• Journal of the Korea Concrete Institute
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• v.20 no.4
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• pp.469-475
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• 2008

It is obvious that chloride penetration through cracks can threaten the durability of concrete substantially, according to the previous studies of author. It was proposed that crack depth corrseponded with critical crack width from the surface is a crucial factor in view of durability design of concrete structures. It is now necessary to deal with chloride penetration through microcracks characterized with the mixing features of concrete. The purpose of this study is examining the effect of mix proportional features of concrete such as coarse aggregate, high strengtherize of concrete and reinforcement of steel fiber on chloride penetration through cracks. Although small size of coarse aggregate can lead to many microcracks in concrete, the cracks should not impact on chloride penetration directly. On the contrary, chloride should penetrate through cracks easily in concrete with a large size of coarse aggregate because mixrocracks are connected to each other. Second, high strength concrete has an excellent performance to resist with chloride penetration. However, for cracked high strength concrete, its performance is reduced upto the level of ordinary concrete. Finally, steel fiber reinforcement is effective to reduce chloride penetration through cracks because steel fiber reinforcement can lead to reduce crack depth significantly.

• Journal of the Korea Concrete Institute
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• v.19 no.6
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• pp.707-715
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• 2007

The vulnerability of concrete to its environment is significantly dependent on the fact that concrete is a porous material. For well-consolidated and well-cured concrete, its service life is a very long and an entrance of aggressive substance might be only pores. However, for cracked concrete, cracks should be preferential channel for the penetration of aggressive substance such as chloride ions. The effect of crack on chloride penetration depends on its size for example, crack width and crack depth. The purpose of this study is examining the effect of crack width and crack depth on chloride penetration. In order to visualize chloride penetration via cracks, RCM (rapid chloride migration) testing is accomplished. Crack width is examined using an optical microscope and CMOD value is used to estimate average crack width. From the examination on the trend of chloride diffusion coefficients of concrete specimens with various crack widths, a critical crack width and a critical crack depth are found out.

• Nuclear Engineering and Technology
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• v.23 no.3
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• pp.299-305
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• 1991

Corrosive environment may be generated within steam generators from condenser cooling water in-leakage. Theoretical analysis of the accumulation of chloride as a sea water impurity is being carried out for the condenser cooling water used at YGN-1,2 nuclear power stations. Calculations have shown that highly concentrated chloride solution would be produced within the steam generators in the case of sea water in-leakage. Maximum allowable design condenser leak rate(0.5 gpm) leads chloride concentration of 2.3 ppm at steam generetor and 0.6 ppm at hotwell with the maximum blowdown rate and condensate purification. Concentration factor at steam generator is dependent only on both blowdoum rate and condensate purification efficiency as follows, Concentration Factor（equation omitted）(B$\neq$O) Blowdown and condensate purification are evaluated as the only effective measures to remove impurities from the secondary systems.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.7 no.3
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• pp.61-69
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• 1987

In water treatment, prechlorination is often carried out to solve the troubles caused by Algae, but produces by-products that are known to be harmfull to human health. In this study, chlorine and chlorine dioxide used for algae removal process were compared in producing trihalomethanes and haloacetonitriles to study the possibilities in using chlorine dioxide as a alternative for chlorine. The raw water used for the study had 10,790 algae cells per one milliliter and Ankistrodesmus sp. were the most common.

• Journal of Korean Society of Environmental Engineers
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• v.37 no.1
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• pp.7-13
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• 2015

In this study, the effective treatment reducing geosmin and dosage of PAC was suggested when taste & odor compounds flow in. The removal efficiency of geosmin was evaluated with types of chlorination. In case of low geosmin concentration below 25 ng/L, removal efficiency of geosmin was estimated at 46% by combined treatment of pre and intermediate-chlorination. But, in the exclusive intermediate-chlorination treatment, removal efficiency of geosmin was increased to 57%. In the medium geosmin concentration (25~79 ng/L), removal efficiency of geosmin was estimated at 59% by combined treatment. But, in the exclusive intermediate-chlorination treatment, removal efficiency of geosmin was increased to 87%. When high geosmin concentration above 80 ng/L flows in, removal efficiency of geosmin was estimated at 69% by combined treatment. However, in the exclusive intermediate-chlorination treatment, removal efficiency of geosmin was increased to 95%. Then, the exclusive intermediate-chlorination has an important effect on removal of geosmin. After correlation of geosmin concentration and dosage of PAC was analyzed, the coefficient of determination was estimated at 0.96. And, the proper PAC dosage chart was proposed. Also, at a initial occurrence of geosmin, when the combined treatment by intermediate-chlorination and PAC was applied, particle-bound geosmin should be removed continuously. Finally, it is proved that the combined treatment was effective to remove the geosmin by threshold levels as well as to reduce the dosage of PAC.

