• Proceedings of the Korean Nuclear Society Conference
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• 1995.10a
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• pp.17-22
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• 1995

열출력 108㎿$_{t}$급의 소형 원자로를 설계하였다. 설계 제한 조건으로 2년의 재장전 주기, 무붕산 노심, 저 출력 밀도를 채택하였고, 핵연료 집합체의 설계는 울진 304호기의 사양을 그대로 사용하였다. 노심 출력 준위 제어는 제어봉만으로 가능하도록 하였다. CASMO-3와 KINS-3를 통해 설계된 노심의 주기 길이 만족 여부 확인, 첨두 계수, 감속재 온도 계수, 출력 계수 등을 계산하였다. 설계 결과, 한국 표준 원전 핵연료집합체 사양으로 저출력 밀도의 소형인자로를 무붕산 운전으로 가정하여 설계 가능함을 알 수 있었으며, 감속재 온도 계수가 음의 안전성을 갖고 있으며, 가연성 독봉의 축방향 Zoning이 필요하며, 기존 상용로의 경우 보다 독봉을 많이 사용되어야 하며, 제어봉이 서양 장기판처럼 배치될 정도로 많이 사용되어야 함을 알았다.

• The Korean Journal of Nuclear Medicine
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• v.35 no.2
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• pp.100-112
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• 2001

Purpose: The purpose of this study was to establish optimal imaging acquisition conditions for the GE $Advance^{TM}$ PET imaging system by performing the acceptance tests designed by National Electrical Manufacturers Association (NEMA) protocol and General Electric Medical Systems (GEMS) test procedures. Materials and Methods: Performance tests were carried out with $^{18}FDG$ radioactivity source and phantoms by using a standard acquisition mode. Transaxial resolution and scatter traction tests were performed with a line source and axial resolution with a point source, respectively. A cylindrical phantom made of polymethylmethacrylate (PMMA) was used to measure sensitivity, count rate losses and randoms, uniformity correction, and attenuation inserts were added to measure remaining tests. The test results were acquired in a diagnostic acquisition mode and analyzed mainly on high sensitivity mode. Results: Transaxial resolution and axial resolution were measured as average of 4.65 mm and 3.98 mm at 0 cm, and 6.02 mm and 6.71 mm at 20 cm on high sensitivity mode, respectively. Average scatter fraction was 9.87%, and sensitivity was $225.8kcps/{\mu}Ci/cc$ of trues. Activity at 50% deadtime was $4.6{\mu}Ci/cc$, and the error of count rate correction at that activity was from 1.49% to 3.83%. Average nonuniformity for total slice w3s 8.37%. The accuracy of scatter correction was -0.95%. The accuracies of attenuation correction were 5.68% for air, 0.04% for water and -6.51% for polytetrafluoroethylene (PTFE). Conclusion: The results satisfied most acceptance criteria, indicating that the GE $Advance^{TM}$ PET system can be optimally used for clinical applications.

• Journal of Energy Engineering
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• v.29 no.1
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• pp.34-43
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• 2020

A study has been done for self-starting torque of vertical axis wind turbine blade. It is especially concentrated to evaluate the torque coefficient before starting rotation. Two different aerofoils(AMI903 and AMI904) are proposed to benchmark the possible best blade(supercritical airfoil) for self-starting performance. Torque coefficients in the tangential direction of rotation are given with respect to the angle of attack in terms of drag coefficient and lift coefficient. Torque coefficient shows that the effect of Reynolds number is minimal. The thicker blade(AMI904) between two different proposed airfoils has bigger torque coefficient, which is attributed to lower lift coefficient and higher drag coefficient.

• Journal of the Korea institute for structural maintenance and inspection
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• v.9 no.1
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• pp.101-111
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• 2005

In this study, it is investigated the modified modulus of elasticity of the reinforced concrete columns including the longitudinal reinforcing steels as well as the confinement effect of the core concrete due to the transverse reinforced steel through the literature reviews. Equations are derived in order to evaluate the modified modulus of elasticity for the reinforced compressive concrete including the confinement effect. The finite element analysis for the 20 story reinforced concrete building is undertaken as a case study depending on the steel ratio and modulus of elasticity, and the analysis results are discussed.

• Nuclear Engineering and Technology
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• v.27 no.6
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• pp.811-824
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• 1995

The CANDU element bowing is attributed to actions of both the thermally induced bending moments and the bending moment due to hydraulic drag and mechanical loads, where the bowing is defined as the lateral deflection of an element from the axial centerline. This paper consider only the thermally-induced bending moments which are generated both within the sheath and the fuel and sheath by an asymmetric temperature distribution with respect to the axis of an element The generalized and explicit analytical formula for the thermally-induced bending is presented in con-sideration of 1) bending of an empty tube treated by neglecting the fuel/sheath mechanical interaction and 2) fuel/sheath interaction due to the pellet and sheath temperature variations, where in each case the temperature asymmetries in sheath are modelled to be caused by the combined effects of (i) non-uniform coolant temperature due to imperfect coolant mixing, (ii) variable sheath/coolant heat transfer coefficient, (iii) asymmetric heat generation due to neutron flux gradients across an element and so as to inclusively cover the uniform temperature distributions within the fuel and sheath with respect to the axial centerline. As the results of the sensitivity calculations of the element bowing with the variations of the parameters in the formula, it is found that the element bowing is greatly affected relatively with the variations or changes of element length, sheath inside diameter, average coolant temperature and its variation factor, pellet/sheath mechanical interaction factor, neutron flux depression factor, pellet thermal expansion coefficient, pellet/sheath heat transfer coefficient in comparison with those of other parameters such as sheath thickness, film heat transfer coefficient, sheath thermal expansion coefficient and sheath and pellet thermal conductivities.

