We are almost obsessed with our battery-powered gadgets. Soon most of our cars and even our aeroplanes will run on batteries. The green revolution is stimulating a huge research effort in the quest for better battery technologies. Almost all our batteries rely on chemical processes to release electrical energy. But there is another way!
Henry Moseley devised the first nuclear battery in 1913, demonstrating how the electrons released in the radioactive beta decay of an isotope of radium (radium-228) could be used to generate an electric current. Although his device was not suitable for practical applications it established the principle of a nuclear battery. A serious effort to develop this technology did not get underway until the 1950s and 1960s.
The Final Frontier
The most common type of nuclear battery is known as a Radioisotope Thermal Generator (RTG). In such a device the decay of a radioactive isotope heats a metal strip that forms part of a thermocouple, producing a temperature difference which generates an electric current. This is a rather inefficient process. Nevertheless, sometimes this is not so important. Nuclear batteries have found applications in remote places that require small amounts of electricity for very long periods of time with minimal maintenance. And you don’t get much more remote than the Voyager spacecraft of the 1970s.
An artist’s conception of Voyager 2 on its approach to Neptune. Credit: NASA.
Voyager 2 was launched in August 1977. It is the only space probe ever to visit either Uranus or Neptune. These were two of the planets Voyager 2 passed on its grand tour of the four outer planets of the solar system and it transformed our understanding of these worlds. Voyager 2 is powered by three nuclear batteries or RTGs containing plutonium-238. Each was designed to generate 157 watts at the time of launch, but plutonium-238 decays with a half-life of 87.7 years, so the power output slowly declines with the passage of time. The RTGs can be seen glowing to the left of the spacecraft in the artist’s conception of Voyager 2 shown above.
The Voyager 2 mission has now been extended as it enters interstellar space. It is over 18 billion kilometres away and has been in operation for 43 years. NASA remains in contact with the craft through its Deep Space Network.
Space Rock
The cover of the 1970 Pink Floyd album Atom Heart Mother.
Pink Floyd released their first chart-topping album in October 1970, seven years before the launch of Voyager 2, with a holstein-friesian cow named Lulubelle III starring on its cover. The title track is an instrumental mélange of psychedelic rock, classical orchestra and choir, composed by all the band members Dave Gilmour, Nick Mason, Roger Waters and Rick Wright along with experimental classical composer Ron Geesin. It is a classic of the progressive rock genre and was provisionally nicknamed The Amazing Pudding, but this name was discarded when the band performed the piece for a BBC recording scheduled for broadcast on 16 July 1970.
DJ John Peel needed a title for his introduction, and the BBC producer Jeff Griffin later recalled that while Peel was reading the Evening Standard, with Waters peering over his shoulder, Peely said:
Come on, what’s the name of this piece? I bet you find something in the paper.’
Waters leafed through the paper, then suddenly said:
That’s it! Atom Heart Mother!
Waters had spotted the headline of an article about a 56-year-old woman Constance Ladell recently fitted with a state-of-the-art pacemaker to regulate the rhythm of her heartbeat. The new cardiac pacemaker contained a nuclear battery powered by the radioactive decay of plutonium. So the deadly element plutonium had been given a life-saving purpose.
X-ray showing a pacemaker in place within the chest cavity.
Plutonium-powered pacemaker battery made in 1974.
The remarkable X-ray image above shows a cardiac pacemaker in place in a patient’s chest cavity. On the right is an example of a plutonium-powered pacemaker battery manufactured in 1974.
The advantage of a plutonium-238 battery was that it would outlast the patient and never need to be replaced, and there are still a few people walking around with a tiny quantity of plutonium in their chest. But today’s cardiac pacemakers are usually fitted with conventional lithium-ion chemical batteries and have to be replaced every ten years or so.
Research into nuclear batteries continues. In 2018 Russian researchers announced the development of a prototype battery powered by the radioactive beta decay of nickel-63, which has a half-life of almost exactly one hundred years. The battery is constructed from layers of nickel-63 interleaved with layers of a diamond-based semi-conductor. This device will no doubt find specialist applications in the near future. But whether nuclear batteries ever find large-scale everyday applications is far less certain.
Further Information
There is a lot more about Henry Moseley in an earlier post: Henry Moseley and the Nuclear Treasure Chest.
You can listen to track Atom Heart Mother on YouTube: Atom Heart Mother.
There is more about the Russian nickel-63 battery here: Prototype Nuclear Battery Packs 10 Times More Power.
