A drone drops a small package near the crater of Stromboli in the summer of 2018. The Stromboli volcano, located off the coast of Sicily, has been erupting almost constantly for the past century. As one of the most active volcanoes on the planet, it has long been a source of fascination for geologists, but collecting data near this ever-churning caldera can be an extremely dangerous endeavor. So a team of researchers from the University of Bristol built a "volcano probe robot" and used a drone to transport it to the top of the volcano, where it can passively monitor every earthquake and tremor until it is inevitably destroyed by an eruption. The robot is a softball sized sensor pod powered by a microdose of nuclear energy from a radioactive battery the size of a chocolate square. The researchers call their creation a "dragon's egg".
The Dragon's Egg robot could help scientists study this violent natural process in unprecedented detail, but for Tom Scott, a materials scientist at the University of Bristol, volcano exploration is just the beginning. For the past few years, Prof. Scott and a small group of collaborators have been developing an upgraded version of the Dragon's Egg nuclear energy battery that could last for thousands of years without ever needing to be recharged or replaced. Unlike most batteries in modern electronics, which generate power through chemical reactions, the battery being studied at the University of Bristol collects particles ejected from radioactive diamonds, which can be made from modified nuclear waste.
Earlier this month, Scott and his collaborator, University of Bristol chemist Neil Fox, created a company called Arkenlight, which aims to commercialize their nuclear diamond battery. commercialize their nuclear diamond battery. While the fingernail-sized battery is still in the prototype stage, it has already shown improvements in efficiency and power density compared to existing nuclear batteries. Once Prof. Scott and his team at Arkenlight have perfected the design they've worked on, they'll set up a pilot facility for mass production. The company plans to have the first commercial nuclear batteries on the market by 2024 - just don't expect to find them in our own laptops .
Traditional chemical or "primary" batteries, such as lithium-ion batteries in smartphones or alkaline batteries in remote controls, can release large amounts of power in a short period of time. A lithium-ion battery only lasts for a few hours without recharging, and after a few years of use, its rechargeability will drop off dramatically. By contrast, nuclear batteries or Betavoltaic batteries (a beta-atomic battery, a battery that converts radioactive beta radiation into an electric current), are among the batteries that can continue to produce tiny amounts of electricity for a very long time. They don't emit enough power to power a smartphone, but based on the nuclear materials they use, are perfectly capable of providing a stable power output for small devices for thousands of years.
"So can we power electric cars with nuclear batteries? The answer is - no. "Morgan Boardman, CEO of Arkenlight, said that to power something so energy-intensive would mean that "the 'mass' of the battery would need to be significantly greater than the 'mass' of the vehicle." Instead, the company is looking to expand in the direction of applications where it's nearly impossible or impossible to replace batteries on a regular basis (and arguably in the direction of disposable, long-term applications), such as sensors in nuclear waste repositories, and remote or hazardous locations on satellites. Boardman also sees applications closer to home, such as using the company's nuclear batteries in pacemakers or wearable devices. He envisions a future where people will keep their batteries and replace their devices, rather than what we have now: frequent battery changes on the same device." You'll be replacing several fire alarms before you even replace the battery, because the battery life has far outlasted those devices." So says Boardman.
Unsurprisingly, most people are certainly resistant to nuclear batteries, due to the belief that they produce radioactivity and are dangerous to their health. But the reported health risks of the Betavoltaic battery are comparable to those of the exit sign, which uses a radioactive material called tritium to achieve its signature red fluorescence. Unlike gamma rays or other more dangerous types of radiation, beta particles need only pass through a few millimeters of shielding to stop them in their tracks. Lance Hubbard, a materials scientist at Pacific Northwest National Laboratory, said, "Usually just the wall of the cell is enough to stop any leakage from it. This makes the inside of a nuclear battery virtually free of radioactivity, which is very safe for people." And, he added, when a nuclear battery runs out of power, it decays to a steady state, meaning there's no nuclear waste left inside.
The first generation of Betavoltaic batteries came out in the 1970s, but until recently, no one had any use for them. They were originally used in pacemakers, where a defective power pack could mean the difference between life and death, until they were eventually replaced by cheaper lithium-ion alternatives. Today, the popularity of low-power electronics heralds a new era for nuclear batteries. "It's a great power option for very low-power devices - this is talking about the microwatt level here, or even the picowatt level." According to Hubbard: "The IoT is driving a renaissance in these energy sources. "
A typical Betavoltaic battery consists of thin, foil-like layers of radioactive material sandwiched between semiconductors. It generates electricity by emitting high-energy electrons, or positrons called beta particles, when the nuclear material naturally decays, which break up the electrons in the semiconductor material, creating an electric current. In this sense, a nuclear battery is similar to a solar panel, except that its semiconductor absorbs beta particles instead of photons.
