Prototype uranium battery reimagines nuclear waste as energy storage.

Converting a global stockpile of nuclear byproduct into a novel form of energy storage, researchers at the Japan Atomic Energy Agency (JAEA) have developed the world's first rechargeable battery powered by depleted uranium – a prototype that reimagines radioactive waste as a potential asset for future energy systems.

Undergoing a complex and carefully managed preparation process before entering a reactor, nuclear fuel typically begins as enriched uranium formed into ceramic pellets and sealed within metal fuel rods. Once installed, these assemblies remain in operation for roughly three to six years, during which only a small fraction of the uranium's total energy potential is consumed.

Despite retaining more than 95% of its original energy content, spent fuel is removed once the buildup of byproducts interferes with the chain reaction needed to sustain power generation.

This untapped energy remains locked within what is conventionally classified as waste – a long-standing constraint of the nuclear fuel cycle now drawing renewed attention as researchers explore new ways to turn discarded material into a viable source of power storage.

Before uranium can be used to generate power, it must first go through a process that increases its concentration so it can function inside a reactor in the first place. This process – known as enrichment – leaves behind a dense gray powder called depleted uranium: chemically stable, weakly radioactive, and produced in far greater quantities than most people realize.

Over decades of fuel preparation, more than 1.7 million metric tons of this material have built up globally, including over 17,600 metric tons in Japan alone.

Once enriched fuel is placed in a reactor, it typically remains in use for three to six years before being removed as spent nuclear fuel – highly radioactive, thermally hot, and subject to strict handling and storage protocols.

After nearly 70 years of global reactor use, the total volume of spent fuel produced would fill only a single football field stacked about 10 yards (30 feet) high – a compact footprint, given the scale of energy it has delivered and the long-term challenge it continues to pose.

Now, in a development that reframes the value of this largely untapped byproduct, the JAEA has developed a prototype battery powered by depleted uranium, marking the first time nuclear material has been directly repurposed as a rechargeable energy source.

"To utilise DU as a new resource, the concept of rechargeable batteries using uranium as an active material was proposed in the early 2000s," JAEA noted. "However, no studies were reporting the specific performance of the assembled uranium rechargeable batteries."

Operating on a principle similar to conventional batteries, the design generates electricity through chemical reactions between an anode and cathode – only here, the uranium itself serves as the active medium.

"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 continued.

Roughly the size of a deck of cards, the uranium-powered prototype is designed to deliver a stable output of 1.3 volts – comparable to a standard AA battery – and has already undergone 10 complete charge and discharge cycles without measurable performance loss. JAEA said it is now aiming to increase the capacity of uranium storage batteries (the amount of electricity they can store) by circulating the electrolyte.

"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," JAEA said. "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."

Testing remains at an early stage, with further evaluation needed to assess durability, performance under load, and long-term stability.

Also, because uranium is involved, even in its depleted form, concerns over radiation exposure, shielding, and handling remain central. Although significantly less radioactive than enriched fuel, depleted uranium still emits ionizing radiation and, according to the researchers, will remain confined to controlled environments for the foreseeable future.

Extensive testing over several years will be necessary before the technology can be considered for broader applications.

If future testing proves successful, one potential application could involve renewable energy storage – where the need for durable, high-capacity systems continues to limit the scalability of intermittent sources like solar and wind.

While any such use remains distant, the concept of converting a nuclear byproduct into grid support infrastructure introduces a new dimension to both waste management and battery innovation.