US liquid metal test facility gets upgrade

Friday, 2 May 2025

The Mechanisms Engineering Test Loop (METL) facility, established in 2018, is an intermediate-scale liquid metal experimental facility that provides purified reactor-grade sodium to various experimental test vessels to test components that are required to operate in a prototypical advanced reactor environment. The METL facility has the capability to test small to intermediate-scale components and systems in order to develop advanced liquid metal technologies.

"Testing different components in METL is essential for the future of advanced fast reactors as it should provide invaluable performance data and reduce the risk of failures during plant operation," according to Argonne National Laboratory.

Argonne National Laboratory has now successfully replaced an aging cold trap device in METL, an upgrade that the Department of Energy (DOE) says is the first of its kind in the USA in more than 30 years.

_{The old cold trap (left) prepped for removal with new cold trap (right) ready for installation into METL (Image: Argonne National Laboratory)}

The cold trap is an essential piece 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. 

Replacing 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", DOE said.  

The METL facility utilises welded construction techniques that are consistent with the maintenance of any advanced liquid metal reactor. The sodium in the old cold trap was frozen and cut out of the system before a new cold trap was welded onto the sodium piping. Argonne National Laboratory consulted with France's Alternative Energies & Atomic Energy Commission (CEA) prior to performing the maintenance.

_{Argonne workers weld an inlet pipe into the new cold trap device at the METL facility (Image: Argonne National Laboratory)}

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.  

Matthew Weathered, a principal nuclear engineer at Argonne National Laboratory, said: "It's exciting. 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 cold trap replacement was funded through DOE's National Reactor Innovation Center, which funds the operations and maintenance activities at the METL facility and works to build or enhance the department's infrastructure to enable the successful 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.

Article researched and written by WNN's Warwick Pipe