• Journal of Radiation Protection and Research
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• 제26권2호
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• pp.51-58
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• 2001

환경방사능과 같은 저준위 방사능 측정에서는 원통형과 Marinelli형 측정용기가 가장 일반적으로 사용된다. 효율교정용 표준선원과 측정시료의 높이 또는 매질의 밀도가 다르면 자체흡수 효과의 차이로 인한 보정이 필요하다. 본 연구에서는 Monte Carlo 방법을 이용하여 HPGe 검출기의 전에너지 피크 효율을 계산하여 측정치와 비교하였다. 원통형 용기에 대해서는 높이에 대한 효율변화 정도를 계산하였고, 원통형 및 Marinelli 측정용기에 대해서는 밀도변화에 따른 효율을 계산하였다. 밀도에 따른 효율의 감소 정도는 1000keV 이하의 에너지 영역에 대해 자체흡수 효과의 보정치 필요하다는 것을 알았다. 또한 계산의 타당성을 검증하기 위하여 NIST SRM 4353 표준물질을 이용하여 계산값과 인증값을 상호비교한 결과 오차범위 이내로 잘 맞는 다는 것을 확인하였다.

• 비파괴검사학회지
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• 제36권6호
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• pp.466-473
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• 2016

선박 건조과정에서 이면부의 도장손상은 용접과정에서 과도한 입열량(heat input)에 따른 전도의 영향으로 손상 방지를 위해서는 용접온도 계측에 의한 적절한 입열량 제어가 필요하다. 온도 계측에는 접촉식, 비접촉식 방법이 있으며 열화상 시스템은 대표적인 비접촉식 방법이다. 하지만 일반적인 열화상 시스템의 탐지센서(detector)는 고온물체에서 방출되는 복사량(radiant quantity)이 과도하면 백화현상(saturation)으로 인해 온도계측이 불가능해진다. 따라서 본 논문에서는 열화상 시스템에 집속되는 과도한 복사량을 차단하기 위해 중성밀도필터(neutral density filter)를 결합하여 고온 물체의 온도를 $3000^{\circ}C$까지 정량적으로 계측하기 위한 복사 에너지 필터링을 연구하였다.

• 한국분말야금학회:학술대회논문집
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• 한국분말야금학회 2002년도 제3회 최신 분말제품 응용기술 Workshop
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• pp.25-37
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• 2002

The most important industrial application of gamma radiation in characterizing green compacts is the determination of the density. Examples are given where this method is applied in manufacturing technical components in powder metallurgy. The requirements imposed by modern quality management systems and operation by the workforce in industrial production are described. The accuracy of measurement achieved with this method is demonstrated and a comparison is given with other test methods to measure the density. The advantages and limitations of gamma ray densitometry are outlined. The gamma ray densitometer measures the attenuation of gamma radiation penetrating the test parts (Fig. 1). As the capability of compacts to absorb this type of radiation depends on their density, the attenuation of gamma radiation can serve as a measure of the density. The volume of the part being tested is defined by the size of the aperture screeniing out the radiation. It is a channel with the cross section of the aperture whose length is the height of the test part. The intensity of the radiation identified by the detector is the quantity used to determine the material density. Gamma ray densitometry can equally be performed on green compacts as well as on sintered components. Neither special preparation of test parts nor skilled personnel is required to perform the measurement; neither liquids nor other harmful substances are involved. When parts are exhibiting local density variations, which is normally the case in powder compaction, sectional densities can be determined in different parts of the sample without cutting it into pieces. The test is non-destructive, i.e. the parts can still be used after the measurement and do not have to be scrapped. The measurement is controlled by a special PC based software. All results are available for further processing by in-house quality documentation and supervision of measurements. Tool setting for multi-level components can be much improved by using this test method. When a densitometer is installed on the press shop floor, it can be operated by the tool setter himself. Then he can return to the press and immediately implement the corrections. Transfer of sample parts to the lab for density testing can be eliminated and results for the correction of tool settings are more readily available. This helps to reduce the time required for tool setting and clearly improves the productivity of powder presses. The range of materials where this method can be successfully applied covers almost the entire periodic system of the elements. It reaches from the light elements such as graphite via light metals (AI, Mg, Li, Ti) and their alloys, ceramics ($AI_20_3$, SiC, Si_3N_4, $Zr0_2$, ...), magnetic materials (hard and soft ferrites, AlNiCo, Nd-Fe-B, ...), metals including iron and alloy steels, Cu, Ni and Co based alloys to refractory and heavy metals (W, Mo, ...) as well as hardmetals. The gamma radiation required for the measurement is generated by radioactive sources which are produced by nuclear technology. These nuclear materials are safely encapsulated in stainless steel capsules so that no radioactive material can escape from the protective shielding container. The gamma ray densitometer is subject to the strict regulations for the use of radioactive materials. The radiation shield is so effective that there is no elevation of the natural radiation level outside the instrument. Personal dosimetry by the operating personnel is not required. Even in case of malfunction, loss of power and incorrect operation, the escape of gamma radiation from the instrument is positively prevented.

