• 한국안전학회지
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• 제27권6호
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• pp.192-204
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• 2012

For a severe accident of nuclear power plant, an approach to estimation of the radiological source term using a severe accident code(MELCOR) has been proposed. Although the MELCOR code has a capability to estimate the radiological source term, it has been hardly utilized for the radiological consequence analysis mainly due to a lack of understanding on the relevant function employed in MELCOR and severe accident phenomena. In order to estimate the severe accident source term to be linked with the radiological consequence analysis, this study proposes 4-step procedure: (1) selection of plant condition leading to a severe accident(i.e., accident sequence), (2) analysis of the relevant severe accident code, (3) investigation of the code analysis results and post-processing, and (4) generation of radiological source term information for the consequence analysis. The feasibility study of the present approach to an early containment failure sequence caused by a fast station blackout(SBO) of a reference plant (OPR-1000), showed that while the MELCOR code has an integrated capability for severe accident and source term analysis, it has a large degree of uncertainty in quantifying the radiological source term. Key insights obtained from the present study were: (1) key parameters employed in a typical code for the consequence analysis(i.e., MACCS) could be generated by MELCOR code; (2) the MELOCR code simulation for an assessment of the selected accident sequence has a large degree of uncertainty in determining the accident scenario and severe accident phenomena; and (3) the generation of source term information for the consequence analysis relies on an expert opinion in both areas of severe accident analysis and consequence analysis. Nevertheless, the MELCOR code had a great advantage in estimating the radiological source term such as reflection of the current state of art in the area of severe accident and radiological source term.

• Nuclear Engineering and Technology
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• 제52권11호
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• pp.2511-2521
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• 2020

The Fukushima accident is characterized by the fact that three reactors at the same site experienced reactor vessel failure and the accident resulted in significant radiological release to the environment, which was about 1/10 of the Chernobyl releases. The safe removal of fuel debris in the reactor vessel and Primary Containment Vessel (PCV) and treatment of huge amount of contaminated water are the major issues for the decommissioning in coming decades. Discussions on the new researches efforts being carried out in the area of investigation of the end state of fuel debris and Boling Water reactor (BWR) specific core melt progression, development of technologies for the mitigation of radiological releases to comply with the strengthened safety requirement set after the Fukushima accident are discussed.

• 대한방사선방어학회:학술대회논문집
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• 대한방사선방어학회 2010년도 춘계 학술발표회 및 심포지엄
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• pp.100-101
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• 2010

• 방사성폐기물학회지
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• 제18권2호
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• pp.195-206
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• 2020

국내 방사능재난대응체계는 일본 후쿠시마 원전 사고와 최근의 국내 대형 재난 교훈 등을 바탕으로 개선돼 오고 있지만, 아직 방사능재난 특성과 후쿠시마 원전 사고 교훈을 완전히 반영하고 있지 못하다. 하나의 방사능재난대응체계에 복수의 국내법이 적용되면서, 실제 상황 시, 대응체계의 실효성을 훼손할 가능성이 있는 법 조항 간 불일치 사항이 존재하기도 한다. 이에 본 논문에서는 방사능재난대응 속성을 분석하고, 방사능재난대응체계 적절성 측면에서 「재난 및 안전관리 기본법」과 「원자력시설 등의 방호 및 방사능 방재 대책법」에서 규정한 방사능재난대응체계, 후쿠시마 원전 사고 시 일본측의 방사능 재난 대응 활동을 분석하고, 이 분석결과를 토대로, 대응체계와 조직 측면에서 국내 방사능재난대응체계 실효성을 제고하기 위해 필요한 개선사항을 도출하여 제시하였다.

• 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.

• Nuclear Engineering and Technology
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• 제54권7호
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• pp.2606-2613
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• 2022

Spent resin often exceeds radiation limits for safe disposal, creating a need for commercial-scale treatment techniques to reduce resin radioactivity. In this study, the radiological safety of a commercialized spent resin treatment device with a treatment capacity of 1 ton/day was evaluated. The results confirm that the device is radiologically safe in the event of an accident. This device desorbs ¹⁴C from the spent resin, allowing disposal as low-level waste instead of intermediate-level waste. The device also reduces overall waste by recycling the extracted ¹⁴C. Potential accident scenarios were explored to enable dose assessments for both internal and external exposure while preventing further spillage of the device and processing the spilled resin. The scenarios involved the development of a surface fracture on the resin mixture separator and microwave systems, which were operated under pressure and temperature of 0-6 bar and 0-150 ℃, respectively. In the case of accidents with separator and microwave device, the maximum allowable working time of worker were derived, respectively, considering external and internal exposures. When wearing the respirator corresponding to APF 50, in the case of the microwave device accident scenario, the radiological safety was confirmed when the maximum worker worked within 132.1 h.

