• Journal of Conservation Science
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• v.26 no.4
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• pp.407-416
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• 2010

Bacteria with ability for iron reduction in the soil can use corrosion products of iron remains as energy source. The activities of this bacteria cause the change of corrosion products. As a result, it can be difficult to identify corrosion products promoting corrosion of iron remains. The purpose of this study, is to investigate the change in corrosion products that bacteria causes and to improve understanding about the corrosion of iron remains. To simulate corroded condition of excavated iron remains, carbon steel corroded by solution of NaCl and $Na_2SO_4$ was prepared. Then the prepared carbon steel was immersed in a liquid medium with bacteria. The incubation period was 42days. After experiment, the carbon steel was analyzed by SEM-EDS, X-ray diffraction method. The result is that the carbon was changed to green because of activity of bacteria and that the plate crystal and lozenge crystal were generated on the corrosion specimen. Also, we confirmed that the activities of bacteria differenciated colors and forms of corrosion products.

• Nuclear Engineering and Technology
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• v.51 no.4
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• pp.1109-1116
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• 2019

It is essential to predict the radioactivity distribution around the reactor cooling system (RCS) during obligatory cyclic operation of AP-1000. A home-developed program CPA-AP1000 is upgraded to predict the response of activated corrosion products (ACPs) in the RCS. The program is written in MATLAB and it uses state of the art MCNP as a subroutine for flux calculations. A pair of cyclic power profiles were superimposed after initial full power operation. The effect of cyclic operation is noticed to be more prominent for in-core surfaces, followed by the primary coolant and out-of-core structures. The results have shown that specific activity trends of $^{56}Mn$ and $^{24}Na$ promptly follow the power variations, whereas, $^{59}Fe$, $^{58}Co$, $^{99}Mo$ and $^{60}Co$ exhibit a sluggish power-following response. The investigations pointed out that promptly power-following response of ACPs in the coolant is vital as an instant radioactivity source during leakage incidents. However, the ACPs with delayed power-following response in the out-of-core components are perceived to cause a long-term activity. The present results are found in good agreement with those for a reference PWR. The results are useful for source term monitoring and optimization of work procedures for an innovative reactor design.

• 한국가스학회:학술대회논문집
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• 2001.10a
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• pp.58-68
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• 2001

Microbiologically influenced corrosion (MIC) of carbon steel gas pipeline in soil environments was investigated at field and laboratory MIC is very severe corrosion and it is not easy to distinguish this corrosion from Inorganic corrosion because of its localized, pitting-type character Therefore, it is important to provide proper assessment techniques for the prediction, detection, monitoring and mitigation of MIC. It is possible to predict the MIC risk, i.e., the activity of sulfate-reducing bacteria (SRB) through the analysis of soil environments. Chemical, microbiological and surface analysis of corrosion products and metal attacked could reveal the possibility of the occurrence of MIC. Various electrochemical and surface analysis techniques could be used for the study of MIC. Among these techniques, thin-film electrical resistance (ER) type sensors are promising to obtain localized corrosion rate of MIC induced by SRB. It is also important to study the effect of cathodic protection (CP) on the MIC In case of coated pipeline, the relationship between coating disbondment and the activity of SRB beneath the disbanded coating is also important.

• Nuclear Engineering and Technology
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• v.24 no.1
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• pp.52-62
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• 1992

Radioactive nuclides deposited on out-of-core surface after the radiation in the core by the transport of corrosion products (CRUD) through the primary coolant system in PWR which is the major plant type in Korea, are leading sources of radiation exposure to plant maintenance personnel. Thus, the optimal chemistry operation method is required for the reduction of radiation exposure by the corrosion products. This study analysed the actual water chemistry operation data of four operating domestic PWRs. And in order to evaluate the coolant chemistry operation data, a computer code which can calculate the activity buildup in the various chemistry conditions of PWR coolant was employed. Through the analysis of comparison between the activity buildup of actual water chemistry operation mode and that of assumed Elevated Li operation mode calculated by the computer code, it was found that the out-of core radioactivity can be reduced by diminishing the deposition of corrosion products on the core in case that the Elevated Li operation mode is applied to the coolant chemistry operation of PWR. And the higher coolant pH operation was shown to have the advantage of the reduction of out-of-core activity buildup if the integrity of system structural materials and fuel cladding is guaranteed.