• Polymer(Korea)
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• v.37 no.5
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• pp.553-556
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• 2013

Chlorine dioxide gas has an excellent ability for sterilization and deodorization, and is harmless to humans. However, it is very unstable and explosive as it is highly concentrated, thus its use in the air clean fields has been limited. Therefore, there is need to control chlorine dioxide gas at a low concentration for a long time. Chlorine dioxide gas could be produced slowly and sustainedly since the release of acetic acid from the polymer hydrogels delayed the reaction between acetic acid and sodium chlorite. In addition, as the amount of both acetic acid sodium chlorite loaded within the hydrogel and on the membrane increased, respectively, the generation amount of chlorine dioxide gas increased. The result shows that the use of polymer hydrogels has the potential to control the generation of chlorine dioxide gas.

• Journal of the Korea Concrete Institute
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• v.17 no.2 s.86
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• pp.179-189
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• 2005

Corrosion of steel due to chloride attack is a major concern in reinforced concrete structures which are located in the marine environments. In this case, Fick's 2nd law has been used for the prediction of chloride diffusion related with service life of concrete structures. However, those studies were confined mostly to the single deterioration due to chloride only, although actual environment is rather of combined type. The purpose of the present study is, therefore, to explore the influences of carbonation to chloride attack in concrete structures and to investigate the validity of Fick's law to chloride attack combined carbonation. The test results indicate that the chloride ion profiles from Fick's law using the diffusion coefficient of immersion tests is not reflected the effect of separation of chloride ions in carbonation region but valid in sound region in case of combined action. On the other hand, the chloride ion profiles from Fick's law using the diffusion coefficient of Tang and Nilsson's method coincide with test results under dry-wet condition but not under combined condition. The results of present study may Imply that the new method for the measurement of diffusion coefficient is required to predict the chloride ion profiles in case of combined action at early.

• Journal of the Korean Institute of Gas
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• v.11 no.4
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• pp.98-103
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• 2007

Likelihood analysis was used for the revision of release probability/frequency in chlorine Injection facilities used in chlorine process. Typically these facilities consist of pressure cylinder, vaporizer, pipeline, measuring equipment and safety equipment. This paper described the incident scenarios considered, likelihood analysis procedure and the selection and application of basic events and for failure rates of mechanical components. Human errors were also considered. The major objective of this paper is to estimate the likelihood of each determined incident scenarios. We estimated failure rates of mechanical components based on likelihood analysis procedure. Human errors were also considered. It was estimated to have $5.73{\times}10^{-5}$ $Cl_2$ leak per year during the major $Cl_2$ handling process. The probability of failure in scrubber system was$4.11{\times}10^{-2}$/demand.

• Journal of the Korean Institute of Gas
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• v.21 no.3
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• pp.46-52
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• 2017

During the transportation of chemicals, quantitative risk assessment for chemical leakage accidents caused by traffic accidents was carried out and the appropriateness of chemical transportation route was evaluated. The quantitative risk assessment method applied to the chemical leakage accidents that may occur in the chemical handling equipments installed in the workplace was presented and applied to the chemical transportation. By analyzing the number of traffic accidents in transportation vehicles, the probability of chemical leakage accidents during chemical transportation was predicted and applied to the quantitative risk assessment of chlorine gas leakage accidents that may occur when transporting liquified chlorine bombe using vehicles. As a result, the most appropriate route of transporting the liquefied chlorine bombe was suggested on the basis of risk.

• Journal of Bio-Environment Control
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• v.28 no.2
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• pp.166-171
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• 2019

This study was conducted to investigate the effect of gaseous chlorine dioxide ($ClO_2$) concentration and treatment method for maintaining marketability in strawberries 'Maehyang' for export. After harvesting strawberry colored with $60{\pm}5%$ of the skin, and the gaseous $ClO_2$ was applied as four treatments in the cold store set with $10^{\circ}C$ which were as follows: i) non-treatment (Control), ii) $0.2mg{\cdot}L^{-1}$ for 30 minutes, iii) $0.4mg{\cdot}L^{-1}$ for 30 minutes, and iv) continuously exposed at $0.4mg{\cdot}L^{-1}$ during the storage period. Weight loss, firmness, soluble solids content, color, incidence of gray mold, and quality grade of strawberries were investigated every 3 days during 16 days storage in cold store. The weight loss was consistently high at $0.2mg{\cdot}L^{-1}\;ClO_2$ treatment, and the weight loss was lower than other treatments when gaseous $ClO_2$ was continuously treated. Firmness was significantly higher at 0.2 and $0.4mg{\cdot}L^{-1}$ $ClO_2$ treatment on the 13th day of storage. Soluble solids content tended to below in continuous gaseous $ClO_2$ treatment. The colors showed no tendency as affected by concentrations and treatment methods of gaseous $ClO_2$. No gray mold was observed in the continuous gaseous $ClO_2$ treatment until the 13th day of storage. The quality grade was lower in gaseous $ClO_2$ treatment group than in the control. As a result, it was possible to decrease the weight loss and the incidence of gray mold by continuously treating the gaseous $ClO_2$ to strawberry 'Maehyang' for export during the storage period after harvest. However, further research is needed on method to maintain quality grades of fruits.