• 한국진공학회:학술대회논문집
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• 한국진공학회 2011년도 제40회 동계학술대회 초록집
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• pp.397-397
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• 2011

In a low aspect ratio (LAR) tokamak reactor with a superconducting toroidal field (TF) coil, the radial build of TF coil and the shield play a key role in determining the size of a reactor. For self-consistent determination of the reactor components and physics parameters, a system analysis code is coupled with one-dimensional radiation transport code. Conceptual design study of a compact superconducting LAR tokamak reactor with aspect ratio less than 2.5 was conducted and the optimum radial build was identified. It is shown that the use of an improved shielding material and high temperature superconducting magnets with high critical current density opens up the possibility of a fusion power plant with compact size and small re-circulating power simultaneously at low aspect ratio, and that by using an inboard neutron reflector instead of breeding blanket, tritium self-sufficiency is possible with outboard blanket only and thus compact sized reactor is viable.

• Composites Research
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• 제31권3호
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• pp.83-87
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• 2018

An object in the Low Earth Orbit (LEO) is affected by many environmental conditions unlike earth's surface such as, Atomic oxygen (AO), Ultraviolet Radiation (UV), thermal cycling, High Vacuum and Micrometeoroids and Orbital Debris (MMOD) impacts. The effect of all these parameters have to be carefully considered when designing a space structure, as it could be very critical for a space mission. Polybenzimidazole (PBI) is a high performance thermoplastic polymer that could be a suitable material for space missions because of its excellent resistance to these environmental factors. A thin coating of PBI polymer on the carbon epoxy composite laminate (referred as CFRP) was found to improve the energy absorption capability of the laminate in event of a hypervelocity impact. However, the overall efficiency of the shield also depends on other factors like placement and orientation of the laminates, standoff distances and the number of shielding layers. This paper studies the effectiveness of using a PBI coating on the front bumper in a multi-shock shield design for enhanced hypervelocity impact resistance. A thin PBI coating of 43 micron was observed to improve the shielding efficiency of the CFRP laminate by 22.06% when exposed to LEO environment conditions in a simulation chamber. To study the effectiveness of PBI coating in a hypervelocity impact situation, experiments were conducted on the CFRP and the PBI coated CFRP laminates with projectile velocities between 2.2 to 3.2 km/s. It was observed that the mass loss of the CFRP laminates decreased 7% when coated by a thin layer of PBI. However, the study of mass loss and damage area on a witness plate showed CFRP case to have better shielding efficiency than PBI coated CFRP laminate case. Therefore, it is recommended that PBI coating on the front bumper is not so effective in improving the overall hypervelocity impact resistance of the space structure.

• 비파괴검사학회지
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• 제33권4호
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• pp.336-341
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• 2013

본 논문에서는 저온-진공 흑체시스템의 설계 및 구성과 함께 흑체시스템의 수학 모델을 이용한 열해석 평가 방법과 그 결과를 제시하였으며 적외선 카메라를 이용한 흑체시스템의 평가 방안 및 결과를 명시하였다. 개발된 흑체시스템은 기존의 시스템에 비해 상대적으로 규모가 소형이며 273 K이하의 저온에서 수증기가 응결될 수 있는 현상을 방지하기 위하여 흑체시스템 내부를 진공 ($2.67{\times}10^{-2}$ Pa) 상태로 유지되도록 제작되었다. 또한 흑체시스템 내부의 열손실로 인한 성능 저하를 막기 위하여 radiator가 설치되는 부위에는 heat sink, heat shield 및 cold shield를 설계하였다. 흑체시스템의 수학 모델에 대한 열 해석을 위해서 변형된 스테판-볼츠만의 정리를 이용하여 radiator의 성능을 검증하였고 실제 흑체시스템에서 방사되는 적외선 신호에 대해서는 적외선 카메라를 이용하여 신호전달함수 및 온도분해능을 측정, 분석하였다. 제안된 설계와 해석 및 실험 결과에 근거하여, 개발된 저온-진공 흑체시스템은 적용온도범위인 268~333 K 구간에서 적외선 측정장치의 캘리브레이션을 위한 기준장치로서 성능이 안정적이고 적용이 적합한 것으로 확인되었다.

• 한국방사성폐기물학회:학술대회논문집
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• 한국방사성폐기물학회 2005년도 춘계 학술대회
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• pp.457-463
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• 2005

현재 HIC는 차폐용기를 이용하여 소내 중간저장시설로 운반되고 있으나, 차폐용기가 국내 방사성폐기물 운반관련 규정에 부합하는지에 대한 논란이 있어왔다. 이에 따라 한국수력원자력(주)에서는 국내 규정 및 IAEA 규정을 만족하는 HIC 전용 운반용기 개발을 추진 중에 있으며, 원자력 환경기술원에서는 이를 위한 개념설계를 수행 중에 있다. 본 연구에서는 원전 현장에서 활용중인 방사성핵종분석 프로그램 자료와 Micro Shield 전산코드를 활용하여 법적기준을 만족하는 차폐체의 두께를 계산하고자 하였다. 차폐체는 구조적 안전성을 고려하여 탄소강으로 결정하였으며, 차폐체의 두께를 HIC 표면선량율 500 R/hr와 100 R/hr의 경우로 각각 나누어 계산하였다. 계산결과 표면선량율이 500 R/hr일 경우 차폐체의 두께가 22 cm, 표면선량율이 100 R/hr일 경우는 차폐체의 두께가 17 cm 일 때 법적 제한치를 만족 하는 것으로 평가 되었다.

