Burbank.Fall.2009.Energywiki

= Nuclear Fusion: Powering the 21st Century? =

Introduction
As a generation, we are faced with a novel crisis. Nowhere or when in history have people been faced with such complex problems on a global scale. We are preparing to inherit a world beset by climate change, dwindling biodiversity, energy, and water availability, poverty, pollution, and overpopulation – one in which the necessity of finding new, renewable sources of power for an ever more energy demanding society can no longer be ignored.

Today, a number of potential solutions exist, from wind-harnessing turbines to sun-powered solar arrays. On the fringes of prospective clean-energy technologies is nuclear fusion, hailed by its promoters as the ultimate clean energy source and dismissed by skeptics as pie-in-the-sky science fiction.

Fortunately, science seems to have way of catching up with science fiction.

In the coming decades, nuclear fusion may become for the 21st century what airplanes and rockets where for the 20th; impossibilities rendered reality through human ingenuity.

// The Problem //
By 2050, the global population is expected to exceed 8 billion people. According to the World Resources Institute, the energy demand by 2030 alone will have grown 80% from 2006 levels. As the Earth’s population grows and urbanizes in developing countries, global energy requirements will significantly increase. Currently, our fossil fuel-driven civilization is a problem with regards to both its detrimental impact on the environment and the limited supply of  

fuel we have left on Earth. As the energy demand increases, the consequences of continued fossil fuel use will become increasingly acute. Alternative energy technologies are critically necessary if further damage to the Earth’s ecosystems and the crisis awaiting us when our fuel reserves run dry are to be averted.

// What is the Driving Force of the Problem?     //
Our civilization is built around fossil fuels. While the clear cut solution to today’s environmental issues and the imminent fuel shortage points to abandoning hydrocarbon-based fuel for renewable alternatives, this grossly oversimplifies the problem. The functioning of modern society, from an individual to a multinational level, is heavily dependent on fossil fuels. In addition to our economic dependence on them, fossil fuels are also cheap; their prices do not reflect the true environmental cost of their use. This makes it difficult for emerging clean energies to compete.

// What is Currently Being Done to Solve the Problem? //
In a broad context, the push to “go green” at every level of society – from families to industries – is an attempt to resolve the climate and energy issue. Attention given to clean energies such as solar, wind, and geothermal show a widespread awareness of and commitment to solve the problem. More specifically focused on the topic of this page, a number of facilities across the globe have committed themselves to making feasible a self-sustaining nuclear fusion reactor for the purpose of producing commercially available energy. Today, nations including the US, UK, France, Korea, and Japan host experimental fusion reactors on their soil. The pursuit of nuclear fusion offers to make clean, renewable, and safe energy a potential reality.

// How They Work //
Fusion itself is possible. We know this because it occurs every day in the core of our Sun and in every other star in the universe. Fusion has also been achieved here on Earth; the explosion of a hydrogen bomb is an uncontrolled fusion reaction initiated by a fission reaction.

First, let’s address the fundamental differences between these two nuclear reactions:

Ø Fission, the process that occurs in modern nuclear power plants, is essentially the splitting on an atom. In brief, a high-energy neutron is used to break a heavy atom – such as U-235, an isotope of uranium – into smaller atoms, neutrons, and energy. The neutrons produced by the fission of one atom can then in turn split the nucleus of another, producing a chain reaction and a tremendous amount of heat energy, which is used in power plants to generate steam and, through conventional processes, electrical energy.

Ø Fusion, by definition, is essentially the opposite of fission: it is the combination of light atoms to produce a heavier one, in the process also generating high-energy neutrons and energy. In stars like our Sun, approximately 600 billion kilograms of hydrogen nuclei fuse to form helium nuclei every second, as a by-product releasing the energy that warms and illuminates our planet.



The nuclear engines of stars might seem like a far cry from anything we could hope to achieve here on Earth; only with incredibly hot temperatures – such as those generated by the crushing gravitational forces in the Sun’s interior – can the electrostatic repulsion between the positively charged protons in atomic nuclei be overcome, allowing the strong, attractive nuclear force to fuse the two nuclei. While strong, the nuclear force can only act over extremely small distances, approximately 1.0E-15 meters. To force atoms into such close proximity requires high temperature and pressure.

Before I go on, let’s explore the basic reaction that occurs in experimental fusion reactors.

Ø The most commonly used reaction is between deuterium and tritium – isotopes of hydrogen. A deuterium (H-2) nucleus contains one proton and one neutron. Tritium (H-3) nuclei are composed of one proton and two neutrons. In a fusion reaction, an H-2 and H-3 nuclei fuse, forming a Helium-4 nucleus (two neutrons and two protons) and releasing a high-energy neutron.

