• Corrosion Science and Technology
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• 제15권2호
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• pp.84-91
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• 2016

The transport and deposition of corrosion products in pressurized water nuclear reactor (PWR) steam generators have led to corrosion (SCC, denting etc.) problems. Lancing, mechanical cleaning and chemical cleaning have been used to reduce these problems. The methods of lancing and mechanical cleaning have limitations in removing corrosion products due to the structure of steam generator tubes. But high temperature chemical cleaning (HTCC) with EDTA is the most effective method to remove corrosion products regardless of the structure. However, EDTA in chemical cleaning aqueous solution and chemical cleaning environments affects the integrity of materials used in steam generators. The nuclear power plants have to perform the pre-test (also called as qualification test (QT)) that confirms the effect on the integrity of materials after HTCC. This is one of the series studies that assess the effect, and this study determines the effects of 20 % EDTA aqueous solution on defective tubes in high temperature chemical cleaning environments. The depth and magnitude of defects in steam generator (SG) tubes were measured by eddy current test (ECT) signals. Surface analysis and magnitude of defects were performed by using SEM/EDS. Corrosion rate was assessed by weight loss of specimens. The ECT signals (potential and depth %) of defective tubes increased marginally. But the lengths of defects, oxides on the surface and weights of specimens did not change. The average corrosion rate of standard corrosion specimens was negligible. But the surfaces on specimens showed traces of etching. The depth of etching showed a range on the nanometer. After comprehensive evaluation of all the results, it is concluded that 20 % EDTA aqueous solution in high temperature chemical cleaning environments does not have a negative effect on defective tubes.

• 국제학술발표논문집
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• The 9th International Conference on Construction Engineering and Project Management
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• pp.295-303
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• 2022

Residential heating systems in South Korea are largely based on the use of ondol pipelines. Heat is transferred to the floor by passing hot water through a metal or plastic pipe buried within the concrete of the floor. Consequently, it is difficult to clean the inside of these pipes after installation. Over time, foreign substances such as scale accumulate in the pipe when the ondol heating method is used for an extended period. Therefore, in the past, pipes were cleaned by removing foreign substances attached to the inside surfaces of the pipes using high-pressure water or by disassembling the pipes and removing foreign substances with chemical agents. Recently, a method for removing foreign substances through the cavitation effect of ultrasound has been proposed. This idea might lead to the development of new technologies for cleaning pipe interiors. Consequently, this study investigated the use of ultrasound to clean pipes embedded in concrete. In this study, devices that generated ultrasonic waves with various frequencies and directions were prepared. After preparing arbitrarily contaminated pipes, the appropriate frequency, output strength, and output direction for each foreign substance were determined through repeated experiments. The results of this experiment could provide important information for future methods of cleaning the interior of ondol piping systems.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 1999년도 추계학술대회 논문집
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• pp.617-620
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• 1999

To reduce the consumption of chemicals and ultra pure water(UPW) in cleaning process used in device manufacturing, we proposed wet processes that use electrolytic ionized water(EIW), which is generated by electrolysis of a diluted electrolyte solution or UPW and systemically investicate the EIW\`s characteristics. EIW\`s pH values are increased in cathode chamber and decreased in anode chamber according to the electrolysis time and its varied ratio is reduced with time increasement. The variation of pH and ORP is increased accordin to the applied voltage until critical voltage. But more than that voltage, the variation is decreased because of ion\`s scattering effect. When electrolyte is added, the effects of electrolysis is increased because electrolyte acts as catalyst. But when the density of electrolyte is increased more than critical value, ion\`s flowage is obstructed and the effects of electrolysis is decreased.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2010년도 춘계학술대회 논문집
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• pp.533-534
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• 2010

• 상하수도학회지
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• 제31권3호
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• pp.229-236
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• 2017

In this study, a direct contact membrane module was manufactured to be used in a pilot scale membrane distillation process to treat $3m^3/day$ of the digestate produced from anaerobic digestion of livestock manure. In order to investigate the performance of the membrane module, permeate flux was measured with and without spacer inside the module under various condition of temperature difference and cross flow velocity (CFV) through the membrane surfaces. Flux recovery rate after chemical cleaning was also investigated by applying three different cleaning methods. Additionally, thermal energy consumption was theoretically simulated based on actual pilot plant operation conditions. As results, we observed flux of the module with spacer was almost similar to the theoretically predicted value because the installation of spacer reduced the channeling effect inside the module. Under the same operating condition, the permeate flux also increased with increasing temperature difference and CFV. As a result of chemical in-line cleaning using NaOCl and citric acid for the fouled membranes, the recovery rate was 83.7% compared to the initial flux when NaOCl was used alone, and 87% recovery rate was observed when only citric acid was used. However, in the case of using only citric acid, the permeate flux was decreased at a rapid rate. It seemed that a cleaning by NaOCl was more effective to recover the flux of membrane contaminated by the organic matter as compared to a cleaning by citric acid. The total heat energy consumption increased with increasing CFV and temperature difference across the membrane. Thus, further studies should be intensively conducted to obtain a high permeate flux while keeping the energy consumption to a minimum for a practical application of membrane distillation process to treat wastewater.

