Underground Nuclear Explosions and Release of Radioactive Noble Gases     

Yuri V. Dubasov 《Pure and Applied Geophysics》2010,167(4-5):455-461

Over a period in 1961–1990 496 underground nuclear tests and explosions of different purpose and in different rocks were conducted in the Soviet Union at Semipalatinsk and anovaya Zemlya Test Sites. A total of 340 underground nuclear tests were conducted at the Semipalatinsk Test Site. One hundred seventy-nine explosions (52.6%) among them were classified as these of complete containment, 145 explosions (42.6%) as explosions with weak release of radioactive noble gases (RNG), 12 explosions (3.5%) as explosions with nonstandard radiation situation, and four excavation explosions with ground ejection (1.1%). Thirty-nine nuclear tests had been conducted at the Novaya Zemlya Test Site; six of them – in shafts. In 14 tests (36%) there were no RNG release. Twenty-three tests have been accompanied by RNG release into the atmosphere without sedimental contamination. Nonstandard radiation situation occurred in two tests. In incomplete containment explosions both early-time RNG release (up to ~1 h) and late-time release from 1 to 28 h after the explosion were observed. Sometimes gas release took place for several days, and it occurred either through tunnel portal or epicentral zone, depending on atmospheric air temperature.  相似文献   

Estimation of Explosion Energy Yield at Chernobyl NPP Accident     

Sergey A. Pakhomov  Yuri V. Dubasov 《Pure and Applied Geophysics》2010,167(4-5):575-580

The value of the ¹³³Xe/^133mXe isometric activity ratio for the stationary regime of reactor work is about 35, and that for an instant fission (explosion) is about 11, which allowed estimation of the nuclear component of the instant (explosion) energy release during the NPP accident. Atmospheric xenon samples were taken at the trajectory of accident product transfers (in the Cherepovetz area); these samples were measured by a gamma spectrometer, and the ¹³³Xe/^133mXe ratio was determined as an average value of 22.4. For estimations a mathematic model was elaborated considering both the value of instant released energy and the schedule of reactor power change before the accident, as well as different fractionation conditions on the isobaric chain. Comparison of estimated results with the experimental data showed the value of the instant specific energy release in the Chernobyl NPP accident to be 2·10⁵–2·10⁶ J/Wt or 6·10¹⁴–6·10¹⁵ J (100–1,000 kt). This result is matched up to a total reactor power of 3,200 MWt. However this estimate is not comparable with the actual explosion scale estimated as 10t TNT. This suggests a local character of the instant nuclear energy release and makes it possible to estimate the mass of fuel involved in this explosion process to be from 0.01 to 0.1% of total quantity.  相似文献   

Erratum to “26Al–26Mg and 207Pb–206Pb systematics of Allende CAIs: Canonical solar initial 26Al/27Al ratio reinstated” [Earth Planet Sci. Lett. 272 (2008) 353–364]     

Benjamin Jacobsen  Qing-Zhu Yin  Frederic Moynier  Yuri Amelin  Alexander N. Krot  Kazuhide Nagashima  Ian D. Hutcheon  Herbert Palme 《Earth and Planetary Science Letters》2009,277(3-4):549

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Nutrient budgets for European seas: a measure of the effectiveness of nutrient reduction policies   总被引：3，自引：0，他引：3  

Artioli Y  Friedrich J  Gilbert AJ  McQuatters-Gollop A  Mee LD  Vermaat JE  Wulff F  Humborg C  Palmeri L  Pollehne F 《Marine pollution bulletin》2008,56(9):1609-1617

Socio-economic development in Europe has exerted increasing pressure on the marine environment. Eutrophication, caused by nutrient enrichment, is evident in regions of all European seas. Its severity varies but has, in places, adversely impacted socio-economic activities. This paper aims to evaluate the effectiveness of recently adopted policies to reduce anthropogenic nutrient inputs to European seas. Nitrogen and phosphorus budgets were constructed for three different periods (prior to severe eutrophication, during severe eutrophication and contemporary) to capture changes in the relative importance of different nutrient sources in four European seas suffering from eutrophication (Baltic Proper, coastal North Sea, Northern Adriatic and North-Western Black Sea Shelf). Policy success is evident for point sources, notably for P in the Baltic and North Seas, but reduction of diffuse sources has been more problematic.  相似文献   

普通球粒陨石 Semarkona中球粒的 Pb-Pb法年龄     

谢智  Yuri AMELIN 《地球化学》2006,35(1):13-18

陨石年代学研究中常用定年工具包括短半衰期和长半衰期放射性同位素体系,其中前者可以给出陨石形成的相对年龄,而后者则可以给出绝对形成年龄。在长半衰期体系中,PbP-b法是目前能获得高精度可靠年龄的最有效方法。普通球粒陨石Sem arkona是最不平衡的LL3.0型陨石,受后期热变质的影响很小,因此其年龄研究对反演陨石起源有重要意义。在本文中,对Sem arkona中球粒用不同的化学浸洗流程,并测定浸洗溶液和残渣中UT-hP-b同位素组成,其中浸洗后的残渣均给出相对较高的206Pb/204Pb比值,表明其中含有较多的放射成因Pb同位素组成,这些残渣构成PbP-b等时线,给出年龄为(4566.9±5.8)M a,M SW D=26,与207Pb/206Pb模式年龄在误差范围内一致。尽管Sem arkona陨石可能经历了后期蚀变的影响,但前人对陨石变质温度的研究结果表明,热变质温度并未足以使球粒中Pb同位素体系重置,因此获得的年龄代表Sem arkona陨石球粒的形成年龄。  相似文献   

