Nuclear Fusion

Respond to this Friday Faithfuls challenge by writing anything about nuclear fusion, or any other source of clean energy, or you can go with whatever else that you think fits.  We are still decades away from nuclear fusion becoming a viable energy source, if it ever does, but we have started making some progress.  Nuclear fusion is a safe form of energy, because even though it does produce a small number of radioactive materials, it does not create any long-lived radioactive nuclear waste.  A fusion reactor produces helium, which is an inert gas.  Fusion is a self-limiting process and if you cannot control the reaction, the machine switches itself off, so you never have a runaway chain reaction meltdown.  The idea of fusion is to fuse two hydrogen nuclei together to create helium isotopes and our sun is constantly creating fusion reactions all the time, burning ordinary hydrogen at enormous densities and temperatures.  So far, the energy input required to produce the temperatures and pressures that enable significant fusion reactions in hydrogen isotopes has far exceeded the fusion energy generated.  Humanity is moving much closer to solving the strongly repulsive electrostatic forces between the positively charged nuclei that prevent them from getting close enough together to collide and allow fusion to occur.

We have had a theoretical understanding of fusion for over a century, but it is a long road from knowing how to do this and actually being able to achieve it.  It is hoped that one day a fusion power plant will be able to produce more power than it consumes once we figure out how to utilize it.  Some promising fusion technologies such as magnetic confinement and laser-based inertial confinement, are getting around some of the problems, but we are still not achieving that breakthrough moment when the amount of energy coming out of a fusion reactor will sustainably exceed the amount going in, producing net energy.  MIT designed a new superconducting magnet that is breaking magnetic field strength records, being ramped up to a field strength of 20 tesla, the most powerful magnetic field of its kind ever created on Earth.  The MIT-CFS fusion design uses high-temperature superconductors, which enable a much stronger magnetic field in a smaller space.  With this successful magnet technology in place, the next step is to create and confine a plasma (hot swirling soup of protons and electrons) which may be ready in 2025.

The U.S. Department of Energy (DOE) and DOE’s National Nuclear Security Administration (NNSA) announced the achievement of fusion ignition at Lawrence Livermore National Laboratory (LLNL) on Dec. 5, 2022 where 192 laser beams delivered more than 2 million joules of ultraviolet energy to a tiny fuel pellet to create fusion ignition.  This is considered to be a major scientific breakthrough that was decades in the making and it should pave the way for advancements in national defense and the future of clean power.  This historic, first-of-its kind unprecedented achievement after several decades of trying is known as a scientific energy breakeven, meaning it produced more energy from fusion than the laser energy used to drive it.  The 192 lasers were aimed at a 0.04-inch (1 mm) pellet of fuel made of deuterium and tritium, two versions of the element hydrogen with extra neutrons to create the self-sustaining fusion reaction.

When the lasers hit the canister, X-rays were produced that heated and compressed the fuel pellet to about 20 times the density of lead and the heat reached more than 5 million degrees Fahrenheit (3 million Celsius) which is about 100 times hotter than the surface of the Sun.  The sad news is that the fuel and canister got vaporized within a few billionths of a second during the experiment and this energy gain did not consider all the energy and electricity needed to fire up the system and run the experiment.  They used 2 million joules of laser energy which is about the amount of power it takes to run a hair dryer for 15 minutes and the reaction released about 3 million joules of energy, making this a watershed moment that proves fusion is possible.  The science and technology challenges on the path to fusion energy is daunting, but this little bit of excitement goes a long way to making long term commitments to fusion as a source of energy.

Fusion is a nuclear reaction that combines two atoms to create one or more new atoms with slightly less total mass.  The difference in mass is released as energy, as described by Einstein’s famous equation, E = mc², where energy equals mass times the speed of light squared.  Since the speed of light is enormous, converting just a tiny amount of mass into energy. like what happens in fusion, produces a similarly enormous amount of energy.  Nuclear fusion mimics the way stars create their own light and heat.  In our sun, hydrogen nuclei fuse together, creating helium and generating a tremendous amount of energy.  Fusion reactions in the sun burn ordinary hydrogen at enormous density and temperature, sustained by an effectively infinite confinement time, and the reaction products are benign helium isotopes.  Artificial (terrestrial) fusion schemes, on the other hand, are restricted to much lower particle densities and much more fleeting energy confinement and are therefore compelled to use the heavier neutron-rich isotopes of hydrogen known as deuterium and tritium, which are 24 orders of magnitude more reactive than ordinary hydrogen.  Our sun has enough hydrogen left to keep burning for another 5 billion years.  No materials exist that can withstand direct contact with this required heat, so to achieve fusion in a lab, scientists have devised a solution in which a super-heated gas, or plasma, is held inside a doughnut-shaped magnetic field.

We are only in the R&D phase, but now that we know fusion is possible, and if scientists and engineers can work together to figure out how to go about building fusion power plants to provides us with a safe and effective amount of clean energy, this could be a good thing, by reducing our dependency on fossil fuels.  The science of fusion is expected to take a long time before it ever becomes a practical reality and it will probably need international cooperation and a whole lot of money.  Fusion is an energy source for tomorrow, but it may make it a little bit easier for us to become green 20-30 years from now.  Microsoft is betting on nuclear fusion, thinking that the technology is nearly ready to plug into the grid.  They signed an agreement with a company called Helion Energy to purchase electricity from a nuclear fusion generator, hoping it can be delivered by 2028.  The goal is to generate at least 50 megawatts of power, a small but significant amount and more than the 42MW that the US’s first two offshore wind farms have the capacity to generate today.  Helion is developing a 40-foot device called a plasma accelerator that heats fuel to 100 million degrees Celsius.  It heats deuterium (an isotope of hydrogen) and helium-3 into a plasma and then uses pulsed magnetic fields to compress the plasma until fusion happens.

The UK-based JET laboratory has smashed its own world record for the amount of energy it can extract by squeezing together two forms of hydrogen producing enough energy to boil about 60 kettles’ worth of water, but they were able to hold it there for five seconds.  The ITER International Thermonuclear Experimental Reactor facility in southern France is the world’s largest fusion experiment and it is supported by a consortium of world governments including thirty-five nations collaborating together, among them are EU member states, the US, China and Russia.  This is expected to be the last step in proving nuclear fusion can become a reliable energy provider in the second half of this century.  Their objective is to build the world’s largest tokamak, a magnetic fusion device that has been designed to prove the feasibility of fusion as a large-scale and carbon-free source of energy based on the same principle that powers our Sun and the stars.  The amount of fusion energy a tokamak is capable of producing is a direct result of the number of fusion reactions taking place in its core.  Scientists know that the larger the vessel, the larger the volume of the plasma and therefore the greater the potential for fusion energy.  Fusion research today is at the threshold of exploring a “burning plasma”, one in which the heat from the fusion reaction is confined within the plasma efficiently enough for the self-heating effect to dominate any other form of heating.  Scientists are confident that the plasmas in ITER will not only produce much more fusion energy but will remain stable for longer periods of time.

Many technical challenges remain, and fusion is never going to be the perfect energy source, or the holy grail of energy, because it is not completely safe.  Deuterium is an isotope, and it is not radioactive, but tritium is radioactive.  Fusion reactors will burn neutron-rich isotopes that are anything but harmless.  Radiation damage will occur, and radioactive waste will accumulate, and we will need biological shielding to protect the plant workers and there is always the potential for nuclear fusion to produce weapons.