• Nuclear Engineering and Technology
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• v.54 no.3
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• pp.1071-1084
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• 2022

The present study aims to investigate the dynamic properties of a novel isolation system composed of separate rubber and wire isolators. The testing program comprised pure compressive, pure-shear, compressive-stress dependence, and shear-strain dependence tests that used full-scale test specimens according to ISO 22762-1. A total of 22 test specimens were fabricated and investigated. Among the tests, the pure compressive test was a destructive test that reached up to the failure stage, whereas the others were nondestructive tests before the failure stage. Similar to the pure-shear test, at each compressive-stress level in the compressive dependence test or at each shear-strain level in the shear-strain dependence test, the cyclic loading was conducted for three cycles. In the nondestructive tests, examination of the dynamic shear properties in the X-direction was independent of the Y-direction. The test results revealed that the increase in the shear strain increased the energy dissipation but decreased the damping ratio, whereas the increase in the compressive stress increased the damping ratio. In addition, a macro model was developed to simulate the load-displacement response of the isolation systems, and the prediction results were consistent with the experimental results.

• Journal of Ocean Engineering and Technology
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• v.37 no.5
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• pp.205-214
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• 2023

As the regulations on greenhouse gas emissions at sea become strict, efforts are being made to minimize environmental pollutants emitted from fossil fuels used by ships. Considering the large sizes of ships in conjunction with securing stable supplies of environment-friendly energy, interest in nuclear energy to power ships has been increasing. In this study, the neutron irradiation that occurs during the nuclear reactor operation and its effect on the structural responses of the stiffened-plate structures are investigated. This is done by changing the material properties of DH36 steel according to the research findings on the neutron-irradiated steels and then performing the structural response analyses of the structures using analytical and finite-element numerical solutions. Results reveal the influence of neutron irradiation on the structural responses of the structures. It is shown that both the strength and stiffness of the structures are affected by the neutron-irradiation phenomenon as their maximum flexural stress and deflection are increased with the increase in the amount of neutron irradiation. This implies that strength and stiffness need to be considered in the design of ships equipped with marine nuclear reactors.

• Steel and Composite Structures
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• v.32 no.6
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• pp.807-819
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• 2019

In recent earthquakes, the failure of ceiling systems has been one of the most widely reported damage and the major cause of functionality interruption in some buildings. In an effort to mitigate this damage, some scholars have studied a series of ceiling systems including plaster ceilings and mineral wool ceilings. But few studies have involved the backdrop metal ceiling used in some important constructions with higher rigidity and frequency such as the main control area of nuclear power plants. Therefore, in order to evaluate its seismic performance, a full-scale backdrop metal ceiling system, including steel runners and metal panels, was designed, fabricated and installed in a steel frame in this study. And the backdrop metal ceiling system with two perimeter attachments variants was tested: (i) the ends of the runners were connected with the angle steel to form an effective lateral constraint around the backdrop metal ceiling, (ii) the perimeter attachments of the main runner were retained, but the perimeter attachments of the cross runner were removed. In the experiments, different damage of the backdrop metal ceiling system was observed in detail under various earthquakes. Results showed that the backdrop metal ceiling had good integrity and excellent seismic performance. And the perimeter attachments of the cross runner had an adverse effect on the seismic performance of the backdrop metal ceiling under earthquakes. Meanwhile, a series of seismic construction measures and several suggestions that need to be paid attention were proposed in the text so that the backdrop metal ceiling can be better applied in the main control area of nuclear power plants and other important engineering projects.

• Journal of the Earthquake Engineering Society of Korea
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• v.20 no.7_spc
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• pp.443-451
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• 2016

A Gyeongju earthquake in the magnitude of 5.8 on the Richter scale (the moment magnitude of 5.4), which was recorded as the strongest earthquake in Korea, occurred in September 12, 2016. Compared with the 2011 Virginia earthquake, the moment magnitude was slightly smaller and its duration was 3 seconds, much shorter than 10 seconds of the Virginia earthquake, resulting in relatively minor damage. But the two earthquakes are quite similar in terms of the overall scale, unexpectedness, and social situation. The North Anna Nuclear Power Plant, which is a nuclear power plant located at 18 km away from the epicenter of the Virginia earthquake, had no damage to nuclear reactors because the reactors were automatically shut down as the design basis earthquake value was exceeded. Ground accelerations of the 2016 Gyeongju earthquake did not exceed the threshold value but the manual shutdown was carried out so that Wolsong Nuclear Power Site was not damaged. Damaged historic homestead house and masonry structures due to the Virginia earthquake have been repaired, reinforced, and rebuilt based on a long-term earthquake recovery project. Likewise, it will be necessary to carefully carry out an earthquake recovery planning program to improve overall seismic performance and to reconstruct the historic buildings and structures damaged as a result of the Gyeongju earthquake.