Like solar panels, nuclear cells have a strict energy limit. Their power density, decreases the farther the radioactive source is from the semiconductor. Thus, if the cell layer is more than a few micrometers thick, the power of the cell drops dramatically. In addition, beta particles are emitted randomly in all directions, which means that only a small fraction of the particles will actually hit the semiconductor, and only a small fraction of those will be converted into electricity. As far as how much radiation a nuclear battery can convert into electricity is concerned, Hubbard said, " At this stage, an efficiency of around 7% is state of the art. "
This is Arkenlight's "Betalight" volt-ampere battery with an integrated sensor package. Unlike the Carbon-14 battery, the "Betalight" is a traditional "sandwich" nuclear battery made of tritium.
This is far from the theoretical maximum efficiency of a nuclear battery, which is about 37%. But this is where a radioactive isotope called carbon-14 can help. Carbon-14 is best known for its role in radiocarbon dating, which allows archaeologists to estimate the age of ancient artifacts, and for powering nuclear batteries, since it can act as both a radioactive source and a semiconductor. It also has a half-life of 5,700 years, which means that carbon-14 nuclear batteries could, in principle, power electronic devices for longer than humans have had a written language.
Scott and his colleagues grew the artificial "carbon-14" diamonds in a special reactor by injecting methane into a hydrogen plasma. When the gas is ionized, the methane decomposes and the carbon-14 collects on a substrate in the reactor and begins to grow in the diamond lattice . But Scott and his colleagues used the radioactive diamonds in a conventional "sandwich" battery configuration, in which the nuclear source and semiconductor are discrete layers. And they patented a method of injecting carbon-14 directly into laboratory equipment to grow diamonds similar to those found in our everyday rings. The result is crystal diamonds with a seamless structure that minimizes the distance traveled by beta particles and maximizes the efficiency of nuclear batteries.
" Until now, the source of radiation has been separate from the diode that receives it and converts it into electricity. " This is a breakthrough," said Boardman. "
"Carbon-14" forms naturally when cosmic rays hit nitrogen atoms in the atmosphere, but it is also produced as a byproduct in the graphite blocks that contain the control rods of nuclear reactors. These blocks eventually become nuclear waste, said Boardman, adding that there are nearly 100,000 tons of this irradiated graphite in Britain alone. The U.K. Atomic Energy Authority recently recovered tritium, another radioisotope used in nuclear batteries, from 35 tons of irradiated graphite chunks, and Arkenlight's team is working with the agency to develop a similar process for recovering carbon-14 from the chunks.
If Arkenlight is successful, it will have the potential to create a nuclear battery.
If Arkenlight succeeds, it could provide a virtually inexhaustible supply of raw materials for making nuclear batteries. The UK's AEA estimates that less than 100 pounds (about 45.36 kg) of carbon-14 would be enough to make millions of nuclear batteries. In addition, by removing the radioactive carbon-14 from the graphite blocks, this will downgrade them from high-level to low-level nuclear waste, making them easier to handle and safer for long-term storage.
At this point, Arkenlight has yet to make a Betavoltaic battery from the modified nuclear waste, said Boardman, who said that the company's nuclear diamond battery would need a few more years of refinement in the lab before it was ready to be put to use. But the technology is already attracting interest from the space and nuclear industries. Bodman went on to say that Arkenlight recently received a contract from the European Space Agency to develop diamond batteries for a project he called "satellite RFID tags," which emit weak radio signals that will continue to identify satellites for thousands of years. Their vision doesn't stop with nuclear batteries, however: Arkenlight is also developing a gamma-volt battery (Gammavoltaic battery), which absorbs gamma rays from nuclear waste repositories and utilizes them to generate electricity.
Arkenlight's prototype Gammavoltaic battery, which will convert gamma rays from nuclear waste repositories into electricity.
Arkenlight isn't the only company working on nuclear batteries. U.S. companies like City Lab and Widetronix have been developing commercial Betavoltaic batteries for decades. These companies focus on more traditional layered nuclear batteries, and they use tritium rather than carbon-14 diamonds as a nuclear power source.
Michael Spencer, an electrical engineer at Cornell University and co-founder of Widetronix, said that radioactive material must be chosen with its application in mind. Carbon-14, for example, radiates fewer beta particles than tritium but has a half-life 500 times longer. That's certainly an advantage if you need something to last forever, but it also means that a carbon-14 nuclear battery would have to be much larger than a tritium battery to provide the same amount of power. " The choice of isotopes brings a lot of tradeoffs. " said Spencer.
If nuclear batteries were once a fringe technology, they seem poised to enter mainstream energy. We don't necessarily need - or want - all our electronics to last for thousands of years. But when we do, we're going to have a battery that's always working ...... probably still working for our next generation, and the next, and the next.
Written by : GolevkaTech