• 대한기계학회논문집A
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• 제37권12호
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• pp.1567-1572
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• 2013

방사성동위원소 열전발전기는 장반감기 알파 혹은 베타 핵종에서 방출하는 하전입자를 차폐하여 방사선에너지를 열에너지로 전환하고 이때 발생하는 열전재료의 온도차를 이용하여 전력을 생산하는 시스템이다. 이 기술은 에너지 밀도가 높고 수명이 길며 신뢰성이 높아 우주개발, 국방 등 극한 환경에서 사용되는 장치, 센서 및 로봇 등의 에너지원으로 그 효용성이 매우 높다. 본 연구에서는 방사선 차폐해석 및 열전달 해석을 통하여 차폐체, 그리고 최대 온도구배를 가지는 열전재료의 형상과 배치를 결정하여 열전발전기 기초설계를 도출하였다.

• 대한인간공학회지
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• 제36권5호
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• pp.559-568
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• 2017

Objective: The aim of this study is to investigate the effective managerial factors influencing dose reduction of the nozzle dam installation and removal tasks ranking within top 3 in viewpoint of average collective dose of nuclear power plant maintenance job. Background: International Commission on Radiation Protection (ICRP) recommended to reduce unnecessary dose and to minimize the necessary dose on the participants of maintenance job in radiation fields. Method: Seven sessions of nozzle dam installation and removal task logs yielded a multiple regression model with collective dose as a dependent variable and work time, number of participants, space doses before and after shield as independent variables. From the sessions in which a significant reduction in collective dose occurred, the effective managerial factors were elicited. Results: Work time was the most important factor contributing to collective dose reduction of nozzle dam installation and removal task. Introduction of new technology in nozzle dam design or maintenance job is the most important factor for work time reduction. Conclusion: With extended task logs and big data processing technique, the more accurate prediction model illustrating the relationship between collective dose reduction and effective managerial factors would be developed. Application: The effective managerial factors will be useful to reduce collective dose of decommissioning tasks as well as regular preventive maintenance tasks for a nuclear power plant.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2012년도 제43회 하계 정기 학술대회 초록집
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• pp.431-431
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• 2012

A compact tokamak reactor concept as a 14 MeV neutron source is desirable from an economic viewpoint for a fusion-driven transmutation reactor. LAR (Low Aspect Ratio) tokamak allows a potential of high "see full txt" operation with high bootstrap current fractions and can be used for a compact fusion neutron source. For the optimal design of a reactor, a radial build of reactor components has to be determined by considering the plasma physics and engineering constraints which inter-relate various reactor components and are constrained to use ITER physics and technology. In a transmutation reactor, the blanket should produce enough tritium for tritium self-sufficiency and the neutron multiplication factor, keff should be less than 0.95 to maintain sub-criticality. The shield should provide sufficient protection for the superconducting toroidal field (TF) coil against radiation damage and heating effects of the fusion neutrons, fission neutrons, and secondary gammas. In this work, characteristics of transmutation reactor based on LAR tokamak is investigated by using the coupled system analysis.

• 한국초전도저온공학회:학술대회논문집
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• 한국초전도저온공학회 2001년도 학술대회 논문집
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• pp.155-158
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• 2001

An intermediate cooling is indispensible to reduce the refrigeration power at superconducting system that is cooled conductively by a cryocooler without liquid cryogens. The cooling load at the intermediate stage is caused by the mechanical supports, the radiation shield and the current lead. From the cooling load calculation, a thermodynamic analysis that take into account the temperature-dependent properties of the materials and the actual performance of the cryocooler is developed. For any given physical dimensions of the various components, it is shown that there exist a unique optimum for the intermediate temperature to minimize the overall refrigeration power. The results of this study can be usefully applied to the selection of the cryocooler as well as the design of the conduction-cooled cryostat.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2007년도 춘계학술대회A
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• pp.1585-1589
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• 2007

The HANARO, a 30 MW multi-purpose research reactor in Korea, will be equipped with a neutron guide system, in order to transport cold neutrons from the neutron source to the neutron scattering instruments in the neutron guide hall near the reactor building. The neutron guide system of HANARO consists of the in-pile plug assembly with in-pile guides, the primary shutter with in-shutter guides, the neutron guides in the guide shielding room with dedicated secondary shutters, and the neutron guides connected to the instruments in the neutron guide hall. The functions of the in-pile plug assembly are to shield the reactor environment from a nuclear radiation and to support the neutron guides and maintain them precisely oriented. The primary shutter is a mechanical device to be installed just after the in-pile plug assembly, which stops neutron flux on demand. This paper describes the mechanical design of the in-pile plug assembly and the primary shutter for the neutron guide system at HANARO. The design of the guide shielding assembly for the primary shutter and the neutron guides is also presented.

• 한국초전도ㆍ저온공학회논문지
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• 제8권4호
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• pp.30-33
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• 2006

Several crucial issues are discussed in the design of cryogenic cooling system for high field magnets. This study is mainly motivated by our ongoing program to develop a 21 T Fourier Transform Ion Cyclotron Resonance Mass Spectrometer (FT-ICR MS). The magnets of this system will be built horizontally to accomplish the requirement of user friendliness and reliability, and the replenishment of cryogen will not be necessary by a closed-loop cooling concept. The initial cool-down and safety are basically considered in this paper. The effects of the helium II volume and the gap distance of the weight load relief valve (or safety valve) on the cool-down time and temperature rising during an off-normal state are discussed. The total amount of cryogenic cooling loads and the required helium flow rate during cool-down are also estimated by a relevant heat transfer analysis. The temperatures of cryogen-free radiation shield are finally determined from the refrigeration power of a cryocooler and the total cryogenic loads.