• Proceedings of the Korean Nuclear Society Conference
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• 1999.10a
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• pp.260.2-260
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• 1999

• Proceedings of the KSME Conference
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• 2004.04a
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• pp.66-71
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• 2004

Estimation of the CANDU pressure tube deflection is important since the deflection may cause significant structural failure due to hydrogen diffusion and blister. However, there is no appropriate engineering model to estimate it exactly. The purpose of this paper is to propose a new analysis method and program to resolve this issue. For development of proper analysis method, a series of finite element analyses has been carried under elastic-creep condition. In addition, for effective estimation of the creep deflection, an analysis program named PC-DAS was developed based on the proposed method. Comparison of simple case study results with corresponding reference ones showed good agreement. Therefore, the proposed method and program can be utilized as one of valuable toolkit for integrity assessment of CANDU pressure tube.

• Proceedings of the KSME Conference
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• 2000.11a
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• pp.843-848
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• 2000

The pressure tube is a major component of the CANDU reactor, which supports nuclear fuel bundle and it's containment vessel. If a flaw is found during the periodic inspection from the pressure tubes, the integrity evaluation must be carried out, and the safety requirements must be satisfied for continued service. In order to complete the integrity evaluation, complicated and iterative calculation procedures are required. Besides, a lot of data and knowledge for the evaluation are required for the entire integrity evaluation process. For this reason, an integrity evaluation system, which provides efficient way of evaluation with the help of attached databases, was developed. The developed system was built on the basis of ASME Sec. XI and FFSG(Fitness For Service Guidelines for zirconium alloy pressure tubes in operating CANDU reactors) issued by the AECL, and covers the delayed hydride cracking(DHC). Various analysis methods are provided for the integrity evaluation of pressure tube. In order to verify the developed system, several case studies have been performed and the results were compared with those from AECL. A good agreement was observed between those two results.

• Journal of Korea Foundry Society
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• v.18 no.5
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• pp.481-487
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• 1998

Shell sand is widely used to make a complex shape castings due to its good collapsibility. When molten metal is poured into the mold, various gases are generated by the thermal decomposition of binder in the shell core. Casting defects such as blow hole and blister come from these gases. If it is possible to predict the evolution of gas quantitatively, it may provide effective solutions for minimizing the casting defects. To examine the gas evolution by shell core quantitatively, casting experiment and calculation were carried out. Gas pressure and gas volume evolved by shell core were measured in the experiment, and temperature distribution in the shell core was obtained by heat transfer analysis. From the result above, prediction on the gas volume evolved during pouring was tried. As forming pressure of the shell core increased and forming temperature decreased, the gas evolution increased. There was a close relationship between the calculated gas volume evolved and the measured one.

• Journal of the Korean Society for Nondestructive Testing
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• v.23 no.4
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• pp.334-341
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• 2003

When the pressure tubes(f are in contact with the calandria tube(CT) in the pressurized heavy water reactor(PHWR), the temperature difference between inner and outer wall of W results in a thermal diffusion of hydrogen (deuterium) and hydride blisters are formed on the outer surface of PT. Because the hydride blisters and zirconium matrix are acoustically continuous, it is not easy to distinguish the blisters from the matrix with conventional ultrasonic method. An ultrasonic velocity ratio method was developed to detect small hydride blisters on the zirconium pressure tube. Hydride blisters were grown in the PT specimen using a steady state thermal diffusion device. The flight times of longitudinal echo and reflected shear echo from the outer surface were measured accurately. The velocity ratio of the longitudinal wave to the shear wave was calculated and displayed using contour plot. Compared to the conventional flight time method of longitudinal wave, the velocity ratio method shows superior sensitivity to detect smaller blisters as well as better images for the blister shapes. Detectable limit of the outer shape of the hydride blisters was conservatively estimated as $500{\mu}m$, with the same specifications of ultrasonic transducer used in the actual PHWR pressure tube inspection.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.24 no.1 s.173
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• pp.206-214
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• 2000

