Category Archives: Fusion Science and Technology

Fusion Milestone at National Ignition Facility

By Dr. Mike Dunne

The National Ignition Facility (NIF) at Lawrence Livermore National Laboratory in California is the world’s largest and most energetic laser system. The facility completed construction in 2009 and is designed to achieve fusion “ignition”—the achievement of a self-sustaining, burning plasma that releases a net amount of energy. If achieved, it would mark the culmination of more than 50 years of research into fusion. In 2012, the NIF laser met and exceeded its design criteria for energy and power, but it has not yet attained the goal of ignition of the fusion fuel.

A key step on the way to ignition at NIF is for the energy generated through fusion reactions to exceed the amount of energy deposited into the deuterium-tritium (DT) fusion fuel—a condition known as “fuel gain.” This has never before been achieved in a laboratory fusion plasma.

An article by LLNL researcher Omar Hurricane and colleagues in the February 12 online issue of Nature reports that through the use of a new implosion process developed over the past few months, fusion fuel gains exceeding unity have been achieved for the first time on any facility.

The experiments show an order-of-magnitude improvement in yield performance over previous NIF shots, as well as a significant contribution to the yield from alpha-particle self-heating, in which the alpha particles (helium nuclei) produced in the fusion process deposit their energy in the DT fuel. The alpha particles further heat the fuel, increasing the rate of fusion reactions, thus producing more alpha particles. This “bootstrapping” process is the mechanism required to accelerate the DT fusion burn rate to eventual self-sustaining fusion burn and ignition.

These recent experiments use a higher initial laser pulse than previous shots, and have become known as the “high foot” design approach. NIF laser pulses are carefully shaped over their few-nanosecond duration to ensure that the implosion is efficient and robust. The “high foot” approach uses a shorter pulse duration and three laser shocks on the target, rather than four. This configuration is designed to reduce hydrodynamic instability growth in the imploding fuel pellet. This helps to inhibit contamination of the DT fusion fuel by the plastic capsule material, which would otherwise “quench” the fusion process and prevent it from burning.

Most importantly, these latest results show good agreement between the experimental data and the computer models used to predict the performance. This is in comparison to prior experiments, where an order of magnitude discrepancy was often seen. Such agreement now provides a more robust platform with which to explore the path for future advances towards ignition. Ignition—defined to be when a megajoule of fusion energy is released—is a threshold process and needs exquisite control of the initial conditions and plasma evolution during the implosion.

Progress made since the experiments reported in Nature have shown further significant improvements in fusion output, with more experiments planned for later this year.

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Dr. Mike Dunne is program manager for Laser Fusion Energy at Lawrence Livermore National Laboratory

Nuclear Matinee: Scientists announce nuclear fusion breakthrough

Researchers at the National Ignition Facility in California announced this week that they had achieved a major milestone on the path toward nuclear fusion as an energy source, as described in a paper published in the science journal Nature. For the first time, the energy produced in a nuclear fusion reaction in a confined hydrogen fuel exceeded the energy put in to start the reaction.  Science reporter Gautam Naik explains at the Wall Street Journal:

Much work remains before the process, in theory, reaches the point of “ignition” in which a fusion reaction continues on its own and is self-sustaining. See Lawrence Livermore Laboratory’s report on the breakthrough, and interviews with some of the scientists involved at the Los Angeles Times, Time Magazine, and the Wall Street Journal.

Great science, breathtaking engineering, and a landmark achievement with the exciting prospect of continued progress and unforeseen future benefits along the way. The promise of massively abundant energy without pollution, radioactive waste, or greenhouse gases seems closer. And as James Conca suggests at Forbes… is it also already here?

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Thanks to the WSJ Digital Network.

Friday Nuclear Matinee – Compact Fusion: Energy for Everyone

Charles Chase and his team at Lockheed Martin’s “Skunk Works” made quite a splash recently by announcing that they are attempting to develop a truck-trailer-sized 100-MW fusion reactor—to be ready for operation in just a few years!

Chase discussed the compact fusion reactor concept at a recent Google “Solve for X” talk:

Not as compact as this:

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But fusion power for 100,000 homes as compact as this:

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Lockheed Martin is trying for an operational prototype by 2018, a commercially available system by 2023, and the ability to meet global baseload energy demand by 2050…

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March/April edition of ANS journal Fusion Science and Technology available

FST_63_2-cover 201x260The March/April 2013 edition of the technical journal Fusion Science and Technology (FST) is available electronically and in hard copy for American Nuclear Society member subscribers and others.

