• The Journal of the Korea Contents Association
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• v.10 no.10
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• pp.68-77
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• 2010

In the case of operating steam generators for long periods in nuclear power plants, sludge is accumulated inside the steam generator. This phenomenon could adversely affect the operation of the steam generator. This paper is about the design of a sludge washing apparatus which can remove the sludge efficiently and the control methods of the apparatus. In this paper, to design the sludge washing apparatus, firstly, we design nozzles for spraying high-pressure water through applying mathematical models and lab tests. Secondly, we establish the mathematical theory for performance parameters required to drive the sludge washing apparatus. Thirdly, we design physical structures of the apparatus based on the established performance parameters. Finally, we present the control methods of the apparatus. The sludge washing apparatus presented in this paper moves along the walls of the steam generator according to cracks in the tube array, and spray the high pressure water to remove the sludge. By this way, a relatively large amount of sludge formed in the inner surfaces can be washed very effectively.

• Journal of Mechanical Science and Technology
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• v.14 no.4
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• pp.456-465
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• 2000

An experiment was conducted to investigate the aerodynamic losses of high pressure steam turbine nozzle (526A) subjected to a large range of incident angles ($-34^{\circ}\;to\;26^{\circ}$) and exit Mach numbers (0.6 and 1.15). Measurements included downstream Pitot probe traverses, upstream total pressure, and end wall static pressures. Flow visualization techniques such as shadowgraph and color oil flow visualization were performed to complement the measured data. When the exit Mach number for nozzles increased from 0.9 to 1.1 the total pressure loss coefficient increased by a factor of 7 as compared to the total pressure losses measured at subsonic conditions ($M_2<0.9$). For the range of incidence tested, the effect of flow incidence on the total pressure losses is less pronounced. Based on the shadowgraphs taken during the experiment, it' s believed that the large increase in losses at transonic conditions is due to strong shock/ boundary layer interaction that may lead to flow separation on the blade suction surface.

• Proceedings of the KIEE Conference
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• 2008.07a
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• pp.1663-1664
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• 2008

Many years ago, most of thermal power plants built in this country were of subcritical pressure, of medium or small size, of constant pressure operations and of drum type steam generators with circulation type boilers. But, nowadays almost all of them were of high efficiency, of supercritical pressure, of big capacity, of sliding pressure operations, and of once through type steam generators. Presently built once through boilers introduce turbine bypass systems to variable pressure operation which eliminates unexpected materials in boiler tube during startup, minimizes fuel loss by short startup period and eventually improve both total efficiency and power system stability.

• Journal of Advanced Marine Engineering and Technology
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• v.15 no.5
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• pp.30-37
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• 1991

Steam ejector systems are widely used for the evacuation systems because of their high working confidence and simlicity. And recently these are used as the thermo-compressors in various energy saving systems. In this practical experiment, we have obtained the results as follows : (1) The velocity coefficient of the motive steam nozzle was 0.92-0.98. (2) The optimal area ratio was 0.00625 at pressure ratio 5.2 and expansion ratio 101.3. (3) The performance and efficiency of the steam ejector were mainly affected by the axial position of nozzle. (4) The good performance of the domestic manufactured steam ejector was confirmed in comparison with the foreign one. And by experimental results, we have carried out the improvement of Computer Aided Design Program of steam ejector which will be helpful for systematic research into the steam ejector.

• 한국신재생에너지학회:학술대회논문집
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• 2009.06a
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• pp.720-722
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• 2009

This work is mainly focused at developing the hydrogen production unit with the capacity of 20 $Nm^3/h$ of high purity hydrogen. At present steam reforming of natural gas is the preferable method to produce hydrogen at the point of production cost. The developed hydrogen production unit composed of natural gas reformer and pressure swing adsorption system. To improve the thermal efficiency of steam reforming reactor, the internal heat recuperating structure was adopted. The heat contained in reformed gas which comes out of the catalytic beds recovered by reaction feed stream. These features of design reduce the fuel consumption into burner and the heat duty of external heat exchangers, such as feed pre-heater and steam generator. The production rate of natural gas reformer was 41.7 $Nm^3/h$ as a dryreformate basis. The composition of PSA feed gas was $H_2$ 78.26%, $CO_2$ 18.49%, CO 1.43% and $CH_4$ 1.85%. The integrated production unit can produce 21.1 $Nm^3/h$ of high-purity hydrogen (99.997%). The hydrogen production efficiency of the developed unit was more than 58% as an LHV basis.

