• Nuclear Engineering and Technology
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• v.43 no.1
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• pp.63-74
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• 2011

The 600 MWe, pool-type, sodium-cooled, metallic fuel loaded KALIMER-600 (Korea Advanced LiquId MEtal Reactor, 600 MWe) has been conceptually designed with an emphasis on safety by self-regulating (inherent/intrinsic) negative reactivity feedback in the core. Its inherent safety under the ATWS (Anticipated Transient Without Scram) events was demonstrated in an earlier study. Initiating events of an HCDA (Hypothetical Core Disruptive Accident), however, also need to be analyzed for assessment of the margins in the current design. In this study, a hypothetical triple-fault accident, ULOF (Unprotected Loss Of Flow) with a reduced pump halving time, is investigated as an initiator of a core disruptive accident. A ULOF with insufficient primary pump inertia may cause core sodium boiling due to a power-to-flow mismatch. If the positive sodium reactivity resulting from this boiling is not compensated for by other intrinsic negative reactivity feedbacks, the resulting core power burst would challenge the fuel integrity. The present study focuses on determination of the limit of the pump inertia for assuring inherent reactivity feedback and behavior of the core after sodium boiling as well. Transient analyses are performed with the safety analysis code SSC-K, which now incorporates a new sodium boiling model. The results show that a halving time of more than 6.0 s does not allow sodium boiling even with very conservative assumptions. Boiling takes place for a halving time of 1.8 s, and its behavior can be predicted reasonably by the SSC-K.

• Nuclear Engineering and Technology
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• v.50 no.1
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• pp.43-53
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• 2018

It is important to clarify the characteristics of flow regimes underlying the debris bed formation behavior that might be encountered in core disruptive accidents of sodium-cooled fast reactors. Although in our previous publications, by applying dimensional analysis technique, an empirical model, with its reasonability confirmed over a variety of parametric conditions, has been successfully developed to predict the regime transition and final bed geometry formed, so far this model is restricted to predictions of debris mixtures composed of spherical particles. Focusing on this aspect, in this study a new series of experiments using nonspherical particles have been conducted. Based on the knowledge and data obtained, an extension scheme is suggested with the purpose of extending the base model to cover the particle-shape influence. Through detailed analyses and given our current range of experimental conditions, it is found that, by coupling the base model with this scheme, respectable agreement between experiments and model predictions for the regime transition can be achieved for both spherical and nonspherical particles. Knowledge and evidence from our work might be utilized for the future improvement of design of an in-vessel core catcher as well as the development and verification of sodium-cooled fast reactor severe accident analysis codes in China.

• Nuclear Engineering and Technology
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• v.45 no.3
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• pp.323-334
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• 2013

During a hypothetical core-disruptive accident (CDA) in a sodium-cooled fast reactor (SFR), degraded core materials can form roughly conically-shaped debris beds over the core-support structure and/or in the lower inlet plenum of the reactor vessel from rapid quenching and fragmentation of the core material pool. However, coolant boiling may ultimately lead to leveling of the debris bed, which is crucial to the relocation of the molten core and heat-removal capability of the debris bed. To clarify the mechanisms underlying this self-leveling behavior, a large number of experiments were performed within a variety of conditions in recent years, under the constructive collaboration between the Japan Atomic Energy Agency (JAEA) and Kyushu University (Japan). The present contribution synthesizes and gives detailed comparative analyses of those experiments. Effects of various experimental parameters that may have potential influence on the leveling process, such as boiling mode, particle size, particle density, particle shape, bubbling rate, water depth and column geometry, were investigated, thus giving a large palette of favorable data for the better understanding of CDAs, and improved verifications of computer models developed in advanced fast reactor safety analysis codes.

• The Journal of the Convergence on Culture Technology
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• v.7 no.1
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• pp.545-550
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• 2021

In this paper, a university curriculum of Automation Robotics Process(RPA) among several goals for digital transformation of companies was developed. In the process of the development of ICT technology and the 4th industrial revolution, the existing analog information has changed through the stages of digitization, digitalization, and digital transformation. Recently, digital transformation has been cited as an essential survival strategy following a disruptive revolution that changes the paradigm of existing industrial systems and business. It is defined as a continuous process by which a company adapts to or promotes disruptive changes in customers and markets by using digital capabilities to create new business models, products and services. To this end, process automation in companies or organizations is an important factor. Accordingly, the need for a curriculum of robotics processes automation in universities has been raised according to these changes, and the related education contents, which have been centered on companies, have been redesigned to introduce the curriculum for universities. Education contents are composed to help students to attain certificates of essential or advanced of AA.