• The Transactions of the Korean Institute of Electrical Engineers D
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• v.55 no.5
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• pp.199-204
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• 2006

To develop a safety-critical network in nuclear power plants that puts more stringent requirements than the competitive commercial ones do, we establish four design criteria - deterministic communication, explicit separation/isolation structure, reliability, verification & validation. According to those design criteria, the fundamental design elements are chosen as follows - a star topology, point-to-point physical link, connection-oriented link control and fixed allocation access control. After analyzing the design elements, we also build a communication architecture with TDM (Time Division Multiplexing) bus switching scheme. Finally, We develop a DDCNet (Deterministic Data Communication Network) based on the established architecture. The DDCNet is composed of 64 nodes and guarantees the transmission bandwidth of 10Mbps and the delay of 10 msec for each node. It turns out that the DDCNet satisfies the aforementioned design criteria and can be adequately utilized for our purpose.

• Proceedings of the Korean Nuclear Society Conference
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• 1997.10a
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• pp.265-270
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• 1997

차세대원자로(II)에서 개발중인 I&C 계통은 기존 아나로그 신호 체계를 가진 한국 표준형이나 웨스팅하우스형의 원전에 비해, 완전 디지탈화 및 소프트웨어에 의한 제어와 보호 기능 수행, 정보 계통의 클라이언트/서버 개념의 도입등 개선된 성능과 신뢰성을 바탕으로한 운전 지원 향상을 주요한 설계 목표로 추진중에 있다. 정보 흐름의 통로 역할을 수행하는 I&C 분야의 Data Communication Network (DCN)의 성능과 신뢰도는 정보 계통의 전체적인 성능과 신뢰도에 매우 중요하며, 특히 Network Architecture가 핵심 기술로써 개발 중에 있다. 본 논문에서는 차세대 원전의 비안전성 정보 계통에 대해 기술하고, Information Network 의 성능 요건을 설정하였다. 또한 Information Network 설계를 위한 Traffic Load 를 간략히 분석한후, 이 결과로부터 Network Performance 증가를 통한 전송 신뢰도 향상을 위한 Information Network Topology 와 Architecture를 개발하였다.

• Nuclear Engineering and Technology
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• v.55 no.6
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• pp.2276-2282
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• 2023

We deploy artificial neural networks to unfold neutron spectra from measured energy-integrated quantities. These neutron spectra represent an important parameter allowing to compute the absorbed dose and the kerma to serve radiation protection in addition to nuclear safety. The built architectures are inspired from convolutional neural networks. The first architecture is made up of residual transposed convolution's blocks while the second is a modified version of the U-net architecture. A large and balanced dataset is simulated following "realistic" physical constraints to train the architectures in an efficient way. Results show a high accuracy prediction of neutron spectra ranging from thermal up to fast spectrum. The dataset processing, the attention paid to performances' metrics and the hyper-optimization are behind the architectures' robustness.

• Nuclear Engineering and Technology
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• v.50 no.4
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• pp.613-618
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• 2018

We are developing a shared remote control mobile robot for aerial work in nuclear power plants (NPPs); a robot consists of a mobile platform, a telescopic mast, and a dual-arm slave with a working tool. It is used at a high location operating the manual operation mechanism of a fuel changer of a heavy water NPP. The robot system can cut/weld a pipe remotely in the case of an emergency or during the dismantling of the NPP. Owing to the challenging control mission considering limited human operator cognitive capability, some remote tasks require a shared control scheme, which demands systematic software design and integration. Therefore, we designed the architecture of the software systematically.

• Proceedings of the Korean Nuclear Society Conference
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• 2004.10a
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• pp.597-598
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• 2004

• Proceedings of the Korean Nuclear Society Conference
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• 2004.10a
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• pp.619-620
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• 2004