[Apr. 17, 2023: Maia Mulko, University of Bristol]
A prototype of Arkenlight’s carbon-14 betavoltaic battery. (CREDIT: University of Bristol)
Nuclear energy is considered a clean source of energy because it emits no carbon dioxide emissions; yet, at the same time, it produces massive amounts of hazardous radioactive waste that accumulates as more and more reactors are built around the world.
Experts have proposed different solutions to this problem in order to take better care of the environment and people’s health. With insufficient safe storage space for nuclear waste disposal, the focus of these ideas is the reuse of materials.
Radioactive diamond batteries were first developed in 2016 and were immediately popular as they promised a new, cost-effective way to recycle nuclear waste. In this context, it is inevitable to deliberate whether they are the ultimate solution to these toxic and deadly 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 at the University of Bristol. The invention was presented as a betavoltaic device, which means that it is powered by the beta decay of nuclear waste.
Beta decay is a type of radioactive decay that occurs when the nucleus of an atom contains an excess of particles and releases some of them to achieve a more stable ratio of protons to neutrons. This produces a kind of ionizing radiation called beta radiation, which involves lots of high-speed, high-energy electrons or positrons called beta particles.
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Beta particles contain nuclear energy which can be converted into electrical energy using a semiconductor.
Beta decay is a type of radioactive decay that occurs when the nucleus of an atom contains an excess of particles and releases some of them to achieve 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 which release electrons into the semiconductor, creating an electric current.
However, the power density of the radioactive source is lower the further it is from the semiconductor. Also, since beta particles are emitted randomly in all directions, only a small number of them will hit the semiconductor, and only a small number of them will be converted into electricity. This means that nuclear batteries are much less efficient than other types of batteries. This is where polycrystalline diamond (PCD) comes in.
Radioactive diamond batteries are made using a process called chemical vapor deposition, which is widely used for making artificial diamonds. It uses a mixture of hydrogen and methane plasma to grow diamond films at very high temperatures. The researchers modified the CVD process to grow radioactive diamonds using radioactive methane containing the radioactive isotope Carbon-14, which is found on irradiated reactor graphite blocks.
Diamond is one of the hardest materials known to mankind – it is even harder than silicon carbide. And it can act both as a radioactive source and as a semiconductor. Expose it to beta radiation and you’ll get a long-lasting battery that doesn’t need to be recharged. The nuclear waste inside fuels it again and again, allowing it to recharge for centuries.
However, the Bristol team warned that their radioactive diamond batteries would not be suitable for laptops or smartphones, as they only contain 1g of carbon-14, which means they provide very low power – only a few microwatts, which is less than a typical AA battery. Therefore, their application is so far limited to small devices that have to remain unattended for a long time, such as sensors and pacemakers.
Radioactive nano-diamond batteries
The origins of nuclear batteries date back to 1913, when English physicist Henry Moseley discovered that particle radiation could generate an electric current. In the 1950s and 1960s, the aerospace industry was very interested in Moseley’s discovery because it could potentially power spacecraft for long-duration missions. The RCA Corporation has 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 to develop and sustain the invention. In this regard, the use of synthetic diamonds is considered revolutionary, as it ensures the safety and conductivity of the radioactive battery. With the addition of nanotechnology, an American company has built a high-powered nano-diamond battery.
A prototype of Arkenlight’s gammavoltaic battery that will convert gamma rays from nuclear waste repositories into electricity. (CREDIT: University of Bristol).
Based in San Francisco, California, NDB Inc. was founded in 2012 with the goal of creating a cleaner, greener alternative to conventional batteries. The startup introduced its version of diamond-based batteries in 2016 and announced two proof-of-concept tests in 2020. It is one of the companies trying to bring radioactive diamond batteries to market.
NDB’s nano-diamond batteries are described as alpha, beta, and neutron voltaic batteries and have several new features according to their website.
Sustainability. The company calculates that the batteries could last up to 28,000 years, meaning they could reliably power space vehicles on long-duration missions, space stations and satellites. Drones, electric cars, and airplanes on Earth would never need to stop for recharging.
Security. Diamond is not only one of the hardest substances, but also one of the most thermally conductive materials in the world, which helps protect against the heat produced by the radioisotopes with which the battery is constructed , turning it into electric current very quickly.
Respect of the market. The thin layers of PCD in these allow the battery to allow for different shapes and forms. This is why nano-diamond batteries can be versatile and penetrate different markets, from the aforementioned space applications to consumer electronics. The consumer release would not last more than a decade, however.
Nano-diamond batteries are expected to hit the market in 2023.
Arkenlight, the English firm that markets Bristol’s radioactive diamond battery, plans to launch its first product, a microbattery, on the market at the end of 2023.
The future of radioactive diamond batteries
The portability of modern electronic devices, the growing popularity of electric vehicles, and the 21st century race to take humanity on long space missions to Mars have led to growing interest in battery technology research in recent years.
Some battery types are more suitable for some applications and less useful for others. But we can say that the conventional lithium-ion batteries we know are not going to be replaced by radioactive diamond batteries anytime soon.
Conventional batteries last less, but they are also much cheaper to manufacture. However, at the same time, the fact that they don’t last as long (they have a lifespan of around five years) is problematic, as they also produce a lot of e-waste, which is not easy to recycle.
Radioactive diamond batteries are more practical, as they have a much longer lifespan than conventional batteries. If they can be developed into a universal battery, as NDB Inc. proposes, we could end up with smartphone batteries that last much longer than the life of the smartphone, and we could just change the battery of a phone to another, as much as we are now transferring the SIM card.
However, the diamond betavoltaics developed by Arkenlight will not go that far. The company is working on designs that stack many of their carbon-14 beta batteries in cells. To provide high power discharge, each cell could be accompanied by a small supercapacitor, which could provide excellent fast discharge capability.
However, this radioactive material also has a lifespan of over 5000 years. If this radiation were to escape from the device in gaseous form, this could be a problem. This is where diamonds come in. In the formation of diamonds, C-14 is a solid, so it cannot be mined and absorbed by living things.
The UK Atomic Energy Authority (UKAEA) has calculated that 100 pounds (about 45 kg) of carbon-14 could enable the manufacture of millions of long-lasting diamond-based batteries. These batteries could also reduce nuclear waste storage costs.
Professor Tom Scott, a researcher at the University of Bristol, told Nuclear Energy Insider: “By removing the carbon-14 from the irradiated graphite directly from the reactor, it would make the remaining waste less radioactive and therefore easier to manage and dispose of. Cost estimates for graphite waste disposal are 46,000 pounds ($60,000) per cubic meter for mid-level waste. [ILW] and 3,000 pounds ($4,000) per cubic meter for low-level waste [LLW].”
Don’t all these features make it one of the best options for the sustainable future we need? We’ll have to wait and see if manufacturers can find a way to manage production costs and low power output, and bring their diamond-based batteries to market in a cost-effective and accessible way.
For more scientific news, see our New Innovations section on The bright side of the news.
Note: The documents provided above by University of Bristol. Content may be edited for style and length.
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