• Title/Summary/Keyword: explosions

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Discimination of Decoupled Explosions from Microearthquakes

  • Kim, So-Gu
    • Proceedings of the Korean Society for Rock Mechanics Conference
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    • pp.108-108
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    • 1995
  • There are always some difficulties to discriminate artificial exlposions from micro-earthquakes, furthermore more difficulties to identify and determine decoupled explosions and/or multiple explosions from micro-earthquakes. In this study we use the synthetic seismogram of the in homogeneous models between the source and the observation station in order to find the source effect of the geological environment. We have found some source characteristics of the air-filled and/or water-filled cavity that we can hardly see P-n and S- waves arrivals and that the high frequency coda waves are well observed compared to the coupled explosions or earthquakes.

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EXPLOSION HAZARDS IN TANKS OF HIGH FLASH POINT LIQUIDS

  • Zalosh, Robert
    • Proceedings of the Korea Institute of Fire Science and Engineering Conference
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    • pp.203-210
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    • 1997
  • Reports of explosions in cargo and storage tanks of high flash point liquids such as residual fuel oil, asphalt, and oily waste water have shown that these explosions have occurred even when the liquid temperatures are well below the liquid nominal flash point. The reasons for these seemingly paradoxical explosions are reviewed and results of recent laboratory tests are presented to better define the conditions leading to flammable vapor atmospheres in these tanks. The potential effectiveness of various prevention measures are discussed including inerting, monitoring tank vapor concentrations, and periodic cleaning of condensation and deposits on the tank walls and roof.

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Discrimination of Underground Explosions from Microearthquakes through the Pure-Continental Path (순수 대륙 경로에서 미소지진과 지하 인공폭발의 구별)

  • 김소구
    • The Journal of Engineering Geology
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    • v.4 no.1
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    • pp.29-42
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    • 1994
  • Discrimination studies between microearthquakes and underground explosions are carried out in the pure-continental path of north-south within the Korean Peninsula. The characteristic waveforms for explosions and microearthquakes are investigated in the light of observation and synthetic seismograms. The characteristic waveform generation is minnly a function of source mechanism and ray-path and former influences more strongly than the latter.A double-couple source mechanism for microeatthquakes and a single-couple(force) mechanism for explosions are presented in this study. It is found for very shallow events to have outstanding of $L_g$ waves in the transverse components that pass through the upper crust with period of 1 - 6 seconds and fundamental modes of Rayleigh waves, $R_g$ in the vertical component with period 8-12 seconds. Furthermore it is pointed out that the first arrival amplitudes of SH waves for explosions are always srnall regardless of azimuth of stations since there is non-existence of nodal lines for the explosion mechanism. Theoretical seismograms for explosions show the first motions of compression with short wavelengths as well as mostly fundamental modes of Rayleight waves, $R_g$ waves and $L_g$ waves, whereas those of micro-earthquakes give either compression or dilatation according to the ack azimuth epicenter to stations and poor or non $R_g$ waves and complicated $L_g$ waves, depending on the focal depth.

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Discrimination of Natural Earthquakes and Explosions in Spectral Domain (주파수 영역에서의 인공지진과 자연지진의 식별)

  • 김성균;김명수
    • Economic and Environmental Geology
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    • v.36 no.3
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    • pp.201-212
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    • 2003
  • Recently, the ability of earthquake detection in the Kyungsang Basin of southeastern Korean Peninsula is greatly improved since seismic stations including seismic network of KIGAM(Korea Institute of Geoscience and Mineral Resources) have been significantly increased. However, a large number of signals from explosions are recorded because of frequent medium to large chemical explosions. The discrimination between natural earthquakes and explosions in the Basin has become an important issue. High frequency local records from 43 earthquakes and 43 explosions with comparable magnitude are selected to establish a reliable discrimination technique in the Basin. Several discrimination techniques in spectral domain using spectral amplitude ratios among Pg, Sg, and Lg waves are widely examined with tile selected data. Among them the Pg/Lg spectral ratio method is appeared to be a good discrimination technique to improve the discrimination power. Multivariate discriminant analysis is also applied to the Pg/Lg spectral ratios. The discrimination power of the Pg/Lg ratios for distance corrected three component record compared to uncorrected vertical component one shows distinct improvement. In the frequency band 4 to 14 Hz, Pg/Lg spectral ratio for distance corrected three component record provides discrimination power with a total misclassification probability of only 0.89%.

