Dragon egg robot can help scientists study this violent natural process with unprecedented detailed data, but for tom scott, a material scientist at Bristol University, volcanic exploration is just the beginning. In the past few years, Professor Scott and a small group of collaborators have been developing an upgraded version of the "Dragon Egg" nuclear battery, which can last for thousands of years without charging or replacing. Unlike most batteries in modern electronic products that generate electricity through chemical reactions, the batteries studied by Bristol University collect particles ejected by radioactive diamonds, which can be made from modified nuclear waste.
Earlier this month, Scott and his collaborator Neil Fox (a chemist from Bristol University) set up a company called "Arkenlight" to commercialize their nuclear diamond battery. Although this nail-sized battery is still in the prototype stage, it has shown an improvement in efficiency and power density compared with the existing nuclear battery. Once Professor Scott and his Arkenlight team have perfected their design, they will set up a test facility for mass production. The company plans to put the first batch of commercial nuclear batteries on the market by 2024-but we don't expect to find them in laptops.
Traditional chemical batteries or "primary batteries", such as lithium-ion batteries in smart phones or alkaline batteries in remote controllers, can release a large amount of electricity in a short time. Lithium-ion battery can only work for a few hours without charging, and its charging ability will drop sharply after several years of use. In contrast, a nuclear battery or a beta battery (beta voltaic battery, a battery that converts radioactive beta radiation into current) is a battery that can continuously generate a small amount of electricity for a long time. They don't generate enough electricity to drive smart phones, but according to the nuclear materials they use, they can provide stable power output for small devices for thousands of years.
"So, can we use nuclear batteries to power electric vehicles? The answer is-No.Morgan Boardman, CEO of Arkenlight, said that to power this energy-consuming thing, it means that "the' quality' of the battery will need to be significantly greater than the' quality' of the vehicle". On the contrary, the company is looking for applications where it is almost impossible or impossible to change batteries regularly (it can also be said that it is a one-time long-term application product direction), such as nuclear waste repositories and sensors in remote or dangerous places on satellites. Boardman also saw applications closer to our lives, such as using the company's nuclear batteries for pacemakers or wearable devices. He envisions a future in which people will keep batteries and replace equipment, instead of changing batteries frequently on the same equipment as they do now. "You will replace several fire alarms before replacing the battery, because the life of the battery has far exceeded these devices." That's what boardman said.
Not surprisingly, most people will definitely resist the nuclear battery, because they think it will produce radioactive substances, which is harmful to the health. However, from the health risk report of Betavoltaic battery, it can be compared with the health risk of "export sign", which uses a radioactive substance called "tritium" to realize its iconic red fluorescence. Unlike gamma rays or other more dangerous radiation types, beta particles can only stop running through a protective layer several millimeters thick. Lance Hubbard, a material scientist at Pacific Northwest National Laboratory, said: "Usually, the battery wall is enough to prevent any leakage. This makes the nuclear battery almost free of radioactive materials and very safe for people. " In addition, he added, when the nuclear battery runs out of energy, it will decay to a stable state, which means there is no nuclear waste left inside.
The first generation of beta voltaic cells appeared in the 1970s, but until recently, no one used them. They were originally used for pacemakers. In this case, defective power packs may mean the difference between life and death until they are finally replaced by cheaper lithium-ion substitutes. Nowadays, the popularity of low-power electronic products indicates that nuclear batteries have entered a new era. "For very low-power equipment, this is a good power supply choice-we are talking about micro-tiles, or even picowatts." Hubbard believes: "The Internet of Things has promoted the revival of these energy sources."
A typical beta voltaic cell consists of a thin foil-like radioactive material layer sandwiched between semiconductors. Its power generation principle is that when nuclear matter naturally decays, it will release high-energy electrons or positrons called beta particles, which will scatter electrons in semiconductor materials, thus generating 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 batteries have strict energy limits. Their power density will decrease as the radiation source moves away from the semiconductor. Therefore, if the thickness of the battery layer exceeds several microns, the power of the battery will drop sharply. In addition, beta particles are randomly emitted in all directions, which means that only a small part of particles will actually hit the semiconductor, and only a small part will be converted into electric energy. As for how much electricity nuclear radiation batteries can convert into, Hubbard said, "At present, the efficiency of about 7% is the most advanced."
