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A fallout shelter is an enclosed space specially designed to protect occupants from radioactive debris or fallout resulting from a nuclear explosion. Many such shelters were constructed as civil defense measures during the Cold War. During a nuclear explosion, matter vaporized in the resulting fireball is exposed to neutrons from the explosion, absorbs them, and becomes radioactive. When this material condenses in the rain, it forms dust and light sandy materials that resembles ground pumice. The fallout emits alpha and beta particles, as well as gamma rays. Much of this highly radioactive material falls to earth, subjecting anything within the line of sight to radiation, becoming a significant hazard. A fallout shelter is designed to allow its occupants to minimize exposure to harmful fallout until radioactivity has decayed to a safer level. == History == During the Cold War, many countries built fallout shelters for high-ranking government officials and crucial military facilities, such as Project Greek Island and Cheyenne Mountain nuclear bunker in the United States and Canada's Emergency Government Headquarters. Plans were made, however, to use existing buildings with sturdy below-ground-level basements as makeshift fallout shelters. These buildings were usually placarded with the yellow and black trefoil sign. The National Emergency Alarm Repeater (NEAR) program was developed in the United States 1956 during the Cold War to supplement the existing siren warning systems and radio broadcasts in the event of a nuclear attack. The N.E.A.R. civilian alarm device was engineered and tested but the program was not viable and was terminated in 1967. In the U.S. in September 1961, under the direction of Steuart L. Pittman, the federal government started the Community Fallout Shelter Program.〔(【引用サイトリンク】title=Civil Defense Museum-Community Shelter Tours Main Page )〕〔(【引用サイトリンク】title=FALLOUT FEVER: Civil Defense shelters dotted area cities during the Cold War – My Web Times )〕 A letter from President Kennedy advising the use of fallout shelters appeared in the September 1961 issue of ''Life'' magazine.〔(DOE.gov )〕 In November 1961, in ''Fortune'' magazine, an article by Gilbert Burck appeared that outlined the plans of Nelson Rockefeller, Edward Teller, Herman Kahn, and Chet Holifield for an enormous network of concrete lined underground fallout shelters throughout the United States sufficient to shelter millions of people to serve as a refuge in case of nuclear war.〔Fortune magazine November 1961 Pages 112–115 et al〕 Similar projects have been undertaken in Finland, which requires all buildings with area over 600 m² to have an NBC shelter, and Norway, which requires all buildings with an area over 1000 m² to have a shelter.〔(【引用サイトリンク】title=FOR 1995-03-15 nr 254: Forskrift om tilfluktsrom )〕 The former Soviet Union and other Eastern Bloc countries often designed their underground mass-transit and subway tunnels to serve as bomb and fallout shelters in the event of an attack. Germany has protected shelters for 3% of its population, Austria for 30%, Finland for 70%, Sweden for 81% and Switzerland for 114%.〔 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「fallout shelter」の詳細全文を読む スポンサード リンク
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