Numerical analyses for the structural assessment of steel buildings under explosions

  • Olmati, Pierluigi;Petrini, Francesco;Bontempi, Franco
    • Structural Engineering and Mechanics
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    • v.45 no.6
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    • pp.803-819
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    • 2013
  • This paper addresses two main issues relevant to the structural assessment of buildings subjected to explosions. The first issue regards the robustness evaluation of steel frame structures: a procedure is provided for computing "robustness curves" and it is applied to a 20-storey steel frame building, describing the residual strength of the (blast) damaged structure under different local damage levels. The second issue regards the precise evaluation of blast pressures acting on structural elements using Computational Fluid Dynamic (CFD) techniques. This last aspect is treated with particular reference to gas explosions, focusing on some critical parameters (room congestion, failure of non-structural walls and ignition point location) which influence the development of the explosion. From the analyses, it can be deduced that, at least for the examined cases, the obtained robustness curves provide a suitable tool that can be used for risk management and assessment purposes. Moreover, the variation of relevant CFD analysis outcomes (e.g., pressure) due to the variation of the analysis parameters is found to be significant.

Discrimination of artificial explosions by using seismo-acoustic data in 2004 and installation of BRDAR (지진-음파 자료를 이용한 2004년도 인공발파 식별과 백령도 지진-음파 관측망 설치)

  • Che, Il-Young;Jeon, Jeong-Soo;Shin, In-Cheol
    • Proceedings of the Earthquake Engineering Society of Korea Conference
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    • pp.68-73
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    • 2005
  • In succession of the previous works, seismo-acoustic analysis was conducted to collect ground truth events and to discriminate surface explosions from natural earthquakes in the Korean Peninsula for 2004. In this period, total 510 seismo-acoustic events corresponding to 10.8 percent of total seismic events occurred in and near the Korean Peninsula were analyzed and discriminated as artificial surface explosions. Events distribution of the seismo-acoustic events in 2004 is similar to the previous results of 1999-2003. And newly determined seismo-acoustic events were added to the surface explosions database. To extend infrasound detection capability, Korea Institute of Geoscience and Mineral Resources (KIGAM) and Southern Methodist University (SMU) installed new seismo-acoustic array (BRDAR) in Baekryoung Island last November, 2004. The array configuration and design is nearly same to previous seismo-acoustic arrays CHNAR, KSGAR, a triangular 1 km aperture. BRDAR consists of 5 short period vertical seismometers (GS-13) in seismic vaults and 13 microbarometers (Chaparral Model 2). Preliminary analysis using data collected from BRDAR shows an extension of infrasound detection capability to western part of the Korean Peninsula. Also, multiple observations of infrasound at BRDAR and other arrays gave an opportunity to localize sound source regions.

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Detection and Analysis of the Artificial Underground Explosions in N. Korea using KSRS data. (KSRS 자료를 이용해서 북한의 인공지하폭발의 탐지 및 분석)

  • 김소구;이승규;마상윤;박용철
    • The Journal of Engineering Geology
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    • v.5 no.2
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    • pp.181-192
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    • 1995
  • The discrimination studies between earthquakes and underground nuclear explosions have been carried out by various seismologists(Nuttli and Kim, 1976; Dahiman and Israelson, 1977; Masse, 1981). The discrimination between local microearthquakes and artificial underground explosions(epicentral distance not greater than 400Km), however, has not been actively studied so far in the light of seismological aspects. Futhermore this kind of research has never been performed in Korea even if it is of great importance for IAEA (International Atomic Energy Agency) to clearly analyze the military nuclear power of North Korea at present. This research has been carried out by using some of the artificial underground explosions(about 100 events) have occurred in North Korea for the last six years. The azimuths, apparent incidence angles, epicentral distances and locations are determined using a single station of 3 - component data. The detection, location and identification are performed through the polarization and the bandpass filtering. This technique can be also applied to study the inhomogeneous crustal structure finding the converted waves.

