A future fusion power plant could do far more than generate electricity: its neutrons could also be used to produce certain fuels for nuclear batteries.
These batteries have almost nothing in common with those in a phone or a car. They draw their energy from the natural decay of radioactive atoms. This transformation continuously releases heat or particles, whose energy can be converted into electricity for years or even decades.
Artist’s impression of the ITER experimental fusion reactor, designed around a tokamak to confine plasma using magnetic fields.
Credit: U.S. Department of Energy / Wikimedia Commons — public domain
Plutonium-238 has already been used for more than 60 years to power equipment far from any electrical outlet. Several space probes use this technology. The problem is availability: global production suitable for these applications is currently measured at only a few kilograms per year.
Researchers are exploring another path through the fusion of deuterium and tritium, two forms of hydrogen. This reaction produces highly energetic neutrons, at around 14 MeV. In a future power plant, they would pass through a blanket surrounding the reactor. Scientists propose placing materials there that could transform under their impact.
Computer simulations show that these neutrons could produce several radioactive elements suitable for long-lasting energy sources. They include the plutonium-238 already in use, as well as plutonium-236, uranium-232 and lead-210. Some pathways could also produce the materials needed for other reactions.
The calculated quantities are very large compared with current production levels. For a fusion output equivalent to one gigawatt over a year, some configurations reach several tonnes of plutonium-238. Other fuels would be produced in quantities ranging from tens to hundreds of kilograms, depending on the material placed around the reactor.
In other words, the facility would use some of the neutrons already generated by fusion to produce another energy fuel. Some of the products studied could provide more energy per unit of mass than their current counterparts. This could make it possible to synthesize energy sources ranging from a few kilowatts to powers far exceeding those of conventional nuclear batteries.
The handling of the resulting products is also an issue. Several pathways generate materials that release substantial heat or penetrating radiation, making their processing demanding.