Fun in Fusion Research

By John Sheffield

This book discusses the fun side of the quest to develop fusion energy—a modern equivalent of the hunt for the Holy Grail. After more than 70 years of research, despite great progress, the goal has not been realized. Do you have to be crazy to love quests like this? Not really, but you do have to have an unshakeable optimism. Through humorous anecdotes, and accessible yet detailed scientific discussion, this book illuminates the enjoyment of scientific research through an account of fifty years working on fusion energy development. The anecdotes bring out the human side of research, in which innovative and sometimes egocentric scientists create both clever and nutty experiments. Among the many stories within are witchcraft at Harwell, shocking experiences, entertaining talks, and the wit of top scientists such as Marshall Rosenbluth. Above all the book highlights the significant advances made in developing practical fusion energy and the promise for an exciting future with the National Ignition Facility and International Thermonuclear Experimental Reactor. This book will be of interest to physicists as well as other students and researchers in the scientific and wider communities.

• Shows the exciting and fun aspects of science research
• Author has spent 54 years working in the area, offering key insights on the history of fusion
• Clear, detailed explanations of fusion energy are supplied, helping non-science readers understand the area

• Language: English
• Publisher: Elsevier Science
• Release date: Feb 20, 2013
• ISBN: 9780124078611

John Sheffield

John Sheffield PhD is known worldwide because of his involvement in numerous multi-national fusion energy projects for the U.S. and Europe. In the 1970s, he was on the design team for the 16-nation, Joint European Torus project at Culham in England; in the 1990s, he served as a U.S. representative on committees that defined and then gave technical advice to the International Thermonuclear Experimental Reactor (ITER)-China, Europe, India, Japan, Korea, Russia, and the United States. He served on the US-DOE’s Fusion Energy Sciences Advisory Committee for over a decade, chairing it from 1996 to 2000. From 1988 to 1994, he was director of Fusion Energy at the Oak Ridge National Laboratory. From 1995 to 2003, he was director for Energy Technology Programs at ORNL, and from 1997 also director of the Joint Institute for Energy and Environment at the University of Tennessee. There he remains as a Senior Fellow in what is now called the Institute for a Secure and Sustainable Environment.

Book preview

1

The Fusion Dream

Endless possibilities… and zero chance of success.

Dr. Walter Marshall, regarding the prospects of fusion energy being realized.

In 1954, the Zero Energy Thermonuclear Assembly (ZETA) came into operation at the United Kingdom Atomic Energy Authority’s (UKAEA) laboratory at Harwell, 15 miles south of Oxford. Great excitement followed the announcement in 1958 that it had produced thermonuclear neutrons. The newspapers had a field day with headlines, which the Daily Mail won for crassness with Unto Us a Sun Is Born.

In 1958, I was finishing my bachelor in physics degree in London at Imperial College and took an optional course on fusion energy—the thermonuclear power source of the sun and other stars—and learned about ZETA and other experiments. Fascinated by this exciting area and thrilled to find an alternative option to national service in the military, I joined the thermonuclear division at Harwell. Later tests showed that the ZETA neutrons had not been produced by fusion. That’s research for you.

At the time I started working in fusion, Dr. Walter Marshall was head of the theory division at the laboratory and subsequently became director. Later, he was knighted and, later still, raised to the peerage as Lord Marshall of Goring. This was a well-deserved award because, as evidenced by the quote at the start of this chapter, he had clearly exhibited the ability to gore.

Although his sarcastic remark was not heartwarming for a young researcher like me, I have retained a fascination with fusion energy and remain convinced that commercial success will be realized in this century.

As I said in the Introduction, scientific research is not the dry, disciplined area that many imagine, which reminds me of something that occurred many years later in Gaithersburg, Maryland, on a dry, chilly day in March. By that time, I was a program leader of fusion work at the Oak Ridge National Laboratory and, along with other program leaders from laboratories and universities, was doing the annual show and tell for the Department of Energy (DOE)’s Office of Fusion Energy. A professor from a major university described how an expensive piece of equipment wouldn’t fit into an access port when they cooled their experiment down.