Mixing metals in the early Universe     

Andrea Ferrara  Max Pettini  Yuri Shchekinov 《Monthly notices of the Royal Astronomical Society》2000,319(2):539-548

We investigate the evolution of the metallicity of the intergalactic medium (IGM) with particular emphasis on its spatial distribution. We propose that metal enrichment occurs as a two-step process. First, supernova (SN) explosions eject metals into relatively small regions confined to the surroundings of star-forming galaxies. From a comprehensive treatment of blowout we show that SN by themselves fail by more than one order of magnitude to distribute the products of stellar nucleosynthesis over volumes large enough to pollute the whole IGM to the metallicity levels observed. Thus, an additional (but as yet unknown) physical mechanism must be invoked to mix the metals on scales comparable to the mean distance between the galaxies that are most efficient pollutants. From this simple hypothesis we derive a number of testable predictions for the evolution of the IGM metallicity. Specifically, we find that: (i) the fraction of metals ejected over the star-formation history of the Universe is about 50 per cent at     that is, approximately half of the metals today are found in the IGM; (ii) if the ejected metals were homogeneously mixed with the baryons in the Universe, the average IGM metallicity would be     at     However, due to spatial inhomogeneities, the mean of the distribution of metallicities in the diffusive zones has a wide (more than 2 orders of magnitude) spread around this value; (iii) if metals become more uniformly distributed at     as assumed, at     the metallicity of the IGM is narrowly confined within the range     Finally, we point out that our results can account for the observed metal content of the intracluster medium.  相似文献   

On the Magnetic Field Orientation and Plasma Flows in Solar Filament Barbs     

Litvinenko  Yuri E. 《Solar physics》2000,196(2):369-375

Speeds of vertical flows in quiescent solar filaments are typically much less than the local Alfvén speed. This is why the flows in filament barbs can be modeled by perturbing a magnetostatic solution describing a balance between the Lorentz force, gravity, and gas pressure in a barb. This approach explains why some of the flows are neither aligned with the magnetic field nor controlled by gravity. Both the observed upflows and the magnetic field dips in barbs are likely to be caused by photospheric magnetic reconnection.  相似文献   

Three-dimensional inversion of airborne data with applications for detecting elongated subvertical bodies overlapped by an inhomogeneous conductive layer with topography     

Marina G. Persova  Yuri G. Soloveichik  Denis V. Vagin  Dmitry S. Kiselev  Alexander M. Grif  Yulia I. Koshkina  Anastasia P. Sivenkova 《Geophysical Prospecting》2020,68(7):2217-2253

We propose the approach to 3D inversion of airborne electromagnetic data, which is intended for discovering subvertical bodies overlapped by essentially inhomogeneous conductive layers. The approach is based on the geometric inversion in which a geoelectrical medium is parameterized with the use of block structures. During the inversion, the coordinates of the borders between the blocks and the rows of the blocks as well as resistivities inside them are determined. In order to solve the forward problem of the airborne electromagnetic survey, we use the non-conforming optimized mesh with the hexahedral cells, which enables us to reduce the number of degrees of freedom and smoothly approximate the curved borders of a geological medium. For a more reliable discovery of subvertical objects, we propose to carry out 3D inversions at several rotations of block structures relative to the flight lines. The workability of this approach is demonstrated using the data which are synthesized for complex geoelectrical models with topography, inhomogeneous overlapping layers and target subvertical bodies oriented differently relative to the flight lines. The results of this investigation show that, in some way or other, the elongated subvertical object is discovered and its orientation (the direction of its long side) is defined at different rotations of block structures used in 3D inversions. However, the most accurate recovery of the subvertical object length is achieved when the direction of its long side almost coincides with the direction of one of the block structures axes. Thus, the block structures rotations allow not only more reliably discovering a target object in complex geoelectrical conditions, but also more exactly defining its orientation and length.  相似文献   

Momentum and heat transfer across the foam-covered air-sea interface in hurricanes     

Golbraikh  Ephim  Shtemler  Yuri M. 《Ocean Dynamics》2020,70(5):683-692

Ocean Dynamics - Procedures of formal averaging over the air-sea interface are applied to both momentum and enthalpy surface-transfer coefficients, CD and CK, in hurricane conditions. The transfer...  相似文献   

Late Holocene distal mud deposits off the Nakdong delta,SE Korea: evidence for shore-parallel sediment transport in a current-dominated setting     

Jong-Hwa Chun  Yuri Kim  Jang-Jun Bahk  Young Jun Kim  Dong-Hyo Kang  Yong Hoon Kim  Gil Young Kim  Byong-Jae Ryu 《Geo-Marine Letters》2015,35(6):475-485

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