• 한국화재소방학회논문지
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• 제29권4호
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• pp.81-88
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• 2015

본 연구에서는 다양한 화재실험에서 광학 연기밀도 측정을 위하여 광소멸법을 이용한 저가형 장치가 개발되었다. 저가형 장치의 상대적 측정 정확도는 He-Ne 레이저, 포토디텍터 및 다양한 광학부품을 이용한 고가의 표준장치에 의해 측정된 연기밀도의 비교를 통해 평가되었다. 저가형 장치는 레이저 모듈, 포토셀 그리고 아크릴 보드로 구성되었다. 연기농도의 조절이 용이한 연기 발생장치 실험을 통해, 저가형 장치는 표준장치에 비해 ${\pm}10%$의 범위 내에서 연기밀도를 측정할 수 있음을 확인하였다. 저가 장치의 신뢰성은 또한 폴리에틸렌 화염을 이용한 실험에서도 확인되었다. 결론적으로 개발된 저가형 장치는 연기밀도 측정을 위한 간편한 설치 및 실시간 측정과 함께 고가의 표준장치를 대신하여 사용될 것으로 기대된다.

• Journal of Radiation Protection and Research
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• 제33권1호
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• pp.35-40
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• 2008

석유화학 공정의 증류탑은 공정유체를 분리, 정제하는 중요한 장치 중의 하나로 가동효율은 설비의 생산성에 큰 영향을 미친다. 본 연구는 밀봉 감마선원을 이용하여 투과 감마선의 세기를 높이별로 측정함으로써 내부 밀도의 변화를 분석하여 공정의 가동 중 내부 상황에 대한 정보를 얻고자 하였다. 이를 위하여 한국원자력연구원에서 개발된 자동 증류탑 검사장치를 이용하여 증류탑 상부 양쪽에 밀봉 감마선원과 방사선검출기를 매달아 수직으로 내리면서 실험을 수행하였으며, 이때 감마선원으로는 Co-60 150 mCi과 방사선검출기로 BGO detector를 각각 사용하였다. 진단결과 설비 내부의 tray에는 구조적 결함이 관찰되지 않았으나, 유체분포를 고려할 때 상부는 기포층(vapor)의 밀도분포가 지배적인 반면에, 하단부에는 기포에 비해 유체가 상대적으로 많이 분포하는 것으로 계측되었다. 본 실험으로부터 밀봉 감마선원을 이용한 가동 중에 있는 대형 증류탑의 tray에 대한 구조적 건전성 및 내부 유체분포에 대한 정보를 성공적으로 제시하였다.

• 한국지구물리탐사학회:학술대회논문집
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• 한국지구물리탐사학회 2005년도 제7회 특별심포지움 논문집
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• pp.73-82
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• 2005

국내에서 처음으로 지구물리검층 보정을 위한 모형시추공이 건설되었으며 이들 모형시추공을 이용한 검출기 보정실험과 케이싱보정을 위한 기초실험을 실시하였다. 여기서는 세 가지 밀도와 세 가지공경으로 구성되는 모형 시추공의 건설 과정과 재원을 소개하고 이를 이용하여 구해진 선형 관계의 밀도-검출기 반응식을 검토하였다. 아울러 케이싱 보정을 위한 기초연구 결과 이격 보정용 차트가 제시되었고 이를 이용하여 이격 정도를 모르는 현장 측정에서도 참 밀도를 구할 수 있음을 밝혔다.

• 한국가시화정보학회지
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• 제3권1호
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• pp.63-70
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• 2005

Optical Line Patternator(OLP) has been applied to get a distribution of the spray at high ambient pressure. OLP is a combined technique of extinction measurement and image processing. The attenuated intensity of laser beam after traversing spray region was measured by using a photo-detector, and the line image of Mie-scattering was captured simultaneously in the path of each laser beam by using a CCD camera. The distribution of extinction coefficient in the spray is obtained by processing these data with the algebraic reconstruction technique. From the distribution of extinction coefficient, the surface distribution of spray can be reconstructed. OLP does not use laser sheet but use laser beam so that the noise effect of multiple scattering, caused by increasing number density of droplet in high pressure environment, is reduced drastically. OLP is expected as a suitable method which can investigate the characteristics of relatively large spray under the high pressure environment such as liquid rocket engine.

