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B International Thermonuclear Experimental Reactor The Sun is currently the site of the only self-sustaining fusion reactions in our solar system. The goal of research on magnetic confinement fusion is to build a controlled “star on Earth”—a fusion reactor—by confining a deuterium-tritium plasma at thermonuclear pressures with magnetic fields. Progress in this grand quest has been steady and dramatic (Figure B.1). In the mid-1990s, two magnetic confinement fusion devices produced multimegawatts of fusion power for a few seconds. Thus the 11-MW Tokamak Fusion Test Reactor (TFTR) in Princeton, New Jersey, and the 16-MW Joint European Torus (JET) in Great Britain demon- strated it is possible to confine, heat, insulate, and control a large volume of ther- monuclear plasma in the laboratory, at least transiently; the similar-sized JT-60U experiment in Japan extended these results in deuterium plasmas. The next and critically important step is to show that one can obtain more heating from fusion reactions than is put into the reaction from external sources—a fusion burning plasma. In both the U.S. and European landmark fusion experi- ments, the self-heating of the plasma from fusion reactions was less than the ap- plied external heating. The next major step in the worldwide magnetic confinement fusion research will be to achieve a fusion burning plasma in which the plasma is dominantly self-heated by the fusion reaction products. This step will be taken in the International Thermonuclear Experimental Reactor, now simply known as ITER, whose construction is slated to begin at Cadarache, in the south of France, in 2008 (Figure B.2). The objectives of the ITER project are as follows: 221

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Plasma science 222 The overall programmatic objective of ITER is to demonstrate the scientific and technological feasibility of fusion energy for peaceful purposes. ITER will accomplish this objective by demonstrating high power amplification and extended burn of deuterium-tritium plasmas, with steady-state as an ultimate goal, by demonstrating technologies essential to a reactor in an integrated system, and by performing integrated testing of the high-heat-flux and nuclear components required to utilize fusion energy for practical purposes. These objectives maintain the strategy to take a single step between today’s experi- ments and the first plant (often called DEMO) to demonstrate reliable electricity production using fusion power.1 Specifically, ITER seeks to achieve its first plasma in 2016 and produce 500 MW of fusion power for hundreds of seconds in about 2020. Key physical parameters of ITER are these: the plasma cross-section will be approximately 4 meters wide by 7 meters tall; magnetic field strength, 5.3 tesla; current in the plasma, 15 MA; and external heating power, 40-50 MW. The construction costs of ITER are estimated at €5 billion over 10 years, and another €5 billion are foreseen for the 20-year op- eration period. The ITER Parties will for the largest part give components for the machine, so-called in-kind contributions. The ITER project was launched as a Reagan-Gorbachev Presidential Initiative in 1985, with equal participation by the United States, Europe, Japan, and the Soviet Union through the 1988-1998 initial design phases of the original ITER project. After the fusion program budget was cut by 33 percent and the fusion program was restructured from an energy technology development program to a science-focused program in the late 1990s, the United States withdrew from the ITER project. From 1998 through 2002 the ITER project was continued by Europe, Japan, and Russia and evolved into the current smaller ITER project with reduced objectives. It ad- opted much of the science-driven reduced scope and advanced concepts the United States had pushed for when it participated in the earlier ITER phases. The NRC Burning Plasma Assessment Committee (BPAC) recommended (in December 2002) that the United States should again participate in the ITER proj- ect. The United States then rejoined the ITER negotiations in January 2003 as a Presidential Initiative. Participation in ITER is now identified as the number one priority future project over the next 20 years by the DOE Office of Science. In the Energy Policy Act of 2005 (Public Law 109-58, August 8), Congress authorized the negotiation of “an agreement for United States participation in the ITER.” Achieve- ment of the U.S. scientific community and government consensus on rejoining ITER was a major accomplishment over the past decade. The partners in the ITER project (host Europe, 45 percent; nonhosts—China, 1As defined on the ITER Web site at http://www.iter.org/a/index_nav_1.htm. Last viewed May 15, 2007.

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FIGURE B.1 The fusion power produced in magnetically confined plasmas has been increasing continuously and dramatically for decades. On aver- age it doubled every year until the mid-1990s, twice as fast as Moore’s law for the increase in computing power of semiconductor chips. ITER is projected to extend fusion power and duration to the crucial burning plasma regime. 22

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Plasma science 224 FIGURE B.2 Cutaway drawing of the International Thermonuclear Experimental Reactor (ITER) to be built over the next decade in Cadarache, France. A man shown in the lower left corner indicates the scale of the device. Detailed characteristics of the ITER device and of the overall ITER project can be obtained from http://www.iter.org. Published with permission of ITER. India, Japan, Russia, South Korea, and the United States—9.1 percent each), de- cided on the Cadarache site on June 28, 2005, and initialed an agreement on May 24, 2006. Final governmental signatures on the ITER Agreement were obtained on November 21, 2006. Because the ITER project has been truly international from its inception in 1985 as an initiative of Presidents Reagan and Gorbachev and is the largest joint international scientific endeavor ever undertaken, it will probably become the model for large international science experiments. Magnetic fusion research has a long history of strong international collabora-

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aPPendix B 22 tion ever since it was declassified at the United Nations Atoms for Peace conference in 1958. During the 1960s, the major players were the United States, Great Britain and the Soviet Union; scientific exchanges began then, but there were few close collaborations. A notable turning point in fusion research was the achievement in 1968 of excellent plasma confinement in the Soviet T-3 tokamak experiment and subsequent confirming measurements by a collaborating team of British scientists. This achievement launched a worldwide quest for fusion energy based primarily on the tokamak concept. The major players became the United States, Europe (Great Britain, France, and Germany), the Soviet Union, and Japan. The United States had about a third of the world fusion budget in 1980 and became the dominating leader in fusion science and technology in the late 1970s; its leadership continued into the early 1990s. Close collaborations between experimental teams on different fusion devices around the world are now quite common, most often to check scaling of the behavior of plasma phenomena across different sizes and types of experiments. While the primary U.S. objective in ITER is burning plasma science (understanding and control of burning plasmas), the primary objective of the European and Japanese programs remains development of fusion energy for commercial electricity production.