Ø The energy released in a fusion reaction is approximately 3.4E14 J per kg of fuel. By comparison, it would require 10 million kg of coal to produce an equivalent amount of energy.

Ø Fusion can occur between many other fuels, however, the only other potential besides deuterium-tritium fusion being investigated is deuterium-deuterium fusion, which produces Helium-3 and a neutron. Although D-D fusion has a higher energy output than D-T fusion, it requires a higher temperature to reach ignition, as its use is therefore not foreseeable in the near future due to technological constraints.

As noted above, these reactions only occur when atomic nuclei are able to come close enough to one another for the strong nuclear force to take effect. To do this, the reactants must be under enormous temperature and pressure. On Earth, scientists use two methods to achieve the conditions necessary for fusion to occur: magnetic confinement and inertial confinement.

Magnetic Confinement: Tokamaks
<span style="font-family: 'Times New Roman','serif'; font-size: 110%;">The most developed technology for magnetic confinement fusion is the tokamak. The tokamak was developed in Soviet Russia in the 1960s and working tokamaks are currently being used experimentally in dozens of countries. Today, tokamaks look most promising for making commercial fusion power viable. A tokamak is a hollow torus (donut-shape) under vacuum. Inside, plasma is heated via electrically-induced current in the plasma, neutral-beam injection, magnetic compression and radiofrequency heating to over 150 million degrees. In order to maintain temperatures this high, the plasma in the tokamak must not be allowed to contact the chamber’s walls, which would cool it and interrupt the fusion reaction. To prevent this, tokamak fusion chambers are encircled by several sets of magnetic coils, which control the flow of plasma (because plasma is composed of charged particles – ions and electrons – it can be magnetically manipulated). Once heated to the point of ignition, the kinetic energy of the neutrons produced would be transferred to a lithium blanket and absorbed by coolant cycling through the blanket. Steam from the energized coolant would then turn a turbine to generate electrical energy.



The largest hurdle currently facing tokamak technology is the ability to sustain a prolonged fusion reaction. So far, tokamak fusion has been limited to brief reactions due to plasma turbulence. Due to temperature gradients in the plasma, turbulence develops and heat is lost. Fusion terminates when the plasma losses enough heat. New tokamaks, such as ITER in the UK, which will become the world’s largest tokamak reactor upon its completion in 2018, will incorporate supercomputers and novel methods to predict and prevent turbulence. ITER is expected to be the first fusion reactor to produce a power surplus, delivering an energy output of 500 MW per every 50 MW of input. ITER itself is intended to be an experimental reactor only. More advanced prototypes for commercial power, such ITER’s successor, DEMO, will not be constructed until the 30s, setting the earliest date for tokamak-generated fusion power a few decades away.

Inertial Confinement
<span style="font-family: 'Times New Roman','serif'; font-size: 110%;">Another approach to fusion began to be explored in the 1970s. Inertial confinement fusion (ICF) uses powerful lasers or particle beams to heat a capsule containing a 50/50 mix of deuterium and tritium fuel. This heating, combined with the resulting compression of the fuel pellet, allows the fuel to reach ignition temperatures. While ICF is being tested in the National Ignition Facility, the method is newer and far behind magnetic confinement in technological terms; stronger lasers with better focusing capabilities are needed it ICF is the progress. While it may become useful in future power generation, it is likely to make its debut decades after commercial tokamaks.

// Carbon Dioxide Produced by Fusion //
<span style="font-family: 'Times New Roman','serif';">One nuclear fusion’s many potential benefits as a power source is that it is entirely clean:

H-2 + H-3 <span style="font-family: Wingdings; font-size: 10pt; line-height: 115%; mso-ascii-font-family: 'Times New Roman'; mso-bidi-font-family: 'Times New Roman'; mso-char-type: symbol; mso-hansi-font-family: 'Times New Roman'; mso-symbol-font-family: Wingdings; msoasciifontfamily: 'Times New Roman'; msobidifontfamily: 'Times New Roman'; msochartype: symbol; msohansifontfamily: 'Times New Roman'; msosymbolfontfamily: Wingdings;">à <span style="font-family: 'Times New Roman','serif'; font-size: 10pt; line-height: 115%;"> <span style="font-family: 'Times New Roman','serif';">2 He-4 + n

No carbon dioxide is formed in fusion reactions. The only gas produced, helium, is inert and nonreactive.

// Nuclear Fusion’s Best Aspects //
<span style="font-family: 'Times New Roman','serif';">If/when fusion power becomes reality, it will be the perfect energy source.