• Nuclear Engineering and Technology
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• 제56권2호
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• pp.666-672
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• 2024

In the present work, a new brick series based on the Vietnamese white clay minerals from the Bat Trang was fabricated to be applied in the radiation protection applications during the decommissioning of the nuclear power reactors. The bricks were constructed under various pressure rates varied from 7.61 MPa to 114.22 MPa. The influence of pressure rate on the physical and γ-ray shielding properties were investigated in the study. The experimental measurement for the material's density using the MH-300A density meter showed an enhancement in the prepared bricks' density by 22.5 % with increasing the applied pressure rate while the bricks' porosity reduced by 31.2 % when the pressure rate increased from 7.61 MPa to 114.22 MPa. The increase in the fabricated bricks density and the reduction in their porosities enhances the bricks' linear attenuation coefficients as measured by the NaI (Tl) detector along the energy range extended from 0.662 MeV to 1.332 MeV. The linear attenuation coefficient increased by 13.8 %, 17.6 %, 17.0 %, and 17.1 % at gamma ray energies of 0.662 MeV, 1.173 MeV, 1.252 MeV, and 1.332 MeV, respectively. The enhancement in the linear attenuation coefficient increases the bricks' radiation protection efficiency by 10.22 %, 14.48 %, 14.09 %, and 14.26 % at gamma ray energies of 0.662 MeV, 1.173 MeV, 1.252 MeV, and 1.332 MeV, respectively.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2009년도 제38회 동계학술대회 초록집
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• pp.475-475
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• 2010

We have generated Ar plasma in dense plasma focus device with coaxial electrodes for extreme ultraviolet (EUV) lithography and investigated an emitted visible light for electro-optical plasma diagnostics. We have applied an input voltage 4.5 kV to the capacitor bank of 1.53 uF and the diode chamber has been filled with Ar gas of pressure 8 mTorr. The inner surface of the cylindrical cathode has been attatched by an acetal insulator. Also, the anode made of tin metal. If we assumed that the focused plasma regions satisfy the local thermodynamic equilibrium (LTE) conditions, the electron temperature and density of the coaxial plasma focus could be obtained by Stark broadening of optical emission spectroscopy (OES). The Lorentzian profile for emission lines of Ar I of 426.629 nm and Ar II of 487.99 nm were measured with a visible monochromator. And the electron density has been estimated by FWHM (Full Width Half Maximum) of its profile. To find the exact value of FWHM, we observed the instrument line broadening of the monochromator with a Hg-Ar reference lamp. The electron temperature has been calculated using the two relative electron density ratios of the Stark profiles. In case of electron density, it has been observed by the Stark broadening method. This experiment result shows the temporal behavior of the electron temperature and density characteristics for the focused plasma. The EUV emission signal whose wavelength is about 6 ~ 16 nm has been detected by using a photo-detector (AXUV-100 Zr/C, IRD). The result compared the electron temperature and density with the temporal EUV signal. The electron density and temperature were observed to be $10^{16}\;cm^{-3}$ and 20 ~ 30 eV, respectively.

• 대한방사선기술학회지:방사선기술과학
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• 제43권6호
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• pp.481-487
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• 2020

Radiation measurement technology has steadily improved and its usage is expanding in various industries such as nuclear medicine, security search, satellite, nondestructive testing, environmental industries and the domain of nuclear power plants (NPPs). Especially, the simultaneous measurements of gamma rays and neutrons can be even more critical for nuclear safety management of spent nuclear fuel and monitoring of the nuclear material. A semiconductor detector comprising cadmium, zinc, and tellurium (CZT) enables to detect gamma-rays due to the significant atomic weight of the elements via immediate neutron and gamma-ray detection. Semiconductor sensors might be used for nuclear safety management by monitoring nuclear materials and spent nuclear fuel with high spatial resolution as well as providing real-time measurements. We aim to introduce a portable nuclide-analysis device that enables the simultaneous measurements of neutrons and gamma rays using a CZT sensor. The detector has a high density and wide energy band gap, and thus exhibits highly sensitive physical characteristics and characteristics are required for performing neutron and gamma-ray detection. Portable nuclide-analysis device is used on NPP-decommissioning sites or the purpose of nuclear nonproliferation, it will rapidly detect the nuclear material and provide radioactive-material information. Eventually, portable nuclide-analysis device can reduce measurement time and economic costs by providing a basis for rational decision making.