• Journal of the Korean Society for Nondestructive Testing
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• v.33 no.5
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• pp.465-471
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• 2013

A steam generator in nuclear power plant is a heatexchager which is used to convert water into steam from heat produced in a nuclear reactor core, and the steam produced in steam generator is delivered to the turbine to generate electricity. Because of damage to steam generator tubing may impair its ability to adequately perform required safety functions in terms of both structural integrity and leakage integrity, eddy current testing is periodically performed to evaluate the integrity of tubes in steam generator. This assessment is normally performed during a reactor refueling outage. Currently, the eddy current testing for steam generator of nuclear power plant in Korea is performed in accordance with KEPIC & ASME Code requirements, the eddy current testing system is consists of remote data acquisition unit and data analysis program to evaluate the acquired data. The KEPIC & ASME Code require that the electrical properties of remote data acquisition unit, such as total harmonic distortion, input & output impedance, amplifier linearity & stability, phase linearity, bandwidth & demodulation filter response, analog-to-digital conversion, and channel crosstalk shall be measured in accordance with the KEPIC & ASME Code requirements. In this paper, the measurement requirements of electrical properties for eddy current testing instrument described in KEPIC & ASME Code are presented, and the measurement results of newly developed eddy current testing instrument by KHNP(Korea Hydro & Nuclear Power Co., LTD) are presented.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.38 no.12
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• pp.1421-1426
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• 2014

To improve the inherent safety of the sodium-cooled fast reactor (SFR), the supercritical $CO_2$ ($S-CO_2$) Brayton cycle is being considered as an alternative power conversion system to steam the Rankine cycle. In the $S-CO_2$ system, a PCHE (printed circuit heat exchanger) is being considered. In this type of heat exchangers, diffusion bonding is used for joining the thin plates. In this study, the diffusion bonding characteristics of various austenitic alloys were evaluated. The tensile properties were measured at temperatures starting from the room temperature up to $650^{\circ}C$. For the 316H and 347H types of stainless steel, the tensile ductility was well maintained up to $550^{\circ}C$. However, the Incoloy 800HT showed lower strength and ductility at all temperatures. The microstructure near the bond line was examined to understand the reason for the loss of ductility at high temperatures.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.35 no.12
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• pp.1285-1292
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• 2011

The characteristics of a semiconductor chiller system with EEV have been experimentally studied. Three experiments on temperature changes (increase and decrease), load variation, and control precision were conducted to investigate the operating characteristics of the semiconductor chiller. The power consumption was 8.9 kW during increase in temperature. The required time was 37.5 min for CH1 and 39.5 min for CH2. Moreover, the time required for falling temperature was 26.5 min. The control precision for partial load operation was relatively low compared to that of a full load operation. In addition, the CH2 equipped with a step motor showed better control precision. The power consumed by the chiller for process cooling water was 1.8 kW, which was one-half of that consumed during the refrigeration cycle. The objective of this study is to provide an optimal control guideline for the semiconductor chiller design.

• Journal of Chest Surgery
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• v.34 no.6
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• pp.465-471
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• 2001

Background: Hypothermia protects the brain by suppressing the cerebral metabolism and it is performed well enough before the total circulatory arrest(TCA) in the operation of aortic disease. Generally, TCA has been performed depending on the rectal or nasopharyngeal temperatures; however, there is no definite range of optimal temperature for TCA or an objective indicator determining the temperature for safe TCA. In this study, we tried to determine the optimal range of temperature for safe hypothermic circulatory arrest by using the intraoperative electroencephalogram(EEG), and studied the role of EEG as an indicator of optimal hypothermia. Material and Method: Between March, 1999 and August 31, 2000, 27 patients underwent graft replacement of the part of thoracic aorta using hypothermia and TCA with intraoperative EEG. The rectal and nasopharyngeal temperatures were monitored continuously from the time of anesthetic induction and the EEG was recorded with a ten-channel portable electroencephalography from the time of anesthetic induction to electrocerebral silence(ECS). Result: On ECS, the rectal and nasopharyngeal temperatures were not consistent but variable(rectal 11$^{\circ}C$ -$25^{\circ}C$, nasopharynx 7.7$^{\circ}C$ -23$^{\circ}C$). The correlation between two temperatures was not significant(p=0.171). The cooling time from the start of cardiopulmonary bypass to ECS was also variable(25-127min), but correlated with the body surface area(p=0.027). Conclusion: We have found that ECS appeared at various body temperatures, and thus, the use of rectal or nasopharyngeal temperature were not useful in identifying ECS. Conclusively, we can not fully assure cerebral protection during hypothermic circulatory arrest in regards to the body temperatures, and therefore, the intraoperative EEG is one of the necessary methods for determining the range of optimal hypothermia for safe circulatory arrest. :

• Journal of the Korean Society of Propulsion Engineers
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• v.22 no.1
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• pp.52-57
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• 2018

This paper presents the design and cold flow test results of oxidizer-rich preburner injectors for a 9 tonf-class staged combustion engine cycle. Three types of coaxial swirl injectors were designed, and 12 injectors were designed for each type. The diameters of the fuel tangential holes are identical. The diameters of the oxidizer tangential holes were varied to investigate the influence of combustion in the oxidizer-rich preburner according to the momentum ratio of the gas oxidizer generated from combustion in the injector chamber and liquid oxidizer through the cooling channel. It will be verified through a powerpack and combustion test using an oxidizer-rich preburner. In the cold flow test, the fuel flow rate and oxidizer tangential hole flow rate reached the target value based on the designed differential pressure.