectors reasonably by making objectives and roles flexibly according to situations in a specific plant.

• Nuclear Engineering and Technology
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• v.26 no.1
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• pp.41-53
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• 1994

A SGTR accident postulated at Kori unit 1 is simulated with Mihama unit experience, which occurred on February 1991, to evaluate the capability of plant to cope with the transient. The system design and plant conditions of Kori Unit 1 are much similar with those of Mihama Unit 2. Therefore, special concern has been given to evaluate the sequence and the resulting consequence of the postulated SGTR accident at the Kori unit 1 An analysis is peformed as realistically as possible, with following the EOP of Kori unit 1. The result indicates that the leak through tube break terminates within about forty minutes, and the Kori unit 1 may be sufficient to cope with SGTR accident with same type of sequence. However, the reconsideration may be required for the design of Kori unit 1 which disconnects non-safety AC power from off-site power on SI signal generation. It may be pointed out that the content of EOP for SGTR accident is not enough to require operator's proper judgements. An analysis of SGTR accident tested in the LSTF which simulated the SGTR accident at the Mihama Unit 2 is peformed using the RELAP5/MOD3. The results indicates that the code yields in general good agreement with the test, except the break flowrate at the early stage of the event.