• Tribology and Lubricants
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• v.22 no.6
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• pp.314-319
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• 2006

In this paper, the friction and wear characteristics of contact type sealing unit far a water turbine have been presented. The sealing unit for a small hydropower generation is to stop a leakage of circulating water from an outside of an impeller to an inside of a rolling bearing. The friction heating between a seal ring and a seal seat may radically increase a surface temperature in which increase a power loss and wear on the rubbing surface. The surface wear strongly affect to the seal life of a mechanical face seal. In this study, the hardness of a stainless steel in which is a heat-treated is 892.8 in Victors hardness and the hardness of silicone carbide of SiC is 714.1 in Victors hardness. The surface hardness of a heat-treated stainless steel is 25% high compared with that of a ceramic material of SiC. The contact modes of rubbing surfaces are a dry friction, a water film friction and a mixed friction that is contaminated by a dust, silt, and moistures, etc. These two factors of a contact rubbing modes and a material property are very important parameters on the tribological performance such as a friction and wear between a seal ring and a seal seat in primary sealing unit. The experimental result shows that the surface hardness of a seal material is very important on the friction coefficient and a wear volume. Thus, the results recommend higher hardness of a seal material, which may reduce a friction loss and increase a wear life of primary seal components.

• Corrosion Science and Technology
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• v.8 no.5
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• pp.188-192
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• 2009

A forced outage due to a steam generator tube leak in a Korean nuclear power plant was reported.1) Primary water stress corrosion cracking has occurred in many tubes in the plant, and they were repaired using sleeves or plugs. In order to develop proper repair criteria, it is necessary to understand the leak behavior of the tubes containing stress corrosion cracks. Stress corrosion cracks were developed in 0.1 M sodium tetrathionate solution at room temperature. Steam generator(SG) tubes with short cracks were successfully fabricated with a restricted solution contact method. The leak rates of the degraded tubes were measured at room temperature. Some tubes with 100 % through wall cracks showed an increase of leak rate with time at a constant pressure.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.28 no.6
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• pp.732-738
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• 2004

One of the main degradation mechanisms in steam generator tubes is stress corrosion cracking induced by residual stress. The resulting damages can cause tube bursting or leakage of the primary water which contains radioactivity. Shot peening technique has been used to prevent stress corrosion crack growth in steam generator tubes. In order to investigate the shot peening effect on stress corrosion cracking stress intensity factors are calculated for the semi-elliptical surface crack which is located in residual stress region. The residual stress distribution in steam generator tubes is obtained from the simple model proposed by Frederick et al.

• Corrosion Science and Technology
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• v.3 no.1
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• pp.30-33
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• 2004

It has been reported that some events of a rupture of seam generator tube have occurred in nuclear power plants around the world. Main causes of the leakage are from various types of corrosion in the steam generator(SG) tubings. Primary water stress corrosion cracking(PWSCC) of steam generator tubings have occurred in many tubes in Korean plant, and they were repaired using sleeves or plugs, In order to develop proper repair criteria, it is necessary to ascertain the leak behavior of the tubings. A high pressure leak and burst testing system was manufactured. Various types of Electro Discharged Machined (EDM) notches were developed on the SG tubes. Leak rate and burst pressure were measured on the tubes at room temperature. Burst pressure of the part through wall defected tubes depends on the defect depth, Water flow rates after the burst were independent of the t1aw types; tubes having 20 to 60 mm long EDM notches showed similar flow rates regardless of the defect depth. A fast pressurization rate gave the tube a lower burst pressure than the case of a slow pressurization.

• Tunnel and Underground Space
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• v.16 no.5 s.64
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• pp.368-376
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• 2006

After heavy rainfall, It was occurred massive plane failure along bedding plane of shale in the center of rock slope. It was observed filling material and trace of underground water leakage around of the slope. We tried to find the cause for slope failure, and the result of examination showed that primary factors of the failure were low shear strength of clay filling material and water pressure formed within tension crack existed in the top of the slope. In this research, in order to examine the features of shear strength of filled rock joint, shear test of filled rock joint was conducted using of artificial filling material such as sand and clay..Also we made an investigation into the characteristics of shear strength with different thickness of filling materials.

• Proceedings of the Korean Geotechical Society Conference
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• 2006.10a
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• pp.256-267
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• 2006

After heavy rainfall, It was occurred massive plane failure along bedding plane of shale in the center of rock slope. It was observed filling material and trace of underground water leakage around of the slope. We tried to find the cause for slope failure, and the result of examination showed that primary factors of the failure were low shear strength of clay filling material and water pressure farmed within tension crack existed in the top of the slope. In this research, in order to examine the features of shear strength of filled rock joint, shear test of filled rock joint was conducted using of artificial filling material such as sand and clay. Also we made an investigation into the characteristics of shear strength with different thickness of filling materials.