You mean it isn’t going to work? his program manager chided. You’ve wasted our money?

The professor reached out toward the projector. Not a big deal. We can fix it. I’ll show you how on the next viewgraph. Suddenly a spark flashed from his finger to the mirror mount. He recoiled and exclaimed, Does this happen often?

From the back of the room, a DOE program manager shouted, Only when you lie.

Big Bang

As I understand it, in the beginning was the Big Bang—the ultimate cosmic sexual experience. Subsequent to the Bang, various forces came into play in our evolving universe—respectively, gravity and the electro weak and strong nuclear forces. Most important, these forces led to fusion, which produced and is still producing the elements today. This fact was first understood when Arthur Eddington proposed that fusion of hydrogen was the source of the sun’s energy.

Figure 1.1 illustrates the important realities of fusion material: it requires high temperatures—the surface of the sun is around 5 million °C. It can be turbulent, as seen in the eruptions from the surface. Nevertheless, it can be contained by gravity in the case of the massive sun and by magnetic fields and inertia on earth.

Figure 1.1 Photograph of the sun. Source: Courtesy of NASA.

In the fusion process, fundamental particles combine to produce a larger particle (Figure 1.2).

Figure 1.2 The three hydrogen isotopes. Source: Courtesy of General Atomics.

For example, and of interest on earth, at high temperatures (unfortunately for us 100 million °C or more), the nuclei of heavy hydrogen—deuterium (D) and tritium (T)—combine to make helium and a neutron in D–T fusion. The initial particles weigh more than the products, and the mass difference is released as a kinetic energy of 17.6 million electron volts (MeV). The equivalence of mass and energy was explained by Einstein as energy, E=mc², where c is the velocity of light and m is the mass (Figure 1.3).

Figure 1.3 Deuterium and tritium nuclei fuse to produce a helium nucleus and a neutron. Source: Courtesy of Fusion Power Associates.

.

Interestingly, nearly all of the energy resources available to us on earth come from nuclear fusion in the core of our sun and other stars, sunlight, which gives us plant growth, wind and waves, water evaporation to rain, and then hydroelectric power. Then there’s the fission of heavy elements, such as uranium and thorium, which are produced in supernovas, fossil fuels made from elements produced by fusion, and geothermal energy, which arises from radioactive decay in the earth’s core.

The evidence for fusion’s formidable power has been made clear in hydrogen bomb tests, but it remains the only energy resource available to us that we have not yet exploited for peaceful purposes. While there may be other sources of energy that are realizable, if they exist at all, they would be related to those forces that were important closer to the Big Bang, and at temperatures far higher than 50 billion °C.

It seems improbable that these other sources could be of practical use since even investigating such a region cannot be done efficiently today. Therefore, it’s far more sensible to consider only those sources of energy that have been identified as economical or potentially economical, which includes fusion.

This example was given to me by Richard Post of the Lawrence Livermore National Laboratory (LLNL) to illustrate the sheer magnitude of the energy contained in the deuterium, which is one part in 6500 of all the hydrogen on the earth:

If we were to extract the deuterium from the water that typically flows through an 18-inch water main, and burn it and its reaction products in fusion reactors, it could continuously supply about 2000 billion watts of electricity—the world’s total electricity supply in use in the early 2000s.

The heaviest isotope of hydrogen (tritium) is radioactive, and it decays. We have to produce it by bombarding lithium with neutrons, and lithium is not a limitless resource.

Deuterium is, in effect, limitless in the oceans. Therefore, the ideal reaction would be deuterium–deuterium (D–D) fusion, but it requires a temperature of around 400 million °C. Consequently, current research focuses on D–T, despite the additional complication introduced by the requirement for lithium.

There are numerous ways to produce temperatures of 100 million °C or more. For example, passing large currents (millions of amperes) through the fusion fuel, heating it with microwaves, and bombarding it with intense particle or laser beams. Using such techniques, more than 500 million °C has already been achieved in the