• Corrosion Science and Technology
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• v.12 no.3
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• pp.125-131
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• 2013

The most common pipe wall thinning degradation mechanisms that can occur in the steam and feedwater systems are FAC (Flow Acceleration Corrosion), cavitation, flashing, and LDIE (Liquid Droplet Impingement Erosion). Among those degradation mechanisms, FAC has been investigated by many laboratories and industries. Cavitation and flashing are also protected on the piping design phase. LDIE has mainly investigated in aviation industry and turbine blade manufactures. On the other hand, LDIE has been little studied in NPP (Nuclear Power Plant) industry. This paper presents the development of prediction system for pipe wall thinning caused by LDIE in terms of erosion rate based on air-water ratio and material. Experiment is conducted in 3 cases of air-water ratio 0.79, 1.00, and 1.72 using the three types of the materials of A106B, SS400, and A6061. The main control parameter is the air-water ratio which is defined as the volumetric ratio of water to air (0.79, 1.00, 1.72). The experiments were performed for 15 days, and the surface morphology and hardness of the materials were examined for every 5 days. Since the spraying velocity (v) of liquid droplets and their contact area ($A_c$) on specimens are changed according to the air-water ratio, we analyzed the behavior of LDIE for the materials. Finally, the prediction equations(i.e. erosion rate) for LDIE of the materials were determined in the range of the air-water ratio from 0 to 2%.

• Journal of Welding and Joining
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• v.25 no.5
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• pp.45-50
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• 2007

The Ni-base superalloy GTD111 DS is used in the first stage blade of high power land-based gas turbines. Advanced repair technologies of the blade have been introduced to the gas turbine industry over recent years. The effect of the filler metal powder on Transient Liquid Phase bonding phenomenon and tensile mechanical properties was investigated on the GTD111 DS superalloy. At the filler metal powder N series, the base metal powders fully melted at the initial time and a large amount of the base metal near the bonded interlayer was dissolved by liquid inter metal. Liquid filler metal powder was eliminated by isothermal solidification which was controlled by the diffusion of B into the base metal. The solids in the bonded interlayer grew from the base metal near the bonded interlayer inward the insert metal during the isothermal solidification. The bond strength of N series filler metal powder was over 1000 MPa. and ${\gamma}'$ phase size of N series TLP bonded region was similar with base metal by influence of Ti, Al elements. At the insert metal powder M series, the Si element fluidity of the filler metal was good but microstructure irregularity on bonded region because of excessive Si element. Nuclear of solids formed not only from the base metal near the bonded interlayer but also from the remained filler metal powder in the bonded interlayer. When the isothermal solidification was finished, the content of the elements in the boned interlayer was approximately equal to that of the base metal. But boride and silicide formed in the base metal near the bonded interlayer. And these boride decreased with the increasing of holding time. The bond strength of M series filler metal powder was about 400 MPa.

• Journal of the Earthquake Engineering Society of Korea
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• v.16 no.5
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• pp.23-32
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• 2012

Research on steel plate concrete (SC) structures for the modularization of nuclear power plants have been performed recently in Korea. In this study, the seismic capacity and stiffness characteristics of unstiffened SC shear walls under the effects of earthquakes were investigated through static pushover tests. Failure modes, sectional strength, and stiffness characteristics of SC structures under lateral loads were inspected by analyzing the experimental results. The strengths obtained by the experiments were also compared with those derived by the design code of the SC structures. One of the main failures of unstiffened SC shear walls was found to be the type of bending shear failure due to the debonding of the steel plate at the concrete interface. The ductility capacity of SC structures was also confirmed to be improved, which is considered to be a confining effect on steel plates in the longitudinal behavior of SC structures.

• Journal of the Institute of Electronics Engineers of Korea CI
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• v.49 no.2
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• pp.13-19
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• 2012

The techniques of 3d image processing have broadly used in the areas including movies, games, performances, exhibitions. In addition, increasing demands for practical uses have gradually extended to the areas of architecture, medicine, nuclear power plant. However, dominant techniques for 3d image processing seem to depend on multi-camera in which two stereo images are merged into one image. Also the pipeline has limitations to provide real-time 3d viewer in ubiquitous computing. It is not able to be applicable onto most general screens as well. In addition, the techniques can be utilized for the real-time 3d game play without a particular monitor or convertor. Hence, the research presented here is to aim at developing an efficient real-time 3d viewer using only mono camera which do not need post processing for editing as well.