• Nuclear Engineering and Technology
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• v.48 no.4
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• pp.952-964
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• 2016

The prototype generation IV sodium-cooled fast reactor (PGSFR) has been developed by the Korea Atomic Energy Research Institute. This reactor uses sodium as a reactor coolant to transfer the core heat energy to the turbine. Sodium has chemical characteristics that allow it to violently react with materials such as a water or steam. When a sodium-water reaction (SWR) occurs due to leakage or breakage of steam generator tubes, high-pressure waves and corrosive reaction products are produced, which threaten the structural integrity of the components of the intermediate heat-transfer system (IHTS) and the safety of the primary heat-transfer system (PHTS). In the PGSFR, SWR events are included in the design-basis event. This event should be analyzed from the viewpoint of the integrities of the IHTS and fuel rods. To evaluate the integrity of the IHTS based on the consequences of the SWR, the behaviors of the generated high-pressure waves are analyzed at the major positions of a failed IHTS loop using a sodium-water advanced analysis method-II code. The integrity of the fuel rods must be consistently maintained below the safety acceptance criteria to avoid the consequences of the SWR. The integrity of the PHTS is evaluated using the multidimensional analysis of reactor safety-liquid metal reactor code to model the whole plant.

• Nuclear Engineering and Technology
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• v.48 no.5
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• pp.1273-1279
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• 2016

Production of iodine-131 by neutron activation of tellurium in tellurium dioxide ($TeO_2$) material requires a target that meets the safety requirements. In a radiopharmaceutical production unit, a new lid for a can was designed, which permits tight sealing of the target by using tungsten inert gaswelding. The leakage rate of all prepared targets was assessed using a helium mass spectrometer. The accepted leakage rate is ${\leq}10^{-4}mbr.L/s$, according to the approved safety report related to iodine-131 production in the TRIGA Mark II research reactor (TRIGA: Training, Research, Isotopes, General Atomics). To confirm the resistance of the new design to the irradiation conditions in the TRIGA Mark II research reactor's central thimble, a study of heat effect on the sealed targets for 7 hours in an oven was conducted and the leakage rates were evaluated. The results show that the tightness of the targets is ensured up to $600^{\circ}C$ with the appearance of deformations on lids beyond $450^{\circ}C$. The study of heat transfer through the target was conducted by adopting a one-dimensional approximation, under consideration of the three transfer modes-convection, conduction, and radiation. The quantities of heat generated by gamma and neutron heating were calculated by a validated computational model for the neutronic simulation of the TRIGA Mark II research reactor using the Monte Carlo N-Particle transport code. Using the heat transfer equations according to the three modes of heat transfer, the thermal study of I-131 production by irradiation of the target in the central thimble showed that the temperatures of materials do not exceed the corresponding melting points. To validate this new design, several targets have been irradiated in the central thimble according to a preplanned irradiation program, going from4 hours of irradiation at a power level of 0.5MWup to 35 hours (7 h/d for 5 days a week) at 1.5MW. The results showthat the irradiated targets are tight because no iodine-131 was released in the atmosphere of the reactor building and in the reactor cooling water of the primary circuit.

• Korean Journal of Remote Sensing
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• v.37 no.3
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• pp.591-601
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• 2021

As the domestic chemical industry continues to develop, handling and transportation of chemicals increases every year. Road freight in Korea accounts for more than 90%, and most of the chemical transportation is done through roads. These chemical vehicles can lead to major accidents if accidents occur. Transportation vehicles are likely to cause water pollution and soil pollution, which are factors of environmental damage, as well as traffic accidents that are the primary damage. In this work, we write a scenario for hydrogen chloride gas leakage by setting Banpo IC and Seocho IC sections as research areas, and use the ALOHA program to measure the predicted distance and analyze the time when hydrogen chloride gas reached according to the distance. In addition, risk assessment using population density was carried out for areas of damage caused by time using GIS. This suggests the need for prevention and countermeasures in areas of damage.

• Journal of Preventive Medicine and Public Health
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• v.33 no.1
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• pp.1-9
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• 2000

Objectives : This study was carried out to investigate the sources of infection and modes of transmission of an outbreak of shigellosis that occurred among pupils of 'M' primary school and residents near the school in Kyongju from Sept. 24 to Oct. 24, 1998. Methods : The subjects who completed a questionnaire and a rectal swab for microbiologic examinations were 1,534 persons (781 males, 753 females), including 469 pupils of 'M' primary school (268 males, 201 females). Bacteriological examinations of underground water and simple piped water were done. Results : The attack rate of diarrhea was 28.7% in the subjects from Sept.24 to Oct. 24, 1958. There was no difference in attack rate of diarrhea by gender, but it was significantly higher in the pupils of 'M' primary school than others (p<0.01). The attack rate of diarrhea by resident areas was no different to the pupils of 'M' primary school, but was significantly higher in the residents of Mohwa 2 Ri except pupils that 'M' primary school is located in (p<0.01). The distribution of date of onset revealed the exposure date to be Sept, 22 and 23 in consideration of incubation periods and common source outbreak followed propagative spread in the epidemic curve. The major characteristics of diarrhea were watery (89.1%) in nature, $1\sim3$ days (72.5%) in duration, $2\sim3$ times (63.9%) in frequency. The clinical symptoms among the diarrheal cases included abdominal pain (74.1%), fever (56.4%), headache (55.9%), chill (40.4%) and tenesmus (31.4%). Conclusions : The source of infection was estimated to be contaminated underground water and simple piped water caused by leakage from the cess pool. It is highly necessary that the management of drinking water and cess fools should be done thoroughly.