• 한국전기전자재료학회논문지
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• 제27권10호
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• pp.618-622
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• 2014

The temperature dependent characteristics on the properties of SiC Schottky Diode has been investigated. In this study, the temperature dependent current-voltage characteristics of the SiC Schottky diode were measured in the range of 300 ~ 500 K. Divided into pre- and post- irradiated device was measured. The barrier height after irradiation device at 500 K increased 0.15 eV compared to 300 K, the barrier height of pre- neutron irradiated Schottky diode increased 0.07 eV. The effective barrier height after irradiation increased from 0.89 eV to 1.05 eV. And ideality factor of neutron irradiated Schottky diode at 500 K decreased 0.428 compared to 300 K, the ideality factor of pre- neutron irradiated Schottky diode decreased 0.354. Also, a slight positive shift in threshold voltage from 0.53 to 0.68 V. we analyzed the effective barrier height and ideality factor of SiC Schottky diode as function of temperature.

• Nuclear Engineering and Technology
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• 제55권3호
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• pp.1036-1044
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• 2023

The combination of MCNP6 and the FISPACT codes was used to predict inventories of radioisotopes produced by neutron exposure of a sample in a research reactor. The detailed MCNP6 model of the Budapest Research Reactor and the specific irradiation geometry of the NAA channel was established, while realistic material cards were specified based on concentrations measured by PGAA and NAA, considering the precursor elements of all significant radioisotopes. The energy- and spatial distributions of the neutron field calculated by MCNP6 were transferred to FISPACT, and the resulting activities were validated against those measured using neutron-irradiated small and bulky targets. This approach is general enough to handle different target materials, shapes, and irradiation conditions. A general agreement within 10% has been achieved. Moreover, the method can also be made applicable to predict the activation properties of the near-vessel concrete of existing nuclear installations or assist in the optimal construction of new nuclear power plant units.

• 한국원자력학회:학술대회논문집
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• 한국원자력학회 2002년도 추계학술발표회요약집
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• pp.387.1-387
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• 2002

• 한국재료학회지
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• 제13권7호
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• pp.409-414
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• 2003

The room-temperature operating semiconductor GaMnN is known to be improved in its magnetic property when a highly conductive precipitate $Mn_3$GaN exists. Therefore, it is useful to investigate the behavior of the precipitate through heat treatments for further improvement of its magnetic property. Furthermore, neutron irradiation may further influence the behavior of the precipitates, and consequently, their effects on the magnetization. With the heat treatment, $Mn_3$GaN decomposed and a new phase of $Mn_3$Ga has generated. The kinetics was accelerated by neutron irradiation, which might generate defects that can help the decomposition of N and/or the formation of $Mn_3$Ga. The increase and decrease of the magnetization of the heat-treated GaMnN thin films were explained consistently by the behavior of the precipitates.

• 한국정밀공학회지
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• 제30권2호
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• pp.223-230
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• 2013

When a new nuclear fuel is developed, an irradiation test needs to be carried out in the research reactor to analyze the performance of the new nuclear fuel. In order to check the performance of a nuclear fuel during the irradiation test in the test loop of a research reactor, sensors need to be attached in and out of the fuel rod and connect them with instrumentation cables to the measuring device located outside of the reactor pool. In particular, to check the temporary temperature change at the center of a nuclear fuel during the irradiation test, a thermocouple should be instrumented at the center of the fuel rod. Therefore, a hole needs to be made at the center of fuel pellet to put in the thermocouple. However, because the hardness and the density of a sintered $UO_2$ pellet are very high, it is difficult to make a small fine hole on a sintered $UO_2$ pellet using a simple drilling machine even though we use a diamond drill bit made by electro deposition. In this study, an automated drilling machine using a CVD diamond drill has been developed to make a fine hole in a fuel pellet without changing tools or breakage of workpiece. A sintered alumina ($Al_2O_3$) block which has a higher hardness than a sintered $UO_2$ pellet is used as a test specimen. Then, it is verified that a precise hole can be drilled off without breakage of the drill bit in a short time.

• Nuclear Engineering and Technology
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• 제55권11호
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• pp.3996-4001
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• 2023

The High-flux Advanced Neutron Application Reactor (HANARO) produces radioisotopes (RIs) (¹³¹I, ¹⁹²Ir, etc.) through neutron irradiation on various RI production targets. Among them, ¹⁷⁷Lu and ¹⁶⁶Ho are particularly promising owing to their theranostic characteristics that facilitate simultaneous diagnosis and treatment. Prior to neutron irradiation, evaluating the nuclear heating of the RI production target is essential for ensuring the thermal-hydraulic safety of HANARO. In this study, the feasibility of producing ¹⁷⁷Lu and ¹⁶⁶Ho using irradiation holes of HANARO was investigated in terms of thermal-hydraulic safety. The nuclear heating rates of the RI production target by prompt and delayed radiation were calculated using MCNP6. The calculated nuclear heating rates were used as an input parameter in COMSOL Multiphysics to obtain the temperature distribution in an irradiation hole. The degree of temperature increase of the ¹⁷⁷Lu and ¹⁶⁶Ho production targets satisfied the safety criteria of HANARO. The nuclear heating rates and temperature distribution obtained through the in silico study are expected to provide valuable insight into the production of ¹⁷⁷Lu and ¹⁶⁶Ho using HANARO.

