Direct Effects of Nuclear Detonations
Environmental Consequences of Nuclear War Volume I: Physical and Atmospheric Effects A. B. Pittock, T. P. Ackerman, P. J. Crutzen, M. C. MacCracken, C. S. Shapiro and R. P. Turco @ 14Sb SCOPE. Published by John Wiley & Sons Ltd CHAPTER 1 Direct Effects of Nuclear Detonations 1.1 HIROSHIMA AND NAGASAKI 1.1.1 Historical Notes The first atomic weapon used in warfare was the bomb dropped on Hi- roshima, Japan at 8:15 AM (local time) on August 6,1945, The second, and only other, weapon so used was dropped on Nagasaki, Japan at 11:02 AM on August 9,1945. The Hiroshima bomb (Little Boy) had an energy yield of about 15:t 3 kilotons (kt; a one kt explosion is equivalent in energy release to the detonation of about 1000 tons of TNT; one megaton, Mt, equals 1000 kT). The Nagasaki bomb (Fat Man) had an energy yield of 21:t2 kilotons (Ohkita, 1985). From these unique events, much of what is known about the effects of nuclear explosions on people and cities has been learned. About 120,000 people were killed outright in both cities, and the eventual fatalities, as of 1981, were about 210,000 (Ishikawa and Swain, 1981). In Hiroshima, an urbanized area of approximately 13 square kilometers was laid to waste, while in Nagasaki, an area approximately 7 square kilometers was destroyed. Figure 1.1 starkly illustrates the extent of the devastation in central Hiroshima; only the hulks of the most resilient steel-reinforced concrete buildings were left standing. 1.1.2 Physical Effects of the Bombings Both the Hiroshima and Nagasaki nuclear explosions were airbursts-at elevations of 580 meters and 500 meters, respectively.
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