| Abstract Scope |
As humanity prepares for missions to Mars and beyond, the limitations of chemical propulsion, long travel times and constrained payloads, have renewed interest in nuclear thermal propulsion (NTP). Offering better thrust efficiency and mission flexibility but requires advanced materials that endure extreme thermal and radiative environments. Shielding mass remains a critical constraint in NTP design, driving demand for lightweight materials, capable of withstanding high temperatures (≈2,000 C) and intense neutron flux (6.1e13 n/cm^2-sec).
To address these challenges, a multilayer metal-ceramic shielding solution was fabricated by diffusion-bonding 316L stainless steel—chosen for its weldability and innate corrosion resistance—to boron carbide, which offers exceptional neutron attenuation, thanks to its high neutron-capture cross-section. Bonding was performed at 1,100~1200 C under 1.25~1.5 MPa perpendicular pressure, annealed for 2~3 hr.
This study presents a pre-irradiation characterization of the diffusion interface microstructure and mechanical properties using electron microscopy, spectroscopy, and diffraction analysis techniques. SEM-EDS revealed the bonding interface to be 20~30 um thick with boron and chromium rich regions, an indication of chromium mobility. Further characterization under higher spatial fidelity reaffirmed the previous analysis and showed bonding within the boron-chromium-iron ternary phase spectra in the interlay.
Ultimately, this work aims to support the development of integrated, application-customizable, multilayer shielding systems that enhances the performance, reliability, and safety of NTP systems, while balancing mass and cost—advancing the feasibility of long-duration crewed spaceflight. |