• Nuclear Engineering and Technology
• /
• 제48권5호
• /
• pp.1230-1236
• /
• 2016

This study aims to determine the effect of fly ash with a high replacing ratio of clay on the radiation shielding properties of bricks. Some interaction parameters (mass attenuation coefficients, half value layer, effective atomic number, effective electron density, and absorption efficiency) of clay fly ash bricks were measured with a NaI(Tl) detector at 661.6 keV, 1,173.2 keV, and 1,332.5 keV. For the investigation of their shielding behavior, fly ash bricks were molded using an admixture to clay. A narrow beam transmission geometry condition was used for the measurements. The measured values of these parameters were found in good agreement with the theoretical calculations. The elemental compositions of the clay fly ash bricks were analyzed by using an energy dispersive X-ray fluorescence spectrometer. At selected energies the values of the effective atomic numbers and effective electron densities showed a very modest variation with the composition of the fly ash. This seems to be due to the similarity of their elemental compositions. The obtained results were also compared with concrete, in order to study the effect of fly ash content on the radiation shielding properties of clay fly ash bricks. The clay fly ash bricks showed good shielding properties for moderate energy gamma rays. Therefore, these bricks are feasible and eco-friendly compared with traditional clay bricks used for construction.

• 한국압력기기공학회 논문집
• /
• 제17권2호
• /
• pp.109-118
• /
• 2021

In the periodic surveillance material test for the spacer component of fuel channel assembly in CANDU, a microstructural characterization analysis is required in addition to the mechanical property evaluation test. In this study, detailed microstructure analysis and simple mechanical property evaluation of archive spacer parts were conducted to indirectly support the surveillance test and assist in the study of spacer material degradation. We investigated the microstructural characteristics of the spacer garter spring coil through comparative analysis with the plate material. The main microstructure characteristics of the garter spring coil X-750 are represented by the fine grain size distribution, the ordering phase distribution developed inside the matrix, the high dislocation density inside the grains, and the arrangement of coarse carbides. In addition, the yield strength of the garter spring coil X-750 was indirectly evaluated to be approximately 1 GPa. We also established an analytical method to elucidate the microstructural evolution of the radioactive spacer garter spring coil X-750 based on Canadian research experiences. Finally, we confirmed the measurement technique for helium bubble formation through TEM examination on the helium implanted X-750 material.

• 농촌계획
• /
• 제12권2호
• /
• pp.57-64
• /
• 2006

The experiment was carried out to determine the distribution of total coliform the translocation of heavy metals and the salt accumulation in soils following the supply of ground water, the domestic wastewater and the ultraviolet treatment of domestic wastewater during the spinach and the chinese cabbage cultivation. There were not much changes in the Total-N, Total-P and cations in soils following the ultraviolet treatment of the domestic wastewater. However, the density of total coliform was dramatically reduced from 894MPN/100mL to 5MPN/100mL. The diagnosis of composition of soil after the harvest of chinese cabbages and spinach has shown that the concentration of Na$^+$ was 3-4 times higher in plot using domestic wastewater than in plot using ground water. When domestic wastewater and ground water were used in growing spinach md chinese cabbage at 50% each, the application of chemical fertilizers reduced about 25% to 50% compared to the criteria set down by the Rural Development Administration and there was not significant difference in terms of harvest. Using non-ultraviolet treatment of domestic wastewater directly on spinach and chinese cabbage has resulted in excessive density of total coliform at 25,000MPN/100mL. Even when ultraviolet treatment, the density was still high at 2,000MPN/100mL. The high density of total coliform even following ultraviolet treatment of domestic wastewater is considered to be caused by photo-reactivation of micro-organism. When reusing domestic wastewater, the application of sterilization such as ultraviolet, ultrasonic and electron-beam for public health and hygiene reasons may provide safe supply of agricultural water.

• 대한전기학회:학술대회논문집
• /
• 대한전기학회 2001년도 하계학술대회 논문집 B
• /
• pp.723-725
• /
• 2001

Ion plating method using plasma is faster as several times than electron beam plating method in plating process. Recently, a variety of techniques for this method are being researched. In this paper to produce sheet plasma with high density for ion plating we designed magnetic circuit of MgO plating device consisting of solenoid coil, rectangular permanent magnet. And, we researched on the effect of those by analyzing magnetic field distribution using FEM.

