US Argonne National Laboratory (ANL) has replaced a key component in its liquid metal test loop, which is used to support development of sodium-cooled fast reactors. The upgrade is the first of its kind in the US in more than 30 years and will help inform the design and operation of sodium-cooled fast reactors that are currently being developed by several US companies.
Argonne researchers replaced an ageing cold trap device on the Mechanisms Engineering Test Loop (METL) that is used to purify more than 750 gallons of reactor-grade sodium. METL is the largest US liquid metal test facility for sodium-cooled fast reactors and is training a new generation of potential operators.
The United States has not operated a fast reactor since the Experimental Breeder Reactor II (EBR-II) shut down. However, projected increases in power demand have now encouraged some companies to revisit the technology. EBR-II operated at ANL from 1964 to 1994 using a metallic alloy fuel containing highly enriched uranium (HEU). It generated power for the lab and supported reactor research and development projects.
METL started operations in 2018 to help advance research on liquid metal technologies and is now being used by industry partners to test different components for potential use in their designs.
The cold trap is essential to any liquid metal reactor design to help filter out oxide impurities present in the sodium that is used to cool the reactor. If not controlled, these impurities could cause accelerated corrosion of the systems and lower flow rates, resulting in degraded performance.
Replacement of the device was required to meet the design specifications of future experiments and played a key role in regaining US experience on replacing sodium loop components.
“It’s exciting,” said Dr Matthew Weathered, a principal nuclear engineer. “The METL team is revitalising and developing these key operations and maintenance techniques to ensure we are able to deploy US sodium cooled reactors in the near future.”
The METL facility utilises welded construction techniques that are consistent with the maintenance of any advanced liquid metal reactor. The sodium in the cold trap was frozen and cut out of the system before a new cold trap was welded onto the sodium piping.
The lab consulted with French Alternative Energies & Atomic Energy Commission (CEA – Commissariat à l’énergie Atomique et aux énergies Alternatives) before undertaking the maintenance. The entire process took two weeks to complete after months of planning, while the rest of the test loop remained hot, molten, and in operation.
The cold trap replacement was funded through the Department of Energy’s National Reactor Innovation Center (NRIC), which funds the operations and maintenance activities at the METL facility. NRIC works to build or enhance DOE infrastructure to support deployment of advanced nuclear technologies. METL plans to expand its testing capabilities in 2026 by activating a fifth test vessel to accommodate additional liquid metal tests.
