Fusion Energy Development and Paradigm Changes in Fusion Plasma Research
Fusion Energy Development and Paradigm Changes in Fusion Plasma Research
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  • 승인 2012.02.10 18:43
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In the 23rd century, the world population is expected to be saturated at about ~11 billion. The explosive growth of population even with the current life standard and industrial capacity to support the growth requires a steep increase rate of energy consumption. It is natural that the consumption rate of fossil fuels such as gas, oil, and coal will escalate with an aid of small portion of green energy. A generous prediction of the end of available fossil fuels would be around year ~2500. An immediate response would be “why do we care about the long term problem?”

The problems that we are going to face are not going to be sudden but a steady escalation of many unpleasant events. Well before the fossil fuel runs out, there will be many large scale energy crises and drastic climate change due to the global warming, if the experimentally observed increase of the CO2 concentration is real and continuing. The conflict over the remaining energy source will lead to a war and rich and powerful countries will prevail and losers will suffer. We have already experienced the preview in the Middle East. Also the temperature increase predicted by the global warming will find no return point, if the CO2 level takes the curve above the critical growth rate. This is evident in the recent melt down of the Antarctic ice and global temperature rise.

There are numerous cascading problems and I’ll leave the rest to your imagination. Where do we find the source of energy that is clean and abundant to replace the fossil fuel in a time scale of a century? We have to take advantage of any forms of clean energy that we know, if we do not want to go back to the Stone Age. Under the name of green energy development, we have already explored many forms of possible clean energy source and all of them are contributing to our life in one way or another. Except for a potentially improved “fission power” as an abundant energy source, we do not have a definitive solution yet. Note that the intrinsic process of the fission reaction leaves long term wastes and occasional runaway reaction like the recent Fukushima and Chernobyl incidents. Therefore, the clean fission may be a challenging subject.

The fact, that the human race has no alternative choice for a large capacity clean energy source other than the fusion energy, which is still in the path of hardening, warrants to continue refining the understanding of the high temperature plasma physics. Among the concept of fusion devices, the magnetic fusion, in which the plasmas at a temperature of a few hundred million degrees are confined, has made a significant progress compared to other concepts. The accumulated empirical understanding in magnetic fusion research led us the construction of the International Thermonuclear Experimental Reactor (ITER) at Cadarache, France, which will demonstrate an engineering viability of the fusion energy. The ITER, “the way” in Latin, is supported by the international consortium (EU, Japan, Russia, China, Korea, India, US). Here, EU takes up ~50% of the total construction cost (~$15B) and the rest is shared by other six countries. It will be operational in 2019 and the DT experiment which will produce a fusion power of ~0.5 GW will be performed in 2025.

Note that one unit of the current fission reactor (one dome) produces ~1GW of electricity. A successful demonstration of this goal will be a herald of an era of the fusion power. Each country in the consortium will start Demo fusion reactor program based on exclusive proprietary scientific and engineering knowledge from the ITER program and Korea will be one of them. We are confident that the ITER will achieve the goal but one drawback is the large size of the ITER. It is due to the fact that the basis of ITER performance is empirical scaling laws which are dominated by the size dependence, instead of the first principle based physics.

Lacking physics basis stems from the fact that the physics of high temperature plasmas is not matured yet and still is in an evolving stage (e.g., first effort on the physics of high temperature plasma physics was after the 2nd world war). A decade later, the first practical magnetic fusion research started with the device called “T-3 tokamak” which was invented by the scientists in the former Soviet Union and followed by the advanced countries. The research in the US, EU and Japan experienced an apex when the three large tokamak research programs (Test Fusion Tokamak Reactor (TFTR), Princeton, USA, Joint European Tokamak (JET), Oxford, UK and Japan Tokamak (JT-60), Japan) demonstrate a plasma regime close to the scientific break even (output power is equivalent to the input power).

The achieved success with the pulsed operation in which the magnetic field is on for a short time (tens of seconds) should be translated to the research with the steady state operation (magnetic field is on all the time) using superconducting magnet technology. For the last two decades, the research program toward the steady state device has been idled in advanced nations. While they have focused on the ITER program, new tokamak devices based on the superconducting magnets such as the Korean Superconducting Tokamak Advanced Research (KSTAR) of Korea, Experimental Advanced Superconducting Tokamak (EAST) of China were built and operational. Japan is also planning a new program “JT60-SA” which is also a steady state device.

Asian countries rekindled the research on the steady state fusion plasma operation that once was craved by advanced countries. The research history of the fusion science in Korea and China is relatively short. As they were able to build the complex superconducting tokamak devices, they have to rapidly absorb the fusion plasma physics. It is desirable translating the accumulated experience and knowledge in the West to the new research facilities in East in order to facilitate the steady state research successfully and effectively. The future clean energy development is not for a specific country but for all human kind. The East and West should work together for one goal, the successful fusion energy development. The paradigm change in fusion plasma research from the pulsed operation in West to the steady state operation in East will be a chance to reestablish the fusion plasma physics in steady state operation of fusion devices.

The physics of high temperature plasma in a strong magnetic field is substantially more complex compared to other branches of physics. Full understanding of the high temperature physics in magnetic fusion devices will enable us to design an advanced fusion reactor which can be a compact size so that the cost can be dramatically reduced. The reduction of the size will not necessarily be the size in the SF movie “Back to the Future”, where the car was running off the fusion engine. The goal of an advanced fusion reactor with a half size of the ITER may be ideal and can be achieved with an optimum design based on first principle physics.

It is clear that the conventional tools for the fusion plasma research have reached the limit in understanding of the stability and energy transport physics. It is largely due to the fact that the complex high temperature physics in magnetic field is dominated by the asymmetries and non-linear phenomena and conventional tools have failed providing the information needed for the completion of theoretical models that are essential for the advanced compact reactor design. In last two decades, the advanced computational capability allowed us the-state-of-the-art 3-D simulations for Magnetohydrodynamic (MHD) and turbulence physics.

However, it is important to validate the steps of the simulation process in depth through the reliable comprehensive diagnostic tools. Here we need another paradigm change in research method. One example would be an exploitation of powerful new 2-D/3-D imaging diagnostic tools that can potentially validate and verify the high temperature plasma physics developed so far. The new generation superconducting fusion devices equipped with the advanced imaging tools will certainly steer the theoretical models to develop the reliable first principle based physics which will not only contribute to the ITER physics program but also create a path to a viable compact fusion reactor in the future.






Hyeon K. Park
Professor of Physics