• 대한전기학회:학술대회논문집
• /
• 대한전기학회 2006년도 제37회 하계학술대회 논문집 C
• /
• pp.1554-1555
• /
• 2006

We have studied the backward wave oscillator, a power pulsed generator oscillator at 20 GHz has higher frequency then current one. An absolute instability linear analysis was used for the purpose of designing the slow wave structure. A large diameter of the slow wave structure was adopted to prevent the breakdown brought about by the increase of power density.

• 대한전자공학회논문지
• /
• 제22권6호
• /
• pp.34-40
• /
• 1985

분자선 에퍼택시 (MBE)방법을 이용하여 (100) GaAs웨이퍼 위에 GaAs에퍼충을 성장시켜 성장된 충에 대한 여러가지 특성을 조사 ·분석하였다. 분자선 에피택시 방법을 이용하여 CaAs에퍼층을 만들 때에는 기판온도와 As와 Ca의 분자선 밀도비 (As/Ga)가 가장 큰 영향을 미친다. 본 실험에서는 좋은 표면상태를 얻기 위해 480℃∼650℃로 유지시키고 As cell의 온도를 230℃, Ga eel함 온도를 917℃로 고정시켜 As와 Ga의 분자선 밀도비를 5∼10 이상으로 유지시켰다. 제작된 GaAs에피층의 표면상태를 SIMS (Seconde,y ion Mass ipectoscopy), AES(Auger Electron Spectroscopy) , SEM (Scanning Elect.on Mic,oscopy) , RHEED (Reflection High Energy Electron Diffraction) 등으로 조사한 결과 기판온도가 540℃일 때 가장 좋은 표면상태를 얻을 수 있었다. 또한 RH-EED관찰 결과 As 안정화된 표면을 관측할 수 있었으며 SIMS로 depth-Profile을 해 본 곁과, Ca 보다 As가 불안정함을 알았다. 또한 반선 회절 검사결과에서 기판온도가 520℃일때와 540℃일때 (400), (200)면에 단결정이 형성되었음을 알 수 있었다.

• Applied Microscopy
• /
• 제36권spc1호
• /
• pp.35-40
• /
• 2006

Self-assembled InAs/GaAs quantum dots (QDs) were grown by the atomic layer epitaxy (ALE) and molecular beam epitaxy (MBE) techniques, The structure and the thermal stability of QDs have been studied by high resolution electron microscopy with in-situ heating experiment capability, The ALE and MBE QDs were found to form a hemispherical structure with side facets in the early stage of growth, Upon capping by GaAs layer, however, the apex of QDs changed to a flat one. The ALE QDs have larger size and more regular shape than those of MBE QDs. The QDs collapse due to elevated temperature was observed directly in atomic scale, In situ heating experiment within TEM revealed that the uncapped QDs remained stable up to $580^{\circ}C$, However, at temperature above $600^{\circ}C$, the QDs collapsed due to the diffusion and evaporation of In and As from the QDs, The density of the QDs decreased abruptly by this collapse and most of them disappeared at above $600^{\circ}C$.

• 대한용접접합학회:학술대회논문집
• /
• 대한용접접합학회 2002년도 Proceedings of the International Welding/Joining Conference-Korea
• /
• pp.612-619
• /
• 2002

