Zeno Power makes cost-effective radioisotope power systems (RPS) for some of the most challenging environments in the solar system. Its systems use a proprietary package that allows a wider variety of isotopes to perform functions previously reserved for Pu-238, a rare isotope that is slowly produced at great expense.
What is the value of RPS?
RPS’s produce power and/or heat by usefully capturing the energy released when radioactive materials decay. Diminishing quantities of heat are produced as the materials release their alpha, beta and/or gamma emissions, with the production rate being governed by the half life of the isotope. It is a power source that is predictable as time; it can neither be accelerated nor decelerated.
By continuously producing useful power for decades at a time without a break, radioisotopes have enabled exploration of the most distant reaches of our solar system while remaining capable of relaying their findings back to Earth. It is a well established technology that has been used since the very beginning of the Atomic Age.
The majority of the radioisotope power supplies that have powered past space missions have used Pu-238, a marvelously capable isotope. It has an 87-year half life and decays with a pure, easily shielded, high-energy alpha particle. Unfortunately, it is slowly produced in specialized reactors and needs expensive processing and refinement. As a result, Pu-238 costs tens of millions of dollars per kilogram. It is only available for the most carefully screened mission applications.
The Strontium-90 option
Strontium-90 has good characteristics as a heat source for RPS. It has a 28.1-year half life and it decays with an energetic beta emission that is reasonably easy to shield.
With its relatively high specific heat generation, Sr-90 has been used in the past for terrestrial applications, but its decay produces occasional gamma radiation in addition to the dominant, heat-producing beta emission. Additionally, as the high energy beta interacts with conventional shielding materials, it produces bremsstrahlung radiations that must also be shielded. As a result Sr-90-based power systems require enough shielding to make them too heavy to launch into space.
Sr-90 RPS have been used to power remote light houses, underwater sensors, navigational buoys and remote weather monitors. Alternative, lower-cost power sources have gradually replaced Sr-90 RPS for each of those applications.
By the 1990s, the US had stopped producing Sr-90 RPS and was decommissioning the systems that had been deployed. A 2009 paper titled End of an Era and Closing the Circle – Disposal of Strontium-90 Radioisotope Thermoelectric Generators contains a statement that almost sounds like a eulogy. “This unique and creative use of nuclear technology is fading into obscurity and soon will be forever a thing of the past.”
Times have changed. With a dramatically growing business of satellites plus lunar and planetary exploration, there is a crying need for reliable power supplies that are more affordable and more available than the ones that need Pu-238. Sr-90 is still available and it still has the physical properties that attracted early developers, but the technology for capturing the energy needed improvement before it could be considered a solution for the growing market.
Zeno Power’s RPS development
During the 2016-2018 period, a trio of Vanderbilt students joined with a professor to find a useful product meeting the needs of identified customers. They wanted to be entrepreneurs and all of them loved science, engineering and creating cool things. They realized early that successful companies produced products that met customer needs at a price they were willing to pay. Any other creations were mere science projects.
Their market research led them to a decision to develop mission-capable radioisotope power systems that could take advantage of isotopes that were more available and more affordable than Pu-238. Strontium-90 (Sr-90), an isotope with a track record as a viable source material for RPS was an obvious starting point. Sr-90 is much more available than Pu-238; it is near the top of the yield curve of radioactive by-products produced in all fission reactors.
Zeno Power’s innovation is a proprietary shielding system that substantially reduces the system weight of an RPS that uses isotopes with a significant gamma component associated with their decay. There are other isotopes with differing characteristics that might eventually be useful in an expanding universe of applications.
Tyler Bernstein, CEO of Zeno Power, visited the Atomic Show to describe his company’s history, products, ethos and mission.
During the relatively short period since its founding, Zeno Power has captured the attention of the space industry and the Department of Energy. With concrete evidence of that interest is has convinced investors that has a clear line of sight to being a growing, profitable company. It has made a few contract announcements already. Tyler promised us that there are more to come in the near future. When the time is right, he will return to provide additional information.
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