• Nuclear Engineering and Technology
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• 제55권5호
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• pp.1783-1790
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• 2023

Barium Bismuth Oxide Borate (BBOB) has been synthesized for the first time using solution combustion technique. SEM analysis reveal flower shape of the nanoparticles. The formation of the nanoparticles has been confirmed through XRD & FTIR studies which gives the physical and chemical structure of the novel material. The UV light absorption is observed in the range 200-300 nm. The present study highlights the radiation shielding ability of BBOB for different radiations like X/Gamma rays, Bremsstrauhlung and neutrons. The gamma shielding efficiency is comparable to that of lead in lower energy range and lesser than lead in the higher energy range. The bremsstrauhlung exposure constant is comparably larger for BBOB NPs than that of concrete and steel however it is lesser than that of lead. The beauty of BBOB nanoparticles lies in, high absorption of radiations and low emission of secondary radiations when compared to lead. In addition, the neutron shielding parameters like scattering length, absorption and scattering cross sections of BBOB are found to be much better than lead, steel and concrete. Thus, BBOB nanoparticles are highly efficient in absorbing X/Gamma rays, neutrons and bremsstrauhlung radiations.

• Nuclear Engineering and Technology
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• 제53권1호
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• pp.273-281
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• 2021

The radiological safety of the spent resin treatment facility with a¹⁴C treatment capacity of 1 ton/day was evaluated in terms of the external and internal exposure of worker according to operation scenario. In terms of external dose, the annual dose for close work for 1 h/day at a distance of more than 1 m (19.8 mSv) satisfied the annual dose limit. For 8 h of close work per day, the annual dose exceeded the dose limit. For remote work of 2000 h/year, the annual dose was 14.4 mSv. Lead shielding was considered to reduce exposure dose, and the highest annual dose during close work for 1 h/day corresponded to 6.75 mSv. For close work of 2000 h/year and lead thickness exceeding 1.5 cm, the highest value of annual dose was derived as 13.2 mSv. In terms of internal exposure, the initial year dose was estimated to be 1.14E+03 mSv when conservatively 100% of the nuclides were assumed to leak. The allowable outflow rate was derived as 7.77E-02% and 2.00E-01% for the average limit of 20 mSv and the maximum limit of 50 mSv, respectively, where the annual replacement of the worker was required for 50 mSv.

• 대한의용생체공학회:의공학회지
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• 제28권1호
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• pp.132-138
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• 2007

MR(magnetic resonance) image of moving organ such as heart shows serious distortion of MR image due to motion itself. To eliminate motion artifacts, MRI(magnetic resonance imaging) scan sequences requires a trigger pulse like ECG(electro-cardiography) R-wave. ECG-gating using cardiac cycle synchronizes the MRI sequence acquisition to the R-wave in order to eliminate image motion artifacts. In this paper, we designed ECG/PPG(photo-plethysmography) gating system which is for eliminating motion artifacts due to moving organ. This system uses nonmagnetic carbon electrodes, lead wire and shield case for minimizing RF(radio-frequency) pulse and gradient effect. Also, we developed a ECG circuit for preventing saturation by magnetic field and a finger plethysmography sensor using optic fiber. And then, gating pulse is generated by adaptive filtering based on NLMS(normalized least mean square) algorithm. To evaluate the developed system, we measured and compared MR imaging of heart and neck with and without ECG/PPG gating system. As a result, we could get a clean image to be used in clinically. In conclusion, the designed ECG/PPG gating system could be useful method when we get MR imaging of moving organ like a heart.

• 터널과지하공간
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• 제17권6호
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• pp.453-463
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• 2007

Terzaghi터널토압 이론은 shield 및 도심 NATM터널의 설계토압으로 현재까지도 사용되고 있다. 본 논문에서 지반의 변형거동과 한계상태를 가정한 Terzaghi 토압과의 상호 관계에 관한 조사를 위해 Terzaghi 터널토압이론, 2차원 실내 터널 모형 실험과 변형률 연화모델을 기본으로한 비선형 수치해석을 실시하였다. 굴착에 따른 터널 토압와 지반 변형거동의 폭넓은 이해와 그들의 상호작용에 대한 효율적인 활용은 경제적인 터널 지보설계와 안정한 시공을 이끌 수 있다.

• Journal of Radiation Protection and Research
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• 제14권1호
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• pp.46-55
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• 1989

사용후 핵연료 용기에 대한 중성자 차폐 해석을 위하여 각분할법 코드인 ONEDANT 및 XSDRN과 몬테칼로 코드인 MCNP를 사용하였다. ORIGEN-S로 부터 결정된 선원항이 ONEDANT및 XSDRN에 각각 이용되었고, MCNP에 입력되는 선원항으로는 ONEDANT와 XSDRN으로 부터 계산된 중성자 스펙트럼을 사용하였으며, 중성자 에너지군은 27군과 10군으로 하였다. 감손 우라늄을 중성자 차폐 물질로 사용하였을 경우, MCNP의 계산 결과에 대하여 ONEDANT의 계산결과는 10%, XSDRN은 20% 이내에서 접근하였다. 또한, MCNP의 계산 결과에 의하면, 고려한 중성자 차폐물질의 성능은 감손 우라늄, 철, 그리고 납의 순으로 좋은 것으로 나타났다.

