The reactor pool is pictured above in the reactor bay inside the High Flux Isotope Reactor at Oak Ridge National Laboratory on Thursday, March 15, 2018. Spent nuclear fuel is stored inside the pool. (Photo by John Huotari/Oak Ridge Today)
For the first time in 30 years, spent nuclear fuel from the High Flux Isotope Reactor at Oak Ridge National Laboratory has been dissolved at the Savannah River Site in South Carolina.
The work is important because it is expected to allow the reactor, known as HFIR, to continue its mission, according to the U.S. Department of Energy Office of Environmental Management.
HFIR, which uses highly enriched uranium, is one of the world’s most powerful nuclear research reactor facilities. It’s the highest flux reactor-based source of neutrons for research in the United States. Flux refers to the rate of flow of fluids, particles, or energy. In HFIR’s case, the flux is measured in neutrons per square centimeter per second. HFIR is used for neutron scattering and isotope production, among other missions.
ORNL will reach its maximum capacity for storing HFIR fuel in fiscal year 2020, the DOE Office of Environmental Management, or EM, said in an “EM Update” electronic newsletter on Tuesday.
The HFIR fuel elements, inner and outer elements, together form a reactor “core.” After the cores are used at HFIR, they are stored at ORNL for eventual shipment to the Savannah River Site, or SRS, which is in Aiken, South Carolina, for processing.
Once the cores arrive at SRS, they are stored in an area called the L Area, in an underwater spent fuel basin that reduces radiation rates. The cores are stored there while awaiting processing in what is referred to as H Canyon at Savannah River.
There are currently 120 HFIR cores stored in the L Area at the Savannah River Site, EM said. That’s the maximum capacity for HFIR fuel storage at SRS.
DOE has directed the Savannah River Site to dissolve HFIR fuel starting this year to ensure that there is sufficient spent nuclear fuel storage for the HFIR reactor to continue its mission, the “EM Update” said.
The newsletter said Savannah River Site’s H Canyon recently began dissolving the spent nuclear fuel from HFIR.
“This campaign marks the first time H Canyon has dissolved HFIR SNF (spent nuclear fuel) since 1988, and is essential for the continued mission of HFIR,” DOE-Savannah River Nuclear Materials Programs Manager Maxcine Maxted said in the “EM Update.”
SRS said it will continue to receive HFIR fuel cores to support the operation of the Oak Ridge reactor. But it’s not clear yet when those shipments might start.
H Canyon Crane Operator Glenn Bowman lowers a High Flux Isotope Reactor core from Oak Ridge National Laboratory into the dissolver at the Savannah River Site in Aiken, S.C. (Photo courtesy U.S. Department of Energy Office of Environmental Management)
H Canyon’s mission is to blend down highly enriched uranium (HEU) spent nuclear fuel from domestic and foreign research reactor fuel into low enriched uranium (LEU). LEU can be used to make fuel for commercial power reactors and also makes the HEU non-proliferable.
“This campaign is also significant in that it marks the first time that there have been three different uranium streams feeding H Canyon simultaneously,” Maxted said. “In addition to HFIR, the other streams are Material Test Reactor spent nuclear fuel and Target Residue Material. Multiple uranium streams allow for better utilization of the canyon capabilities.”
To begin the chemical processing that turns HEU spent nuclear fuel into LEU, H Canyon reconfigured one dissolver and replaced a second dissolver that contained a failed cooling coil last year. Preparation for the HFIR mission also included revising the safety analysis and procedures, training of personnel, and a lot of practice in both H Canyon and L Area, the “EM Update” said.
“It took a lot of hard work and dedication to prepare for this campaign,” Maxted said. “However, we knew that the employees of L Area and H Canyon, the only hardened radiochemical separations facility operating in the United States, were up to the task. H Canyon is once again proving that it is a crucial element in enabling other DOE research facilities, such as the DOE national laboratory at Oak Ridge, to continue operation. It is this kind of collaboration that makes the DOE complex effective.”
Lindsey MonBarren contributed to the “EM Update” used for this story.
More information will be added as it becomes available.
The thermal and cold neutrons produced by HFIR, which operates at 85 megawatts, are used to study physics, chemistry, materials science, engineering, and biology. Learn more about HFIR here.
A High Flux Isotope Reactor core from Oak Ridge National Laboratory is dropped into the H Canyon dissolver at the Savannah River Site in Aiken, S.C. (Photo courtesy U.S. Department of Energy Office of Environmental Management)
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