• 한국의학물리학회지:의학물리
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• 제29권1호
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• pp.16-22
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• 2018

Current dosimetry protocols recommend the use of parallel-plate chambers in electron dosimetry because the electron fluence perturbation can be effectively minimized. However, substitutable methods to calibrate and measure the electron output and energy with the widely used cylindrical chamber should be developed in case a parallel-plate chamber is unavailable. In this study, we measured the correction factors and absolute dose-to-water of electrons with energies of 4, 6, 9, 12, 16, and 20 MeV using Farmer-type and Roos chambers by varying the dose rates according to the AAPM TG-51 protocol. The ion recombination factor and absolute dose were found to be varied across the chamber types, energy, and dose rate, and these phenomena were remarkable at a low energy (4 MeV), which was in good agreement with literature. While the ion recombination factor showed a difference across chamber types of less than 0.4%, the absolute dose differences between them were largest at 4 MeV at approximately 1.5%. We therefore found that the absolute dose with respect to the dose rate was strongly influenced by ion-collection efficiency. Although more rigorous validation with other types of chambers and protocols should be performed, the outcome of the study shows the feasibility of replacing the parallel-plate chamber with the cylindrical chamber in electron dosimetry.

• 한국방사선학회논문지
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• 제3권4호
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• pp.23-28
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• 2009

단색 엑스선은 적은 방사선 피폭으로 대조도가 높은 의료영상을 만들 수 있다. 엑스선 튜브와 다층박막 거울을 결합하면 높은 플루언스의 단색 엑스선을 얻을 수 있다. 몰리브덴(Mo) 타깃을 갖는 엑스선 튜브에서 Mo 특성방사선(17.5keV)을 높은 반사율로 획득하기 위한 W/C 다층박막 거울의 최적화를 수행하였다. 반사율이 최대가 되는 조건에서 두께주기와 두께비를 결정하였다. 최적 설계된 다층박막 거울에 대한 두께주기와 브래그 정렬에 대한 공차를 구하였다. 증착(deposition) 공차 0.2nm와 회전정렬 공차 ${\pm}0.01^{\circ}$에서 이론 반사율의 85% 이상에 해당하는 반사율이 얻어질 수 있다. 다층박막 거울을 이용하면 높은 플루언스의 특성방사선을 얻어 낼 수 있기 때문에 의료영상 획득 장치에 많이 사용될 것이다.

• Journal of Nutrition and Health
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• 제36권5호
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• pp.491-499
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• 2003

Selenium is a strong antioxidant trace mineral, scavenging free radicals. The prevalence of chronic degenerative diseases is increasing in Korean adults with increasing age. The increased cell damage from free radicals has been implicated in the etiology of these diseases, and evidence is accumulating that the low selenium status that comes with advanced aged is involved in the prevalence of age-associated diseases. However, little is known about the selenium status of Koreans, its age-related change and its relationship to dietary nutrient intake. In this study, the serum selenium levels of healthy adult females according to life cycle and its association with blood albumin levels and nutrient intake were examined. Serum selenium level was measured with the Huwo research reactor using the neutron activation analysis method (NAA). The overall proportion of women with selenium deficiency, serum selenium concentrations below 7.0 $\mu\textrm{g}$/dl, was 9.4%. The average serum selenium levels were 12.39 $\mu\textrm{g}$/dl, 9.45 $\mu\textrm{g}$/dl and 9.16 $\mu\textrm{g}$/dl in the young adult, middle-aged and elderly groups, respectively, showing a reduction of selenium status with advancing age. Selenium deficiency was seen only in the elderly group. Generally, serum selenium levels positively or negatively correlated with nutrient intake, but these association patterns differed depending on the age. The nutrients that showed positive correlations with selenium levels were proteins and phosphate in the young adult group (p < 0.05, p < 0.05), and total calcium, potassium and vegetable-origin calcium in the middle-aged group. Vitamin C and fiber were the negative correlated nutrients with serum selenium levels in the elderly group (p < 0.05, p < 0.05). Multiple stepwise regression analysis of the determining factors responsible for selenium status showed that age and serum albumin levels were important factors which explained up to 26.9% variances in serum selenium levels. The average selenium concentrations of Korean adult female subjects were above the deficiency levels in all three age groups. There was a tendency toward decreasing selenium levels as the age of the subjects increased. The factors with the strongest in-fluence on selenium status in healthy adult Korean females were age and serum protein status. (Korean J Nutrition 36(5): 491~499, 2003)

