Can Nuclear Waste Power Rockets? Exploring the Feasibility of Nuclear Saltwater Rockets

The age-old question of whether nuclear waste could be repurposed for rocket propulsion has stirred interest in the scientific community. While direct utilization of nuclear waste presents numerous challenges, innovative technologies like the Liquid Fluoride Thorium Reactor (LFTR) and Nuclear Saltwater Rockets (NSWR) offer promising avenues.

Nuclear Waste: A Brief Overview

Nuclear waste consists of radioactive materials with unstable nuclei that emit various forms of radiation in an effort to become more stable. Though highly hazardous to living tissue, the energy imparted to matter by this radiation is minimal. For instance, an absorbed dose of 1000 rad of gamma radiation is generally lethal to humans, while raising the temperature of STP pure water by 1 degree requires a substantial 100,000 rad of energy.

Radioisotopic Thermoelectric Generators (RTGs)

Radioisotopic Thermoelectric Generators (RTGs) use the decay heat from materials such as plutonium-238, which decays by alpha emission at a rate of 0.57 watts per gram. These generators produce around 100 to 400 watts of power, a far cry from the billions of watts required for rocket propulsion. In conventional light-water uranium-fueled reactors, by-products can continue to produce meaningful power for several minutes after fissioning ceases, but this is insufficient for propulsion purposes.

Nuclear Saltwater Rockets (NSWR)

One intriguing approach is the use of Liquid Fluoride Thorium Reactors (LFTR) to reprocess nuclear waste and produce nuclear saltwater rocket fuel, a concept known as the Nuclear Saltwater Rocket (NSWR). Pyroprocessing, a technique that separates and processes the waste in a molten salt pool at high temperatures, could enable the production of rocket fuel. In the NSWR design, a high-concentration salt solution containing dissolved uranium or thorium ions would be heated to generate thrust.

Commercial Applications of Nuclear Waste

Although primarily developed for space missions, the potential to use spent uranium fuel rods from commercial power plants in RTGs is an exciting possibility. This could significantly reduce the costs and environmental impacts associated with the storage of nuclear waste. By using plutonium-238, RTGs power Deep Space missions, particularly the latest class of Martian rovers. However, the scarcity of plutonium-238 and the pressure on NASA to allocate limited resources among various future projects pose significant challenges.

Regulatory and Safety Considerations

Even if the technological challenges are overcome, regulatory and safety considerations remain paramount. For example, the energy density and potential hazards of spent uranium fuel rods in a rocket environment need careful evaluation to ensure the safety and success of any mission.

Conclusion

While it is challenging to directly use nuclear waste for rocket propulsion, advancements in reactor technologies like LFTR and NSWR offer new possibilities. Future research and development could transform waste into a valuable resource, providing sustainable and efficient energy for space exploration.