• Journal of Radiation Protection and Research
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• v.41 no.3
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• pp.216-221
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• 2016

Background: Very fine radiation-induced aerosol particles are produced in intense radiation fields, such as high-intensity accelerator rooms and containment vessels such as those in the Fukushima Daiichi nuclear power plant (FDNPP). Size measurement of the aerosol particles is very important for understanding the behavior of radioactive aerosols released in the FDNPP accident and radiation safety in high-energy accelerators. Materials and Methods: A combined technique using wire screens and imaging plates was developed for size measurement of fine radioactive aerosol particles smaller than 100 nm in diameter. This technique was applied to the radiation field of a proton accelerator room, in which radioactive atoms produced in air during machine operation are incorporated into radiation-induced aerosol particles. The size of $^{11}C$-bearing aerosol particles was analyzed using the wire screen technique in distinction from other positron emitters in combination with a radioactive decay analysis. Results and Discussion: The size distribution for $^{11}C$-bearing aerosol particles was found to be ca. $70{\mu}m$ in geometric mean diameter. The size was similar to that for $^7Be$-bearing particles obtained by a Ge detector measurement, and was slightly larger than the number-based size distribution measured with a scanning mobility particle sizer. Conclusion: The particle size measuring method using wire screens and imaging plates was successfully applied to the fine aerosol particles produced in an intense radiation field of a proton accelerator. This technique is applicable to size measurement of radioactive aerosol particles produced in the intense radiation fields of radiation facilities.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• 2014.10a
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• pp.83-84
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• 2014

This study evaluated the effectiveness of biostimulating agent in contaminated coastal sediment. The study was conducted via column tests in coastal sea wherein two separate columns were employed for two different polymers used and another column for a blank. The biostimulating agent was made by mixing sea sediment with biostimulants viz acetate, nitrate, sulfate. The biostimulating agent was then rolled into balls, dried and coated with either Cellulose Acetate (CA) or Polysulfone (PS) to control the release of the biostimulants. The pH was around 7.6~8 for 4 months while COD, TP and TN were significantly lower in the column containing biostimulating agents. Heavy metal(Fe, Zn, Cd, Cr, Pb, Cu) was converted to stable forms and PS coated biostimulating agent had a high efficiency of heavy metals distribution.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.18 no.3
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• pp.303-309
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• 2005

Numerical analysis is carried out to identify the appropriateness of the design codes that is available for the tensile design of fastening system at Nuclear Power Plant (NPP) in this study. This study is intended for the cast-in-place anchor that is widely used for the fastening of equipment in Korean NPPs. The microplane model and the elastic-perfectly plastic model are employed for the quasi-brittle material like concrete and for the ductile material like anchor bolt as constitutive model for numerical analysis and smeared crack model is employed to simulate the clack and damage phenomena. The developed numerical model is verified on a basis of the various test data of cast-in-place anchor. The appropriateness of both ACI 349 Code and CEB-FIP Code is evaluated for the tensile design of cast-in-place anchor and it is proved that both design codes give a conservative results for real tensile capacity of cast-in-place anchor.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.35 no.10
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• pp.1105-1110
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• 2011

Flow-accelerated corrosion (FAC) is a well-known phenomenon that may occur in piping and components. Most nuclear power plants have carbon-steel-pipe wall-thinning management programs in place to control FAC. However, various other erosion mechanisms may also occur in carbon-steel piping. The most common forms of erosion encountered (cavitation, flashing, Liquid Droplet Impingement Erosion (LDIE), and Solid Particle Erosion (SPE)), have caused wall thinning, leaks, and ruptures, and have resulted in unplanned shutdowns in utilities. In particular, the damage caused by LDIE is difficult to predict, and there has been no effort to protect piping from erosive damage. This paper presents an evaluation method for LDIE. It also includes the calculation results from prediction models, a review of the experimental results, and a comparison between the UT data in the damaged components and the results of the calculations and experiments.

• Plant Journal
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• v.14 no.2
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• pp.45-50
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• 2018

Nuclear safety law's amendment caused many problems to use radiography testing(RT). Phased array ultrasonic testing(PAUT) was adapted instead of RT for NDE of welding points in boiler tubes these days. Unfortunately, PAUT doesn't give us the discrimination characteristics about flaws distinction and flaws size clearly. In this thesis, the distinction characteristics of flaw types and the detection characteristics of flaw size using PAUT of welding points in boiler tubes were analyzed. It was concluded that PAUT can distinguish between planar flaws and rounded flaws, but it is hard to tell apart the types of flaw respectively. We paid attention to the discrimination of flaws size because PAUT tends to underestimate the flaw size of porosity and underestimate or overestimate the flaw size of porosity.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.20 no.11
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• pp.2007-2013
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• 2016

It was found to have hacking attempts totaling 115,000 to target the public sector since 2011 to 2015. National Intelligence Service was conducting survey information security management states of a wide range of national-public institutions up to 800 including government agencies in the 2012, while instructing to complement shortcomings. However, there is still going to occur invasions, such as Korea Hydro & Nuclear Power hacking. Even though KHNP's security personnel was only 53 people, in the total 20,000 workforces, got the almost perfect score in the 2013 and 2014 related to information security personnel. Through them, we can confirm that between the organizational response to information security incidents and something theoretical is very far. In this paper, we suggest solutions not using the professional staff management but the non-professional staff management to upgrade the level of public agencies information security.