The dynamic behavior of Al-Mg alloys plasma was very unstable and this instability was closely related to the unstable motion of keyhole during laser irradiation. The keyhole fluctuated both in size and shape and its fluctuation period was about 440 ${\mu}{\textrm}{m}$. This instability has been estimated to be caused by the evaporation phenomena of metals with different boiling point and latent heats of vaporization. Therefore, the authors have conducted the spectroscopic diagnostics of plasma induced in the pulsed YAG laser welding of Al-Mg alloys in air and argon atmospheres. In the air environment, the identified spectra were atomic lines of Al, Mg, Cr, Mn, Cu, Fe and Zn, and singly ionized Mg line, as well as strong molecular spectrum of AlO, MgO and AIH. It was confirmed that the resonant lines of Al and Mg were strongly self-absorbed, in particular in the vicinity of pool surface. The self-absorption of atomic Mg line was more eminent in alloys containing higher Mg. These facts showed that the laser-induced plasma was relatively a low temperature and high density metallic vapor. The intensities of molecular spectra of AlO and MgO were different each other depending on the power density of laser beam. Under the low power density irradiation condition, the MgO band spectra were predominant in intensity, while the AlO spectra became much stronger in higher power density. In argon atmosphere the band spectra of MgO and AlO completely vanished, but AlH molecular spectra was detected clearly. The hydrogen source was presumably the hydrogen solved in the base Metal, absorbed water on the surface oxide layer or H$_2$ and $H_2O$ in the shielding gas. The temporal change in spectral line intensities was quite similar to the fluctuation of keyhole. The time average plasma temperature at 1 mm high above the surface of A5083 alloy was determined by the Boltzmann plot method of atomic Cr lines of different excitation energy. The obtained electron temperature was 3, 280$\pm$150 K which was about 500 K higher than the boiling point of pure aluminum. The electron number density was determined by measuring the relative intensities of the spectra1lines of atomic and singly ionized Magnesium, and the obtained value was 1.85 x 1019 1/㎥.

• Nuclear Engineering and Technology
• /
• 제47권3호
• /
• pp.380-387
• /
• 2015

A lead slowing-down spectrometer (LSDS) system is a promising nondestructive assay technique that enables a quantitative measurement of the isotopic contents of major fissile isotopes in spent nuclear fuel and its pyroprocessing counterparts, such as $^{235}U$, $^{239}Pu$, $^{241}Pu$, and, potentially, minor actinides. The LSDS system currently under development at the Korea Atomic Energy Research Institute (Daejeon, Korea) is planned to utilize a high-flux ($>10^{12}n/cm^2{\cdot}s$) neutron source comprised of a high-energy (30 MeV)/high-current (~2 A) electron beam and a heavy metal target, which results in a very intense and complex radiation field for the facility, thus demanding structural shielding to guarantee the safety. Optimization of the structural shielding design was conducted using MCNPX for neutron dose rate evaluation of several representative hypothetical designs. In order to satisfy the construction cost and neutron attenuation capability of the facility, while simultaneously achieving the aimed dose rate limit (< $0.06{\mu}Sv/h$), a few shielding materials [high-density polyethylene (HDPE)eBorax, $B_4C$, and $Li_2CO_3$] were considered for the main neutron absorber layer, which is encapsulated within the double-sided concrete wall. The MCNP simulation indicated that HDPE-Borax is the most efficient among the aforementioned candidate materials, and the combined thickness of the shielding layers should exceed 100 cm to satisfy the dose limit on the outside surface of the shielding wall of the facility when limiting the thickness of the HDPE-Borax intermediate layer to below 5 cm. However, the shielding wall must include the instrumentation and installation holes for the LSDS system. The radiation leakage through the holes was substantially mitigated by adopting a zigzag-shape with concrete covers on both sides. The suggested optimized design of the shielding structure satisfies the dose rate limit and can be used for the construction of a facility in the near future.

• Journal of Magnetics
• /
• 제11권4호
• /
• pp.182-188
• /
• 2006

The search for high-density recording materials has been one of most active and vigorous field in the field of magnetism. $FePt-L1_{0}$ nanoparticle has emerged as a potential candidate because of its high anisotropy. In this paper, we provide an overview of recent work at Argonne National Laboratory that contributes to the ongoing dialogue concerning the relation between structure and properties of the FePt nanoparticle system. In particular we discuss the ability to control structure and properties via dosing with Cr. Cr-dosed FePt films were grown via molecular beam epitaxy and annealed at $550^{\circ}C$ in an ultrahigh vacuum chamber, and were studied with the surface magneto-optic Kerr effect (SMOKE), scanning electron microscopy (SEM) and x-ray magnetic circular dichroism (XMCD). We found that small dosage of Cr helps to generate $L1_{0}$ phase FePt magnetic nanoparticles with small size, defined shape and regular spatial distribution on MgO (001) substrate. The nanostructures are ferromagnetic with high magnetic coercivity (${\sim}0.9T$) and magnetic easy axis in the desired out-of-plane orientation. We also show that controlling the lateral region where nanostructures exist is possible via artificial patterning with Cr.