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High Flux Isotope Reactor

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High Flux Isotope Reactor

The High Flux Isotope Reactor (HFIR) is a nuclear research reactor 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 physics research in the United States, and it has 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 about 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 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.

The next major shutdown for a beryllium reflector replacement is planned for 2028-2029. In parallel, this program foresees in an extension to the cold guide hall to allow for reconfiguring and optimizing of the cold neutron instruments, and provide space for new instruments. 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.

In January 1958, the U.S. Atomic Energy Commission (AEC) reviewed the status of transuranium isotope production in the United States. By November of that 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 start 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 ~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 review and evaluation of the facility. After thorough reevaluation last over two years, 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. The primary coolant pressure and core power were reduced to preserve vessel integrity while maintaining thermal margins, and 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. After the April 1989 restart, a further shutdown of nine months occurred due to a question as to procedural adequacy. During this time, oversight of HFIR was transferred to the DOE Office of Nuclear Energy; previously, oversight was through the Office of Energy Research. 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.

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