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The Mk/B53 was a high-yield bunker buster thermonuclear weapon developed by the United States during the Cold War. Deployed on Strategic Air Command bombers, the B53, with a yield of 9 megatons, was the most powerful weapon in the U.S. nuclear arsenal after the last B41 nuclear bombs were retired in 1976. The B53 was the basis of the W-53 warhead carried by the Titan II Missile, which was decommissioned in 1987. Although not in active service for many years before 2010, fifty B53s were retained during that time as part of the "Hedge" portion〔"Hedge stockpile": fully operational, but kept in storage; available within minutes or hours; not connected to delivery systems, but delivery systems are available (i.e. missile and bomb stockpiles kept at various Air Force bases)〕 of the Enduring Stockpile until its complete dismantling in 2011. The last B53 was disassembled on 25 October 2011, a year ahead of schedule. With its retirement, the largest bomb currently in service in the U.S. nuclear arsenal is the B83, with a maximum yield of 1.2 megatons. The B53 was replaced in the bunker-busting role by a variant of the two-stage B61 nuclear bomb. ==History== Development of the weapon began in 1955 by Los Alamos National Laboratory, based on the earlier Mk 21 and Mk 46 weapons. In March 1958 the Strategic Air Command issued a request for a new Class C (less than five tons, megaton-range) bomb to replace the earlier Mk 41. A revised version of the Mk 46 became the TX-53 in 1959. The development TX-53 warhead was apparently never tested, although an experimental TX-46 predecessor design was detonated 28 June 1958 as Hardtack Oak, which detonated at a yield of 8.9 Megatons. The Mk 53 entered production in 1962 and was built through June 1965.〔 About 340 bombs were built. It entered service aboard B-47 Stratojet, B-52G Stratofortress,〔 and B-58 Hustler bomber aircraft in the mid-1960s. From 1968 it was redesignated B53. Some early versions of the bomb were dismantled beginning in 1967. About 50 bomb and 54 Titan warhead versions were in service through 1980. After the Titan II program ended, the remaining W-53s were retired in the late 1980s. The B53 was also intended to be retired in the 1980s, but 50 units remained in the active stockpile until the deployment of the B61-11 in 1997. At that point the obsolete B53s were slated for immediate disassembly; however, the process of disassembling the units was greatly hampered by safety concerns as well as a lack of resources. In 2010 authorization was given to disassemble the 50 bombs at the Pantex plant in Texas. The process of dismantling the last remaining B53 bomb in the stockpile commenced on 25 October 2011 and was completed soon afterwards. 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「B53 nuclear bomb」の詳細全文を読む スポンサード リンク
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