Areas of Research

The 2023 CSNR Summer Fellowship Program, June 5 through August 11, 2023, will be the 18th year of this intense, innovative exploration of applications of nuclear energy in space. Stipends being offered this year for the 10-week session to $6500 for undergraduate juniors and seniors, $8000 for MS candidates and $9000 for PhD candidates. Housing will be provided to interns who choose this in-person fellowship.

The challenges we’ll tackle during the 2023 CSNR Summer Program will involve the operational dynamics of an NTP rocket and the behavior of the fuel in the NTP reactor.

Future human exploration of Mars and the outer solar system will require the use of nuclear energy to reduce travel time and thus the exposure of the crew to energetic protons (i.e. cosmic rays and solar flares) in space. Such a reduction in travel time cannot be achieved using conventional rockets because of the lower exhaust velocities of the combustion gasses. There are several concepts for attaining higher exhaust velocities (i.e. higher specific impulse) through the use of nuclear energy. All of these concepts are in an early stage of development. Some nuclear space propulsion concepts involve acceleration of ionized particles or plasmas by electrostatic fields. While such concepts achieve high specific impulse, the thrust produced is so small that a long duration burn is required to attain the change in velocity needed. Centrifugal Nuclear Thermal Propulsion, in which molten uranium held in rotating porous tubes as the hydrogen propellent is heated as it flows radially inward. CNTP has the potential for achieving a specific impulse, Isp, of about 1800 seconds when used on an Earth - Martian mission.  The 2023 CSNR Summer Program will tackle several issues facing materials when used in a CNTP reactor.

The candidate materials for the tubes are:

            Silicon Carbide (SiC)                SiC/SiC filament wound composite

            Titanium Carbide (TiC)            TiC/ZrC filament wound composite

            Tungsten (W) or W-coated Molybdenum (Mo)

                                                            Hoop-wound W-ZrC with W-coated Mo matrix composite

The project has been divided into four tasks:

  1. Structural Model of Porous Reactor Tubes
    Determine the strength of the tube materials as functions of porosity and fracture toughness. The tubes will have a density of 80-85% of the theoretical density. Density below 80% TD will have poor fracture toughness because the larger pores are crack initiation sites, while densities greater than 85% TD will not have the connected pores necessary for hydrogen flow through the tube wall and into the molten uranium. Determine the hoop stress in the rotating tube, the tube diameter and wall thickness for each of the candidate materials and the maximum allowable rotational speed for each material.
  2. Transport model for hydrogen flow radially into the rotating tube
    Determine the surface tension of the molten uranium within the porous tube wall. Given the force balance on the uranium, determine the required external H2 pressure. Consider the evolution of Rayleigh-Taylor instabilities at the hydrogen-uranium interface.
  3. Dissolution Thermodynamics of the candidate materials in molten uranium
    Develop a convection dissolution transport model to account for the temperature range in the uranium (1500 K to 5500 K) across the fuel bed. Some transport of the tube materials into the uranium may be avoided by loading the U metal with a few percent of W or SiC.
  4. Hydrogen reaction kinetics with candidate materials
    Some reactions of molten uranium with the tube materials may be slow despite their being thermodynamically possible. Given the ten to thirty operating hours of the CNTP reactor over its lifetime, these slow reactions may not be a problem. Some reactions may to slowed by W coatings on the filaments of matrix particles. Review the known kinetics of reactions of hydrogen with the candidate materials to identify reactions of concern. Suggest experiments to provide needed data.

The Summer Fellows are divided into teams, based on the different fields of expertise needed by each project. The Summer Program gives the CSNR Summer Fellows a chance to explore fields beyond those within their majors, so that nuclear, chemical and aerospace engineers have an opportunity to learn a cross-disciplinary approach to some challenging, real-world problems.

During the summer, the Fellows will be asked to make short presentations of the results of their research and a final oral/written presentation to the laboratory management.