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5 Fallout and Tools for Calculating Effects of Release of Hazardous Materials
Pages 52-72

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From page 52...
... Government Printing Office, Washington, D.C., §2.18­2.21, §2.23­2.31, §2.91­2.95, §2.99­2.100; A Study of Base Surge Phenomenology, Kaman Science Corporation, November 5, 1986; and The DTRA Nuclear Weapons Effects Technology Information (NWETI) Fallout Guide, 2004, by Joseph McGahan.
From page 53...
... Within 1 to 24 hours after the burst, for example, the total gamma ray activity decreases by a factor of about 60. The following sections focus on the problem of fallout associated with surface and subsurface bursts.
From page 54...
... In addition, the large-scale circulation of the atmosphere drives the long-range transport of the cloud. The larger particles in the nuclear cloud cannot remain in suspension, and hence they settle to the ground.
From page 55...
... This is the delayed (or worldwide) fallout, to which residues from nuclear explosions of various types-air, high-altitude, surface, and shallow subsurface -- may contribute.
From page 56...
... , injuries due to fallout were completely absent. On the other hand, a nuclear explosion occurring at or near the ground surface can result in severe contamination by the radioactive fallout.
From page 57...
... Furthermore, variations in the winds -- from the time of burst until the particles reach the ground perhaps several hours later -- affect the fallout pattern following a nuclear explosion. Shallow Underground Explosion Phenomena When a nuclear weapon is exploded underground, a sphere of extremely hot, high-pressure gases, including vaporized weapon residues and rock, is formed.
From page 58...
... For depths of burst of 2 to 3 scaled meters, the fraction of activity in the base surge is typically less than a few percent of the total activity. CALCULATING THE EFFECTS OF RELEASE OF HAZARDOUS MATERIALS The calculation of the effects of the release of a chemical or biological agent or of nuclear radioactivity can be broken down into several stages: (1)
From page 59...
... Parameters are adjusted to fit the available data from nuclear tests at the Nevada Test Site. Operational Planning Tools of the Defense Threat Reduction Agency The Department of Defense uses primarily the DTRA-developed HPAC for estimating effects resulting from a release of CBRN materials.
From page 60...
... KDFOC was originally written to model fallout from Plowshare tests, which involved nuclear explosives designed to produce craters with minimum fallout. Consequently, the code's emphasis has been on surface and buried explosives, and parameters have been adjusted to fit the data available from nuclear tests at the Nevada Test Site and the Pacific Proving Ground.
From page 61...
... Source Term The source term for nuclear explosions is a fit to the 10 or so surface-burst and buried-burst tests that were carried out at the Nevada Test Site in the 1960s and 1970s. It has also been tested against more limited data from the Pacific Proving Ground and from unintentional releases of radioactivity (e.g., from tests that vented)
From page 62...
... For modeling particle transport to predict the effects of hazardous materials dispersed in nuclear attacks on hardened targets or attacks with conventional weapons on chemical and biological agent facilities, it is probably more important to include more factors like topography in existing models than to build more sophisticated transport models. The exact distance at which hazardous materials of a particular concentration are deposited may be incorrectly estimated, but unless deposition is near the boundary of a populated area, that assumption will often not affect the predictions of casualties (the casualties will just occur in different places)
From page 63...
... The chemical and biological communities have begun to focus on the real-world potential lethality of various toxic chemical and biological agents, but the variation in lethality, agent route exposure, agent lifetime, sensitivity to environmental factors, and releasability in virulent form is vastly wider than that for nuclear fallout. Current models incorporate these factors to some extent, but no sensitivity studies were presented to the committee that describe the ways in which each of these factors affects the lethality of various agents (and nearly every issue reduces the potency of an agent)
From page 64...
... In particular, this upgrading should include the following: · Improve the characterization and validation of the nuclear source terms for a more detailed set of the geological and meteorological conditions characterizing the locations of hard and deeply buried targets; · Incorporate global effects, including environmental impacts (on crop production, fishing, and so on) and low-dose-rate effects on humans across the full demographic spectrum, from infants to the elderly, using results from Chernobyl as well as from the Nevada Test Site and Pacific Proving Grounds; · Address the needs of emergency responders; · Refine population databases to include demographics and to account for movement of people, migration, and evacuation; · Develop, integrate, and maintain three-dimensional urban and topographic databases; · Validate the transport models more thoroughly, including over a broader range of realistic environmental conditions (e.g., topography, microclimates, and so on)
From page 65...
... For biological agents, 10 percent, 20 percent, 30 percent, and 40 percent of the agents are released under light, moderate, severe, and total damage, respectively. For chemical or industrial agents, the corresponding percentages of agents released are 15 percent, 30 percent, 45 percent, and 60 percent.
From page 66...
... It is an empirical code based on tests at the Nevada Test Site that define an effective nuclear mushroom cloud, characterizing its initial altitude, particle size, and associated quantity of radioactivity. NEWFALL, used for shallow buried bursts, surface bursts, and airbursts, models particle size, agglomeration, and radiation distributions.
From page 67...
... generated by others -- the Air Force Weather Service, the Navy Fleet Numerical Operations Center, applications of the DTRA Operational Multiscale Environment Model with Grid Adaptivity (OMEGA) , the National Oceanic and Atmospheric Administration, and allied weather models -- or it operates on simple input such as a single wind vector, uniform throughout the domain, or an interpolation between two or more atmospheric soundings.
From page 68...
... Only HPAC includes a subroutine that calculates casualties from a nuclear event. HPAC calculates or predicts chemical and biological agent dosages and isopleths based either on program defaults or on user input.
From page 69...
... For environmentally sensitive agents, the duration of exposure to sunlight and to photochemically produced compounds and radicals is an important factor in their loss of viability or toxicity. Biological agents released by explosive destruction of the sites where they are stored will be subject to inactivation by the high temperatures generated in the explosion, and chemical agents will be degraded to the extent that they are affected by very high temperatures.
From page 70...
... Upper-air weather data are more representative for larger domains and for longer-duration hazards such as those produced by the use of nuclear weapons or the release of biological agents, or for higher-altitude releases of materials (releases above 500 meters)
From page 71...
... Both of these effects alter the local wind direction as well as the downwind transport and turbulent diffusion processes. The ATD models account for terrain.
From page 72...
... 5. Todd Hann, Defense Threat Reduction Agency, August 13, 2004, personal communication.


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