• Analytical Science and Technology
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• v.23 no.2
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• pp.103-108
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• 2010

Single crystals of $ZnWO_4$ with [100], [010] and [001] directions were successfully grown by the Czochralski method. The seed crystals for the single crystal growth of $ZnWO_4$ could be induced by the crystal growth using platinum wires applied by the capillary action from the melt. The growth conditions in each direction were investigated in terms of the variations of rotation speed, pulling rate and diameter of the grown crystals. The formation of cracking in the grown crystals during the cooling process could be prevented by annealing effect. The growth directions of the grown crystals were determined using Laue back reflection. The microscopic characteristics of the grown crystals in each direction were discussed, and their physical properties were evaluated for hardness, thermal expansion coefficients and dielectric constants.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.35 no.12
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• pp.1391-1398
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• 2011

Design and performance analysis of a steam turbine for variations of degree of reaction were performed by computer simulation. Design parameters such as blade angles, exit areas, and heights of the nozzle and moving blade were represented as functions of the degree of reaction. The main performance factors such as turbine power, diagram efficiency, and axial thrust were also expressed in terms of the degree of reaction. For further information about the design and performance, the blade angles and main performance factors were investigated as functions of the flow coefficient. The turbine power and diagram efficiency reached a maximum value for a given degree of reaction and flow coefficient, and the symmetric shape of the moving blade showed distortion as the degree of reaction was increased.

• Korean Chemical Engineering Research
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• v.52 no.4
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• pp.516-521
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• 2014

Axial and overall heat transfer coefficients were investigated in a bubble column with relatively high viscous and low surface tension media. Effects of superficial gas velocity (0.02~0.1 m/s), liquid viscosity ($0.1{\sim}0.3Pa{\cdot}s$) and surface tension ($66.1{\sim}72.9{\times}10^{-3}N/m$) on the local and overall heat transfer coefficients were examined. The heat transfer field was composed of the immersed heater and the bubble column; a vertical heater was installed at the center of the column coaxially. The heat transfer coefficient was determined by measuring the temperature differences continuously between the heater surface and the column which was bubbling in a given operating condition, with the knowledge of heat supply to the heater. The local heat transfer coefficient increased with increasing superficial gas velocity but decreased with increasing axial distance from the gas distributor and liquid surface tension. The overall heat transfer coefficient increased with increasing superficial gas velocity but decreased with increasing liquid viscosity or surface tension. The overall heat transfer coefficient was well correlated in terms of operating variables such as superficial gas velocity, liquid surface tension and liquid viscosity with a correlation coefficient of 0.91, and in terms of dimensionless groups such as Nusselt, Reynolds, Prandtl and Weber numbers with a correlation of 0.92; $$h=2502U^{0.236}_{G}{\mu}^{-0.250}_{L}{\sigma}^{-0.028}_L$$ $$Nu=325Re^{0.180}Pr^{-0.067}We^{0.028}$$.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.38 no.6
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• pp.655-662
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• 2014

This study conducted tensile tests on an Alloy 690TT tube at room temperature (RT) and at $343^{\circ}C$ using tube- and ring-type specimens to investigate the stress-strain behavior and tensile properties of a steam generator (SG) tube in the axial and circumferential directions at RT and at the design temperature of a nuclear power plant (NPP). The results of the axial tensile test showed that yield point phenomena appeared at both RT and $343^{\circ}C$, and serrated flow in the stress-strain curve appeared at $343^{\circ}C$. Yield and tensile strengths for both directions were clearly lower at $343^{\circ}C$ compared to RT; however, the elongations were approximately the same at both test temperatures. Regardless of the test temperature, the strengths in the circumferential direction were lower by approximately 5~10 % than those in the axial direction. In addition, the test data revealed that the reduction in the yield and tensile strengths of the Alloy 690TT SG tube with the test temperature was more significant than that estimated by the temperature correction factor of ASME Sec.II.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.13 no.1
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• pp.87-95
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• 2000

The two eigenvalues (elastic critical load and natural frequency of lateral vibration) of sinusoidally tapered bats with simply supported ends were determined by the finite element method. For the convenience of structural engineers who are engaged in the structural design or vibration analysis of tapered beam-columns, eigenvalue coefficients were expressed by simple algebraic equations. The validity of each algebraic equation was confirmed by the value of unity for each correlation coefficient. The influence of axial thrust on the lateral vibration frequency was also investigated. For this purpose, the axial thrust was increased successively and the corresponding frequency was calculated. The approximate linear relationship between the axial thrust and the square of the frequency was confirmed lot each of the tapered members.