General Atomics has received tax-credit funding from the state of California to design and develop a new facility in San Diego to test a key fusion reactor component that will allow the reactor to create its own fuel while generating power.
Though it always seems to be 25 years away no matter what calendar you look at, the potential payoff of a practical fusion reactor is so earth-shattering that there is tremendous incentive to pursue the technology. The thing is, the problem isn't just creating a nuclear fusion reaction – any halfway decent physics lab can do that on a benchtop. The real trick is to build a commercial reactor that is net-energy positive and practical.
Aside from coming up with a reactor design that can steadily produce more energy than it consumes, fusion reactors must be able to turn that energy into power. They must also withstand the immense stresses produced by powerful magnetic fields, extreme heat, and the intense neutron radiation caused by the fusion process.
The development of these engineering components is a major focus of current fusion research, and one key component is called a "fusion breeding blanket." As the name implies, this is a blanket of lithium alloy that lines the magnetic confinement chamber (tokamak) holding the hydrogen plasma.
The purpose of this blanket is twofold. First, it captures the energy of the fusion neutrons and turns it into heat that can be converted into electricity. Second, it creates more fuel to feed the ongoing reaction.
Fusion depends on a mixture of two hydrogen isotopes: deuterium and tritium. Deuterium is relatively easy to harvest from water, but tritium is trickier. It has a radioactive half-life of about 12.32 years, meaning there is only about 4 kg (7.7 lb) of natural tritium on Earth at any one time; so the reactor's fuel must be manufactured artificially – usually by bombarding lithium with neutrons.
Here is where the fusion breeding blanket comes in. As the fusion neutrons bombard the lithium lining, some are absorbed by the nuclei of the lithium atoms, splitting them into helium and tritium, and releasing a whacking great amount of thermal energy, according to the formula: ⁶Li+n→⁴He+³H+4.8MeV
While the principle is simple, the engineering is anything but. For this reason, General Atomics is building its Blanket Component Test Facility in collaboration with the United States Department of Energy, Idaho National Laboratory, the University of California San Diego, and additional industrial and academic partners.
The goal of the facility will be to test full-scale fusion breeding blankets to see how well they stand up to realistic reactor conditions, as well as how much heat and tritium they produce. If things go according to plan, by the time the first commercial reactors are constructed, they will already have validated blankets that make them entirely self-sufficient when it comes to fuel.
Source: General Atomics
