Can Science Really Sing a ‘Song of Ice and Fire’: Weekly Donga

[GETTYIMAGES]

Sun is 4.6 billion years old. It seems quite a lot, but in terms of stars, it is a time to be passionate about working. But the sun can’t last forever. It will probably be corrected until about 6.3 billion years old, but after that, it will gradually become brighter and bigger and gradually cool down at the end. Of course, in the process of growing, there is a possibility that it threatens the earth. What will happen to us when the sun disappears? You’ll probably shiver on the chilly planet’s surface and lose everything and collapse.

When the word artificial sun or research results are often encountered in the media, some may think that it may be created to replace the sun that will disappear someday. Artificial organs replace human organs, and artificial respiration helps us to breathe naturally, which we cannot do on our own. However, the artificial sun is not created to replace the brightly shining sun from 150 million km away. Of course, the method itself is not easy, but the purpose itself is to obtain energy from the sun on the earth rather than to replace the sun.

First of all, in order to properly understand what an artificial sun that obtains energy from a nuclear reaction is, it is necessary to clearly understand nuclear fission and nuclear fusion, which are representative nuclear reactions. Nuclear fission is the principle of nuclear power as we know it. When a neutron collides with a heavy atomic nucleus such as uranium or plutonium, it splits into two light atomic nuclei, which releases energy. Conversely, nuclear fusion

A reaction in which two atomic nuclei fuse to form a larger and heavier atomic nucleus. Since the same principle of reaction is occurring in the sun, the resulting product is called an artificial sun. Curiously, in both fission and fusion, the mass of the resulting mass is always smaller than before, and this reduced mass is converted into energy according to Einstein’s famous formula (E=mc2). Since the speed of light is so fast, even a very small mass appears as an equivalent exchange of enormous energy.

Nuclear power generation through nuclear fission is a really good source of energy. More than 30% of the electrical energy we use depends on nuclear power, and it emits almost no greenhouse gas, so it has little impact on global warming. However, when neutrons collide with uranium to obtain energy during nuclear fission, the resulting fission products continue to decay in an unstable state and emit radiation. Of course, radiation emissions from well-managed facilities are predictable, so there is no big problem. However, large-scale accidents resulting from natural disasters, such as the Fukushima nuclear power plant accident in Japan, cause enormous damage to mankind. If possible, we have no choice but to constantly think about how to find an energy source that generates enough electricity without emitting radiation.

Fortunately, the movie has already been treated like reality. It’s Iron Man from Marvel’s superheroes. Near his chest is an arc reactor that generates near-infinite energy, and the technology used here is nuclear fusion and artificial sun. Scientists are trying to create an artificial sun on Earth, which, if successful, could yield huge amounts of energy without problems with radiation. Of course, even if it is not a simple task, it will be fully understood without needing to explain it.

Realistic worries to realize the impossible imagination

An artificial sun can be created through a nuclear fusion reaction in which two atomic nuclei fuse to form a larger and heavier atomic nucleus. [GETTYIMAGES]

There is a fantasy drama called ‘Game of Thrones’, which received great acclaim from the beginning, but ended with a dragon-headed sword, and is still aroused by viewers. The characters’ great acting skills and realistic visuals embroidered the screen splendidly, but the key element of the box office’s success was the detailed and meticulous storyline. The reason that it was possible to create a complex narrative structure was because the original novel was supported. The original fantasy novel, first published in 1996, was titled ‘A Song of Ice and Fire’. And here surprisingly, there are realistic ideas that could make the nuclear fusion of our dreams come true.

The idea of ​​making helium by combining hydrogen, which is familiar to us, instead of uranium, a radioactive isotope, has been around for quite some time. Fortunately, the deuterium atom required for this is in the sea for a lifetime, and nuclear fusion energy made from 1 ton of seawater is as efficient as energy produced from coal or 270 tons of oil. The problem is to create a sun-like environment on Earth where the fusion reaction takes place. At least two conditions are required to fuse atomic nuclei that they hate each other so much. When a solid is heated to a very high temperature, it passes through a liquid and a gas to a state called plasma, which can be regarded as the most violent moment. Nuclear fusion occurs only when the nuclei are moved so vigorously that they can collide, or they are confined in a very narrow room and applied high pressure to crush each other. The mass of the sun is so high that its core can fuse when its core temperature reaches only 15 million degrees Celsius. On a low-mass Earth, the pressure is much weaker, so a much higher temperature is required.