• 한국정밀공학회지
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• 제28권10호
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• pp.1217-1223
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• 2011

In this paper, the dielectric barrier discharge plasma generator has been studied for producing of the high concentration ozone gas. Proposed plasma generator has the structure of extremely narrow discharge air gap(0.15mm) in order to realize the high electric field discharge. We investigate the performance of the dielectric barrier discharge plasma generator experimentally and the results show that the generator has very high ozone concentration characteristics of 13.7[wt%/$O_2$] at the oxygen flow rate of 1[${\ell}$/min] of each discharge cell. So, we confirmed that the proposed plasma generator is suitable for the high concentration ozone production facility of the eco-friendly ozone functional water cleaning system in the electronic components cleaning process.

• 대한영양사협회학술지
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• 제1권1호
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• pp.31-42
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• 1995

The aims of this study are to enhance the students' knowledge of the drinking water and its reliability by investigating drinking water situation and the degree of students' knowledge on the drinking water. The results are as follows 1. Status and drinking behavior about school drinking water (1) 97.53% of the schools are using the tap water as the resource of drinking water (2) 46 schools are in possession of water tank and 18 schools of them are using the water tank as the resource of drinking water. The cleaning and sanitization of the tank are carried out once in a year with hypochloronatrium by the low-level officials, nurse teachers, and dietitian. 2. The degree of students' knowledge about drinking water (i) This survey represent that students favor the spring water best and think the tap water worst for drinking. (2) 83% of the students think that the tap water is polluted and these conception are formed mostly by the mass communication. 80% of boys and 90% of girls answered they don't drink plain tap water.

• 한국정밀공학회지
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• 제31권12호
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• pp.1107-1113
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• 2014

In this article, the megasonic cleaning system for cleaning micro/nano particles from flat panel display (FPD) surfaces was developed. A piezoelectric actuator and a waveguide were designed by finite element method (FEM) analysis. The calculated peak frequency value of the quartz waveguide was 1002 kHz, which agreed well with the measured value of 1003 kHz. The average acoustic pressure of the megasonic cleaning system was 43.1 kPa, which is three times greater than that of the conventional type of 13.9 kPa. Particle removal efficiency (PRE) tests were performed, and the cleaning efficiency of the developed system was proven to be 99%. The power consumption of the developed system was 64% lower than that of the commercial system. These results show that the developed megasonic cleaning system can be an effective solution in particle removing from FPD substrate with higher energy efficiency and lower chemical and ultra pure water (UPW) consumption.

• 마이크로전자및패키징학회지
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• 제16권1호
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• pp.45-50
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• 2009

레이저를 이용 실리콘 관통형 접속기술인 TSV(Through-Silicon-Via)를 형성할 경우 Debris(파편물) 및 Particle이 발생되므로 이를 제거하기 위한 세정공정을 연구하였다. 계면활성제를 이용한 화학적 세정과 Brush를 이용한 물리적 세정을 검토하기 위하여 세정기를 제작하고 8인치 CMOS Image Sensor wafer에 직경 $30{\mu}m$, 깊이 $100{\mu}m$를 갖는 Via를 제작하여 두 가지의 세정방법을 연구하였다. 세정액은 DI Water와 계면활성제의 혼합비 2:1에서 Debris 범위가 $73{\mu}m^2$로 희석비가 낮을수록 세정력이 우수하였다. 레이저의 주파수와 속도변위에 따른 가공 조건 변화에는 Debris 분포차가 5% 미만으로 세정력에는 영향이 없었다. Brush를 이용하여 Debris를 제거하는 실험에서 Strip $1000{\sim}3000rpm$, Rinse $50{\sim}3000rpm$, Brush $200{\sim}300rpm$ 으로 증가시켜 세정하였을 때 Crack이나 손상 없이 Debris의 분포가 감소하였다. 따라서 화학적 세정과 물리적 세정으로 Debris를 제거할 수 있다.

• 한국물환경학회지
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• 제20권5호
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• pp.391-396
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• 2004