• Nuclear Engineering and Technology
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• v.54 no.2
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• pp.589-600
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• 2022

Investigations on the molten-pool sloshing behavior are of essential value for improving nuclear safety evaluation of Core Disruptive Accidents (CDA) that would be possibly encountered for Sodium-cooled Fast Reactors (SFR). This paper is aimed at synthesizing the knowledge from our recent studies on molten-pool sloshing behavior with solid particles conducted at the Sun Yat-sen University. To better visualize and clarify the mechanism and characteristics of sloshing induced by local Fuel-Coolant Interaction (FCI), experiments were performed with various parameters by injecting nitrogen gas into a 2-dimensional liquid pool with accumulated solid particles. It was confirmed that under different particle-bed conditions, three representative flow regimes (i.e. the bubble-impulsion dominant, transitional and bed-inertia dominant regimes) are identifiable. Aimed at predicting the regime transitions during sloshing process, a predictive empirical model along with a regime map was proposed on the basis of experiments using single-sized spherical solid particles, and then was extended for covering more complex particle conditions (e.g. non-spherical, mixed-sized and mixed-density spherical particle conditions). To obtain more comprehensive understandings and verify the applicability and reliability of the predictive model under more realistic conditions (e.g. large-scale 3-dimensional condition), further experimental and modeling studies are also being prepared under other more complicated actual conditions.

• Journal of the Society of Disaster Information
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• v.18 no.3
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• pp.660-671
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• 2022

Purpose: This study is intended to confirm the business disruptive risk in the Serious Accidents, and propose a plan to comply with the Serious Accidents Punishment Act through the Disaster Mitigation Activity Management System. Method: Through literature review and case studies, the requirements and characteristics of each of the Serious Accidents Punishment Act, the Disaster Mitigation Activity Management System, and ISO 45001 were compared and analyzed, and implications were derived. Result: The business disruption and financial adverse effects caused by industrial accidents were identified. Based on this and by using the Disaster Mitigation Activity Management System, measures to link the documentation requirements of the the Serious Accidents Punishment Act to the Disaster Mitigation Activity Management System, and to manage the implementation records of the Serious Accidents Punishment Act's duty were derived. Conclusion: When establishing and operating the Disaster Mitigation Activity Management System, it can not only comply with the Serious Accidents Punishment Act but also contribute to maintaining business continuity and ESG management through the prevention of various disasters and the minimization of secondary damage, etc.

• Corrosion Science and Technology
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• v.4 no.4
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• pp.164-170
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• 2005

Pipelines have the highest capacity and are the safest and the least environmentally disruptive means for transmitting gas or oil. Recently, failures due to corrosion defects have become a major concern in maintaining pipeline integrity. A number of solutions have been developed for the assessment of remaining strength of corroded pipelines. In this paper, a Fitness-For-Purpose(FFP) type limit load solution for corroded city gas pipelines is proposed. For this purpose, a series of burst tests with various types of machined defects were performed. Finite element simulations were carried out to derive an appropriate failure criterion. Based on such solution along with existing solutions, an integrity evaluation program for corroded city gas pipeline, COPAP-CITY, has been developed.

• Electronics and Telecommunications Trends
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• v.35 no.6
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• pp.56-67
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• 2020

The core technologies of the 4th Industrial Revolution, such as artificial intelligence, the Internet of Things, the cloud, big data, and mobile networks, are inspiring major changes and innovations in the defense sector worldwide. The United States, China, and Russia are pursuing defense research and development strategies that seek to maintain their leadership on the battlefield in the future through the overwhelming superiority of defense science technology. Defense science and technology concentrate on the development of challenging new disruptive technologies to efficiently respond to future battlefield environments, where the immediate process of determining the outcome of a war will lead to combat power. In this paper, we first look at the development strategies of the 4th Industrial Revolution in major countries and describe the latest trends in defense science and technology accordingly.

• Journal of The Korean Astronomical Society
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• v.25 no.1
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• pp.47-64
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• 1992

Cores of globular clusters are an ideal place for close encounters between stars. The outcome of tidal capture can be stellar mergers, close binaries between normal stars (W UMa type), cataclysmic variables composed of white dwarf and normal star pairs, or low-mass X-ray binaries consisting of a neutron star and a normal star pairs. Stellar mergers can be the origin of blue stragglers in dense globular clusters although they are hard to observe. Low mass X-ray binaries would eventually become binary pulsars with short pulse periods after the neutron stars accrete sufficient amount of matter from the companion. However, large number of recently discovered, isolated millisecond pulsars (as opposed to binary pulsars) in globular clusters may imply that they do not have to gain angular speeds during the X-ray binary phase. We propose that these isolated millisecond pulsars may have formed through the disruptive encounters, which lead to the formation of accretion disk without Roche lobe filling companion, between a neutron star and a main-sequence star. Based on recently developed multicomponent models for the dynamical evolution of globular clusters, we compute the expected numbers of various systems formed by tidal capture as a function of time.

• Journal of the Korean Society of Industry Convergence
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• v.8 no.4
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• pp.197-204
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• 2005

It is well known that pipelines have the highest capacity and are the safest and least environmentally disruptive form of transporting oil and gas. However, pipeline damages caused by both internal and external corrosion is a major concern threatening the reliability of oil and gas transportation and the soundness of pipeline structure. In this study, we estimated the expected allowable damage defect by comparing the ASTM B31G code which has been developed as the evaluation method of reliability and incident prevention of damaged pipelines based on the amount of loss due to corrosion and the yield strength of materials to a modified theory considering diverse detailed corrosional forms. Furthermore, we suggested the method that estimates the expected life span of used pipelines by utilizing the reliability method based on major variables such as, the depth and length of damage and corrosional rate affecting the life expectancy of pipelines.