Mechanisms Engineering Test Loop Facility

The Mechanisms Engineering Test Loop (METL) facility, established in 2018, is an intermediate-scale liquid metal experimental facility that provides purified R-grade sodium to various experimental test vessels to test components that are required to operate in a prototypical advanced reactor environment. Experiments conducted in METL significantly assist the development of advanced reactors.

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.

Some examples of technologies that can be tested in METL include:

1. Components of an advanced fuel handling system – Fuel handling systems are used for the insertion and removal of core assemblies located within the reactor vessel. Undoubtedly, these components are essential to the successful operation of fast reactors. For liquid metal applications, fuel handling systems need to work inside the primary vessel and typically penetrate through the cover gas of the primary system. As a result, fuel handling systems must address issues associated with ​‘sodium-frost’ buildup.
2. Mechanisms for self-actuated control and shutdown systems – These components have been conceived by various designers to provide added defense-in-depth for reducing the consequences of beyond-design-basis accidents. These self-actuated control and shutdown mechanisms include devices such as curie-point magnets and fusible linkages.
3. Advanced sensors and instrumentation – Advanced fast reactors contain sensors and instrumentation for monitoring the condition of the plant. Sometimes these components are required to work while immersed in the primary coolant. This category includes but is not limited to, sensors for the rapid detection of hydrogen presence in sodium (which is indicative of a leak), the detection of impurities in the coolant (i.e., improvement of plugging meters or oxygen sensors), alternative methods of leak detection, improved sensors for level measurement (E. Kent, 2019) and other advanced sensors or instrumentation that improve the overall performance of the advanced reactor system.
4. In-service inspection and repair technologies – These systems include visualization sensors for immersed coolant applications and technologies for the welding and repair of structures in contact with the primary coolant.
5. Health Monitoring of METL systems and components – The development of sensors and prognostic techniques for deployment that can monitor and quantify materials degradation in liquid metal-cooled fast reactor primary systems.  Technologies that detect degradation early, can survive in typical liquid metal-cooled fast reactor environments over extended periods of time, and can be embedded in/on structural materials to enable structural health monitoring (e.g., nondestructive examination techniques, remote or automated inspection techniques including visualization in optically opaque coolants) can be tested in METL.
6. Thermal hydraulic testing in prototypic sodium environment – A thermal hydraulic test loop could be used to acquire distributed temperature data in the cold and hot pools of a small-scale sodium fast reactor during simulated nominal and protected/unprotected loss of flow accidents. This testing could allow for the articulation of the heated region in the core to allow for a parametric study of IHX/core outlet height difference and its effect on thermal stratification of sodium in the hot pool. Ultimately this data will be used for validating CFD and systems level code.
7. Human Machine Interface Technology – Technologies for improving the ability of operators to understand what is happening inside the sodium environment. One example would be the ability to provide a refueling system operator to see in-vessel refueling in a virtual environment during in-vessel refueling.
8. Artificial Intelligence (AI) and Machine Learning (ML) Algorithm Technology Demonstrations – METL has the potential to support various AI/ML research initiatives and applications. Software developers may deploy commercially available or under development programs at METL to monitor the ecosystem and notify operators of anomalies and provide corrective actions. METL has been logging data for years of operation, generating a large data set of in-situ values, which would serve as a realistic basis for training neural networks. The METL ecosystem also has a database of work performed and component failures which can be used in conjunction with the digital logbook and instrumentation data for demonstrating predictive/prescriptive maintenance software thereby reducing O&M costs of advanced reactors/METL.

METL also provides development opportunities for younger scientists, engineers, and designers who will ultimately lead the advancement of U.S. liquid metal technologies. The hands-on experience with METL, both successes and perceived failures; will ultimately lead to better liquid metal technology programs that can support the commercialization of advanced reactors.

Current capabilities that reside in the METL facility include:

• 750 Gallons of Reactor Grade Sodium
• Prototypic Reactor Temperatures of 650°C
• 4 Test Vessels
• 4 Additional Test Loops
• 300 Heater Zones
• 1000+ Sensors
• 2 Operational Tanks with Ports for Experiments
• Sodium Purification and Contamination Monitoring

METL is now funded under the U.S. Department of Energy, Office of Nuclear Energy’s National Reactor Innovation Center.