• Nuclear Engineering and Technology
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• 제42권2호
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• pp.203-210
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• 2010

The $\underline{H}igh$ flux $\underline{A}dvanced$ $\underline{N}eutron$ $\underline{A}pplication$ $\underline{R}eact\underline{O}r$ (HANARO), an open-tank-in-pool type reactor, is one of the multi-purpose research reactors in the world. Since the commencement of HANARO's operations in 1995, a significant number of experimental facilities have been developed and installed at HANARO, and continued efforts to develop more facilities are in progress. Owing to the stable operation of the reactor and its frequent utilization, more experimental facilities are being continuously added to satisfy various fields of study and diverse applications. The irradiation testing equipment for nuclear fuels and materials at HANARO can be classified into capsules and the Fuel Test Loop (FTL). Capsules for irradiation tests of nuclear fuels in HANARO have been developed for use under the dry conditions of the coolant and materials at HANARO and are now successfully utilized to perform irradiation tests. The FTL can be used to conduct irradiation testing of a nuclear fuel under the operating conditions of commercial nuclear power plants. During irradiation tests conducted using these capsules in HANARO, instruments such as the thermocouple, Linear Variable Differential Transformer (LVDT), small heater, Fluence Monitor (F/M) and Self-Powered Neutron Detector (SPND) are used to measure various characteristics of the nuclear fuel and irradiated material. This paper describes not only the status of HANARO and the status and perspective of irradiation devices and instrumentation for carrying out nuclear fuel and material tests in HANARO but also some results from instrumentation during irradiation tests.

• Nuclear Engineering and Technology
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• 제52권4호
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• pp.827-834
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• 2020

Damage of tungsten due to helium ions of a PF device was studied. The tungsten was analyzed by SEM and AFM after irradiation. SEM revealed fine bubbles of helium atoms with diameters of a few nanometers, which join and form larger bubbles and blisters on the surface of tungsten. This observation confirmed the results of molecular dynamics simulation. SEM analysis after etching of the irradiated surface indicated cavities with depth range of 35-85 nm. The average fluence of helium ion of the PF device was calculated about 5.2 × 10¹⁵ cm^-2 per shot, using Lee code. Energy spectrum of helium ions was estimated using a Thomson parabola spectrometer as a function of dN/dE ∝ E^-2.8 in the energy range of 10-200 keV. The characteristics of helium ion beam was imported to SRIM code. SRIM revealed that the maximum DPA and maximum helium concentration occur in the depth range of 20-50 nm. SRIM also showed that at depth of 30 nm, all of the tungsten atoms are displaced after 20 shots, while at depth of higher than 85 nm the destruction is insignificant. There is a close match between SRIM results and the measured depths of cavities in SEM images of tungsten after etching.

• Nuclear Engineering and Technology
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• 제52권8호
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• pp.1784-1791
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• 2020

The 14 MeV neutron generator facility is being developed by the Institute for Plasma Research India to conduct the lab scale experiments related to Indian breeding blanket system for ITER and DEMO. It will also be utilized for material testing, shielding experiments and development of fusion diagnostics. Occupational radiation exposure control is necessary for the all kind of nuclear facilities to get the operational licensing from governing authorities and nuclear regulatory bodies. In the same way, the radiation exposure for the 14 MeV neutron generator facility at the occupational worker area and accessible zones for general workers should be under the permissible limit of AERB India. The generator is designed for the yield of 10¹² n/s. The shielding assessment has been made to estimate the radiation dose during the operational time of the neutron generator. The facility has many utilities and constraints like ventilation ducts, accessible doors, accessibility of neutron generator components and to conduct the experiments which make the shielding assessment challenging to provide proper safety for occupational workers and the general public. The neutron and gamma dose rates have been estimated using the MCNP radiation transport code and ENDF -VII nuclear data libraries. The ICRP-74 fluence to dose conversion coefficients has been used for the assessment. The annual radiation exposure has been assessed by considering 500 h per year operational time. The provision of local shield near to neutron generator has been also evaluated to reduce the annual radiation doses. The comprehensive results of radiation shielding capability of neutron generator building and local shield design have been presented in the paper along with detailed maps of radiation field.

