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A cobalt bomb is a theoretical type of "salted bomb": a nuclear weapon designed to produce enhanced amounts of radioactive fallout, intended to contaminate a large area with radioactive material. The concept of a cobalt bomb was originally described in a radio program by physicist Leó Szilárd on February 26, 1950. His intent was not to propose that such a weapon be built, but to show that nuclear weapon technology would soon reach the point where it could end human life on Earth, a doomsday device. Such "salted" weapons were requested by the U.S. Air Force and seriously investigated, but not deployed. In the 1964 edition of the DOD/AEC book ''The Effects of Nuclear Weapons,'' a new section titled radiological warfare clarified the "Doomsday device" issue.〔Samuel Glasstone, ''The Effects of Nuclear Weapons'', 1962, Revised 1964, U.S. Dept of Defense and U.S. Dept of Energy, pp.464–5. This section was removed from later editions, but, according to Glasstone in 1978, not because it was inaccurate or because the weapons had changed.〕 As far as is publicly known, no cobalt bombs have ever been built. The Operation Antler/Round 1 test by the British at the Tadje site in the Maralinga range in Australia on September 14, 1957 tested a bomb using cobalt pellets as a radiochemical tracer for estimating yield. This was considered a failure and the experiment was not repeated. Furthermore the triple "taiga" nuclear salvo test, as part of the preliminary March 1971 Pechora–Kama Canal project, produced substantial amounts of Co-60, with this fusion generated neutron activation product being responsible for about half of the gamma dose now (2011) at the test site, with photosynthesizing vegetation existing all around the lake that was formed.〔(【引用サイトリンク】title=Radiological investigations at the “Taiga” nuclear explosion site: Site description and in situ measurements )〕〔(【引用サイトリンク】title=Radiological investigations at the “Taiga” nuclear explosion site, part II: man-made γ-ray emitting radionuclides in the ground and the resultant kerma rate in air )〕 In 2015, a Russian nuclear-armed torpedo design was apparently leaked. It has been speculated that the warhead would be a cobalt bomb, designed for "creating wide areas of radioactive contamination, rendering them unusable for military, economic or other activity for a long time".〔http://www.bbc.co.uk/news/world-europe-34797252〕 ==Mechanism== A cobalt bomb could be made by placing a quantity of ordinary cobalt metal (59Co) inside a nuclear bomb. When the bomb explodes, the neutrons produced by the explosion would transmute the cobalt to the radioactive isotope cobalt-60 (60Co), which would be vaporized by the explosion. The cobalt would then condense and fall back to Earth with the dust and debris from the explosion, contaminating the ground. The deposited cobalt-60 would have a half-life of 5.27 years, decaying into 60Ni. The nickel nucleus is activated, and emits two gamma rays with energies of 1.17 and 1.33 MeV, hence the overall nuclear equation of the reaction is: + n → → + e− + gamma rays. Nickel-60 is a stable isotope and undergoes no further decays after emitting the gamma rays. The 5.27 year half life of the 60Co is long enough to allow it to settle out before significant decay has occurred, and to render it impractical to wait in shelters for it to decay, yet short enough that intense radiation is produced.〔 Many isotopes are more radioactive (gold-198, tantalum-182, zinc-65, sodium-24, and many more), but they would decay faster, possibly allowing some population to survive in shelters. In a fission bomb, it has been suggested, the weapon's tamper could be made of cobalt. In a fusion bomb the radiation case around the weapon, normally made of 238U, could be made of cobalt. These changes would reduce the explosive power (yield) of the weapon somewhat. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Cobalt bomb」の詳細全文を読む スポンサード リンク
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