• Nuclear Engineering and Technology
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• v.50 no.4
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• pp.562-569
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• 2018

Recently, human errors have very rarely occurred during power generation at nuclear power plants. For this reason, many countries are conducting research on smart support systems of nuclear power plants. Smart support systems can help with operator decisions in severe accident occurrences. In this study, a smart support system was developed by integrating accident prediction functions from previous research and enhancing their prediction capability. Through this system, operators can predict accident scenarios, accident locations, and accident information in advance. In addition, it is possible to decide on the integrity of instruments and predict the life of instruments. The data were obtained using Modular Accident Analysis Program code to simulate severe accident scenarios for the Optimized Power Reactor 1000. The prediction of the accident scenario, accident location, and accident information was conducted using artificial intelligence methods.

• Nuclear Engineering and Technology
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• v.46 no.2
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• pp.207-216
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• 2014

This paper revisits the Fukushima accident to draw lessons in the aspect of nuclear safety considering the fact that the Fukushima accident resulted in core damage for three nuclear power plants simultaneously and that there is a high possibility of a failure of the integrity of reactor vessel and primary containment vessel. A brief review on the accident progression at Fukushima nuclear power plants is discussed to highlight the nature and characteristic of the event. As the severe accident management measures at the Fukushima Daiich nuclear power plants seem to be not fully effective, limitations of current severe accident management strategy are discussed to identify the areas for the potential improvements including core cooling strategy, containment venting, hydrogen control, depressurization of primary system, and proper indication of event progression. The gap between the Fukushima accident event progression and current understanding of severe accident phenomenology including the core damage, reactor vessel failure, containment failure, and hydrogen explosion are discussed. Adequacy of current safety goals are also discussed in view of the socio-economic impact of the Fukushima accident. As a conclusion, it is suggested that an investigation on a coherent integrated safety principle for the severe accident and development of innovative mitigation features is necessary for robust and resilient nuclear power system.

• Nuclear Engineering and Technology
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• v.49 no.2
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• pp.313-326
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• 2017

The systematic management of plant risk is crucial for enhancing the safety of nuclear power plants and for designing new nuclear power plants. Accident sequence precursor (ASP) analysis may be able to provide risk significance of operational experience by using probabilistic risk assessment to evaluate an operational event quantitatively in terms of its impact on core damage. In this study, an ASP methodology for two operation mode, full power and low power/shutdown operation, has been developed and applied to significant accident precursors that may occur during the operation of nuclear power plants. Two operational events, loss of feedwater and steam generator tube rupture, are identified as ASPs. Therefore, the ASP methodology developed in this study may contribute to identifying plant risk significance as well as to enhancing the safety of nuclear power plants by applying this methodology systematically.

• Korean journal of communication and information
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• v.76
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• pp.124-150
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• 2016

The aim of this study is to see the change of the general characteristics and frame of nuclear power plant news in Korea from comparing the before Fukushima nuclear accident in Japan on March 11, 2011 with the after. To this aim, the national daily newspapers and the local daily newspapers in Busan located nuclear power plants were selected, and the content analysis of the newspaper stories about nuclear power plants was done. In research results, the stories about nuclear power plants in Korean newspapers increased greatly after Fukushima nuclear accident. Before the accident the nuclear power plant stories about economy held a large majority, while after the accident the stories about society held. Fukushima nuclear accident served as the momentum that the nuclear power plant stories in Korea became main news. Meanwhile, the frame of nuclear power plant stories in Korean newspapers changed greatly after the accident. Justly the environmental security frame increased greatly, because of increasing greatly the stories about security of nuclear power plants with Fukushima nuclear accident. Particularly in the local daily newspapers in Busan before the accident the environmental security frame was 29.3% of stories about nuclear power plants, and after the accident the frame was 77.6%.

• Proceedings of the Korean Nuclear Society Conference
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• 1997.05a
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• pp.464-470
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• 1997

Severe accident analysis has been performed for the Wolsung nuclear power plants in Korea to investigate severe accident phenomena of CANDU-600 reactors as a part of Level II PSA study. The accident sequence analyzed in this paper is loss of active heat sinks(LOAH) which is caused by loss of off-site power, diesel generators, and DC power. ISAAC (Integrated Severe Accident Analysis Code)computer code developed by KAERI (Korea Atomic Energy Research Institute) was used in this analysis. This paper describes the important thermal-hydraulics and source term behaviors in the primary system and inside containment, and the failure mechanism of calandria vessel and containment. In addition, some insights for accident management program(AMP) are also given.

• Nuclear Engineering and Technology
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• v.55 no.10
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• pp.3787-3800
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• 2023

Reactivity Initiated Accident (RIA) scenarios require special attention using advanced simulation techniques due to their complexity and importance for nuclear power plant (NPP) safety. While the conservative approach has traditionally been used for safety analysis, it may lead to unrealistic results which calls for the use of best estimate plus uncertainty (BEPU) approach, especially with the current advances in computational power which makes the BEPU analysis feasible. In this work an Uncontrolled Control Element Assembly (CEA) Withdrawal at Full Power accident scenario is analyzed using the BEPU approach by loosely coupling the thermal hydraulics best-estimate system code (RELAP5/SCDAPSIM/MOD3.4) to the statistical analysis software (DAKOTA) using a Python interface. Results from the BEPU analysis indicate that a realistic treatment of the accident scenario yields a larger safety margin and is therefore encouraged for accident analysis as it may enable more economic and flexible operation.

