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The Lady Godiva device〔 was an unshielded, pulsed nuclear reactor〔 originally situated at the Los Alamos National Laboratory (LANL), New Mexico, U.S. It was one of a number of criticality devices within Technical Area 18 (TA-18). Specifically, it was used to produce bursts of neutrons and gamma rays for irradiating test samples, and inspired development of Godiva-like reactors. Physicist Otto Frisch remembered the Los Alamos team called an earlier unshielded uranium-235 assembly in 1944 "Lady Godiva". The radiation source within the Godiva device was a fissile metallic mass (usually highly enriched 235U),〔McLaughlin et al. page 109, "93%"〕 about 30 cm in diameter. This was located at the top of a two-metre-high metal tower. The burst of radiation was produced when a piston of fissile material was quickly inserted and extracted from a cavity within the larger fissile mass. During the time these two masses were combined, they formed a critical mass and a nuclear chain reaction was briefly sustained.〔Garcia page 1〕 Godiva's design was inspired from a self terminating property discovered when incorrectly experimenting with the Jemima device in 1952. Jemima operated by remotely lifting one stack of enriched uranium-235 disks up towards another, fixed, stack. On 18 April 1952, due to a miscalculation, Jemima was assembled with too many disks; this caused an excursion of 1.5 x 1016 fissions—an automatic scram—but no damage.〔 On 3 February 1954 and 12 February 1957, accidental criticality excursions occurred causing damage to the device, but fortunately only insignificant exposures to personnel. This original Godiva device, known as ''Lady Godiva'', was irreparable after the second accident and was replaced by the ''Godiva II''.〔McLaughlin et al. pages 78, 80-83. "Jemima ... apparent self terminating property of this excursion stimulated study with Lady Godiva,46,47,48"〕 ==Godiva II== Godiva II was constructed inside a concrete building with walls and roof in a canyon a quarter-mile away from the control room.〔Engelke pages 3-4〕 In 1959, Los Alamos agreed to make Godiva II available to DOD contractors free of charge for 2 days each month, acknowledging its unique facility for radiation tests.〔Zipprich, L.J.〕 Godiva's success in creating intense bursts spurred development of similar pulsed reactors, which also suffered accidental excursions, for example: 28 May 1965 at the 1965 White Sands Missile Range (parts were thrown 15 feet);〔McLaughlin et al. page 86, "Unreflected uranium–molybdenum metal fast burst reactor"〕 and 6 September 1968 at the Aberdeen Proving Ground (middle melted, disks warped and bolts stretched).〔Kazi et al., "center third of the safety block was melted"〕 In December 2002, the U.S. Department of Energy announced it was to move its TA-18 testing equipment including the Godiva burst machine from the LANL to the Device Assembly Facility (DAF) at the Nevada Test Site (NTS).〔〔U.S. Department of Energy page 1〕 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「Godiva device」の詳細全文を読む スポンサード リンク
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