<span style="font-family: 'Times New Roman','serif'; mso-fareast-font-family: 'Times New Roman'; msofareastfontfamily: 'Times New Roman'; msolist: Ignore;">1. <span style="font-family: 'Times New Roman','serif';">Nuclear fusion produces no greenhouse gas pollution <span style="font-family: 'Times New Roman','serif'; mso-fareast-font-family: 'Times New Roman'; msofareastfontfamily: 'Times New Roman'; msolist: Ignore;">2. <span style="font-family: 'Times New Roman','serif';">Fuel is abundant; deuterium and tritium are common in water and minerals respectively. 10 gallons of water has enough deuterium to produce an equivalent amount of energy as a supertanker of fossil fuels. Fuel would be essentially inexhaustible. <span style="font-family: 'Times New Roman','serif'; mso-fareast-font-family: 'Times New Roman'; msofareastfontfamily: 'Times New Roman'; msolist: Ignore;">3. <span style="font-family: 'Times New Roman','serif';">Fusion is efficient; as stated above, to generate the same amount of energy as a single kilogram of H-2 and H-3 fuel, it would take 100 million kilograms of oil. <span style="font-family: 'Times New Roman','serif'; mso-fareast-font-family: 'Times New Roman'; msofareastfontfamily: 'Times New Roman'; msolist: Ignore;">4. <span style="font-family: 'Times New Roman','serif';">Fusion is safe; unlike fission, which presents the danger of uncontrollable meltdowns like Chernobyl, an unstable fusion reaction is no hazard – the reactor could simply be shut down. <span style="font-family: 'Times New Roman','serif'; mso-fareast-font-family: 'Times New Roman'; msofareastfontfamily: 'Times New Roman'; msolist: Ignore;">5. <span style="font-family: 'Times New Roman','serif';">Fusion, unlike fission, creates no long-term radioactive waste. As the reaction has no radioactive products, only the material of the reaction chamber would become radioactive, and rather than remaining radioactive for generations, the material, due to a short half-life, would be non-hazardous within a century. Non fusion by-product could be used in nuclear weaponry. <span style="font-family: 'Times New Roman','serif'; mso-fareast-font-family: 'Times New Roman'; msofareastfontfamily: 'Times New Roman'; msolist: Ignore;">6. <span style="font-family: 'Times New Roman','serif';">Once self-sustaining fusion is achieved, it will become a consistent, reliable power source. This gives it an advantage over other green energies such as wind, solar, and tidal power, the power output of which is dependent on environmental conditions. <span style="font-family: 'Times New Roman','serif'; mso-fareast-font-family: 'Times New Roman'; msofareastfontfamily: 'Times New Roman'; msolist: Ignore;">7. <span style="font-family: 'Times New Roman','serif';">Finally, the expected cost of fusion energy is similar to that of fossil fuels, making it a competitive, in addition to environmentally friendly, renewable, reliable, and safe.

// How the Critics See It //
<span style="font-family: 'Times New Roman','serif'; font-size: 110%;">Nuclear fusion has its skeptics – not because it is impossible – but because it might be impossible to harness in the near future. Despite nearly a half century of research, nuclear fusion is still predicted to be decades away; the joke seems to be that for the last forty years fusion power has been forty years away. While this is due in part to a lack of technological sophistication, it is also due to a lack of funding. Annual research expenditures are tiny: a fraction of a percent of the global total in energy. While fusion energy offers all of the benefits of fission (and then some), without the drawbacks, critics doubt that it will arrive in time to become a solution to the climate and energy crisis. However, researchers committed to its success believe that – given sufficient funding – nuclear fusion reactors could soon become reality. As Edward Moses, scientist at the NIF of Lawrence Livermore National Lab commented in Newsweek’s article on the research, “ People live in a state of arrested development. They get stuck in one place. They say this can't be done because we couldn't do it in the 1960s. It's like saying we can't have cell phones because we couldn't do cell phones in the 1960s.”

// Why Nuclear Fusion Does Not Currently Contribute to Global Energy Supply //
<span style="font-family: 'Times New Roman','serif';">Fusion is under development as a technology. Before it can begin to generate energy on a large scale, several obstacles must be cleared:

<span style="font-family: Wingdings; mso-bidi-font-family: Wingdings; mso-fareast-font-family: Wingdings; msobidifontfamily: Wingdings; msofareastfontfamily: Wingdings; msolist: Ignore;">Ø <span style="font-family: 'Times New Roman','serif';">Fusion reactions must be made self-sustaining. Presently, fusion lasts no more than seconds after ignition.

<span style="font-family: Wingdings; mso-bidi-font-family: Wingdings; mso-fareast-font-family: Wingdings; msobidifontfamily: Wingdings; msofareastfontfamily: Wingdings; msolist: Ignore;">Ø <span style="font-family: 'Times New Roman','serif';">In order to achieve prolonged fusion reactions, tokamaks will need the ability to create a stable plasma. Methods to do so will be tested in coming years.