• Environmental and Resource Economics Review
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• v.22 no.2
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• pp.367-391
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• 2013

After the Fukushima nuclear accident, the external costs of generating electricity from nuclear power plants such as additional safety compliance costs and possible accident risk action costs have gained increasing attention from the public, policy-makers and politicians. Consequently, estimates of the external costs of nuclear power are very deliberate issue that is at the center of the controversy in Korea. In this paper, we try to calculate the external costs associated with the safety of the nuclear power plants, particularly focusing on additional safety compliance costs and possible accident risk action costs. To estimate the possible accident risk action costs, we adopt the damages expectation approach that is very similar way from the external cost calculation of Japanese government after the Fukushima accident. In addition, to estimate additional safety compliance costs, we apply the levelized cost of generation method. Furthermore, we perform the sensitivity analysis to examine how much these social costs increase the electricity price rate. Estimation results of the additional security measure cost is 0.53Won/kWh ~ 0.80Won/kWh depending on the capacity factor, giving little change on the nuclear power generation cost. The estimates of possible accident risk action costs could be in the wide range depending on the different damages of the nuclear power accident, probability of the severe nuclear power accident and the capacity factor. The preliminary results show that it is 0.0025Won/kWh ~ 26.4188Won/kWh. After including those two external costs on the generation cost of a nuclear power plant, increasing rate of electricity price is 0.001%~10.0563% under the capacity factor from 70% to 90%. This paper tries to examine the external costs of nuclear power plants, so as to include it into the generation cost and the electricity price. This paper suggests one of the methodologies that we might internalize the nuclear power generations' external cost, including it into the internal generation cost.

• Nuclear Engineering and Technology
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• v.47 no.4
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• pp.461-471
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• 2015

Recently, the estimation of the social cost of energy sources has been emphasized as various novel energy options become feasible in addition to conventional ones. In particular, the social cost of introducing measures to protect power-distribution systems from power-source instability and the cost of accident-risk response for various power sources must be investigated. To account for these risk factors, an integrated societal risk assessment framework, based on power-uncertainty analysis and accident-consequence analysis, is proposed. In this study, we applied the proposed framework to nuclear power plants, solar photovoltaic systems, and wind-turbine generators. The required capacity of gas-turbine power plants to be used as backup power facilities to compensate for fluctuations in the power output from the main power source was estimated based on the performance indicators of each power source. The average individual health risk per terawatt-hours (TWh) of electricity produced by each power source was quantitatively estimated by assessing accident frequency and the consequences of specific accident scenarios based on the probabilistic risk assessment methodology. This study is expected to provide insight into integrated societal risk analysis, and can be used to estimate the social cost of various power sources.

• Nuclear Engineering and Technology
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• v.55 no.2
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• pp.493-505
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• 2023

Comprehensive condition monitoring of large industry systems such as nuclear power plants (NPPs) is essential for safety and maintenance. In this study, we developed novel system-scale diagnostic technology based on deep-learning and IR thermography that can efficiently and cost-effectively classify system conditions using compact Raspberry Pi and IR sensors. This diagnostic technology can identify the presence of an abnormality or accident in whole system, and when an accident occurs, the type of accident and the location of the abnormality can be identified in real-time. For technology development, the experiment for the thermal image measurement and performance validation of major components at each accident condition of NPPs was conducted using a thermal-hydraulic integral effect test facility with compact infrared sensor modules. These thermal images were used for training of deep-learning model, convolutional neural networks (CNN), which is effective for image processing. As a result, a proposed novel diagnostic was developed that can perform diagnosis of components, whole system and accident classification using thermal images. The optimal model was derived based on the modern CNN model and performed prompt and accurate condition monitoring of component and whole system diagnosis, and accident classification. This diagnostic technology is expected to be applied to comprehensive condition monitoring of nuclear power plants for safety.

• Nuclear Engineering and Technology
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• v.49 no.3
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• pp.632-637
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• 2017

Even though the potential for an accident in nuclear power plants is very low, multiple emergency plans are necessary because the impact of such an accident to the public is enormous. One of these emergency plans involves a robotic system for investigating accidents under conditions of high radiation and contaminated air. To develop a robot suitable for operation in a nuclear power plant, we focused on eliminating the three major obstacles that challenge robots in such conditions: the disconnection of radio communication, falling on uneven floors, and loss of localization. To solve the radio problem, a Wi-Fi extender was used in radio shadow areas. To reinforce the walking, we developed two- and four-leg convertible walking, a floor adaptive foot, a roly-poly defensive falling design, and automatic standing recovery after falling methods were developed. To allow the robot to determine its location in the containment building, a bar code landmark reading method was chosen. When a severe accident occurs, this robot will be useful for accident condition monitoring. We also anticipate the robot can serve as a workman aid in a high radiation area during normal operations.