DARPA Selects Seven Projects for ‘Rads to Watts’ Program to Develop Radioisotope Power for Deep-Sea and Space Environments

American Nuclear Society USA

Overview

DARPA has selected seven innovative projects for its ‘Rads to Watts’ program, focused on designing radioisotope voltaic cells to provide long-term power in extreme environments like deep-sea and space. The program emphasizes developing technology to directly convert radioactive decay energy into electricity via semiconductor converters. Participating teams, including BWXT and City Labs, aim to improve high-radiation-tolerant semiconductors and plutonium-238 power extraction efficiency, potentially revolutionizing autonomous system power delivery.

In Depth

Key Findings

The Defense Advanced Research Projects Agency (DARPA) has selected seven promising projects for its groundbreaking ‘Rads to Watts’ program. This initiative aims to design radioisotope voltaic cells capable of providing long-duration power in extreme environments, such as deep-sea and outer space. The program specifically focuses on developing technology to directly convert the decay energy of radioisotopes into electricity through semiconductor converters, holding the potential to revolutionize power supply for autonomous systems.

Technical Details

Radioisotope voltaic cells generate electricity by directly irradiating semiconductor p-n junctions with charged particles (electrons or alpha particles) emitted from radioactive decay processes like beta or alpha decay. Unlike traditional radioisotope thermoelectric generators (RTGs) which produce electricity via heat, radioisotope voltaic cells offer direct conversion, making them generally smaller, more efficient, and longer-lasting. The seven selected projects are concentrating on the following key technical challenges:

• Development of High-Radiation-Tolerant Semiconductors: Optimizing material science and device structures for wide-bandgap semiconductors (e.g., SiC, GaN, diamond) to ensure long-term operation in extreme environments.
• Enhancing Conversion Efficiency: Innovating semiconductor design and integration techniques to maximize the conversion of energy from emitted radioactive particles into electrical power.
• Selection and Utilization of Radioisotopes: Investigating the optimal use of isotopes with varying half-lives and energy outputs, such as tritium (pioneered by City Labs), nickel-63, and plutonium-238 (researched by BWXT), with plutonium-238 expected to offer higher power outputs.
• Miniaturization and Integration: Developing compact battery designs and thermal management techniques to facilitate integration into sensors and small probes.

These technological advancements aim to realize self-contained power sources capable of operating maintenance-free for decades.

Background & Industry Context

For deep-sea probes and long-duration space missions (lunar bases, deep-space probes, high-orbit satellites), autonomous and highly reliable long-term power sources are indispensable where solar power or cabled power supply is difficult or impossible. DARPA’s ‘Rads to Watts’ program seeks to bridge this gap, addressing U.S. national security and scientific exploration needs. Technologies in this domain not only expand the frontiers of space exploration but also promise wide-ranging civilian applications, including remote sensor networks, emergency power during disasters, and implantable medical devices. The participation of companies like City Labs, a pioneer in the small nuclear battery market, represents a significant step towards practical implementation.

Strategic Significance & Outlook

The seven selected projects will progress from concept validation to prototype development over the coming years. The ultimate goal is to develop practical radioisotope voltaic cells that can supply stable power in locations where conventional power systems are infeasible. This will unlock new possibilities in military operations, space exploration, and scientific research, significantly enhancing human capabilities in extreme environments. The program’s success is expected to establish a new paradigm in energy conversion technology, profoundly influencing the design of future autonomous systems.

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