[Reading Science] Humanity Finally Ignites Fire in the Atom

USA Achieves First-Ever 'Ignition' Using Laser Nuclear Fusion
Scientific Principle of Nuclear Fusion Energy Demonstrated for the First Time
Research on Pollution-Free, Clean, Infinite Energy Source 'Artificial Sun' Expected to Accelerate
Challenges for Commercialization Including Laser Scale-Up Remain, Minimum 20-30 Years Required
South Korea Leads Research on Another Method 'Magnetic Confinement' Nuclear Fusion

[Asia Economy Reporter Kim Bong-su] The United States has recently opened a new horizon in nuclear fusion research, regarded as the next-generation infinite and clean energy source. It has succeeded in the first step of energy generation, called 'ignition,' using laser nuclear fusion. Let’s examine what this means, its limitations and challenges, and how it differs from South Korea’s nuclear fusion research.

Lighting a ‘fire’ in atoms

Nuclear fusion is the exact opposite of nuclear power generation, which uses nuclear fission. It forcibly fuses light atoms such as hydrogen and harnesses the energy released in the process. Since it operates on the same principle as the fusion occurring in stars like the sun, it is nicknamed the ‘artificial sun.’ The principle is as follows: by applying ultra-high temperature and ultra-high pressure as in the sun, deuterium and tritium fuse to form helium and neutrons. Helium plays the role of heating surrounding atoms to sustain a chain nuclear fusion reaction (α-particle or alpha particle). Adding lithium allows it to combine with neutrons to produce tritium. Although neutrons are emitted, unlike nuclear fission, no radiation is released, so there is no concern about contamination. Deuterium is contained at 0.15% in seawater, allowing for infinite supply, and lithium is so common that the amount used in a typical cellphone battery can produce enough electricity for a household for 80 years. Although tritium is scarce, costing about 30 million won per gram and having a half-life of only 12 years, it can be infinitely recycled during the power generation process. This nuclear fusion energy idea originated in the 1950s among researchers involved in the development of the hydrogen bomb in the United States. The idea was that if nuclear fusion could be controlled, managed, and utilized, it could solve humanity’s energy problems.

However, despite decades of research, nuclear fusion had not even succeeded in proving the basic scientific principle. To be used as an energy source, nuclear fusion must be initiated and maintained for a long time, and at the same time, economic feasibility and efficiency must be demonstrated?that is, more energy must be obtained than the resources invested?but no such demonstration had been achieved even in laboratories.

On the 5th, the U.S. Lawrence Livermore National Laboratory (LLNL) finally succeeded in nuclear fusion ignition, marking humanity’s first step toward bringing the ‘sun’ into a reactor on Earth. The research team conducted an experiment by inserting deuterium and tritium into a 1mm plastic bead and firing 192 lasers to induce nuclear fusion inside the bead, successfully producing more output energy than input. LLNL explained, "We delivered 2.05 megajoules (MJ; 1MJ = 1 million joules; 1J = 1 newton meter) of energy to the target and extracted 3.15 MJ of energy, surpassing the critical threshold of nuclear fusion," adding, "This demonstrated for the first time the fundamental scientific principle of inertial fusion energy (laser nuclear fusion)."

Scientists emphasize the significance of experimentally proving the principle of nuclear fusion energy, which had been theoretical until now. It is the first time in history that ignition, the chain reaction of nuclear fusion, has been successfully initiated in a laboratory setting, demonstrating the scientific principle that artificial nuclear fusion can be sustained for a long time and the heat generated can be used to produce electricity. Moreover, this is the first time in human history that any energy source has exceeded the break-even point (Q>1), producing more energy than was input. Typical power generation yields only about 30% energy output relative to input, and even ordinary light bulbs have an energy efficiency of only 20%.

Dr. Lim Chang-hwan of the Korea Atomic Energy Research Institute explained, "Over the past decade, LLNL has improved the target size to about 1mm rather than focusing on the laser itself, resulting in good outcomes. Although the principle is similar to that of a hydrogen bomb, the fusion region is only about 100 micrometers due to the very small target size, making it safely manageable."

Laser Nuclear Fusion vs Magnetic Confinement Nuclear Fusion

There are two main approaches to nuclear fusion research aimed at creating such an ‘artificial sun’ on Earth. In stars like the sun, the ultra-high temperature, ultra-high pressure environment and energy expansion are confined by gravity, called ‘gravitational confinement.’ However, on Earth, special devices are required to initiate and safely manage nuclear fusion.

Currently, scientists study two nuclear fusion methods: ‘Magnetic Confinement Fusion (MCF),’ which uses magnetic fields, and ‘Inertial Confinement Fusion (ICF),’ which uses the principle of hydrogen bombs. LLNL’s laser nuclear fusion research follows the ICF method. Simply put, the concept is to create a small ‘hydrogen bomb’ inside a reactor that continuously explodes, producing thermal energy to generate electricity.

