• Geomechanics and Engineering
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• v.18 no.6
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• pp.567-574
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• 2019

In order to study the effect of stress and water pressure on the permeability of fractured rock mass under three-dimensional stress conditions, a single fracture triaxial stress-seepage coupling model was established; By using the stress-seepage coupling true triaxial test system, large-scale rock specimens were taken as the research object to carry out the coupling test of stress and seepage, the fitting formula of permeability coefficient was obtained. The influence of three-dimensional stress and water pressure on the permeability coefficient of fractured rock mass was discussed. The results show that the three-dimensional stress and water pressure have a significant effect on the fracture permeability coefficient, showing a negative exponential relationship. Under certain water pressure conditions, the permeability coefficient decreases with the increase of the three-dimensional stress, and the normal principal stress plays a dominant role in the permeability. Under certain stress conditions, the permeability coefficient increases when the water pressure increases. Further analysis shows that when the gob floor rock mass is changed from high stress to unloading state, the seepage characteristics of the cracked channels will be evidently strengthened.

• Journal of the Korean Institute of Gas
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• v.9 no.1 s.26
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• pp.26-32
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• 2005

This paper presents the design safety of metal seals in pressure vessels. For a high-pressure vessel, a metal seal is usually used as a primary sealing, and an elastomeric rubber O-ring is adopted as a secondary sealing unit. The FEM computed results show that an aluminium material for sealing a gas leakage is superior to a steel one because of the thermal expansion rate. The deformation and stress distributions on the metal seal and pressure vessel structures are mainly dominated by transferred temperature compared to those of the gas pressure in which is supplied by an external pump. Thus, the temperature of a metal seal material should be restricted to under $200^{\circ}C$.

• Nuclear Engineering and Technology
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• v.47 no.7
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• pp.884-894
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• 2015

Background: Fibers in concrete resist the growth of cracks and enhance the postcracking behavior of structures. The addition of fibers into a conventional reinforced concrete can improve the structural and functional performance of safety-related concrete structures in nuclear power plants. Methods: The influence of fibers on the ultimate internal pressure capacity of a prestressed concrete containment vessel (PCCV) was investigated through a comparison of the ultimate pressure capacities between conventional and fiber-reinforced PCCVs. Steel and polyamide fibers were used. The tension behaviors of conventional concrete and fiber-reinforced concrete specimens were investigated through uniaxial tension tests and their tension-stiffening models were obtained. Results: For a PCCV reinforced with 1% volume hooked-end steel fiber, the ultimate pressure capacity increased by approximately 12% in comparison with that for a conventional PCCV. For a PCCV reinforced with 1.5% volume polyamide fiber, an increase of approximately 3% was estimated for the ultimate pressure capacity. Conclusion: The ultimate pressure capacity can be greatly improved by introducing steel and polyamide fibers in a conventional reinforced concrete. Steel fibers are more effective at enhancing the containment performance of a PCCV than polyamide fibers. The fiber reinforcementwas shown to bemore effective at a high pressure loading and a lowprestress level.

• Journal of the Korea Safety Management & Science
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• v.24 no.4
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• pp.101-107
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• 2022

To test a flameproof enclosure for the safety certificate, a reference pressure of explosion needs to be determined. However, the explosion pressure may be changed according to relative humidity of explosive gases. Therefore, the guideline on relative humidity should be recommended for measuring the explosion pressure for accurate and reproducible testings. This study examined the relationship of explosion pressure with relative humidity of hydrogen (31 vol %)-air and acetylene (14 vol %)-air mixture gases. The explosion pressures were measured by increasing the relative humidity of the gases by 10 % from dry state to 80 % in a cylindrical explosion enclosure of 2.3 L. on ambient temperature and atmospheric pressure (1 atm). The maximum explosive pressures were remained almost constant until the relative humidity reached 10 % for the hydrogen-air mixture and 20 % for the acetylene-air mixture. However, the maximum explosive pressures linearly decreased as the relative humidity increased. Based on the results of the study, it would be recommended to use 10 % relative humidity for the hydrogen-air mixture and 20 % for the acetylene-air mixture as the critical value in testing a flameproof enclosure.

