New 'MULE' Reactor Design Could Power Future Permanent Moon Bases

• Researchers from the Technical University of Munich have proposed the 'MULE' (Microreactor Utilisation for Lunar Exploration), a nuclear reactor designed to support permanent lunar settlements.
• The system is engineered to provide both the intense heat required for in-situ resource utilization (ISRU) and the electricity needed for base operations, bypassing the challenges of the 14-day lunar night.

Thermal Cascade Design

• The reactor uses a cascading thermal process to maximize energy utility:
  • 1000°C: Powers the molten salt electrolysis (MSE) process to extract oxygen and metallic alloys from lunar regolith.
  • 750°C: Drives a closed-loop Brayton cycle to generate electricity via a turbine.
  • 150°C: Used for habitat heating.
  • 75°C: Residual heat is rejected into deep space via radiators.

Core Specifications and Safety

• Reactor core: Features an all-ceramic silicon carbide structure loaded with 37 hexagonal fuel assemblies using TRISO (TRIstructural-ISOtropic) particles, making the fuel virtually melt-proof.
• Fuel enrichment: Uses 93% U-235 uranium-carbide kernels.
• Control system: Utilizes six perimeter pivot drums coated with either a neutron absorber (boron-carbide) or a neutron reflector (beryllium oxide) instead of traditional control rods.
• Portability: Measures 2.3m by 0.78m and weighs 2.1 metric tons, suitable for transport by heavy-lift rockets like Starship.

Performance and Challenges

• Simulations via the Serpent 2 software indicate the reactor could operate for up to 95 years without refueling.
• Engineering hurdles: Include managing hot helium gas transfer, ceramic thermal shock resilience, and the lack of existing robotic excavation technology to bury the reactor for radiation shielding.