A novel radioisotope battery has been developed that converts radioactive decay energy into electricity by utilizing cyclotron radiation emitted by electrons in strong magnetic fields, demonstrating high conversion efficiency and long-term operational stability for diverse applications.

Conceptual diagram of a radioisotope beta-decay energy conversion device using cyclotron radiation

Launched in 1977, the Voyager spacecraft is the farthest human-made object from Earth. Nearly 50 years after its launch, Voyager continues to carry out its mission thanks to the radioisotope power system (RPS) onboard Voyager 1. Radioisotopes release energy through radioactive decay, enabling stable power generation over long periods ranging from several decades to hundreds of years, depending on their half-lives. For this reason, in environments such as deep-space or deep-sea exploration—where periodic replacement of power sources is impractical—radioisotope power systems are virtually irreplaceable. However, the high cost of radioisotopes and the low efficiency of conventional energy conversion technologies have limited their application primarily to specialized fields such as defense and space exploration.

Figure 1 The operation principle of radioisotope cyclotron generator

To overcome these limitations, a joint research team led by Professors Jee Hyun Seong and Young-Cheol Ghim from the Department of Nuclear and Quantum Engineering at KAIST has proposed an entirely new high-efficiency energy conversion approach. The team introduced a novel concept that directly converts radioactive decay energy into electrical energy by exploiting cyclotron radiation, which is emitted when electrons undergo circular motion in a strong magnetic field (Figure 1).

Figure 2 Spatial distribution of beta particles confined in the magnetic trap computed by PIC simulation

To quantitatively evaluate the energy conversion efficiency, the researchers employed the Particle-In-Cell (PIC) simulation method, widely used in fusion plasma research, to calculate the trapping efficiency of electrons generated through beta decay (Figure 2). In addition, the device was designed in the form of a resonant cavity to enable efficient collection and conversion of the emitted electromagnetic radiation.

Simulation results indicate that the proposed battery can achieve an energy conversion efficiency of up to 30% or higher. This represents a significant improvement compared to conventional semiconductor-based beta batteries, which typically exhibit efficiencies in the range of 1–2%. Such high efficiency could substantially reduce the amount of radioisotope required, leading to a dramatic reduction in cost. Furthermore, this advancement is expected to expand the application of radioisotope batteries beyond traditional defense and space sectors to civilian fields such as wireless sensor networks.

The radioisotope battery concept proposed in this study is currently under patent review and was presented at the 2024 American Nuclear Society (ANS) Winter Conference and Expo. The research team plans to conduct experimental validation using radioisotopes in future studies.