• Transactions of the Korean Society of Pressure Vessels and Piping
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• v.10 no.1
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• pp.7-14
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• 2014

There has been extensive experience associated with the operation of SGs wherein it was believed, based on NDE, that throughwall tube indications were present within the tubesheet. The installation of the SG tubes usually involves the development of a short interference fit, referred to as the tack expansion, at the bottom of the tubesheet. The tack expansion was usually effected by a hard rolling process and thereafter, in most instance, by the expansion of a urethane plug inserted into the tube end and compressed in the axial direction. The rolling process by its very nature is considered to be intensive with regard to metalworking at the inside surface of the tube and would be expected to lead to higher residual surface stresses. Alternate repair criteria(ARC) in the tack expansion area have been developed and applied to nuclear power plants in USA, however domestic nuclear power plants have not applied ARC for tubes in tubeheet area yet. In consideration of the degradation characteristics of tubes in the Steam Generator tubesheet, this paper suggests ARC application for tubes in the steam generator tubesheet of the domestic nuclear power plants in order to assure life time of the steam generator as well as nuclear power plants.

• Transactions of the Korean Society of Pressure Vessels and Piping
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• v.9 no.1
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• pp.40-47
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• 2013

The capacity factor of nuclear power plant in Korea is the highest level in the world. However, the integrity assessment of nuclear power plant is depended on foreign country. Especially, most eddy current testing systems for inspecting steam generators in nuclear power plant are currently imported from USA, Canada, and so on. Therefore, the eddy current testing system can react more active and adaptive from economic and managerial standpoint for actual nuclear power plants in Korea is required. In this paper, an eddy current testing system for inspecting steam generators in nuclear power plants is introduced. Frequency generator, analog circuit, analog digital converter circuit, and digital control circuit are composed in eddy current testing system. A benchmarking of acquisition system and acquisition software, eddynet 11i made by Zetec, and modifications are carried out based on the test environment of Korea nuclear power plants. Finally, all eddy current apparatus are integrated to inspect steam generator tubes in nuclear power plants.

• Proceedings of the KSME Conference
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• 2002.08a
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• pp.835-838
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• 2002

An experiment has been performed using a facility, which simulates the safety depressurization system (SDS) and in-containment refueling water storage tank (IRWST) of APR1400, an advanced PWR being developed in Korea, to investigate the dynamic load resulting from the blowdown of steam from a steam generator through a sparser. The influence of the key parameters, such as air mass, steam pressure, submergence, valve opening time, and pool temperature, on frequency and peak toads was investigated. The blowdown phenomenon was analyzed to find out the real cause of the initiation of bubble oscillation and discrepancy in frequencies between the experiment and calculation by conventional equation for bubble oscillation. The cause of significant damping was discussed and is presumed to be the highly tortuous flow path around bubble. The Rayleigh-Plesset equation, which is modified by introducing method of image, reasonably reproduces the bubble oscillation in a confined tank. Right after the completion of air discharge the steam discharge immediately follows and it condenses abruptly to provide low-pressure pocket. It may contribute to the negative maximum being greater than positive maximum. The subsequently discharging steam does not play as at the driving force anymore.

• Transactions of the Korean Society of Pressure Vessels and Piping
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• v.11 no.2
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• pp.13-19
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• 2015

Steam generator is one of the most important component of nuclear power plant, and it's integrity and reliability are to be assured to high level by pre-service inspection and in-service inspection. To improve the reliability of steam generator heat exchanger tubes and to secure the management of nuclear power plant safely, KHNP CRI recently has developed eddy current testing system for steam generator. KHNP CRI have performed a series of experimental verification and field application to confirm the performance of the developed ECT system in accordance with ASME Code requirements. The ECT system consists of a remote data acquisition unit, an ECT signal acquisition and analysis software, a water chamber robot controller and a probe push-puller. In this paper, we will details of the developed ECT system and the software and their experimental performance. And also we will report the field applying performance and the issues for further steps.

• Journal of the Korean institute of surface engineering
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• v.42 no.3
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• pp.139-144
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• 2009

A microwave plasma torch at the atmospheric pressure by making use of magnetrons operated at the 2.45 GHz and used in a home microwave oven has been developed. This electrodeless torch can be used to various areas, including industrial, environmental and military applications. Although the microwave plasma torch has many applications, we in the present work focused on the microwave plasma torch operated in pure steam and several applications, which may be used in future and right now. For example, a high-temperature steam microwave plasma torch may have a potential application of the hydrocarbon fuel reforming at one atmospheric pressure. Moreover, the radicals including hydrogen, oxygen and hydroxide molecules are abundantly available in the steam torch, dramatically enhancing the reaction speed. Also, the microwave plasma torch can be used as a high-temperature, large-volume plasma burner by injecting hydrocarbon fuels in gas, liquid, and solid into the plasma flame. Finally, we briefly report treatment of soils contaminated with oils, volatile organic compounds, heavy metals, etc., which is an underway research in our group.