• 대한전기학회논문지:전기기기및에너지변환시스템부문B
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• 제50권3호
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• pp.101-106
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• 2001

Air-cored superconducting synchronous generator(ASSG) is characterized by an air-cored machine with its rotor iron and stator iron teeth removed. For this reason, in the case of the shape optimum design of ASSG, other design variables different from an iron-cored machine should be considered, which will lead to substantial improvement on the performance. The major design variables that are considered by using Three-dimensional Finite element Method(3D FEM) in this paper are : 1) field coil width, 2) axial length of magnetic shield, and 3) armature winding method. End-ring of armature winding is considered in the calculation of EMF. When it comes to field coil width, as field coil width enlarges, its effective field increases but the maximum field on the superconductor decreases. this determines the critical current density. this study presents an effective field coil width, axial length of magnetic shield, and armature winding method, and also the analysis is verified by the experimental results.

• 대한방사선기술학회지:방사선기술과학
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• 제46권6호
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• pp.493-499
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• 2023

This study developed education contents of measuring spatial dose with virtual reality simulation and applied to students majoring radiological science. The virtual reality(VR) contents with measuring spatial dose rate in the radiation controlled area was developed based on the simulation from pilot study. In this simulation, the tube voltage and tube current can be set from 60 to 120 kVp in 10 kVp steps and 10 to 40 mAs in 10 mAs increments, and the distance from source can be set from 30 to 400 cm continuously. Iron and lead shields can be placed between the source and the detector, and shielding thickness can be set by 1 mm increments ranging from 1 to 20 mm. We surveyed to students for evaluating improvement of understanding spatial dose rate between before and after education by VR simulation. The survey was conducted with 5 questions(X-ray exposure factors, effects by distance from the source, effects from using shield, depending on material and thickness of shield, concept and measuring of spatial dose rate) and all answers showed significant improvement. Therefore, this VR simulation content will be well used in education for spatial dose rate and radiation safety environments.

• 한국산업정보학회논문지
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• 제7권4호
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• pp.37-45
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• 2002

본 연구에서는 다짐 성토의 밀도 및 수분을 측정하기 위해서 중성자 검출기는 2개 그리고 감마선 검출기는 5개를 사용하여 설계하였고, 또한 방사능 대비 방사선 방출수가 다른 선원에 비하여 우수한 Co-60 감마선원과 Cf-252 중성자 선원을 본 시스템에 이용하는 것이 정밀도를 향상시키기 위하여 유리하다는 것을 알 수 있었다. 특히 중성자와 감마선의 상호 반응으로 인한 간섭을 제거하기 위하여 2개의 중성자와 5개의 감마선 검출부 사이에 차폐체인 납을 각각 설치하였으며, 제시된 기준값 이하로 완전히 차폐하기 위한 최적 설계를 수행하였다. 이러한 최적 선계에 의하여 휴대용으로 사용될 본 시스템은 각 검출부 사이에 차폐체를 설치함에 따라 5.2[kg]의 무게를 경감할 수 있었고, 이는 산업 현장에서 쉽게 이동하고 간편하게 사용될 수 있을 것으로 사료된다.

• 대한방사선기술학회지:방사선기술과학
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• 제3권1호
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• pp.67-72
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• 1980

To shield the radiation, we can make use of various materials, but the scattered rays can be caused by the shielding materials. The degree of the scattered rays production is influenced by the nature of the shielding materials and the energy of the radiation, therefore to choose the proper shielding material is the most important matter in radiation protection. Authors made an experimental study on the scattered rays generated from the shielding materials, and obtained the results as follows: 1. In the ranking of the scattered rays production: Cement bricks, black colored fire bricks, and red colored fire bricks were marked the first the second, and the third ranking respectly, and the last order was lead plates. 2. In the relative ranking of the scattered rays production by energy increase: Lead plates were marked the first order, the next and third order were red colored fire bricks and black colored fire bricks respectly, and cement bricks were marked the last order. 3. The scattered ray ratio of lateral-back point per lateral point were generally decreased by energy increment. The diminishing orders were that lead plates were the first order, and the next and the third order were red colored fire bricks and black colored fire bricks respectly, cement bricks were marked the last order.

• Journal of Radiation Protection and Research
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• 제23권3호
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• pp.175-184
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• 1998

1998년에 고리 1호기로부터 교체될 증기발생기의 선량율을 계산하기 위하여 Smear 오염검사 결과와 튜브 손상원인을 규명하기 위하여 인출하였던 증기발생기 튜브의 선량을 측정결과로부터 증기발생기 내부의 방사성핵종 재고량을 평가하였다. 방사성 핵종 재고량을 토대로 QAD-CG 컴퓨터 코드를 이용하여 증기발생기 표면의 접촉 선량율과 1 m 이격 선량율을 계산하였는데, 접촉 선량율은 Channel Head의 하부에서 최저인 11.5 mR/hr를 나타냈으며, Shell Barrel의 중간 지점에서 최대값인 37.7 mR/hr를 나타냈다. 한편 접촉 선량율과 1 m 이격 선량율은 증기발생기의 크기로 인해 큰 차이를 보이지 않았다 또한 증기발생기의 차폐가 필요할 경우 요구되는 기본적인 데이터를 마련하기 위하여 납과 탄소강의 차폐 특성을 비교해 보았다. 납을 차폐체로 사용할 경우 2 mm 두께만으로도 증기발생기 Shell Barrel 중간 지점에서의 표면 선량율이 37.7 mR/hr에서 15.7 mR/hr로 감소되었다. 그러나 탄소강의 경우에는 차폐체의 두께를 2 cm로 증가시킨다고 하더라도 차폐효과가 매우 낮았다. 이러한 차폐효과 차이는 저에너지 광자에 대한 납과 탄소강의 감쇄효과 차이와 축적인자 차이 때문에 발생되는 것으로 추정된다.