Americium: The Nuclear Element Keeping Your Home Safe and Now Powering Spacecraft

Most people have never even heard of Americium and while it sounds like something from a Marvel movie, it’s really important for part of NNL’s business. But in a more every day context, almost every home in the UK contains some. Probably upstairs and downstairs. Any guesses? If you thought smoke detectors, you’d be right! There’s a full explanation of exactly why it’s there and what it does in the side bar but for now, it’s essentially what detects the smoke and sets off the alarm. Not only is it safe, it’s working to keep you safe.

There’s a real contrast between something so rare and largely unknown (to most people anyway) being so common and widespread and doing something most of us would consider fairly ordinary. But as well as helping to keep your family safe, Americium has another much less ordinary use too. The UK’s National Nuclear Laboratory has developed a method to use it in batteries which can power space craft for decades. We’ve been collaborating with Leicester University and the Joint Research Centre (in Germany) to develop this nuclear battery technology on behalf of the European Space Agency.

Why do spacecraft need batteries?

It’s perhaps not something that most of us speculate on a daily basis but how to ensure spacecraft have enough power to run for many years is something that scientists at ESA and NNL are concerned with. Solar power is an excellent way for a lot of near-earth operations but any craft which is intended to spend a lot of time in space and certainly anything that is travelling beyond Mars, needs a more reliable, on-board, power source.

At present, many spacecraft use plutonium for this source. It’s fairly long lasting and a good source of energy. But it has the disadvantage of being rare and increasingly expensive. Americium on the other hand is abundant and relatively inexpensive and has the advantage of lasting 4 times as long as plutonium (as a power source). And now, thanks to the work of NNL and its partners, a proven method of using it in space batteries has been established.

Why do we need Americium powered batteries?

Professor Tim Tinsley of the National Nuclear Laboratory explains:

NNL is currently the only producer of Americium in the UK. We’re also the only company who has the facilities to handle the experimentation and production. This unique position means that NNL can truly add value to UK plc and help build for the future.


What does Americium do in smoke detectors?

There’s not much Americium needed in your smoke detector. 1g is enough for 5000 smoke detectors. That tiny amount is used as a source of alpha particles (see side bar). What actually happens is that the americium ionizes air molecules. All that means is that it makes some of the normally neutrally charged air molecules, positive and others negative. Inside the smoke detector there are two small charged plates - one positive and one negative. In conjunction with the americium doing its job, these plates create a constant flow of ions. Smoke interrupts this flow which sends a signal and the smoke alarm sounds.