Nuclear waste from Britain’s power plants is set to be blasted into space as a new power source onboard the next generation of Moon missions and Mars rovers.
For the first time a radioactive element called americium can be extracted from nuclear waste, instead of being buried underground, to create batteries that will power the future of space exploration. The development is the result of a collaboration between the UK Space Agency and National Nuclear Laboratory (NNL).
The power source has “game-changing potential for the UK’s space ambitions”, industry leaders have said, as it would end a reliance on the more expensive and limited supply of fuel that is currently used for space batteries and produced in the United States and Russia. Probes, rovers and satellites that operate near the Earth can often rely largely on solar panels to generate their power. Those sent to moons and planets in the outer solar system can no longer rely on solar energy as sunlight becomes too dim at such distances.
These probes are usually designed to operate for several years, with some, such as the Voyager space probes, still functioning after almost 50 years as they sail beyond our solar system through interstellar space. Keeping them powered requires a nuclear power source to emit heat that can prevent freezing and can also be turned into electricity to keep instruments running.
The most common fuel used for such batteries is plutonium-238, a form of plutonium with 94 protons and 144 neutrons in each atom.
“It’s really difficult to make plutonium-238 and really expensive,” said Professor Tim Tinsley of the NNL. “There isn’t enough to do many missions. It is all made by the Americans or the Russians. The only way Europe and the UK can do missions to anywhere where the sun doesn’t shine is to get on board a US or a Russian mission, which isn’t always attractive. What we identified is that there is an alternative to plutonium-238, an isotope called americium-241.”
Americium is used in tiny quantities in smoke detectors in most homes.
“What we discovered,” Tinsley added, “through almost a twist of fate, is that we have in the UK a large amount of americium in surplus material [from nuclear power plants] that eventually will end up a hole in the ground as there is no use for it. It is a waste [product].”
The UK has around 140 tonnes of plutonium stored at Sellafield in Cumbria, including a type called plutonium-241 that decays over time into americium-241 “like a cheese maturing”, Tinsley said.
Technicians at the NNL have found a way to separate and extract this americium by dissolving the nuclear material in nitric acid and adding special oils. The plutonium dissolves in the acid while the americium is attracted into the oil droplets. As the oil floats to the surface, it carries the americium with it, allowing it to be separated.
Scientists are now working at a new £19 million laboratory in Cumbria on incorporating the fuel into battery-like cells that can be sent into space.
The americium provides only a quarter of the power of the plutonium but it does not decay as quickly, so designers would require only twice as much by weight to create an effective power source — around an extra kilogram of material.
Dr Paul Bate, chief executive of the UK Space Agency, said: “Supporting the National Nuclear Laboratory’s expansion will make the UK the only country in the world capable of producing this viable alternative to plutonium, reducing the global space community’s reliance on limited supplies, which are increasingly difficult and costly to obtain.”