• 대한기계학회논문집A
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• 제26권1호
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• pp.188-195
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• 2002

To investigate the degradation of mechanical properties induced mainly by neutron irradiation, the tensile tests were conducted from room temperature to 300\\`c using the irradiated and the unirradiated Zr-2.5Nb pressure tube materials. The irradiated longitudinal and transverse specimens were collected from the coolant inlet, middle, and outlet parts of M-11 tube which had been operated in Wolsung CANDU Unit-1 and exposed to different operating temperatures and irradiation fluences. The different tensile behavior was characterized not by the fluences of irradiation but by the tensile loading direction. The transverse specimen showed the higher strength and lower elongation than those of the longitudinal one. It was believed that these phenomena resulted from the microstructure anisotropy caused by the extrusion process. The increased strength hardening and decreased elongation embrittlement of the irradiated material were compard to those of the unirradiated one. While the tensile strength of the inlet was higher than that of the outlet, the elongation of the inlet was lower than that of outlet. Considering the operation condition, it was proposed that the operating temperature could be a more effective parameter than the irradiation fluence for long-time life. Through the TEM observation, it was found that while the a-type dislocation density was increased, the c-type dislocation was not changed in the irradiated. The fact that the higher dislocation density was sequentially distributed over the inlet, the middle, and the outlet parts was consistent with the distribution of the tensile strength.

• Journal of Radiation Protection and Research
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• 제36권4호
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• pp.200-208
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• 2011

Fluence monitor(F/M)는 조사 시편을 원자로의 노심에 넣은 후 방사화 된 조사 시편의 방사능을 측정한 후 역산하여 중성자의 선량을 계산하는 기법으로 원자로내의 중성자 분포를 조사하기 위하여 반드시 필요한 기술이다. 이 기술은 중성자에 대한 에너지 스펙트럼 측정이 간접적으로 가능하며, 현존하는 중성자 분포 측정 기법 중에서 우수한 정밀도를 지니고 있다. 하나로(HANARO)에서 수행하는 재료조사 시험에서의 중성자량 측정을 위하여 본 연구에서는 지름 0.1 mm, 길이 3 mm 미만의 질량 150~200 ${\mu}g$ 범위, 순도 99.9% 이상의 Fe, Ni, Ti 와이어를 F/M 시편으로 사용하였다. 이 시편은 알루미늄 캡슐에 봉입하여 30 MW 의 하나로 OR5공에 약 25일간 조사하였다. 조사를 마친 시편은 high purity germanium (HPGe) detector를 이용하여 감마선을 측정하였고, SAND-II code로 reaction rate와 중성자 cross-section등을 고려하여 fluence monitor 위치에서의 중성자 플루언스를 계산하였다. F/M이 장착 되었던 하나로 OR5공의 중성자 플루언스 값은 MCNP 코드를 이용하여 계산된 결과를 사용하였으며, SAND-II code로 장착된 F/M 위치에서의 중성자 플루언스를 계산하여 적용된 시편의 reaction에 따른 결과값의 차이를 비교 분석하였다.

• 대한전기학회논문지:전기물성ㆍ응용부문C
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• 제51권7호
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• pp.298-304
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• 2002

Transmuted impurity atoms formed in neutron-irradiated ZnO thin films were theoretically identified first and then experimentally confirmed by photoluminescence (PL). ZnO thin films grown by plasma-assisted molecular beam epitaxy were irradiated by neutron beam at room temperature. The ZnO films consist of eight constituent (Zn and O) isotropes, of which four are transmutable by neutron-irradiation; $^{64}$ , $^{68}$ Zn, $^{70}$ Zn and $^{18}$ O were expected to transmute into $^{65}$ Cu, $^{69}$ Ga, $^{71}$ Ga, and $^{19}$ F, respectively. The concentrations of these transmuted atoms were estimated in this study by considering natural abundance, neutron fluence and neutron cross section. The neutron-irradiated ZnO thin films were characterized by PL. In the PL spectra of the ZnO thin films, the Cu-related PL peaks were seen, but the Ga- or F-associated PL peaks were absent. This observation confirmed the existence of $^{65}$ Cu in the ZnO, but it could not do the formation of the other two. In this paper, the emission mechanism of Cu impurities is described and the reason for the absence of the Ga- or F-associated PL peaks is discussed as well.

• 한국재료학회지
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• 제27권4호
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• pp.216-220
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• 2017

The effect of electron beam (EB) irradiation on the electrical properties of Zn-Sn-O (ZTO) thin films fabricated using a sol-gel process was investigated. As the EB dose increased, the saturation mobility of ZTO thin film transistors (TFTs) was found to slightly decrease, and the subthreshold swing and on/off ratio degenerated. X-ray photoelectron spectroscopy analysis of the O 1s core level showed that the relative area of oxygen vacancies ($V_O$) increased from 10.35 to 12.56 % as the EB dose increased from 0 to $7.5{\times}10^{16}electrons/cm^2$. Also, spectroscopic ellipsometry analysis showed that the optical band gap varied from 3.53 to 3.96 eV with increasing EB dose. From the results of the electrical property and XPS analyses of the ZTO TFTs, it was found that the electrical characteristic of the ZTO thin films changed from semiconductor to conductor with increasing EB dose. It is thought that the electrical property change is due to the formation of defect sites like oxygen vacancies.