• Corrosion Science and Technology
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• v.19 no.6
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• pp.326-336
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• 2020

Galvalume steel (GL) is widely used in marine and industrial environments. It is characterized by better corrosion resistance than carbon steel. However, corrosion and economic losses may occur as the usage time is increased. Therefore, in this study, an outdoor exposure test of GL for 36 months was conducted across six regions of Korea. Parameters such as corrosion rate, chrominance (color, chroma, and brightness), glossiness, and surface appearance were analyzed. The results showed no significant change in appearance, and the initial corrosion rate was large, but a tendency to decrease with time was observed. Increased outdoor exposure time led to increase in the level of corrosion products. In the case of coastal areas where S, Cl, and other elements were detected, a relatively high decrease in Zn content was observed. Al forms a protective oxide film and exists in the coating layer, but Zn dissolves due to its chemical activity and low potential.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.38 no.3
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• pp.259-267
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• 2014

Fatigue tests were performed in various simulated body environments reflecting various factors (such as body fluids, artificial saliva) relevant within a living body. First, the fatigue limit under a simulated body environment (artificial saliva) was evaluated and the governing factors of implant fatigue strength were looked into by observing the fracture mode. The fatigue life of an implant decreased in the artificial saliva environment compared with that in the ringer environment. Furthermore, in the artificial saliva environment, the implant fracture mode was fatigue failure of fixture as opposed to the abutment screw mode in the ringer environment. In the fatigue test, corrosion products were observed on the implant in the simulated body environment. A larger amount of corrosion products were generated on the artificial saliva specimen than on the ringer specimen. It is thought that the stronger corrosion activity on the artificial saliva specimen as compared with that on the ringer specimen led to an overall decrease of fatigue life of the former specimen. In the case of the implant with a nitrided abutment screw eliminated hardened layer (TixN), a several times increase in fatigue life is achieved in comparison with tungsten carbide-coated implants.

• Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
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• v.12 no.3
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• pp.211-216
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• 2014

Corrosion products are released to the primary coolant in the corrosion process of structural materials. They are deposited on fuel surfaces and activated on exposure to a neutron flux with formation of radionuclides that can become incorporated into out-of-core surface films. To get a clear understanding of activated crud formation process, the specific activity and core residence time of fuel cruds was calculated as a function of exposure time to the core neutron flux on the assumption that parent nuclide is being deposited continuously. Fuel cruds were sampled in the fuel scraping campaign from Hanul Unit 1 Cycle 17 and analyzed for elemental concentration and radioisotope activity.

• Corrosion Science and Technology
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• v.23 no.2
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• pp.139-144
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• 2024

Recently, due to the rapid spread and continuation of COVID-19, customer demand for health and hygiene has increased, requiring the development of new products that express antiviral and antibacterial properties. In particular, viruses are much smaller in size than bacteria and have a fast propagation speed, making it difficult to kill. POSCO has developed eco-friendly PCM color coated steel sheets with excellent antiviral properties by introducing inorganic composite materials to the color coating layer on the surface of Zn-Al-Mg alloy plated steels. The virus is not only destroyed by adsorption of metal ions released from the surface of the coating film, but is also further promoted by the generation of reactive oxygen species by the reaction of metal ions and moisture. As a result of evaluating the developed products under the International Standard Evaluation Act, the microbicidal activity was 99.9% for viruses, and 99.99% for bacteria and 0% fungi. In particular, excellent results were also shown in the durability evaluation for life cycle of the product. The developed product was applied as a wall of school classrooms and toilets and ducts for building air conditioning, resulting in excellent results. Developed products are being applied for construction and home appliances to practice POSCO's corporate citizenship.

