The UK’s National Nuclear Laboratory (NNL) and University of Leicester have generated usable electricity from the chemical element americium in what it believes to be a global first. The achievement is seen as a step towards potential use of americium in so-called space batteries, which may mean future space missions can be powered for up to 400 years.
Americium is an element not found in nature, but which is produced by the radioactive decay of plutonium – which itself is produced during the operation of nuclear reactors. A team led by NNL has extracted americium from some of the UK’s plutonium stocks, and used the heat generated from this highly radioactive material to generate electric current, which in turn lit up a small light bulb – all within a specially shielded area of NNL’s Central Laboratory in Cumbria, England.
Space batteries are power sources for space probes which would use the heat from americium pellets to power sensors and transmitters as the probes head into deep space where other power sources such as solar panels will no longer function, NNL said. In this way, such probes can carry on sending back vital images and data to Earth for many decades – far longer than would otherwise be possible.
The breakthrough means potential use of americium in radioisotope power systems for missions which would use the heat from americium pellets to power spacecraft heading into deep space or to challenging environments on planet surfaces where other power sources, such as solar panels, no longer function. In this way, NNL said, such space missions can carry on sending back vital images and data to Earth for many decades, far longer than would otherwise be possible.
Science Minister Chris Skidmore said: “This remarkable breakthrough sounds like something from a science fiction film but it is another brilliant testament to our world leading scientific and university communities and their commitment to keeping the UK at the very frontier of developments in space technology and research for energy requirements in difficult environments. It is on the foundations of such discoveries that we can create the highly skilled jobs of the future, supported through our modern Industrial Strategy and record level of government investment in R&D.”
The technical programme to deliver this world first has been running for several years, supported by funding from the European Space Agency (ESA), and has seen NNL working very closely with the University of Leicester. The work of European Thermodynamics Ltd in helping to develop the thermoelectric generator unit was a vital part of this collaboration, and support from the Nuclear Decommissioning Authority, who permitted the use of plutonium from the UK stockpile under their stewardship, was also essential.
Richard Ambrosi, professor of Space Instrumentation and Space Nuclear Power Systems at the University of Leicester, said: “In order to push forward the boundaries of space exploration, innovations in power generation, robotics, autonomous vehicles and advanced instrumentation are needed. Radioisotope power sources are an important technology for future European space exploration missions as their use would result in more capable spacecraft, and probes that can access distant, cold, dark and inhospitable environments. This is an important step in achieving these goals.”
Tim Tinsley, NNL’s account director for the work, said: “Seeing this lightbulb lit is the culmination of a huge amount of specialist technical work carried out by the teams from NNL and Leicester, working in collaboration with other organisations such as ESA and UK Space Agency. Leicester University’s capability in development of the radioisotope power systems was complimented by NNL’s expertise in handling and processing americium in our unique lab facilities. It is great to think that americium can be used in this way, recycling something that is a waste from one industry into a significant asset in another.”
Although NNL can’t be 100% certain the achievement is a world first, it does believe it is the first time that the heat from americium has been used to generate electricity, Tinsley said.
“You need access to americium, which is not easy. Current technology uses Pu238 instead which is very hard and very expensive to produce,” he told World Nuclear News.
NNL has had interest from space agencies, he said, other than ESA, which wants to have the system ready to power a lunar mission later next decade. There is also interest for applications on the Earth where a power source that potentially lasts 100s of years has benefits, he said, adding that it could be valuable commercial and export opportunity for the UK.
NNL spokesman Adrian Bull added: “Some current probes use an isotope of plutonium for this purpose – but that’s in increasingly short supply. This route of using Americium takes something that’s generally regarded as a problem and turns it into an asset. Our work is funded by the European Space Agency and they are interested to use the americium approach for future European space missions.”
The plutonium is not recycled, Tinsley noted. “We ‘clean’ the americium from it, which would have been a waste. With sufficient applications, all of the UK plutonium could be ‘cleaned’ of the americium. The returned plutonium is in a better condition, ready for further storage or reuse as nuclear fuel.”
Bull added: “The americium in plutonium is potentially a problem for re-using the plutonium as new fuel. In extracting the americium from aged plutonium stocks, we end up with both the separated americium and also ‘cleaner’ plutonium – for potential re-use in the fuel cycle. So it’s a win-win.”
Keith Stephenson, the programme lead from ESA for the work, said the “unrivalled energy density” of nuclear power sources enables a whole range of missions that would be otherwise impossible. “This successful collaboration between the nuclear and space sectors has created a brand-new capability for Europe, and opens the door to a future of ambitious and exciting exploration of our solar system,” he said.
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