The pressure tube is a major component of the CANDU reactor, which supports nuclear fuel bundle and it's containment vessel. If a flaw is found during the periodic inspection from the pressure tube s. the integrity evaluation must be carried out. and the safety requirements must be satisfied for continued service. In order to complete the integrity evaluation, complicated and iterative calculation procedures are required. Besides, a lot of data and knowledge for the evaluation are required for the entire: integrity evaluation process. For this reason. an integrity evaluation system, which provides efficient of evaluation with the help of attached databases, was developed. The developed system was built on the basis of ASME Sec. XI and FFSG(Fitness For Service Guidelines for zirconium alloy pressure tubes in operating CANDU reactors) issued by the AECL, and covers the delayed hydride cracking(DHC). This system does not only provide various databases including the 3-D finite element analysis results on pressure tubes, inspection data and design specifications but also is compatible with other commercial database software. In order to verify the developed system, several case studies have been performed and the results were compared with those from AECL. A good agreement was observed between those two results.

• Journal of Korea Foundry Society
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• v.40 no.3
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• pp.66-75
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• 2020

The aim of this study was to optimize a solid solution treatment for a high pressure die casting Al-10Si-0.3Mg-0.6Mn alloy to avoid blistering and to improve the strength of the alloy. To achieve this goal, the number density of the blisters and the strength of the alloy under various solid solution treatment (SST) conditions were evaluated. The SST was performed at 470, 490, 510 and 530℃ for 20, 60, 120, 240 and 480 min on the alloy. The number density of the blisters increased with the increasing temperature and time of the SST and the defect area fraction. The yield strength of the alloy after the T6 heat treatment increased with the increasing SST temperature and time. Based on the results, it is suggested that SST should be performed at 510℃ within 60 min. or at 470 and 490℃ within 240 min. to avoid blistering and to improve the strength.

• Journal of Haehwa Medicine
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• v.10 no.2
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• pp.91-96
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• 2002

We arrived at the following conclusions after we have studied esophagitis through the literatures of oriental and western medicine. 1. The western medical causes of acute esophagitis are corrosiveness chemical material, esophageal or gastric disease, trauma, blister stomatitis, filamentous fungus infection and uremia of chronic patient etc, and the oriental medical causes are qi and blood stagnation, blood stasis and stagnation, stagnant phlegm by coldness, heating, dyspepsia and food poisoning etc. 2. The western medical causes of chronic esophagitis are malfunction of lower esophageal sphincter, esophageal tom chink and hernia, increase of gastric pressure by overeating, fatness, pregnancy and ascites etc, and the oriental medical causes are asthenic cardiac qi, hepatic qi attacking stomach by seven kinds of depression, cold-damp stagnation and insufficiency of gastric qi by overeating, excessive drinking and sexual indulgence etc. 3. The main symptoms of acute esophagitis are severe chest pain, instantly vomiting, swallowing pain etc, and chronic esophagitis are occasionally light chest pain, heart bum, anorexia, dysphagia, dizziness, general body weakness etc. These symptoms are come under thoracic obstruction, acid regurgitation, vomiting and chest pain of oriental medicine. 4. The western medical diagnoses of acute and chronic esophagitis have used radiation test, esophageal endoscopy, esophageal pressure test and biopsy etc, and the oriental medical diagnoses have used syndrome differentiation by four examination of inspection, listening and smelling examination, inquiring, pulse-taking and palpitation. 5. The western medical treatments of acute esophagitis have regarded preservation stability of esophagus as a principle, and the oriental medical treatments mainly have used expelling pathogen of expelling cold and regulating qi, cooling and removing stasis, promoting blood circulation to remove blood stasis, eliminating phlegm and regulating qi. 6. The western medical treatments of chronic esophagitis have regarded decrease flowing backward of gastric juice as a purpose, and the oriental medical treatments mainly have used strengthening body resistance of replenishing and strengthening cardioqi, dispersing stagnated hepatoqi, expelling cold and dehygrosis, invigorating stomach and nourishing qi.