The Effects on the Atmosphere of a Major Nuclear Exchange (1985) / Chapter Skim
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4 Dust
4 Dust
Pages 17-35
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From page 17... ...
The following sections of this chapter summarize the dynamics of nuclear clouds, the source mechanisms of dust, the available data that give estimates for dust lofting, and finally, an analysis of dust lofting in this baseline case. _ The submicron fraction could range from a few NUCLEAR CLOUD DYNAMICS Unlike soot from the long-lasting fires, dust from a nuclear explosion would be lofted to its stabilization altitude within 3 to 4 min.
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From page 18... ...
Fireball expansion reduced the internal pressure (radiative losses contributed a relatively minor reduction) until, at a few seconds, the pressure reached atmospheric levels.
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From page 19... ...
Because the density of the expanding vortex would not drop with altitude as fast as the density of the atmosphere, the fireball would eventually lose buoyancy and, after a few minutes, stop rising at the so-called stabilization altitude. Figure 4.1 (from Glasstone and Dolan, 1977, p.
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From page 20... ...
Although no recent explosion, man-made or natural, has approached 150 Mt. conceivable multiburst attacks on very hard targets as well as some natural explosions such as meteor impacts could exceed this energy.
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From page 21... ...
These situations will be discussed in more detail in the section on excursions below. DUST LOFTING BY A NUCLEAR CLOUD A rising fireball can carry gas and relatively large particles to great altitude.
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From page 22... ...
The actual loading would be about a factor of 10 less, a probable result of such factors as the limit of energy available for vaporization of rock, poor drag coupling of the large particles that dominate the mass distribution of crater ejecta, and particle-particle interactions. Analysis of particle samples obtained by aircraft from the stabilized clouds of high-yield surface bursts detonated over water and/or coral islands indicates that the clouds loft about 0.2 Tg/Mt (Gutmacher et al., 1983~.
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From page 23... ...
Recondensed vaporized material is an important source of fine particles in nuclear clouds from surface bursts. Most of the vapor is derived from rock and soil.
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From page 24... ...
The total mass of small particles derived from the rock vapor and melt would be roughly 0.2 Tg/Mt, an estimate in good agreement with the observations described below. The principal remaining sources of dust are solid particles ejected from the crater or swept up by the afterwinds.
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From page 25... ...
Because these processes are relatively insensitive to soil and rock type, data from high-yield explosions on coral islands can reasonably be used to estimate the dust lofted by continental bursts. These considerations of source mechanisms suggest that the mass of particulates lofted to stabilization altitude by surface bursts would be a few times 0.1 Tg/Mt.
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From page 26... ...
Unfortunately, fallout samples are generally not representative of the particle distribution in the stabilized cloud. Even in the early days of atmospheric nuclear weapons testing, samples of bomb debris were collected from the nuclear clouds with both manned and unmanned drone aircraft.
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From page 27... ...
the collection and counting scheme becomes increasingly inefficient at smaller particle sizes, thus decreasing the apparent fine particle component. PARTICLE SIZE DISTRIBUTIONS The principal results concerning particle size distribution are to be found in Nathans et al.
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From page 28... ...
OPTICAL PROPERTIES OF AIRBORNE DUST The optical properties of dust raised in nuclear clouds have not been directly determined. However, much information is available for volcanic dust and for natural windblown dust.
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From page 29... ...
give a submicron mass fraction of 8 percent.
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From page 30... ...
At some infrared wavelengths the imaginary optical constants may differ by an order of magnitude between various rock types. However, near the 8- to 12-pm band centers, which are the crucial wavelengths since they lie in the atmospheric window, the measurements appear to be within a factor of 2 or 3 for different rock types and different measurement techniques.
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From page 31... ...
CThe tropospheric dust is the sum of the stem dust and the portion of the cloud dust below the troposphere. dThe submicron mass is calculated assuming 8 percent of the dust mass lies in the submicron size range.
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From page 32... ...
The committee also considered a simultaneous attack totaling 500 Mt of surface bursts against a cluster of closely spaced hard targets. As discussed earlier, the rise of the resulting giant fireball would be qualitatively different from the rise of single-megaton buoyant fireballs.
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From page 33... ...
An excursion involving higher yield weapons or concentrated attacks on hard targets might increase the masses to as much as 1000 Tg (total) and 80 Tg (stratospheric submicron particles)
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From page 34... ...
(1970) The specific activity of nuclear debris from ground surface bursts as a function of particle size.
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From page 35... ...
(1973) A finite difference scheme for time-dependent, spherical radiation hydrodynamics problems.
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