This is Arkenlight's "Betalight" volt-ampere battery, which integrates a sensor package. Unlike C-14 battery, "Betalight" is a traditional "sandwich" nuclear battery made of tritium.
This is far from the theoretical maximum efficiency of nuclear batteries (about 37%). However, this is where a radioactive isotope called "carbon-14" can help. "Carbon-14" plays the most famous role in radiocarbon dating. It enables archaeologists to estimate the age of ancient cultural relics, and it can also provide power for nuclear batteries, because it can be used as both radioactive source and semiconductor. Its half-life is also 5700 years, which means that carbon-14 nuclear battery can provide electronic equipment with a longer time than human written language in principle.
Scott and his colleagues cultivated the artificial "carbon-14" diamond by injecting methane into hydrogen plasma in a special reactor. When the gas is ionized, methane decomposes, and carbon-14 gathers on the substrate in the reactor and begins to grow in the diamond lattice. However, Scott and his colleagues used this radioactive diamond in the traditional "sandwich" battery configuration, in which the radioactive source and the semiconductor are discrete layers. Moreover, they applied for a patent to directly inject carbon-14 into laboratory equipment to cultivate diamonds. Diamonds made in this way are similar to those on our daily rings. The result is a crystal diamond with seamless structure, which minimizes the moving distance of β particles and improves the efficiency of nuclear battery.
"So far, the radioactive source has been separated from the diode that receives the radioactive source and converts it into electrical energy." Boardman said: "This is a breakthrough."
When cosmic rays hit nitrogen atoms in the atmosphere, "carbon-14" naturally forms, but it is also produced as a by-product in graphite blocks containing control rods of nuclear reactors. These lumps will eventually become nuclear waste. According to Boardman, there are nearly 654.38 million tons of irradiated graphite in Britain alone. The British Atomic Energy Agency recently recovered tritium, another radioactive isotope used in nuclear batteries, from 35 tons of irradiated graphite blocks. Arkenlight's team is working with the agency to develop a similar process to recover carbon-14 from graphite blocks.
If Arkenlight is successful, it will provide almost inexhaustible raw materials for manufacturing nuclear batteries. According to the data of AEA in Britain, less than 100 pounds (about 45.36 kilograms) of carbon-14 is enough to manufacture millions of nuclear batteries. In addition, by removing radioactive carbon-14 from graphite block, it will be downgraded from high-level radioactive nuclear waste to low-level radioactive nuclear waste, thus making it easier to handle and safer for long-term storage.
At present, Arkenlight has not made a beta battery from the modified nuclear waste. Boardman said that the company's nuclear diamond battery needs several years of improvement in the laboratory before it can be put into use. But this technology has attracted the interest of space and nuclear industry. Boardman went on to say that Arkenlight recently won a contract from the European Space Agency to develop a diamond battery for what he called a "satellite RFID tag", which can emit weak radio signals and continuously identify satellites for thousands of years. However, their eyes did not stop at the nuclear power pool. Arkenlight is also developing a gamma-ray battery, which can absorb gamma rays emitted by nuclear waste warehouses and use them to generate electricity.
Arkenlight's prototype gamma volt battery will convert gamma rays in the nuclear waste repository into electric energy.
Arkenlight is not the only company that studies nuclear batteries. American companies such as City Lab and Widetronix have been developing test batteries for decades. These companies focus on more traditional layered nuclear batteries. They use tritium as the nuclear power source instead of carbon-14 diamond.
Michael Spencer, an electrical engineer at Cornell University and co-founder of Widetronix, said that their applications must be considered when selecting radioactive materials. For example, carbon-14 releases less beta particles than tritium, but its half-life is 500 times longer. If what you need can last forever, this is indeed its advantage, but it also means that the carbon-14 nuclear battery must be much larger than the tritium battery to provide the same amount of electricity. "The choice of isotopes will bring many trade-offs," Spencer said.
If the nuclear battery was once a marginal technology, it seems to be ready to enter the mainstream energy now. We don't necessarily need-or hope-that all our electronic products can be used for thousands of years. But when we do this, we have a battery that works all the time ... Maybe our next generation, next generation, next generation can still work.
By GolevkaTech