Mayank Chhaya-
Over eighty years after it was first theorized, nuclear fusion that powers stars, including the Sun, is now a reality on Earth, at least on the laboratory scale.
The breakthrough was announced today after the National Ignition Facility (NIF) at Lawrence Livermore Laboratory in Livermore, California, managed to produce more energy output than input using fuel heated by lasers. The breakthrough was achieved on December 5 but announced today.
The NIF produced 3.15 megajoules (MJ) using an input of 2.05 MJ. This is a potentially huge breakthrough as nuclear fusion has long been considered the “holy grail” of clean, limitless energy.
In simple terms, nuclear fusion occurs when two nuclei are fused into a single heavier nucleus which in turn releases energy since the total mass of the single nucleus is less than the two individual ones. The surplus mass converts into energy as predicted famously by Albert Einstein.
According to the laboratory, the breakthrough came after 192 high-energy lasers converged on a target “about the size of a peppercorn, heating a capsule of deuterium and tritium to over three million degrees Celsius and briefly simulating the conditions of a star and achieving ignition.”
Speaking at the announcement event, the White House science chief, Dr. Arati Prabhakar, said, “They shot a bunch of lasers at a pellet of fuel and more energy was released from that fusion ignition than the energy of the lasers.”
To the inevitable question of when nuclear fusion could be produced at the industrial scale, Kimberly Budil, director of the Livermore Lab, struck a cautious note saying there are “very significant hurdles, not just in the science but in technology. This is one igniting capsule one time.”
She said to realize commercial fusion energy many more things have to be done, including “many many fusion ignition events per minute and a robust system of drivers to enable that.”
“So probably decades,” she said of the timeline, adding, “not six decades, I think, not five decades, which is what we used to say. I think it is moving into the foreground.” She added that it would require concerted effort in investment and a few decades in the underlying research which could put the world in a position to produce fusion energy.
Nuclear fusion was first discovered by the Nobel Prize winning physicist Hans Bethe who in 1938 proved that energy is also liberated when light nuclei combine to form heavier ones. Fusion is a sort of mirror image of nuclear fissions where atoms are split to liberate energy as in the atomic bomb or nuclear power. Incidentally, Bethe was also a key figure in the Manhattan Project that produced the world’s first atomic bomb.
Over the last eight decades there have been many claims of nuclear fusion, but they have all come to nothing significant until the one announced today. It is nobody’s claim that nuclear fusion as an everyday source of energy is now at hand because it will take a great deal of efficient scaling up and technology in order to have nuclear fusion-based power plants.1
The energy gain of 1.10 MJ, while significant as a proof of the principle, is rather minuscule as an indicator of largescale clean energy. Scientists have said the energy gain will have to be much greater for fusion to become a scalable alternative to energy produced by the burning of fossil fuels, which have caused a havoc with Earth’s climate. The distance from the lab to a power plant could be a long one but given the often-exponential growth in technologies, once a breakthrough is achieved, it is not altogether inconceivable that in the next three decades or so fusion could emerge as a global alternative.
One of the main attractions of nuclear fusion, according to the International Atomic Energy Agency, is that “Fusion could generate four times more energy per kilogram of fuel than fission (used in nuclear power plants) and nearly four million times more energy than burning oil or coal.”
One of the biggest challenges to make fusion industrial scale after the NIF breakthrough is the amount of energy required to create extremely high temperatures to make deuterium and tritium fuse. In stars and the sun, their intense gravity does the trick by forcing the nuclei to fuse and that too constantly.
For nuclear fusion power plants to become a viable source of energy they will have to be able to produce constant fusion in order to release energy. According to scientists, a fusion power plant will have to release energy ten times a second.
That energy-gain efficiency will have to be dramatically improved for it become a regular source of energy that rivals electricity produced in the traditional fuel or coal-powered plants.
The way it works in the Sun, with its gravity almost 28 times that of Earth, it ”traps” hydrogen from its atmosphere. That hydrogen in turn fuels the Sun’s fusion reaction via a highly complex process known as nuclear fusion that goes from forming the heavy isotope of known as deuterium followed by helium 3 and helium 4.
All this takes place at the Sun’s core with a temperature of 15 million degree Celsius turning hydrogen into a plasma, the fourth state of matter where a complete separation between negatively charged electrons and positively charged atomic nuclei also known ions occurs. These nuclei move around furiously frequently colliding and releasing enormous energy.
[Photo caption: The target chamber of the Lawrence Livermore National Laboratory’s National Ignition Facility, where 192 laser beams delivered more than 2 million joules of ultraviolet energy to a tiny fuel pellet to create fusion ignition on Dec. 5, 2022. (Photo: LLLN)]
