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South Korean researchers are studying radiocarbon as a source for safe, small and affordable nuclear batteries that could last decades or longer without charging. They have developed a prototype betavoltaic battery powered by the radioactive carbon-14 isotope.

Su-Il In is a professor at Daegu Gyeongbuk Institute of Science & Technology. He presented a report on his work at the spring meeting of the American Chemical Society, held on 23-27 March. Funding for the carbon-14 battery research was supplied by the National Research Foundation of Korea, as well as the Daegu Gyeongbuk Institute of Science & Technology Research & Development Program of the Ministry of Science and Information and Communication Technology of Korea.

With the increasing number of connected devices, data centers and other computing technologies, the demand for long-lasting batteries is rising. In says that the performance of lithium-ion (Li-ion) batteries is “almost saturated”. His team is therefore working on the development of nuclear batteries as an alternative to lithium batteries.

The researchers have produced a prototype betavoltaic battery with carbon-14 which is an unstable and radioactive form of carbon, called radiocarbon. In said, “I decided to use a radioactive isotope of carbon because it generates only beta rays”. A by-product of the operation nuclear power plants, radiocarbon is inexpensive, readily available and easy to recycle. And since radiocarbon degrades very slowly, a radiocarbon-powered battery could theoretically last for millennia.

To significantly improve the energy conversion efficiency of their new design, the Korean team used a titanium dioxide-based semiconductor, a material commonly used in solar cells, sensitized with a ruthenium-based dye. They improved the bond between the titanium dioxide and the dye with a citric acid treatment. When beta rays from radiocarbon collide with the treated ruthenium-based dye, a cascade of electron transfer reactions, called an electron avalanche, takes place. Then the avalanche travels through the dye and the titanium dioxide collects the generated electrons.

The new Korean battery prototype also has radiocarbon in the dye-sensitized anode and a cathode. By treating both electrodes with the radioactive isotope, the researchers increased the quantity of beta rays generated and reduced distance-related beta-radiation energy loss between the two components.

During testing of the prototype battery, the researchers found that beta rays released from radiocarbon on both electrodes triggered the ruthenium-based dye on the anode to generate an electron avalanche that was collected by the titanium dioxide layer and passed through an external circuit resulting in usable electricity.

In said that these long-lasting nuclear batteries could enable many applications. These include powering implants, remote applications, satellites and many more. A pacemaker would last a person’s lifetime, eliminating the need for surgical replacements.

This betavoltaic design converted only a tiny fraction of radioactive decay into electric energy, leading to lower performance when compared to conventional Li-ion batteries. In suggests that further efforts to optimize the shape of the beta-ray emitter and develop more efficient beta-ray absorbers could improve the battery’s performance and increase power generation.

Daegu Gyeongbuk Institute of Science & Technology

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The Japan Atomic Energy Agency (JAEA) is a nuclear research and development organization in Japan. JAEA carries out research and development in various fields with the intent of assisting in the realization of a carbon-neutral, resource-efficient society as well as contributing to human society. JAEA has developed the world’s first “uranium rechargeable battery”. Testing of the new battery prototype has verified its performance in charging and discharging.

A betavoltaic device (betavoltaic cell or betavoltaic battery) is a type of nuclear battery that generates electric current from beta particles (electrons) emitted from a radioactive source, using semiconductor junctions. Unlike most nuclear power sources which use nuclear radiation to generate heat which then is used to generate electricity, betavoltaic devices use a non-thermal conversion process, converting the electron-hole pairs produced by the ionization trail of beta particles traversing a semiconductor into electricity. Betavoltaic power sources (and the related technology of alphavoltaic power sources which have not been technologically successful to date primarily because the alpha particles damage the semiconductor material) are particularly well-suited to low-power electrical applications where long life of the energy source is needed, such as implantable medical devices or military and space applications

The uranium storage battery utilizes depleted uranium (DU) as the negative electrode active material and iron as the positive one according to the JAEA. The single-cell voltage of the prototype uranium rechargeable battery is one and three tenths volts, which is close to that of a common alkaline battery at one and five tenths volts.

The prototype battery was charged and discharged ten times, and the performance of the battery was virtually unchanged, which indicates relatively stable cycling characteristics.

JAEA noted, “To utilize DU as a new resource, the concept of rechargeable batteries using uranium as an active material was proposed in the early 2000s. “No studies were reporting the specific performance of the assembled uranium rechargeable batteries. If uranium rechargeable batteries are increased in capacity and put to practical use, the large amount of DU stored in Japan will become a new resource for output controls in the electricity supply grid derived from renewable energy, thereby contributing to the realization of a decarbonized society.” JAEA is now working on increasing the capacity of uranium storage batteries (the amount of electricity they can store) by circulating the electrolyte.

According to JAEA, there is currently about sixteen thousand tons of depleted uranium stored in Japan and about one and sixths tenths million tons stored worldwide.

JAEA said, “Specifically, we will be examining whether it is possible to increase capacity by increasing the amount of circulating electrolyte and the concentration of uranium and iron, and what the optimal materials are for the electrodes and membranes that make up the storage battery. If we are successful in increasing the capacity of uranium storage batteries and put them to practical use and implemented in society using depleted uranium stored in Japan, we can expect them to play new roles such as adjusting supply and demand for mega solar power plants.”

JAEA explained that the need for rechargeable batteries has been rising in recent years with an increase in the introduction of renewable energy sources. Power generation from solar, wind, and other sources is affected by weather conditions and has the problem of fluctuating power generation. To stabilize the power supply in this situation, output controls via energy storage devices such as rechargeable batteries are required, and the development of new energy storage technologies is attracting attention.

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Japan Atomic Energy Agency