A diamond that turns radioactivity into electricity could operate as an energy source in circumstances where small amounts of power are needed for very long periods of time. The product could also prove a useful way to dispose of stocks of nuclear waste.
Nuclear power stations produce a lot of radioactive waste, and long-term storage of this product has proven more difficult than anticipated. One of the major forms of waste is carbon-14, a radioactive isotope of carbon that has a half life of more than 5,000 years. This carbon-14 needs to be kept isolated from the environment for many half-lives, far longer than any civilization on Earth has survived.
To that extent, University of Bristol scientists experimented with heating the graphite rods that contain this carbon-14, releasing most of it as a gas, which would then be turned into artificial diamonds. The legendary toughness of diamonds keeps the waste contained, but more importantly, the diamonds can be connected to circuits and serve as a source of electricity.
As the carbon-14 atoms in the diamond decay to stable nitrogen-14 they release electrons (beta radiation) and this generates a current. Most diamonds are insulators, but with suitable doping they can have the free electrons that allow them to conduct electricity.
“There are no moving parts involved, no emissions generated and no maintenance required, just direct electricity generation. By encapsulating radioactive material inside diamonds, we turn a long-term problem of nuclear waste into a nuclear-powered battery and a long-term supply of clean energy,” said Professor Tom Scott in a statement issued to accompany the announcement of a successful prototype and the university's annual Ideas to Change the World lecture.
The carbon-14 diamonds are too radioactive to be safely used anywhere near living things unshielded, so the Bristol team enveloped them in a larger diamond of stable carbon-12. The use of a diamond outer layer, while more expensive than other potential shielding devices, maximizes the capture of radioactivity, generating far more electricity than the carbon-14 diamond would do alone.
The electricity is released very, very slowly, so even with large quantities of such diamonds connected in parallel, the power available would be far too small for most purposes. On the other hand, it would barely diminish for centuries, making this a very useful source of energy where refueling is difficult. Spacecraft traveling to the outer Solar System, where solar panels are of little use, look like an obvious application, along with vessels exploring the deep ocean.
Those aren't likely to produce sufficient demand to dispose of the world's vast stocks of carbon-14 on their own, so the Bristol team is seeking public suggestions for other potential uses.
Sadly, despite the Bond film's propaganda, diamonds are not always forever. A sharp shock will shatter them, so protection in some circumstances would be required. Nevertheless, Scott and colleagues think they are a step closer to the world envisaged in Neal Stephenson's influential science fiction novel, The Diamond Age.