Fusion startup Inertia Enterprises said it has reduced the time required to make fuel pellets from several days to minutes in some stages of the process, and from a week or more to approximately two or three hours per pellet when the entire process is taken into account. The company believes this development removes one of ten obstacles it must overcome before building a profitable commercial fusion power plant.
Inertia relies on technology developed at the National Ignition Facility (NIF), a complex research facility operated by Lawrence Livermore National Laboratory. Manufacturing fuel pellets at NIF took a week or more and cost substantial sums because the facility produces a limited number of pellets annually for experimental purposes, not to supply an industrial-scale power plant.
From an Experimental Model to a Manufacturable Process
Jeff Lawson, the company’s co-founder and CEO, said Inertia treated NIF pellets as prototypes that should be converted into a product that could be manufactured in large quantities. For this reason, the company brought in industrial engineers, including employees hired from companies such as Apple, to redesign the process for repeated production inside a factory.
The pellet consists of a spherical diamond shell, followed by a thin frozen layer of deuterium and tritium, the two hydrogen isotopes used as fusion fuel. The crystalline layers contain a gaseous mixture of the two isotopes. The layers must be extremely close to a perfect spherical shape because small defects can hinder ignition and limit the energy produced.
The pellet is then covered with a gold casing known as a hohlraum, which converts laser energy into X-rays that compress the fuel. When the process succeeds, the atoms fuse and release energy. Inertia therefore had to accelerate manufacturing without departing too far from the physical characteristics demonstrated by NIF experiments.
What Is Changing in Practice?
After rounds of development, the company said it had managed to grow the crystals in about 30 minutes, instead of a period that could reach one week at NIF. It also developed the process in cooperation with NIF through a public-private partnership, and says it can be scaled to an industrial level.
Inertia plans to use a laser four times as powerful as the laser currently at NIF. The company says the additional energy gives it a larger margin that allows it to tolerate a degree of defects in the pellets, which also helped reduce manufacturing time. According to Lawson, increasing laser power is part of the company’s strategy to provide operating margin in the system’s other components.
The Impact of the Reduction on Tritium and Plant Size
The impact of accelerating pellet manufacturing is not limited to productivity. Tritium is a radioactive material that requires special care when handled, and it is also expensive; a gram costs approximately $30,000, while the global inventory is only about 25 kilograms, according to Science magazine.
Inertia plans to produce its own tritium with the help of fusion reactions, but it will need an initial inventory to begin operations. Reducing the time required to manufacture pellets limits the amount of tritium that must be kept on hand at any given time. The company expects its large-scale commercial plant to consume ten fuel pellets per second, making manufacturing and storage time practical factors that affect the facility’s size and efficiency, although they do not by themselves resolve the remaining challenges required to achieve a profitable plant.