• Nuclear Engineering and Technology
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• v.53 no.10
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• pp.3319-3326
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• 2021

As a form of industrial control systems (ICS), nuclear instrumentation and control (I&C) systems have been digitalized increasingly. This has raised in turn cyber security concerns. Cyber security for ICS is important because cyber-attacks against ICS can cause not only equipment damage and loss of production but also personal and public safety hazards unlike in general IT environments. Numerous risk analyses have been carried out to enhance the safety of ICS and recently, many studies related to the cyber security of ICS are being conducted. Many existing risk analyses and cyber security studies have considered safety and cyber security separately. However, both safety and cyber security perspectives should be considered when analyzing risks for complex and critical ICS facilities such as nuclear power plants (NPPs). In this paper, the STPA-SafeSec methodology is selected to consider both safety and security perspectives when performing a risk analysis for NPPs in order to assess impacts on the safety by cyber-attacks against the digital I&C systems. The STPA-SafeSec methodology was applied to a test-bed system that simulates a condensate water (CD) system in an NPP. The process of the application up to the development of mitigation strategies is described in detail.

• Proceedings of the Korean Society of Marine Engineers Conference
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• 2002.05a
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• pp.29-34
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• 2002

As the makeup water entering the boiler feed water cycle usually contains corrosive gases, particularly oxygen and carbon dioxide, so the corrosive gases should be eliminated by a deaerator. While the other domestic companies have made a deaerator for land industrial field, our company has developed and is able to produce a spray & scrubber type deaerator for marine to maintain below the level of 7ppb of dissolved oxygen in the condensate. In this paper, we describe the principle, design technique and experimntal results of the spray & scrubber type deaerator.

• Magazine of the Korea Concrete Institute
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• v.7 no.5
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• pp.189-199
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• 1995

Naphthalene sulfonated condensate has been widely used as a superplasticizer for cement and concrete, but the application was limited due to its large slump loss with elapsed time. To complement this demerit of NSF, polycarboxylic acid copolymer from nlaleic anhydride and acryl~c acid(MA) was synthesized to retain the mobility of cement and concrete, and then mixed with NSF. The physical properties, such as fluidity, fluidityretention and rheology, were measured by applying these admixtures to cement paste as a function of elapsed time. And also compressive strength of mortar was measured with curing time. NIv-l and NM-2 containing 10, 20 wt% of MA respectively had a excellent fluidity and a fluidity- retention. In rheological property, the increases of shear stress and viscosity with elapsed time were delayed with the increasing of shear rate in cornparision with NSF only. The marked slump loss of cement paste could be controlled by these admixture. Also the added ainount of admixture and the ratio of water to cement affected these properties.

• Proceedings of the Korean Society for Agricultural Machinery Conference
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• 2000.11c
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• pp.777-783
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• 2000

Composting by negative aeration is a reasonable proposition to control odor generated during composting process. Cattle manure and rice hulls mixtures were composted in a bin composting system by negative aeration. Continuous(CA) and intermittent(IA) aeration methods were applied to analyze the composting characteristics. The composting temperature and the ammonia emission during composting were investigated according to the aeration methods. The main problem for the negative aeration was the generation of condensate in the suction line of blower. The quantity of condensate was significant for continuous aeration. The aeration method should be modified to escape from the cooling effect of continuous aeration at the initial stage of composting. It took a longer time to finish a composting for intermittent aeration on account of lower aeration. It was concluded that the composting by negative aeration could be accomplished by either continuous or intermittent aeration method if the flow rate would be controlled more efficiently and the water vapor in suction line of blower could be removed effectively. Ammonia emission increased up to maximum value of 675ppm for continuous aeration while 300ppm for intermittent aeration. However, the cumulative value of ammonia emission was larger for intermittent aeration than for continuous aeration.

• Journal of the Korean Society of Tobacco Science
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• v.12 no.1
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• pp.3-7
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• 1990

Cigarette smoke is an aerosol consisted of both vapor and Particulate phases. In this study, the smoke condensates from several blended cigarettes were dissolved in water and the pH of the resulting solution was determined. The pH of the smoke condensate decreased with increase of puff number. In the beginning the pH decreased a little, while decreased remarkably from puff No.5 to puff No.10.