• 한국원자력학회:학술대회논문집
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• 한국원자력학회 2004년도 요약집 춘계학술발표대회
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• pp.398-398
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• 2004

• Nuclear Engineering and Technology
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• 제54권4호
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• pp.1516-1525
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• 2022

Interfacing the output of severe accident analysis with the input of radiological consequence analysis is an important and mandatory procedure at the beginning of Level 3 PSA. Such interfacing between the severe accident analysis code MELCOR and MACCS, one of the most commonly used consequence analysis codes, is relatively tractable since they share the same chemical groups, and the related interfacing software, MelMACCS, has already been developed. However, the linking between MAAP, another frequently used code for severe accident analyses, and MACCS has difficulties because MAAP employs a different chemical grouping method than MACCS historically did. More specifically, MAAP groups by chemical compound, while MACCS groups by chemical element. An appropriate interfacing method between MAAP and MACCS has therefore long been requested by users. This study suggests a way of extracting relevant information from MAAP results and providing proper source term information to MACCS by an appropriate treatment. Various parameters are covered in terms of magnitude and manner of release in this study, and special treatment is made for a bypass scenario. It is expected that the suggested approach will provide an important contribution as a guide to interface MAAP and MACCS when performing radiological consequence analyses.

• Journal of Radiation Protection and Research
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• 제45권1호
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• pp.16-25
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• 2020

Background: To investigate radiological effects on biota, it is necessary to assess radiation dose for flora and fauna living in a terrestrial ecosystem. This paper presents a dynamic model to assess radioactivity concentration and radiation dose of terrestrial flora and fauna after a nuclear accident. Materials and Methods: Litter, organic soil, mineral soil, trees, wild crops, herbivores, omnivores, and carnivores are considered the major components of a terrestrial ecosystem. The model considers the physicochemical and biological processes of interception, weathering, decomposition of litter, percolation, root uptake, leaching, radioactive decay, and biological loss of animals. The predictive capability of the model was investigated by comparison of its predictions with field data for biota measured in the Fukushima forest area after the Fukushima nuclear accident. Results and Discussion: The predicted radioactive cesium inventories for trees agreed well with those for evergreens and deciduous trees sampled in the Fukushima area. The predicted temporal radioactivity concentrations for animals were within the range of the measured radioactivity concentrations of deer, wild boars, and black bears. The radiation dose for the animals were, for the whole simulation time, estimated to be much smaller than the lower limit (0.1 mGy·d^-1) of the derived consideration reference level given by the International Commission on Radiological Protection for terrestrial flora and fauna. This suggested that the radiation effect of the accident on the biota in the Fukushima forest would be insignificant. Conclusion: The present dynamic model can be used effectively to investigate the radiological risk to terrestrial ecosystems following a nuclear accident.

• Journal of Radiation Protection and Research
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• 제48권3호
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• pp.107-116
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• 2023

This article reviews the experience of applying the Identification, Diagnosis, Prospective, and Action (IDPA) facilitating method as a means of promoting practices of dialogue between stakeholders in the radiological protection field. After presenting the characteristics of the IDPA method and its ability to promote active listening, participation, and dialogue among stakeholders facing complex situations, as well as the procedural aspects associated with its practical implementation, the article describes three examples of the application of the method in the field of radiological protection. The first one presents how the IDPA method supported a debate among decision-makers, authorities, experts, professionals, and representatives of non-governmental organizations about how to engage stakeholders in radiological protection. The second example presents how the IDPA method was used in a series of dialogue meetings to explore the challenges of the post-nuclear accident situation resulting from the Fukushima Daiichi Nuclear Power Plant accident. The third one presents the application of the method in the context of a training course organized by Nagasaki University in the affected area close to the damaged plant. Experience has shown that the IDPA method makes it possible to develop responses to problems posed in very different contexts and, in many cases, to find compromises regarding their solutions. The IDPA method has the merit of allowing each of the participants to better understand the situation they are faced with, even if such a positive result is not always achieved.