• Nuclear Engineering and Technology
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• v.54 no.1
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• pp.186-192
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• 2022

Flow accelerated corrosion (FAC) is a type of pipe corrosion in which the pipe thickness decreases depending on the fluid flow conditions. In nuclear power plants, FAC mainly occurs in the carbon steel pipes of a secondary system. However, because the temperature of a secondary system pipe is over 150 ℃, in situ monitoring using a conventional ultrasonic non-destructive testing method is difficult. In our previous study, we developed a waveguide ultrasonic thickness measurement system. In this study, we applied a waveguide ultrasonic thickness measurement system to monitor the thinning of the pipe according to the change in pH. The Korea Atomic Energy Research Institute installed FAC-proof facilities, enabling the monitoring of internal fluid flow conditions, which were fixed for ~1000 h to analyze the effect of the pH. The measurement system operated without failure for ~3000 h and the pipe thickness was found to be reduced by ~10% at pH 9 compared to that at pH 7. The thickness of the pipe was measured using a microscope after the experiment, and the reliability of the system was confirmed with less than 1% error. This technology is expected to also be applicable to the thickness-reduction monitoring of other high-temperature materials.

• Korea-Australia Rheology Journal
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• v.15 no.3
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• pp.117-124
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• 2003

Elastohydrodynamic lubrication (EHL) film is measured under the condition of viscosity index improver added to base oil. In-situ optical contact method using the interference principle make the measuring resolution of ~5 nm possible and enables the measuring range all over the contact area of up to ~300 $\mu\textrm{m}$ diameter. What is more important to the developed method by the author is that the measurement of EHL film thickness is possible in the range from 100 nm to 2 $\mu\textrm{m}$, which is the regime of worst contact failures in precision machinery. Viscosity index improver (VII) is one of the major additives to the modem multigrade lubricants for the viscosity stability against temperature rise. However, it causes shear thinning effects which make the film thickness lessened very delicately at high shear rate (over $10^5 s^{-1}$) of general EHL contact regime. In order to exactly verify the VIIs performance of viscosity stability at such high shear rate, it is necessary to make the measurement of EHL film thickness down to ~100 nm with fine resolution for the preliminary study of viscosity control. In this work, EHL film thickness of VII added lubricant is measured with the resolution of ~5 nm, which will give very informative design tool for the synthesis of lubricants regarding the matter of load carrying capacity at high shear rate condition.

• Journal of KSNVE
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• v.1 no.2
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• pp.107-113
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• 1991

When non-contact type vibration probes are used for the precision measurement of shaft vibration, they can induce the measurement errors due to the shaft curvature since they have been calibrated for the flat plate. In this study the errors due to the shaft radius and the misalignment between the shaft and probe centerlines are analyzed, and an in-situ calibration tool, which can be conveniently used for calibration independent of the shaft curvature and material, is introduced.

• Nuclear Engineering and Technology
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• v.51 no.7
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• pp.1828-1834
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• 2019

The performance of a plastic scintillator for use in an in situ measurement system was analyzed using simulation and experimental methods. The experimental results of four major pure beta-emitting radionuclides, namely $^3H$, $^{14}C$, $^{32}P$, and $^{90}Sr/^{90}Y$, were compared with those obtained using a Monte Carlo N-particle (MCNP) code simulation. The MCNP simulation and experimental results demonstrated good agreement for $^{32}P$ and $^{90}Sr/^{90}Y$, with a relative difference of 1.95% and 0.43% between experimental and simulation efficiencies for $^{32}P$ and $^{90}Sr/^{90}Y$, respectively. However, owing to the short range of beta particles in water, the efficiency for $^{14}C$ was extremely low, and $^3H$ could not be detected. To directly measure the low-energy beta radionuclides considering their short range, a system where the source could flow directly to the scintillator was developed. The optimal thickness of the plastic scintillator was determined based on the suggested diameter. Results showed that the detection efficiency decreases with an increase in the depth of the water. The detection efficiency decreased drastically to approximately 10 cm, and the tendency was gradually constant.