• Journal of Korean Society on Water Environment
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• v.22 no.3
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• pp.437-443
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• 2006

The Water usage is relationship which is close with the administrative cost from industrial facility. It is not easy to reduce a water usage. This research is the optimization of the waste water quantity which process waste water integration of the standard thermal power plant in system operate time. The turbine rotates by force of the steam and it produces an electricity. Demineralization Water is manufacture purity manufacturing equipment and it is supplied in power plant channel. We knew a possibility of reducing from pure control process. When it is reduced the Back Washing time, Rinsing time of the gravity filter and the activated carbon filter. Also, It is possible even from regeneration phase in Condensate Polishing Demineralization System. In addition, There is also the water which the drain of the sampling water for watching the condition of power plant process will be able to use. Integrates these processes it will be able to reduce an annual 30,000 ton degree. The research is want to use the fundamental data for the water curtailment of the power plant.

• Proceedings of the KIEE Conference
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• 2007.07a
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• pp.614-615
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• 2007

There are roughly a hundred types of cables in power plants. The distribution of circuits in a nuclear plant is comprised of 20% instrument cables, 61% control cables, 13% AC power cables, 1% DC power cables, and 5% communication lines. In the nuclear power plant, medium voltage cables are generally included in the scope of systems reviewed for safety and are included in a plant's maintenance program. Medium voltage cables provide power to many critical components in plants, including feed water pumps, circulating water pumps, and condensate pumps. Among these cables, high temperature sections of cables feeding electrical power to the circulating water pump and the condenser extraction pump were found. The evaluation for these cables is performed to find the maximum allowable current and temperature. The result shows that the load current flowed about 85% of the allowable current ampacity, and the temperature of conductor at full load current did not exceed the limited temperature. Therefore, existing cables for circulating water pump and condenser extraction pump system are going to be used during design life.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.9 no.3
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• pp.599-604
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• 2008

An experimental study has been performed to investigate the air-side capacity and pressure drop of the fin-tube heat exchanger for a fan coil unit under a cooling condition. The experimental data of five kinds of slit fin-tube heat exchangers were measured using an air-enthalpy calorimeter and a constant temperature water bath. Cooling capacities at the air and water rating flow rates were larger at the lower inlet water temperature. With increasing the water flow rate, the cooling capacity increased at the constant rate. Under the lower inlet water temperature, since the condensate was generated more on the fin-tube surface, the air-side pressure drop of the heat exchanger was larger.

• Nuclear Engineering and Technology
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• v.51 no.1
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• pp.60-72
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• 2019

The air-cooled passive decay heat removal system (APDHR) was proposed to provide the ultimate heat sink for non-LOCA accidents. The APDHR is a modified one of Passive Auxiliary Feed-water system (PAFS) installed in APR+. The PAFS has a heat exchanger in the Passive Condensate Cooling Tank (PCCT) and can remove decay heat for 8 h. After that, the heat transfer rate through the PAFS drastically decreases because the heat transfer condition changes from water to air. The APDHR with a vertical heat exchanger in PCCT will be able to remove the decay heat by air if it has sufficient natural convection in PCCT. We conducted the thermal-hydraulic simulation by the MARS code to investigate the behavior of the APR + selected as a reference plant for the simulation. The simulation contains two phases based on water depletion: the early phase and the late phase. In the early phase, the volume of water in PCCT was determined to avoid the water depletion in three days after shutdown. In the late phase, when the number of the HXs is greater than 4089 per PCCT, the MARS simulation confirmed the long-term cooling by air is possible under extended Station Blackout (SBO).

• Proceedings of the Korea Concrete Institute Conference
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• 1995.04a
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• pp.142-147
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• 1995

In this study, styrene-maleic anhydride copolymer (SMA) was synthesized from styrene and maleic anhydride and further reacted with sulfuric acid to obtain water-soluble SMA and the flow and strength tests of cement mortar mixed with copolymers were carried out to evaluate the capability of copolymers as high range water reducer for the concrete. It was found from flow experiment that the fluidity of cement mortar mixed with sulfonated SMA (SSMA) was larger than that miced with aminophenol-substituted SSMA (SmSMA). The decreasing rate of the flow of cement mortar mixed with SSMA and SmSMA was decreasing rate of the flow of cement mortar mixed with SSMA and SmSMA was significantly lower than that mixed with naphthalene condensate (NSC). The compressive strength of the hardened cement mortars containing 0.5% copolymers after 28 days curing was examined. The compressive strength of hardened cement mortar containing SSMA and SmSMA was increased up to 32% and 13%, respectively, when compared to the plain. As the results, the copolymers (SSMA and SmSMA) used in this study are greatly expected as a good high range water reducers for the concrete.