Scientists at the U.S. Department of Energy’s Oak Ridge National Laboratory (ORNL) are taking a fresh look at neptunium, a rare radioactive metal that plays a crucial role in producing plutonium-238, the fuel that powers spacecraft exploring deep space.
Their new research is helping improve understanding of this little-known element and could support future missions to distant planets and beyond.
Plutonium-238 is used in radioisotope thermoelectric generators, or RTGs, which provide long-lasting electricity for spacecraft that travel far from the Sun.
Solar panels become much less effective in deep space, and conventional batteries cannot survive the extreme conditions for years or decades.
RTGs solve this problem by converting heat from radioactive decay into electricity, allowing missions such as NASA’s Perseverance rover on Mars to operate continuously.
Because plutonium-238 is so important, scientists must understand how to produce it efficiently.
Neptunium is a key ingredient in that process, acting as a starting material that eventually becomes plutonium-238 through nuclear reactions. However, neptunium’s chemistry is complex and not fully understood, making it difficult to optimize production.
The ORNL team studied how neptunium changes when heated, a process known as thermal decomposition.
By gradually raising the temperature of neptunium samples from about 150 to 600 degrees Celsius, the researchers were able to observe how the material’s structure and chemical bonds evolved.
This helped them identify intermediate stages that occur before the final products form, providing clues about how to control the process more precisely.
To examine these changes, the scientists used advanced tools including Raman spectroscopy, which uses laser light to detect vibrations within molecules.
By shining lasers on the heated samples, they could track how the internal structure shifted as the temperature increased.
They also used computer modeling to compare theoretical predictions with their experimental results. One of their major achievements was producing the first detailed “fingerprint” of a particular neptunium oxide, a compound important in the production chain.
These findings not only improve knowledge of neptunium itself but also help refine the methods used to create plutonium-238.
A better understanding of the material means scientists can design more efficient production processes and ensure a stable supply for future missions. Demand for plutonium-238 is growing as interest in long-duration space exploration increases.
The research highlights the importance of materials science in space technology. Even though neptunium is extremely rare in nature, studying it can have a large impact on how humanity explores the solar system.
The work also supports energy security by strengthening domestic production capabilities for this critical material.
For the scientists involved, the project combines cutting-edge research with the excitement of space exploration. By unlocking the secrets of a little-known element, they are helping build the power systems that will allow spacecraft to travel farther and operate longer than ever before.
As plans for missions to the outer planets, moons, and possibly interstellar space continue to grow, reliable power sources will be essential.
Advances in neptunium chemistry could play a quiet but vital role in making those journeys possible, ensuring that future explorers — robotic or human — have the energy they need to venture deeper into the cosmos.