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Eruptive mechanisms and processes at Udo tuff cone, Udo Island, Korea (우도응회과의 분출기기구와 분출과정)

  • Hwang, Sang-Koo
    • The Journal of the Petrological Society of Korea
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    • v.1 no.2
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    • pp.91-103
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    • 1992
  • Eruptive mechanisms and processes at Udo tuff cone can be inferred from indicative characters of products, bedforms and lithofacies, and ring faults. In terms of bedforms and lithofa-cies in particular, massive lapilli tuff beds and chaotic lapilli tuff beds are derived from subaerial falls of aggregated tephra of wet tephra finger jets, occurring dominantly at the lower sequences of proximal part at the tuff cone. Crudely stratified lapilli tuff are derived from subaerial falls of slightly aggregated tephra of less wet tephra finger jets, whereas reversely graded lapilli tuff beds are from slightly disaggregated subaerial falls of continuous uprush. Both beds frequently occur in the middle sequences at proximal and near medial part of the tuff cone. Block and lapilli tephra lenses, ash-coated lapilli tephra beds(lenses) and thin-bedded tuff beds are derived from extremely disaggregated subaerial falls of dry tephra in the continuous uprush, frequently occurring at the upper sequences of medial part at the tuff cone. Udo tuff cone is a basaltic volcano emergent through the sea water surface while water could flood across or into the vent area. Emergence of the tuff cone was from the type-Surtseyan eruption characterized by earlier tephra finger jets and later continuous uprush columns of tephra with copious volumes of steam. Explosions began when boiling of wter produced a bubble column reducing the hydrostatic pres-sure, allowing exsolution of gases from the magma. This expansion of magma into a vesiculating froth fragmented the magma and permitted mixing of magma and water so that a more vigorous generation of steam could proceed. Tephra finger jetting explosions continued to build the crater rims, then remove water from the vent that their deposits flowed like slsurries until the continuous uprush explosion ensued. Continuous uprush explosions were associated with most rapid accumula-tion of tephra. The increasing volume rate led to partial removal of water from the vent area by the newly tephra ring so that more vigorous activity could be attended by a reducing water supply. This might restrain surplus of cold water entering the vent and thus enhance the vigour of the eruption by allowing optimal heat exchange. Eventually the crater became so deep and unsuported that piecemeal sliding, or massive subsidence on indipping ring faults, filled and closed the vent, and the cycle of explosions and collapse began anew.

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INVESTIGATIONS ON THE RESOLUTION OF SEVERE ACCIDENT ISSUES FOR KOREAN NUCLEAR POWER PLANTS

  • Kim, Hee-Dong;Kim, Dong-Ha;Kim, Jong-Tae;Kim, Sang-Baik;Song, Jin-Ho;Hong, Seong-Wan
    • Nuclear Engineering and Technology
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    • v.41 no.5
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    • pp.617-648
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    • 2009
  • Under the government supported long-term nuclear R&D program, the severe accident research program at KAERI is directed to investigate unresolved severe accident issues such as core debris coolability, steam explosions, and hydrogen combustion both experimentally and numerically. Extensive studies have been performed to evaluate the in-vessel retention of core debris through external reactor vessel cooling concept for APR1400 as a severe accident management strategy. Additionally, an improvement of the insulator design outside the vessel was investigated. To address steam explosions, a series of experiments using a prototypic material was performed in the TROI facility. Major parameters such as material composition and void fraction as well as the relevant physics affecting the energetics of steam explosions were investigated. For hydrogen control in Korean nuclear power plants, evaluation of the hydrogen concentration and the possibility of deflagration-to-detonation transition occurrence in the containment using three-dimensional analysis code, GASFLOW, were performed. Finally, the integrated severe accident analysis code, MIDAS, has been developed for domestication based on MELCOR. The data transfer scheme using pointers was restructured with the modules and the derived-type direct variables using FORTRAN90. New models were implemented to extend the capability of MIDAS.

PIV Measurements on the Flame Initiation and Propagation under Gas Explosions by Electrostatic Discharge Energies in a Confined Chamber with an Obstacle (장애물이 있는 챔버 내부의 정전기 방전 에너지에 의한 가스 폭발시 초기화염과 화염전파 특성에 대한 PIV 계측)

  • Park, Dal-Jae;Lee, Seok-Hwan;Sung, Jae-Yong;Lee, Young-Soon
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.33 no.9
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    • pp.682-687
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    • 2009
  • In order to investigate the effects of three different electrostatic discharge energies on gas explosions, a high-speed PIV system has been applied. The present study paid attention to the flame initiation by the gas explosions and its propagation at the existence of an obstacle within a chamber. Three different ignition energies such as 0.56 mJ, 52.87 mJ and 112.5 mJ were used. It is found that the ignition kernel is bent by the electrostatic discharge during the flame initiation. Tangential velocities of unburnt mixture ahead of initially propagating flame fronts are increased with increasing ignition energy, which makes the flame propagation faster before it reaches the obstacle. Although the flame speed was found to be less sensitive to the ignition energies, the flame developments were different. The effects of the energies on explosion pressures were also discussed.