Photograph by the Department of Energy/Lynn Freeny
The High Flux Isotope Reactor at Oak Ridge National Laboratory was restarted Tuesday following its extended fall outage — the second longest of the year — in which several projects of importance were completed.
Tim Powers, the director of ORNL’s Research Reactors Division, provided a summary of activities carried out during the shutdown period that began in mid-August. One of the biggies was installation of a new fuel grid into the vessel, he said.
“HFIR’s fuel as well as the target bundle rest on top of this device,” Powers said via email. “The last time it was replaced was in the early 2000s.”
He said workers also performed “an extremely important” hydrostatic test that is done only about once every five years. “It involves pressurizing the system to about twice HFIR’s normal operating pressure while we check for leaks,” he said. “It takes about 100 people, and we passed.”
In addition, reactor workers also installed a “vacuum box” that will provide for better understanding of material samples that are targeted in the Biological Small Angle Neutron Scattering Detector — one of the advanced research instruments used at the ORNL reactor.
Among the other maintenance activities or repairs that took place during the lengthy outage: continued work on a number of seismic upgrades at the reactor; replaced several breakers in the electrical switch gear; installed another new Instrument Air Drier (the second of the year); replaced level switches for multiple tanks; replaced HEPA filters in various systems; repaired an outside dike that contains an acid tank; replaced portable water main isolation valves; made upgrades to an experimental device called the Materials Irradiation Test Facility; and installed new power supplies in the Guide Hall.
Powers also cited a number of corrective or preventive maintenance activities, such as repairing of power indication meters and several electrical ground faults, and work on some primary coolant pumps and electrical motor control centers.
The ORNL official said the plan is to operate the research reactor for 24 days and shut it down on Oct. 30 for an 18-day maintenance and refueling period.
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