[May 17, 2023: Maia Mulko, University of Bristol]

A prototype of Arkenlight’s carbon-14 diamond betavoltaic battery. (CREDIT: University of Bristol)

Nuclear power is considered a clean energy source because it has zero carbon dioxide emissions; yet, at the same time, it produces massive amounts of hazardous, radioactive waste that pile up as more and more reactors are built around the world.

Experts have proposed different solutions for this issue in order to take better care of the environment and people’s health. With insufficient safe storage space for nuclear waste disposal, the focal point of these ideas is the reutilization of the materials.

Radioactive diamond batteries were first developed in 2016 and were immediately acclaimed because they promised a new, cost-effective way of recycling nuclear waste. In this context, it’s unavoidable to deliberate whether they’re the ultimate solution to these toxic, lethal residues.

What Are Radioactive Diamond Batteries?

Radioactive diamond batteries were first developed by a team of physicists and chemists from the Cabot Institute for the Environment of the University of Bristol. The invention 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.

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Beta particles contain nuclear energy that can be converted into electric energy through a semiconductor.

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. (CREDIT: MikeRun/WikimediaCommons)

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. On top of this, because beta particles are randomly emitted in all directions, only a small number of them will hit the semiconductor, and only a small number of those will be converted into electricity. This means that nuclear batteries are much less efficient than other types of batteries. This is where the polycrystalline diamond (PCD) comes in.

The radioactive diamond batteries are made using a process called chemical vapor deposition, which is widely used for artificial diamond manufacture. It uses a mixture of hydrogen and methane plasma to grow diamond films at very high temperatures. Researchers have modified the CVD process to grow radioactive diamonds by using a radioactive methane containing the radioactive isotope Carbon-14, which is found on irradiated reactor graphite blocks.

Diamond is one of the hardest materials that humanity knows — it’s even harder than silicon carbide. And it can act as both a radioactive source and a semiconductor. Expose it 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 self-charge for ages.

However, the Bristol team warned that their radioactive diamond batteries wouldn’t be suitable for laptops or smartphones, because they contain only 1g of carbon-14, meaning that they provide very low power —only a few microwatts, which is less than a typical AA battery. Therefore, their application so far is limited to small devices that must stay unattended for a long time, such as sensors and pacemakers.

Nano Diamond Radioactive Batteries

The origins of nuclear batteries can be traced back to 1913, when English physicist Henry Moseley found out that particle radiation could generate an electric current. In the 1950s and 1960s, the aerospace industry was very interested in Moseley’s discovery, as it could potentially power spacecraft for long-duration missions. The RCA Corporation also researched an application for nuclear batteries in radio receivers and hearing aids.

Nano diamond crystals. (CREDIT: D. Mukherjee/Wikimedia Commons)

But other technologies were needed in o