Back in 2016, a group of researchers, physicists and chemists at the University of Bristol, started working on what came to be known as radioactive diamond batteries. The invention that they came up with was presented as a betavoltaic device, which means that it’s powered by the beta decay of nuclear waste.

Beta decay is a type of radioactive decay that occurs when an atom’s nucleus has an excess of particles and releases some of them to obtain a more stable ratio of protons to neutrons. This produces a kind of ionizing radiation called beta radiation, which involves a lot of high-speed and high-energy electrons or positrons known as beta particles.

A typical betavoltaic cell consists of thin layers of radioactive material placed between semiconductors. As the nuclear material decays, it emits beta particles that knock electrons loose in the semiconductor, creating an electric current. However, the power density of the radioactive source is lower the further it is from the semiconductor. This means that nuclear batteries are much less efficient than other types of batteries. This is where the polycrystalline diamond (PCD) comes in.

Radioactive batteries are made through a process called chemical vapour deposition, which is widely used for artificial diamond manufacture. Researchers have modified the process to grow radioactive diamonds by using radioactive methane containing the radioactive isotope Carbon-14, which is found on irradiated reactor graphite blocks. These diamonds can act both as a radioactive source as well as a semiconductor. 

When exposed to beta radiation and you’ll get a long-duration battery that doesn’t need to be recharged. The nuclear waste in its interior fuels it over and over again, allowing it to charge itself for ages, with very little to no measurable degradation over hundreds of years. Theoretically speaking a single battery can be used for over a thousand years, without having to be replaced or recharged.