Another important issue is where to put it. It can be used technically only if the surrounding environment can withstand it while maintaining the hot temperature at which nuclear fusion can occur. Korean researchers are trying to do this through ‘KSTAR’, a Korean-type nuclear fusion research that was independently developed in 2007. Here, the world’s hottest material is placed in the coldest bowl and coexists at a very close distance. 100 million degrees of ultra-high temperature plasma is generated inside the KSTAR device, and the superconducting magnet that creates a strong magnetic field to confine the plasma is in a state of -269 degrees below zero. A true song of ice and fire will flow.

To understand this in more detail, consider the donut-shaped tokamak device. Inside, the vacuum exhaust device completely removes air to create an extremely high vacuum similar to the universe, and a superconducting coil on the outside of the device creates a very strong magnetic field inside the tokamak. Then, put gas inside it to create a plasma state, and then start a nuclear fusion reaction. When heated to 100 million degrees through a complex external heating device, the particles that form plasma inside undergo a fusion reaction with each other, so fusion reactions can be properly tested. The Korean research team also heated the plasma temperature to 100 million degrees after testing numerous heating devices, and succeeded in maintaining it for a whopping 30 seconds. Now this year, I’m working hard to keep it up to 50 seconds and drive.

Can we really get electricity from the artificial sun?

‘KSTAR’ is a nuclear fusion research that Korea has successfully developed independently. [사진 제공 · 한국핵융합에너지연구원]

To sing a song of ice and fire, scientists continued to develop very challenging devices. Two heating devices were built to raise the plasma temperature to 100 million degrees. One of them is a plasma heating device that works on a principle similar to a microwave oven commonly used in everyday life. The principle is to select electrons carefully and heat them by firing a microwave, a type of electromagnetic wave, into the plasma inside the fusion device. The other is a neutral particle beam heating device that heats up the particles at a high speed and neutralizes them by colliding the high-speed energy with the plasma inside the fusion device.

When making a cold superconducting magnet, liquid helium, which is mainly used for cooling, is used. The helium distribution device precisely delivers liquid helium within the superconducting magnet and maintains a very low temperature. In addition, similar diagnostic devices exist in KSTAR, just as a doctor diagnoses with an X-ray image or a stethoscope sound when you go to a hospital and get sick. From the outside, it is impossible to know whether the equipment is running or what the situation is, so you can take a 2D image of the plasma to see what is happening inside. Even KSTAR is the result of the independent research results of Korean companies in many areas, so Korea’s technological prowess is internationally recognized.

Because of the possibility of solving the Earth’s energy problem in the future and the difficulty of approaching it, seven countries, including Korea, are gathering in France to build a superconducting tokamak research device similar in shape and shape to KSTAR. A tokamak with 27 times the volume and 3 times the width, length, and height of the KSTAR device is scheduled to be completed in 2025. It has an important connection with the KSTAR device and is almost similar in shape, so it is likely that the achievements of Korean researchers will be immediately available when it starts operating in earnest. If the International Fusion Test Reactor (ITER) successfully verifies that substantial nuclear power generation is possible and that it can be operated efficiently and stably, the next step is to build a fusion power plant to generate electricity that can be used in real life. It is not yet possible to generate electricity from the heat generated by plasma through nuclear fusion. To solve this problem, a demonstration fusion power plant (DEMOnstration Power Plant (DEMO)) is also being prepared for the first time to check how much heat energy is emitted beyond that input to the plasma.

The time may come when we now create parts of the sun on Earth that we could not even look directly at in the past. If we can get electricity from the artificial sun by implementing our technologies comprehensively, we can solve the most important energy problem for mankind at once. Of course, like the situation in which cryogenic and ultra-high temperatures coexist, we have to solve numerous problems with ideas that we can never come up with. There is no reason to be afraid. We are already the most special beings in the universe, creating and singing songs of ice and fire that did not exist in the world and possessing endless possibilities of imagination.

_{The track is…
After graduating from the Department of Astronomy and Space at Yonsei University, he worked at the Korea Astronomy and Space Science Institute’s Space Monitoring Center and Yonsei University’s Space Flight Control Lab. Under the stage name of ‘Orbit’, he is running the podcast ‘Exaggerated Chang’, YouTube ‘Science’ and ‘Two Much Science’, and his book is ‘Science Bluff of Orbit’.}

Weekly Donga No. 1341 (p52~54)