<span style="font-family: Wingdings; mso-bidi-font-family: Wingdings; mso-fareast-font-family: Wingdings; msobidifontfamily: Wingdings; msofareastfontfamily: Wingdings; msolist: Ignore;">Ø <span style="font-family: 'Times New Roman','serif';">ICF technology requires the development of more powerful and accurate lasers.

<span style="font-family: Wingdings; mso-bidi-font-family: Wingdings; mso-fareast-font-family: Wingdings; msobidifontfamily: Wingdings; msofareastfontfamily: Wingdings; msolist: Ignore;">Ø <span style="font-family: 'Times New Roman','serif';">Fusion needs to become economically viable: currently, due to short reaction times, nuclear fusion in experimental reactors has not been able to produce a net output of energy.

<span style="font-family: Wingdings; mso-bidi-font-family: Wingdings; mso-fareast-font-family: Wingdings; msobidifontfamily: Wingdings; msofareastfontfamily: Wingdings; msolist: Ignore;">Ø <span style="font-family: 'Times New Roman','serif';">As with many scientific endeavors, capital is a factor. As discussed above, one of the most critical barriers to rapid progress in fusion technology is a lack of funding. Without adequate funds, necessary advances in technology cannot be made.

// What Nuclear Fusion Needs To Become Large-Scale //
<span style="font-family: 'Times New Roman','serif'; font-size: 110%;">First and foremost, fusion needs a successful self-sustained reaction in a test reactor. If this can be achieved, it is hard to believe that fusion would not be embraced with open arms, revolutionizing the energy sector. Brief reactions are achieved consistently in laboratories. A prolonged reaction, one capable of generating an amount of energy exceeding the energy used to heat the plasma, is the holy grail of fusion technology. Reactors must be incredibly complex; they push the limits of technology. As science progresses our understanding of plasmas and how they behave and we prefect the technology used to control them, we come closer to being able to sustain and harness fusion’s immense energy.

// Nuclear Fusion’s Role in Solving the 21st Century’s Problems //
<span style="font-family: 'Times New Roman','serif'; font-size: 110%;">Nuclear fusion is still in its developmental stage an currently plays no role in energy production. If a breakthrough was to occur, allowing commercial fusion power plants to join the global energy grid, nuclear fusion would revolutionize the world. Nuclear fusion is the ultimate clean, reliable, and safe energy. Nuclear fusion could help halt atmospheric buildup of carbon dioxide, as fusion reactions produce no greenhouse gases. Fusion, being a far more efficient producer of energy than any other chemical or nuclear method, could easily meet the rapidly increasing demand for energy. Essentially, if nuclear fusion power can be realized, it would render all other energies obsolete. But with urgent action needed on the energy and climate fronts, fusion may not arrive in time to make much of a positive impact. However, interest in fusion from the commercial sector could accelerate progress. In a recent energy summit, Wal van Lierop, CEO of Chrysalix Energy Venture Capital stated, “Within five years, large companies will start to think about building fusion reactors.” It might be that the planet’s current crisis, which has put green energy on the agenda, is exactly what fusion needs to get off the ground.

// Conclusions //
<span style="font-family: 'Times New Roman','serif'; font-size: 110%;">In the course of creating this page, I took the opportunity to explore a concept that I knew little about. As I became more familiar with fusion during my research I came to believe that nuclear fusion could be the solution to many of the impossibly complex and urgent problems we are faced with today. News reports featuring the globe-spanning scale of the climate and energy crisis and condemning the lack of a clear, organized agreement to combat it are evidence of attitudes prevalent today. As common as alarmist articles and fatalistic reports have become, you rarely come across much optimism. Faith in human endeavor and invention seem to have fallen from style. In researching fusion - an elusive, science fiction technology, I felt inspired – reminded of a not-long removed era when a rickety homemade airplane took to the air, defying authorities who wrote human flight off as undoable, and when rockets and human feet went to impossible places.

I generally adhere to the idea that there is no single cure to this crisis. I think that change has to come from many places – from many new energies, from reduced input, reduced output, less waste, more conservation, from the individual to the national, from the mom-and-pop business to the multinational corporation. As firmly as I believe that it there is no silver bullet, I think that fusion, if we can make it a reality in the coming decades, is a critical piece to the puzzle. If I could change one thing about fusion, it would be how we think about it. It cannot and should not be dismissed as pie-in-the-sky fantasy. If we do that, we sell ourselves short. If I could do one thing, I would invite the world to take a look backwards at the long and grand history of human scientific achievement before considering what we can and cannot do. This century and our generation are faced with a crisis. With a little ingenuity, we can rise to the challenge.

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