• 한국신재생에너지학회:학술대회논문집
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• 2010.11a
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• pp.122.2-122.2
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• 2010

Knowledge of ground thermal properties is most important for the proper design of BHE(borehole heat exchanger) systems. The configure type, pipe size and thermal performance of the BHE is highly dependent on the ground source heatpump system-efficiency and instruction cost. Thermal response tests with mobile measurement devices were developed primarily for in-situ determination of design data for Standing Column Well apply. The main purpose has been to determine in-situ values of effective ground thermal conductivity and thermal resistance, including the effect of ground-water flow and natural convection in the boreholes. The test rig is set up on a some trailer, and contains a sub-circulation pump, a boiler, temperature sensors, flow meter and a data logger for recording the temperature and circulation fluid flow data. A constant heating power is injected into the SCW through the test rig and the resulting temperature change in the SCW is recorded. The recorded temperature data are analysed with a line-source model, which gives the effective in-situ values of rock thermal conductivity and thermal resistance of SCW.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2007.11a
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• pp.979-982
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• 2007

The effect of a scattering wall surfaces on sound diffusion can be assessed by determining the scattering and diffusion coefficients in the laboratory. However, the sound field in a concert hall including scattered reflections is different from the laboratory measurement condition. Therefore, there is a need for objective investigation of diffusion in real sound fields. In this paper, possible acoustical parameters of in-situ measurements are discussed.

• Journal of the Korean Geotechnical Society
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• v.18 no.2
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• pp.65-74
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• 2002

The measurement of in-situ stress is essential to estimate the ground displacement and the stress distribution of a tunnel and an underground structure. In this study, the in-situ stress distribution of the Southern Korean peninsula was re-evaluated by the new 380 in-situ data which were determined by overcoring and hydrofracturing methods, and the three-din erosional numerical analysis of tunnelling was performed. The results of in-situ stress distribution show that the distribution of horizontal stress tends to be more irregular in metamorphosed(gneiss) and granite areas than in sedimentary and volcanic areas. The ratio of horizontal to vertical stresses(K-value) in volcanic area is less than 1 below the depth of 150m. The direction and magnitude of three dimensional in-situ stresses were shown simultaneously in a figure for the first time in Korea. The three-dimensional numerical analysis of tunnelling indicates that the orientation and magnitude of displacement around a tunnel are controlled mainly by the difference between the maximum and minimum horizontal stresses.

• Proceedings of the Korean Society of Agricultural Engineers Conference
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• 2000.10a
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• pp.431-437
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• 2000

The aim of the work described in this paper is to develope a pavement method for farm road. To this ends, a series of material test are conducted on in-situ soil which was mixed additives-coarse aggregate, polypropylene fiber, excellent soil compound etc. With the laboratory test results, in-situ pavement test was conducted during two years. The serious problem of the pavement is not appeared up to this time. And the measurement of field data is continued presently. The majority merits of this pavement method is low cost and using environmental materials.

• Journal of the Korean institute of surface engineering
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• v.32 no.3
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• pp.297-302
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• 1999

In situ measurement of infrared absorption spectra has been performed during low-temperature plasma-enhanced chemical vapor depositiion of silicon-oxide films using tetramethoxysilane as a silicon source. Several absorption bands due to the reactant molecules are clearly observed before deposition. In the plasma, these bands completely disappear at any oxygen mixing ratio. This result shows that most of the tetramethoxysilane molecules are dissociated in the rf plasma, even C-H bonds. Existence of Si-H bonds in vapor phase and/or on the film surface during deposition has been found by infrared diagnostics. We observed both a decrease in Si-OH absorption and an increase in Si-O-Si after plasma off, which means the dehydration condensation reaction continues after deposition. The rate of this reaction is much slower than the deposition ratio of the films.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2003.06a
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• pp.686-689
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• 2003

Many technologies are applied to the measurement of elastohydrodynamic lubrication (EHL) film thickness. In particular, optical in-situ interferometric method has many advantages in making the actual contact behaviors realized with the experimental apparatus. Careful selection of incident lights greatly enhances the fringe resolution up to nanometer scale by using image processing technology. In this work, it is found that dichromatic incident light can provide much finer resolution of EHL film thickness than monochromatic incident light, because it has much more variables of color components to be discriminated among the wavelengths of colors according the variations of EHL film thickness. Some simulated interferometric images are shown how the film thickness is resolutionized in nanometer scale