About 600 experiments and roughly 500 users were affected by the nearly year-long shutdown of the High Flux Isotope Reactor at Oak Ridge National Laboratory, the lab said Thursday.
HFIR, which is used for research and isotope production, restarted October 29, 2019. It had been shut down since November 13, 2018, after an elevated radiation level was detected in the reactor’s primary cooling system.
Reactors users who had approved proposals when HFIR was shut down have been running those experiments since it restarted in the fall, according to a response to questions provided by ORNL spokesperson Morgan McCorkle on Thursday. The backlog is expected to be completed by the spring.
The shutdown did not affect the production of plutonium-238, but it did delay the production and distribution of some medical and industrial isotopes, the lab’s response said.
“It is our understanding that some of the end users were able to temporarily fill the supply gap using other suppliers,” ORNL said.
During the shutdown, the lab said it completed facility improvements and significant upgrades to 10 of the 12 neutron beam line instruments in HFIR. The upgrades included more advanced beam delivery systems, enhanced sample environments, better optics, and improved data acquisition systems and detectors. Five of the 10 instrument projects were considered major upgrades. (For more information, see instrument upgrades story here.)
The facility improvements included upgrades to the coolant supply pipes, maintenance on control rod and extension tube assemblies, upgrades to the reactor pool heating system, and installation of concrete electrical duct banks for future improvements, ORNL said. Many valves, actuators, sensors, electrical switches, filters, and cables were repaired or replaced, and hundreds of existing systems were inspected to ensure proper operation, the lab said.
ORNL said about $10 million is set aside each year by the U.S. Department of Energy for upgrades at HFIR and the Spallation Neutron Source, which is also at ORNL.
It was not the longest shutdown in HFIR history. HFIR was shut down for about 2.5 years for an evaluation from November 1986 to April 1989 after tests indicated that the reactor vessel was being embrittled by neutron irradiation at a rate faster than predicted.
HFIR is the only Category I nuclear facility in Oak Ridge. It is regulated by DOE. A Hazard Category I nuclear facility has the potential for significant off-site consequences.
DOE is investigating fuel element performance in HFIR after the elevated radiation level was found in the cooling system, possibly due to a pinhole leak. In the meantime, ORNL said HFIR is back to normal operations.
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