• Transactions of the Korean Society of Pressure Vessels and Piping
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• v.9 no.1
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• pp.20-24
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• 2013

Reactor Vessel Internals(RVIs), which are installed within the reactor pressure vessel and support the fuel assembly, take responsibility for safety of reactor core. In operating Nuclear Power Plants(NPPs), the RVIs have been exposed to severe conditions such as neutron irradiation, high temperature, high pressure, and high velocity of coolant flow and have degraded by materials aging with long-term operation. Therefore, the effective aging management plan and the appropriate regulatory requirements are necessary to maintain the integrity of RVIs. The purpose of this paper is to provide a review guide for Periodic Safety Review(PSR) of RVIs in presurized water reactor. The review guide is developed based on the revised review guides and reports established from IAEA and USNRC, and the analysis results of design characteristics, aging mechanisms, and operating experiences of RVIs in domestic and international NPPs. Consequently, the developed review guide for PSR of RVIs is expected to contribute an overall strategy and standard for the PSR of RVIs.

• Journal of the Korean Institute of Gas
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• v.23 no.2
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• pp.9-16
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• 2019

The frequency of major accidents which has probability of occurrence at the high pressure underground pipeline of industrial estate such an Ulsan, Yeo-ju by the other construction such as an excavation work will be compared to city gas underground pipeline to derive the basic event by the FTA and present. Also, Observe and analyze the pipe damage impact factor such as an excavation frequency, patrol cycle. As a result, It contributes to the safety improvement of high pressure gas buried pipeline due to obtain importance and sensitivity of the pipe damge impact factors.

• Journal of the Korean Society of Safety
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• v.31 no.2
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• pp.133-142
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• 2016

The purpose of this study was to investigate the factors that influence safety rule violation at work. Semi-structured interviews were conducted with 337 participants from nine manufacturing plants. The results of the content analysis revealed the following six categories: Individual characteristics, safety commitment, safety support and resources, safety competence and communication, production pressure, and problems with rules. Among the 14 factors in the six categories above, indirect accident experience in the individual characteristics category and no action for complying with laws in the problems with rules category had not been identified in previous studies. However, some factors, such as age, peer pressure, pay type, the lowering of risk, a masculine way of working, and supervisor position were not found in this study. The implications and limitations are discussed.

• Transactions of the Korean Society of Pressure Vessels and Piping
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• v.13 no.1
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• pp.1-15
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• 2017

After Kyeongju earthquake occurred in September 12, 2016, the seismic safety of nuclear power plants became important issue in our country. The seismic safety of nuclear power plant against beyond design basis earthquake became very important to secure the public safety. In this paper, the current status of the seismic safety assessment methodology is reviewed and some aspects for the reliability improvement of the seismic safety assessment results are proposed. Seismic margin analysis and probabilistic seismic safety assessment have been used for the seismic safety evaluation of a nuclear power pant. The basic procedure and the related issues and proposals for the probabilistic seismic safety assessment are investigated.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.25 no.3
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• pp.189-197
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• 2016

Green vehicles include electric vehicles, natural gas vehicles, and fuel cell vehicles (FCVs). In FCVs, pressure vessels have cylinder valves to control hydrogen flow. These valves should be of high quality in terms of safety because hydrogen is stored at ultra-high pressure in pressure vessels. Hence, safety evaluation of these valves is necessary to secure the safety of the FCV. A structural analysis of the cylinder valve was conducted in this study by using a commercial finite element analysis code. The results showed that the safety factor of valve component ranged 1.06-186.44. After categorizing, the stress components at critical points of the cylinder valve parts were evaluated using the corresponding allowable design criteria in the ASME code. The pressurization cycle test was performed as per the regulation to evaluate the safety of the valve.

• Journal of the Korean Institute of Gas
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• v.23 no.6
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• pp.74-80
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• 2019

Hydrogen refueling stations that use compressed hydrogen at high pressure provide safety distances between facilities in order to ensure safety. Most accidents occurring in hydrogen stations are accidental leaks. When a leak occurs, various types of ignition sources generate a jet flame. Therefore, the analysis of leaked gas diffusion and jet flame due to high pressure hydrogen leakage is one of the most important factor for setting the safety distance. In this study, the leakage accidents that occur in the hydrogen refueling station operated in high pressure environment are simulated for various leakage source sizes. The results of this study will be used as a reference for the future safety standards.