• 한국의학물리학회지:의학물리
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• 제23권1호
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• pp.42-47
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• 2012

본 연구는 최근 의공학 분야에서 중요한 영역으로 대두되고 있는 광학과 초음파의 장점을 결합한 영상 방법인 AOT (Acousto-Optical Tomography)의 수학적 모델을 제시하였다. AOT는 광학 필드를 초음파 기둥에서 변화 시켜서 초음파 기둥의 위치 정보를 이용하여 영상을 재구성하는 방법이다. AOT의 수학적 모델은 두 단계로 나뉠 수 있다. 첫 번째 단계에서는 광학 필드의 복원을 하고, 두 번째 단계에서는 획득한 광학 필드를 기반으로 확산 방정식의 역문제를 풀어 흡수함수 ${\mu}$ (absorption coefficient)를 산출한다. 본 연구에서는 두 번째 단계에 해당하는 역문제의 해를 구하기 위하여 수치해석적인 최소화 문제로 변환하고, 수치적 팬텀을 이용하여 시뮬레이션 하였다. 전통적인 기울기 하강 방법을 이용하여 역 문제 시뮬레이션의 결과를 보였다. 전변동 정규화 기반의 최소화 문제를 제안하여 기울기 하강 방법의 결과에서 보인 번짐 효과를 개선하였다.

• 한국세라믹학회지
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• 제23권6호
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• pp.37-44
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• 1986

Yttria-antimonia-stabilized zirconia was investigated with respect to the amount of $Sb_2O_3$ addition in the range of 0.5~5mole% to the base composition of $(ZrO)_{0.92}(Y_2O_3)_{0.08}$ The sinterbility modulus of rupture Vickers hardness evaporation of components phase form-tion and mcicrostructure were evaluated with antimonia content. Also two probe A. C conductivity measurement was subjected to all specimens and the best results are achieved with 1mol% $Sb_2O_3$ as a sinter agent and relative density of~98% obtained at 140$0^{\circ}C$ and this composition has a maximum electrical conductivity due to the possible substition of $Sb^{3+}$ for $Zr^{4+}$ site. The effect of $Sb_2O_3$ on the electrical conductivity of th bulk and the grain boundaries has on investigated using frequency dispersion analysis (5~106 Hz) Antimonia addition has a negative in-fluence on both the bulk and the grain boundary conductivity except for a 1 mon% addition. The additive antimonia has improve a modulus of rupture to 60~MPa due to metastable-tetragonal phase apparence and decrease the hardness with increasing the $Sb_2O_3$ content.

• 대한전자공학회논문지SD
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• 제37권11호
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• pp.25-35
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• 2000

금속-산화막-반도체 소자의 산화막에 존재하는 느린 준위에 의한 전류반응 특성을 양방향 전류-전압 측정기술을 적용하여 분석하였다. 게이트 바이어스에 따라 나타나는 충전 및 방전시의 순간전류를 유지시간, 지연시간, 전자주입 방향 및 전자주입량, 그리고 전자 주입후 상온 방치시간의 함수로서 조사하였다. 느린 준위의 전하교환에 따른 전류 성분을 게이트 전압에 따라 실리콘 내 캐리어의 이동에 의해 나타나는 변위전류와 분리하여 해석하였다. 충전 및 방전시 나타나는 전하교환 전류는 산화막내 정전하 밀도뿐만 아니라 계면준위 밀도에도 크게 의존이 되며, 본 연구에서는 느린 준위의 전하교환 메카니즘을 제시하였다.

• Journal of Radiation Protection and Research
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• 제2권1호
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• pp.1-8
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• 1977

중성자(中性子) 선량(線量) 측정목적(測定目的)으로 사용(使用)할 Posi필름 고체비적검출기(固體飛跡檢出器)의 알파입자(粒子) 비적검출(飛跡檢出) 효율(效率)과 화학부식(化學腐蝕)에 의(依)한 그의 비적형성(飛跡形成) 최적조건(最適條件)을 실험적(實驗的)으로 결정(決定)하였다. $^{10}B$ 및 $^{27}Al$박(箔)과 posi 필름 고체비적검출기(固體飛跡檢出器)로 이루어진 중성자(中性子) 선량계(線量計)를 제작(製作)하고 이것에 의(依)한 중성자(中性子) 선속밀도(線束密度) 및 선량(線量)의 측정범위등(測定範圍等)을 실험결과(實驗結果)와 이론적(理論的)인 근거하(根據下)에서 산출(算出)하였다. 그 결과(結果) posi 필름 고체비적검출기(固體飛跡檢出器)는 핵분열성(核分裂性) 물질(物質)을 입자방출체(粒子放出體)로 병용(倂用)함이 없이 중성자(中性子) 측정(測定)에 효과적(效果的)으로 응용(應用)될 수 있음이 판명(判明)되었다.