FST is the leading journal of information on fusion plasma and plasma engineering and is edited by Nermin Uckan.

The March/April issue contains the following peer-reviewed articles:

ANS journals are available for purchase by edition or by article. Please click here to go to the online journals page. A menu of ANS’s publications is available online by clicking here.

A saga on nuclear fusion from an eyewitness

A review of Search for the Ultimate Energy Source: A History of the U.S. Fusion Energy Program, by Stephen O. Dean

By Robert Margolis

A small cutting from the superconducting cable used in the windings of the MFTF-B. Note the vents for directing liquid helium flow, and that the ring is actually a set of small NbTi wires. These wires, when cooled to 4.5 deg K, would have conducted approximately 5000 amps to generate an over 5 Tesla magnetic field.

In the summer of 1984, a certain sophomore engineering student was on a tour of a magnet winding facility operated by General Dynamics in San Diego. The device being wound was the main coil for the Mirror Fusion Test Facility (MFTF-B), which was a cylindrical mirror fusion device. The tour ended with each attendee allowed to take a small scrap piece of superconducting cable as a souvenir.

Construction of the MFTF-B at Lawrence Livermore National Laboratory (LLNL) was completed in 1986—followed by closure that same year without any fusion experiments performed.

How MFTF-B came to be closed without ever being used, as well as the overall roller coaster history of nuclear fusion research in the United States, is detailed in the new book “Search for the Ultimate Energy Source” by Dr. Stephen O. Dean. Dean was one of the pioneers in nuclear fusion research, having joined the Atomic Energy Commission’s Controlled Thermonuclear Research office in 1962. He would go on to found the Fusion Power Associates in 1979 to work with industry to advocate for fusion development.

In this new book, Dean begins with an introduction to the science and technology of nuclear fusion, including a case for pursuing this energy option. He goes on to provide a comprehensive history of the fusion program, both from a documentary standpoint as well as his own eyewitness perspective. He contrasts scientific work and achievements that may not be known to the public (e.g., production of megawatt levels of fusion power using deuterium-tritium mixtures in US and UK devices) with the changing politics that dogged the US fusion program.

Decades of commissions, panels, and committees, along with their myriad of acronyms, are recounted in this authoritative chronicle. Discussions and decisions from various government agencies are carefully documented, providing a clear view of the changing policy environment in which the fusion program operated. While the innate difficulties of the science and engineering of fusion are daunting, and have engendered controversy both within and outside of the nuclear research community, Dean reveals the constant shifting of policies and priorities that further hampered fusion research.

Although the book makes the case for continued support of nuclear fusion research, its primary strength is its detailed and far-reaching treatment of the political maelstrom throughout the timeline of fusion development. This book is ideal for historians and students of science and technology for its complete and in-depth coverage of nuclear fusion technology and policy. Dean has made a valuable contribution to the discussion of not merely the difficulties facing nuclear fusion, but the challenges of sustaining long-term energy policy in general.

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Robert Margolis, PE, is a nuclear (fission) engineer having over 26 years’ experience as a reactor engineer, startup test engineer, project engineer, and safety analyst. Margolis is an individual affiliate member of Fusion Power Associates and still has the superconducting keepsake.

 

November edition of ANS’s Fusion Science and Technology available

The November 2012 edition of the technical journal Fusion Science and Technology (FST) is available electronically and in hard copy for American Nuclear Society member subscribers and others. Non-subscribers click here to  subscribe to FST and other ANS titles.

FST is the leading journal of information on fusion plasma and plasma engineering and is edited by Nermin Uckan.

The November issue contains the following peer-reviewed articles:

TECHNICAL PAPERS

Selected Papers from

SEVENTH FUSION DATA VALIDATION WORKSHOP 2012 (Part 2)

ANS journals are available through annual subscriptions and by individual edition or article. Please click here to go to the online journals page. A menu of ANS’s publications is available online by clicking here.

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October’s Fusion Science & Technology journal is available

The October 2012 issue of the technical journal Fusion Science and Technology is available electronically and in hard copy for American Nuclear Society member subscribers and others.  Non-subscribers click here to learn how to subscribe to FST and other ANS titles.

FST is the leading journal for information on fusion plasma and plasma engineering. The journal is edited by Dr. Nermin Uckan.

The October issue contains the following peer-reviewed articles:

ANS journals are available for purchase by issue or by article. Please click here to go to the online journals page. A menu of ANS’s publications is available online by clicking here.

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