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The High Flux Isotope Reactor (or HFIR) is a nuclear research reactor located at Oak Ridge National Laboratory (ORNL) in Oak Ridge, Tennessee, United States. Operating at 85 MW, HFIR is one of the highest flux reactor-based sources of neutrons for condensed matter research in the United States, and it provides one of the highest steady-state neutron fluxes of any research reactor in the world. The thermal and cold neutrons produced by HFIR are used to study physics, chemistry, materials science, engineering, and biology. The intense neutron flux, constant power density, and constant-length fuel cycles are used by more than 500 researchers each year for neutron scattering research into the fundamental properties of condensed matter. HFIR has approximately 600 users each year for both scattering and in-core research. The neutron scattering research facilities at HFIR contain a world-class collection of instruments used for fundamental and applied research on the structure and dynamics of matter. The reactor is also used for medical, industrial, and research isotope production; research on severe neutron damage to materials; and neutron activation to examine trace elements in the environment. Additionally, the building houses a gamma irradiation facility that uses spent fuel assemblies and is capable of accommodating high gamma dose experiments. With projected regular operations, the next major shutdown for a beryllium reflector replacement will not be necessary until approximately 2023. This outage provides an opportunity to install a cold source in radial beam tube HB-2, which would provide an unparalleled flux of cold neutrons feeding instruments in a new guide hall. With or without this additional capability, HFIR is projected to continue operating through 2040 and beyond. In November 2007 ORNL officials announced that time-of-flight tests on a newly installed cold source (which uses liquid helium and hydrogen to slow the movement of neutrons) showed better performance than design predictions, equaling or surpassing the previous world record set by the research reactor at the Institut Laue-Langevin in Grenoble, France.〔(Data suggest world record at Oak Ridge reactor ), By Frank Munger, ''Knoxville News Sentinel'', November 26, 2007〕 ==History== In January 1958, the U.S. Atomic Energy Commission (AEC) reviewed the status of transuranium isotope production in the United States. By November of the same year, the commission decided to build the High Flux Isotope Reactor (HFIR) at Oak Ridge National Laboratory, with a fundamental focus on isotope research and production. Since it first went critical in 1965, the in-core uses for HFIR have broadened to include materials research, fuels research, and fusion energy research, in addition to isotope production and research for medical, nuclear, detector and security purposes. A low-power testing program was completed in January 1966, and operation cycles at 20, 50, 75, 90, and 100 MW began. From the time it attained its design power of 100 MW in September 1966, a little over five years from the beginning of its construction, until it was temporarily shut down in late 1986, HFIR achieved a record of operation time unsurpassed by any other reactor in the United States. By December 1973, it had completed its 100th fuel cycle, each lasting approximately 23 days. In November 1986, tests on irradiation surveillance specimens indicated that the reactor vessel was being embrittled by neutron irradiation at a rate faster than predicted. HFIR was shut down to allow for extensive reviews and evaluation of the facility. Two years and five months later, after thorough reevaluation, modifications to extend the life of the plant while protecting the integrity of the pressure vessel, and upgrades to management practices, the reactor was restarted at 85 MW. Coincident with physical and procedural improvements were renewed training, safety analysis, and quality assurance activities. Documents were updated, and new ones were generated where necessary. Technical specifications were amended and reformatted to keep abreast of the design changes as they were accepted by the U.S. Department of Energy (DOE), formerly the AEC. Not only were the primary coolant pressure and core power reduced to preserve vessel integrity while maintaining thermal margins, but long-term commitments were made for technological and procedural upgrades. After a thorough review of many aspects of HFIR operation, the reactor was restarted for fuel cycle 288 on April 18, 1989, to operate initially at very low power levels (8.5 MW) until all operating crews were fully trained and it was possible to operate continuously at higher power. Following the April 1989 restart, a further shutdown of nine months occurred as a consequence of a question as to procedural adequacy. During this period, oversight of HFIR was transferred to the DOE Office of Nuclear Energy (NE); previously, oversight was through the Office of Energy Research (ER). Following permission by Secretary of Energy James D. Watkins to resume startup operation in January 1990, full power was reached on May 18, 1990. Ongoing programs have been established for procedural and technological upgrade of the HFIR during its operating life. In 2007, HFIR completed the most dramatic transformation in its 40-year history. During a shutdown of more than a year, the facility was refurbished and a number of new instruments were installed, as well as a cold neutron source. The reactor was restarted in mid-May; it attained its full power of 85 MW within a couple of days, and experiments resumed within a week. Improvements and upgrades include an overhaul of the reactor structure for reliable, sustained operation; significant upgrading of the eight thermal-neutron spectrometers in the beam room; new computer system controls; installation of the liquid hydrogen cold source; and a new cold neutron guide hall. The upgraded HFIR will eventually house 15 instruments, including 7 for research using cold neutrons. Although HFIR's main mission is now neutron scattering research, one of its original primary purposes was the production of californium-252 and other transuranium isotopes for research, industrial, and medical applications. HFIR is the western world's sole supplier of californium-252, an isotope with uses such as cancer therapy and the detection of pollutants in the environment and explosives in luggage. Beyond its contributions to isotope production and neutron scattering, HFIR also provides for a variety of irradiation tests and experiments that benefit from the facility's exceptionally high neutron flux. 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「High Flux Isotope Reactor」の詳細全文を読む スポンサード リンク
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