The principle is as follows: a hydrogen bomb uses an atomic bomb to create an ultra-high temperature and pressure state that fuses hydrogen atoms. Instead of an atomic bomb, the LLNL team uses high-power lasers as a kind of detonator. They created a very small 1mm gold bead with an extremely smooth surface to minimize laser reflection, filled it with frozen deuterium and tritium, and injected deuterium and tritium gas at its core. Then, 192 high-power lasers delivering 2.05 MJ were fired uniformly from 360 degrees within about 4 nanoseconds. The laser energy instantly vaporizes the gold surface of the bead, releasing it outward. By inertia (action-reaction law), ultra-high pressure is applied inward to the deuterium and tritium inside the bead, causing nuclear fusion and forming neutrons and helium. The helium trapped under high pressure acts as alpha particles, triggering a chain nuclear fusion reaction.

This laser nuclear fusion method was intensively researched under the U.S. National Nuclear Security Administration’s (NNSA) Stockpile Stewardship program in the 1990s, which aimed to store, manage, and verify the performance of existing hydrogen bombs. Dr. Jung Hyun-kyung of the Korea Institute of Fusion Energy explained, "The laser shockwave generates high pressure, reducing the volume of the small beads under 1mm by more than a thousandfold, creating a hotspot with a temperature exceeding 100 million degrees Celsius due to alpha particles. The surrounding frozen deuterium and tritium are heated by high pressure, triggering a chain reaction."

However, many challenges remain for laser nuclear fusion. First, some scientists argue that the experiment only caused about 2% of the deuterium and tritium atoms injected into the bead to undergo thermonuclear reactions, making it difficult to consider it a full ‘ignition.’ Also, the National Ignition Facility (NIF) where the experiment was conducted cost about 5 trillion won to build and requires an annual operating budget of 500 billion won, yet it is only for experimental purposes. The facility uses an enormous laser system the size of three football fields. The energy efficiency is extremely low: 300 MJ of electricity is input to produce 2 MJ of laser energy, which then yields only about 1 MJ of additional energy.

NIF’s high-power lasers can only be fired 10 times per week, far less than the 10 times per second needed to sustain a practical nuclear fusion chain reaction. To discuss energy generation, power and equipment capable of firing ultra-high power lasers at any time must be developed. The cost and technical difficulty of manufacturing the targets, i.e., the gold beads, are also problematic. LLNL reportedly spent about 500 billion won on target production alone. Moreover, uniformly irradiating the bead with high-power lasers from 360 degrees is a very challenging technology, and the bead’s surface must be extremely smooth to prevent laser reflection. Dr. Jung noted, "While NIF’s recent success confirms the scientific principle, the U.S. Department of Energy’s (DOE) cautious statement about the potential for nuclear fusion energy use suggests many limitations remain."

In South Korea, the Korea Atomic Energy Research Institute (KERI) acquired a high-power laser facility from Osaka University in Japan in 2008, establishing a foundation for laser nuclear fusion research. Nearly 7 billion won was invested including renovations. However, aside from a few international collaborative projects with Japan and China until 2013, there have been no domestic research achievements, and the project has effectively been dormant. Professor Bang Woo-seok of Gwangju Institute of Science and Technology (GIST) said, "The recent U.S. success proves that there can be various methods of nuclear fusion. Besides the tokamak method, Korea should continue laser nuclear fusion research."

China is showcasing artificial sun and nuclear fusion technology at the China Pavilion of Astana Expo.

Another nuclear fusion method is MCF. Although there are several types, the tokamak method, which uses a vacuum-sealed container capable of withstanding high temperature and pressure and applies a very strong magnetic field to control and maintain fusion plasma for a long time, is the most actively researched. South Korea’s Korean Superconducting Tokamak Advanced Research (K-STAR) is considered one of the world’s most advanced. K-STAR studies methods to trigger and sustain nuclear fusion by heating deuterium to plasma state exceeding 100 million degrees Celsius using electromagnetic waves. Its most notable feature is the use of superconducting magnets to form a strong magnetic field to confine plasma. Last year, it succeeded in maintaining ion temperatures above 100 million degrees for 30 seconds, setting a world record and leading MCF research. Based on these achievements, South Korea has been actively participating in the international thermonuclear experimental reactor (ITER) project, jointly pursued by seven countries since 2003. The MCF method is fundamentally similar to how a microwave oven heats food with microwaves.

By firing a powerful electromagnetic beam to heat deuterium to ion temperatures exceeding 100 million degrees, helium (alpha particles) begins to be produced. It is expected that maintaining this continuously for at least 400 seconds will achieve chain nuclear fusion reactions, i.e., ignition. However, K-STAR currently has too low a plasma density for alpha particles to sustain chain heating reactions. Researchers expect that ignition will be possible once ITER, which is much larger than K-STAR, is completed and can confine alpha particles to increase density. The problem is that despite over 60 years of research since the 1950s, ignition has not yet been achieved.

Dr. Jung said, "By the 2030s, whether laser nuclear fusion or tokamak methods, the burning stage of nuclear fusion will be achieved, and full-scale energy generation research will begin. Once ITER is completed and a fusion reactor capable of shielding neutrons and recycling is built, research to maintain heating for over 400 seconds will start."