• Advances in nano research
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• v.15 no.4
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• pp.355-366
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• 2023

Biological corrosion, a crucial aspect of metal degradation, has received limited attention despite its significance. It involves the deterioration of metals due to corrosion processes influenced by living organisms, including bacteria. Soil represents a substantial threat to pipeline corrosion as it contains chemical and microbial factors that cause severe damage to water, oil, and gas transmission projects. To combat fouling and corrosion, corrosion inhibitors are commonly used; however, their production often involves expensive and hazardous chemicals. Consequently, researchers are exploring natural and eco-friendly alternatives, specifically nano-sized products, as potent corrosion inhibitors. This study aims to environmentally synthesize silver nanoparticles using an extract from Lagoecia cuminoides L and evaluate their effectiveness in preventing biological corrosion of buried pipes in soil. The optimal experimental conditions were determined as follows: a volume of 4 ml for the extract, a volume of 4 ml for silver nitrate (AgNO3), pH 9, a duration of 60 minutes, and a temperature of 60 degrees Celsius. Analysis using transmission electron microscopy confirmed the formation of nanoparticles with an average size of approximately 28 nm, while X-ray diffraction patterns exhibited suitable peak intensities. By employing the Scherer equation, the average particle size was estimated to be around 30 nm. Furthermore, antibacterial studies revealed the potent antibacterial activity of the synthesized silver nanoparticles against both aerobic and anaerobic bacteria. This property effectively mitigates the biological corrosion caused by bacteria in steel pipes buried in soil.

• Nuclear Engineering and Technology
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• v.55 no.10
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• pp.3543-3548
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• 2023

Shutdown chemistry evolution is performed in nuclear power plants at each refueling outage (RFO) to establish safe conditions to open system and minimize inventory of corrosion products in the reactor coolant system (RCS). After hydrogen peroxide is added to RCS during shutdown chemistry evolution, corrosion products are released and are removed by filters and ion exchange resins in the chemical volume control system (CVCS). Shutdown chemistry evolution including RCS clean-up time to remove released corrosion products impacts the critical path schedule during RFOs. The estimation of clean-up time prior to RFO can provide more reliable actions for RCS clean-up operations and transients to operators during shutdown chemistry. Electric Power Research Institute (EPRI) shutdown calculator (SDC) enables to provide clean-up time by Co-58 peak activity through operational data from nuclear power plants (NPPs). In this study, we have investigated the results of EPRI SDC by shutdown chemistry data of Co-58 activity using NPP data from previous cycles and modeled the estimated clean-up time by EPRI SDC using average Co-58 activity of the NPP. We selected two RFO data from the NPP to evaluate EPRI SDC results using the purification time to reach to 1.3 mCi/cc of Co-58 after hydrogen peroxide addition. Comparing two RFO data, the similar purification time between actual and computed data by EPRI SDC, 0.92 and 1.74 h respectively, was observed with the deviation of 3.7-7.2%. As the modeling the estimated clean-up time, we calculated average Co-58 peak concentration for normal cycles after cycle 10 and applied two-sigma (2σ, 95.4%) for predicted Co-58 peak concentration as upper and lower values compared to the average data. For the verification of modeling, shutdown chemistry data for RFO 17 was used. Predicted RCS clean-up time with lower and upper values was between 21.05 and 27.58 h, and clean-up time for RFO 17 was 24.75 h, within the predicted time band. Therefore, our calculated modeling band was validated. This approach can be identified that the advantage of the modeling for clean-up time with SDC is that the primary prediction of shutdown chemistry plans can be performed more reliably during shutdown chemistry. This research can contribute to improving the efficiency and safety of shutdown chemistry evolution in nuclear power plants.