Research Programs

• Further info at MIT Center for Nanofluids Technology

Investigation of Nanofluids for Nuclear Applications

Nanofluids are engineered colloids made of a base fluid and nanoparticles (1-100 nm). Common base fluids include water, organic liquids and oils. Materials commonly used for nanoparticles include chemically stable metals (e.g., gold, copper), metal oxides (e.g., alumina, silica, zirconia, titania) and carbon in various forms (e.g., diamond, graphite, carbon nanotubes, fullerene). Contrary to the milli- and micro-size particle slurries explored in the past, nanoparticles are relatively close in size to the molecules of the base fluid, and thus can realize very stable suspensions with little deposition over long periods of time. The presence of the nanoparticles produces four major effects on the thermal-hydraulic behavior of the fluid:

• Increase of the thermal conductivity
• Increase of the viscosity
• Increase of the single-phase convective heat transfer
• Increase of Departure from Nucleate Boiling (DNB) heat flux

The occurrence and magnitude of these effects depends on nanoparticle loading, material and shape, in ways that are not clear yet. Given their potential for superior heat removal performance, nanofluids are being investigated for numerous applications, including electronics, manufacturing, chemical processes, cosmetics, pharmaceuticals, power generation, etc. At Nuclear Science and Engineering Department of MIT we have initiated a research program to assess the feasibility of nanofluids for nuclear applications. In principle, the use of water-based nanofluids could improve the performance of any water-cooled nuclear system that is heat removal limited. Potential applications include Pressurized Water Reactor (PWR) primary coolant, standby safety systems, accelerator targets, plasma divertors, etc. The application to Boiling Water Reactors (BWR) does not seem very promising because nanoparticle carry-over to the turbine and condenser would raise erosion and fouling concerns. Thus, our initial focus is on the PWR.

The overarching objectives of our research program are to measure and understand key transport phenomena in nanofluids, and evaluate nanofluids applicability to nuclear systems. The program comprises the following activities, which are currently sponsored by the Idaho National Laboratory (INL), AREVA and the MIT Nuclear Reactor Laboratory:

• Procurement of water-based nanofluids, i.e., C, SiO₂, ZrO2, Al2O₃.
• Nanofluid characterization with TEM (nanoparticle size and shape), neutron activation and ICP analysis (nanoparticle loading and trace element composition).
• Property measurements: thermal conductivity (transient hot wire method) and viscosity (ultrasonic viscometer).
• Property modeling with Molecular Dynamics simulations.
• Single-phase heat transfer and pressure drop measurements in flow loop (Figure 1).
• Single-phase heat transfer modeling, both conceptual and CFD.
• Critical Heat Flux (CHF) measurements: experiments with heated wire, and in flow loop with PWR-equivalent annulus and Zircaloy heated surface (see Figure 2).
• Nuclear applications: subchannel, safety and neutronic analyses of PWRs with nanofluid coolant.

The program currently involves two members of the faculty, four research staff and five students.