• Nuclear Engineering and Technology
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• v.47 no.3
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• pp.240-252
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• 2015

In the original licensing application for the prototype fast-breeder reactor, MONJU, the event progression during an unprotected loss of flow (ULOF), which is one of the technically inconceivable events postulated beyond design basis, was evaluated. Through this evaluation, it was confirmed that radiological consequences could be suitably limited even if mechanical energy was released. Following the Fukushima-Daiichi accident, a new nuclear safety regulation has become effective in Japan. The conformity of MONJU to this new regulation should hence be investigated. The objectives of the present study are to conduct a preliminary evaluation of ULOF for MONJU, reflecting the knowledge obtained after the original licensing application through CABRI experiments and EAGLE projects, and to gain the prospect of in-vessel retention for the conformity of MONJU to the new regulation. The preliminary evaluation in the present study showed that no significant mechanical energy release would take place, and that thermal failure of the reactor vessel could be avoided by the stable cooling of disrupted-core materials. This result suggests that the prospect of in-vessel retention against ULOF, which lies within the bounds of the original licensing evaluation and conforms to the new nuclear safety regulation, will be gained.

• Nuclear Engineering and Technology
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• v.37 no.3
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• pp.221-230
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• 2005

This paper reviews the pivotal phases of the evolution of the current technology-dependent nuclear power safety regulation in the United States. Understanding of this evolution is essential to the development of any future regulatory paradigm, including the technology-neutral regulatory approach that the U.S. Nuclear Regulatory Commission (NRC) has recently embarked on to develop. The paper proposes and examines the implications of a predominately rationalist and best-estimate probabilistic regulatory framework called safety goals-driven performance-based regulation. This framework relies on continuous assessment of performance of a set of time-dependent safety-critical systems, structures and components that assure attainment of a broad set of technology-neutral protective, mitigative, and preventive goals. Finally, the paper discusses the steps needed to develop a corresponding technology-neutral regulatory system from the proposed framework.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.24 no.11
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• pp.2866-2874
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• 2000

This paper is concerned with the optimum design for external reinforcement of a nuclear reactor pressure vessel(RPV) in a severe accident. During the severe reactor accident of molten core, the temperature and the pressure in the nuclear reactor rise to a certain level depending on the initial and subsequent condition of a severs accident. The reis of the temperature and the internal pressure cause deterioration of the load carrying capacity and could cause failure of the RPV lower head. The deterioration of failure can be mitigated by the external cooling or the reinforcement of the lower head with additional structures. While the external cooling forces the temperature of an RPV to drop to the desired level, the reinforcement of the lower head can attain both the increase of the load carrying capacity and the temperature drop. The reinforcement of the lower head can be optimized to have the maximum effect on the collapse pressure and the temperature at the inner wall. Optimization results are compared to both the result without the reinforcement and the result with the designated reinforcement.

• Proceedings of the Korea Society for Energy Engineering kosee Conference
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• 2002.05a
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• pp.9-20
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• 2002

기존의 원자력 발전기술이 안고 있는 대부분의 고유한 문제점인 핵안전성, 핵확산방지 및 핵폐기물 관리 문제는 물론 더 나아가 국내의 핵원료자원의 공급안정과 원자력에 대한 국민적 신뢰성 회복을 비롯하여 원자력의 평화적 이용확대를 위해 필수적으로 고려해야할 사항들을 반영한 새로운 개념의 250 MW$_{th}$ 실증로급 AMBIDEXTER(Advanced Molten-salt Break-even Inherently-safe Dual-missioning EXperimetal and TEst Reactor) 원자력 에너지 시스템을 현재 개념 설계 중에 있다.(중략)

• Nuclear Engineering and Technology
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• v.55 no.6
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• pp.2047-2052
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• 2023

Risk-informed approach has been widely applied in the safety design, regulation, and operation of nuclear reactors. It has been commonly accepted that risk-informed design optimization should be used in the innovative reactor designs to make nuclear system highly safe and reliable. In spite of the risk-informed approach has been used in some advanced nuclear reactors designs, such as Westinghouse IRIS, Gen-IV sodium fast reactors and lead-based fast reactors, the process of risk-informed design of nuclear reactors is hardly to carry out when passive system reliability should be integrated in the framework. A practical method for new passive safety reactors based on probabilistic safety assessment (PSA) and passive system reliability analyze linking is proposed in this paper. New three-dimension frequency-consequence curve based on risk concept with three variables is used in this method. The proposed method has been applied to the determination optimization of design options selection in a 10 MWth lead-based research reactor(LR) to obtain one optimized system design in conceptual design stage, using the integrated reliability and probabilistic safety assessment program RiskA, and the computation resources and time consumption in this process was demonstrated reasonable and acceptable.

• Proceedings of the KIEE Conference
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• 2004.07c
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• pp.1885-1887
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• 2004

This paper presents the aspect and distribution of voltage and current harmonics being made at low voltage power systems. The voltage and current harmonics in power systems supplying various loads were monitored and analyzed. We have examined the results compared to advanced countries' harmonics control standards. As a result, the current harmonics were significantly greater than the voltage harmonics. In particular, the harmonics of currents flowing through loads with power switching electronics was pronounced. Also, the contents of current harmonics of street lamp circuits was about 30%, and it was decreased to 12.3% with the installation of scries reactor. On the whole, The measured results of voltage and current harmonics exceeds the regulation limits recommended by IEEE std 519-1992.

• Proceedings of the Korean Institute of IIIuminating and Electrical Installation Engineers Conference
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• 2004.05a
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• pp.100-103
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• 2004

This paper presents the aspect and distribution of voltage and current harmonics being made at low voltage power systems. The voltage and current harmonics in power systems supplying various loads were monitored and analyzed. We have examined the results compared to advanced countries' harmonics control standards. As a result, the current harmonics were significantly greater than the voltage harmonics. In particular, the harmonics of currents flowing through loads with power switching electronics was pronounced. Also, the contents of current harmonics of street lamp circuits was about 30%, and it was decreased to 12.3% with the installation of series reactor. On the whole, The measured results of voltage and current harmonics exceeds the regulation limits recommended by IEEE 519-1992.