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The SL-1, or Stationary Low-Power Reactor Number One, was a United States Army experimental nuclear power reactor which underwent a steam explosion and meltdown on January 3, 1961, killing its three operators. The direct cause was the improper withdrawal of the central control rod, responsible for absorbing neutrons in the reactor core. The event is the only known reactor incident in the United States which resulted in immediate fatalities. The incident released about of iodine-131,〔(The Nuclear Power Deception ) Table 7: Some Reactor Accidents〕 which was not considered significant due to its location in the remote high desert of eastern Idaho. About of fission products were released into the atmosphere.〔Horan, J. R., and J. B. Braun, 1993, ''Occupational Radiation Exposure History of Idaho Field Office Operations at the INEL'', EGG-CS-11143, EG&G Idaho, Inc., October, Idaho Falls, Idaho.〕 The facility, located at the National Reactor Testing Station (NRTS) approximately west of Idaho Falls, was part of the Army Nuclear Power Program and was known as the Argonne Low Power Reactor (ALPR) during its design and build phase. It was intended to provide electrical power and heat for small, remote military facilities, such as radar sites near the Arctic Circle, and those in the DEW Line. The design power was 3 MW (thermal), but some 4.7 MW tests were performed in the months prior to the accident. Operating power was 200 kW electrical and 400 kW thermal for space heating. During the incident the core power level reached nearly 20 GW in just four milliseconds, precipitating the steam explosion.〔〔(LA-3611 ''A Review of Criticality Accidents'' ), William R. Stratton, Los Alamos Scientific Laboratory, 1967〕〔(LA-13638 ''A Review of Criticality Accidents'' (2000 Revision) ), Thomas P. McLaughlin, et al., Los Alamos National Laboratory, 2000.〕 ==Design== From 1954 to 1955, the U.S. Army evaluated their need for nuclear reactor plants that would be operable in remote regions of the Arctic. The reactors were to replace diesel generators and boilers that provided electricity and space heating for the Army's radar stations. The Army Reactors Branch formed the guidelines for the project and contracted with Argonne National Laboratory to design, build, and test a prototype reactor plant to be called the Argonne Low Power Reactor (ALPR). Some of the more important criteria included: *All components able to be transported by air *Use of standard components *Minimal on-site construction *Simplicity and reliability *3-year fuel operating lifetime per core loading The prototype was constructed at the NRTS site from July 1957 to July 1958. It was operational on October 24, 1958. The 3 MW (thermal) boiling water reactor (BWR) used 93.20% highly enriched uranium fuel. It operated with natural circulation, using light water as a coolant and moderator. ANL used its experience from the BORAX experiments to design the BWR. The circulating water system operated at flowing through fuel plates of uranium-aluminum alloy. The plant was turned over to the U.S. Army in December 1958 after extensive testing, with Combustion Engineering acting as the lead contractor beginning in February 1959. Members of the U.S. Army, called ''cadre'', began training as plant operators, although some Navy personnel also trained with them. The majority of the plant equipment was located in a cylindrical steel reactor building in diameter and an overall height of . The reactor building known as ARA-602 was made of plate steel, most of which had a thickness of 1/4 inch (6 mm). Access to the building was provided by an ordinary door through an enclosed exterior stairwell from ARA-603, the Support Facilities Building. An emergency exit door was also included, with an exterior stairwell going to the ground level. The reactor building was not a pressure-type containment shell as would have been used for reactors located in populated areas. Nevertheless, the building was able to contain most of the radioactive particles released by the eventual explosion. The reactor core structure was built for a capacity of 59 fuel assemblies, one source assembly, and 9 control rods. The core in use, however, had 40 fuel elements and was controlled by 5 cruciform rods. The 5 active rods were in the shape of a plus symbol (+) in cross section: 1 in the center (Rod Number 9), and 4 on the periphery of the active core (Rods 1, 3, 5, and 7). The control rods were made of thick cadmium, clad with of aluminum. They had an overall span of and an effective length of . The 40 fuel assemblies were composed of 9 fuel plates each. The plates were thick consisting of of uranium-aluminium alloy "meat" covered by of X-8001 aluminum cladding. The meat was long and wide. The water gap between fuel plates was . The initial loading of the 40 assembly core was highly enriched with 93.2% uranium-235 and contained of U-235. The deliberate choice of a smaller fuel loading made the region near the center more active than it would have been with 59 fuel assemblies. The four outer control rods weren't even used in the smaller core. In the operating SL-1 core, Rods Number 2, 4, 6, and 8 were dummy rods, had cadmium shims, or were filled with test sensors, and were shaped like the capital letter T. The effort to minimize the size of the core gave the central rod an abnormally large reactivity worth. 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「SL-1」の詳細全文を読む スポンサード リンク
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