Capabilities

Nek5000 is an open-source CFD code developed at Argonne National Laboratory written in FORTRAN 77 and C. It uses an explicit time marching scheme to solve the unsteady Navier-Stokes equations with spatial discretization done using the spectral element method (SEM). Nek5000 can solve both laminar and turbulent flow cases using either direct numerical simulations (DNS), large eddy simulations (LES), or Reynolds-averaged Navier-Stokes (RANS) modeling. Nek5000 was used for this study as it has a long history of being used for high-fidelity, nuclear engineering applications. Much of the work done within the research group involving Nek5000 uses LES due to the higher-fidelity offered compared to RANS models but lower computational cost than DNS. 

Modular Separate Effects Test Facility - Surrogate Twin Natural Circulation Loop (MSETF-STNCL)

To support development of molten salt reactor (MSR) technologies, experimental natural convection loops were constructed to predict the thermal hydraulic behavior and develop digital twins as part of a collaborative effort between Virginia Commonwealth University (VCU), University of Texas-Austin (UT), and Abilene Christian University (ACU) through the TRIDENT project. VCU addresses the thermal hydraulic performance for irradiated molten salt systems using a surrogate thermal convection loop to understand the impact of thermal physical property changes for fuel and coolant salts. Thermocouples and fiber optic sensors are used throughout the loop and surrounding environment to understand the temperature effects of varying heat inputs and outputs. The fiber optic sensors allow for real time, distributive temperature measurements while the thermocouples act as a reliable baseline to compare the fiber optic measurements to.

MSETF-SLUDGE is a power fluidic loop designed to investigate the transport and handling of radioactive liquids and sludge using maintenance-free power fluidic pumps. The loop consists of a storage tank, charge vessel, Jet Pump Pair (JPP), piping, and instrumentation for measuring pressure, flow rate, and temperature. It operates through repeated suction, drive, and vent cycles to move fluid through the system without mechanical moving parts. The system utilizes additively manufactured JPPs fabricated through stereolithography (SLA), allowing different geometries and nozzle configurations to be rapidly produced and tested. Experimental testing of different JPP configurations and operating pressures provides data to evaluate system performance and support the development of reliable fluid transport technologies for nuclear fuel reprocessing.

Modular Separate Effects Test Facility (MSETF) - Tritium Removal Investigation of Transport Interactions Using Mass-transfer (TRITIUM)

During molten salt reactor (MSR) system operation, tritium is generated in significantly larger quantities when compared to other reactors. Tritium poses a significant radiological risk due to the high permeability and solubility of the fission product. Gas sparging poses a potential removal method of tritium and other fission products for fluoride based MSRs. The gas sparging components use a sparging (noble) gas that is bubbled through molten salt. The bubbles absorb dissolvable fission products and are extracted from the component to the off-gasing system. The current understanding of the tritium striping/extraction performance has gaps for relevant MSR operating conditions.

The reported experiments in this work emulate the mass transfer of tritium in FLiBe based on scaling theory. The experiments are performed using a surrogate fluid at lower temperatures and scaled geometric configurations to study the mass transfer phenomena within gas spargers. The scaled experimental facility is the Modular Separate Effects Test Facility (MSETF) - Tritium Removal Investigation of Transport Interactions Using Mass-transfer (TRITIUM) flow loop. MSETF-TRITIUM is used to study the convective mass transfer that occurs within the system as argon (helium in the MSR) is bubbled into the surrogate fluid (water- glycerol mixture) to remove the oxygen (tritium in the MSR) present in the surrogate fluid. The thermophysical properties of the surrogate fluid and sparging gas will be varied to match the Schmidt number to that of the tritium dissolved FLiBe and sparging gas. The MSEFT-TRITIUM loop is equipped with dissolved oxygen sensors, high speed imaging for bubble measurements, and temperature/flow process measurements. These measurements are used to determine the Sherwood number from volumetric mass transfer coefficient based on set Schmidt and Reynolds Numbers. This presentation will discuss the recent loop modifications, loop validation against existing correlations, and present a roadmap for future studies of novel gas sparging designs.