A new space race is underway, with six or seven countries and alliances vying to be recognized as a 21st century space power as they rush to build a new generation of landers and rovers on the moon. NASA is gearing up to deliver on its promise to establish a permanent human presence on the lunar surface.Under a UK Space Agency contract, Bangor University in Wales is developing a new nuclear fuel for a Rolls-Royce microreactor that will power a future manned lunar outpost by 2030.
A major obstacle to launching a long-duration mission or establishing a permanent outpost on the moon is the 14-day long lunar night, when daytime temperatures drop from 250°F (120°C) to -208°F (-130°C). This combination of freezing cold and darkness means that machines and outposts must rely on nuclear power systems if they are to survive, let alone function. For anything that needs to do actual work, that means nuclear reactors rather than wireless thermal generators.
These reactors differ from the large conventional reactors used on Earth that rely on fuel rods. Instead, they will be very small, factory-built reactors using so-called TRISO particle fuel.
TRISO fuel is a variation of pebble bed reactor fuel that uses billiard ball-sized fuel pellets instead of fuel rods. What makes Bangor TRISO fuel different is that the fuel pellets are shrunk to the size of a poppy seed. These fuel pellets are made from enriched uranium, carbon and oxygen through 3D printing technology, with the uranium core sealed in layers of carbon and ceramics.
Unlike fuel rods, these fuel particles are very strong and can withstand very high temperatures and resist damage from neutron irradiation, corrosion and oxidation.
Led by Simon Middleberg, professor of nuclear materials and co-director of the Nuclear Futures Institute at Bangor University, Bangor University is developing TRISO fuel suitable for lunar reactors being developed by companies such as Rolls-Royce. It could be used not only in power reactors but also in future nuclear propulsion systems.
The important thing about the TRISO fuel reactor is that its design is relatively simple and can be air-cooled simply by placing it under the shadow of a radiator umbrella over the coolant system. By operating at higher temperatures, these reactors are more efficient than traditional pressurized water reactors.
During operation, fuel particles are fed into the top of the reactor. When the fuel is used up, it migrates to the bottom and the spent fuel is removed. Because reactor temperatures are high, if the reaction is too violent, the rising heat will inhibit the reaction and return the reactor to a safe level.
"This project will take our Nuclear Futures Institute's expertise in nuclear fuels and apply it to one of the most exciting applications: space exploration," Middleberg said. "On the moon and planetary bodies with day and night, we can no longer rely on the sun for energy, so systems such as small microreactors must be designed to sustain life. Nuclear energy is the only way we currently can power such long journeys into space. The fuel must be very durable, able to withstand the impact of launch, and operate reliably for many years."
"The outstanding scientists and engineers at the Institute for Nuclear Futures are rising to this challenge, but many more will be needed in the coming years, and we hope the University's new engineering major will provide a host of exciting opportunities for students who want to pursue a career in these exciting areas of research and development."