The light at the end of the tunnel may be located at the spot marked A in southern France on the map of Fig. 8.22. It is here, in a town called Cadarache near Aix-en — Provence that ITER is being built. Magnetic confinement of plasma gets better with

Fig. 8.22 Map of France, showing the location of Cadarache

size, and it has long been clear that a much larger machine has to be built to achieve ignition, a machine so large that no single country can bear the whole cost. Thus was born the international thermonuclear experimental reactor, now known only by its initials, ITER. Coincidentally, ITER in Latin means a path, a journey. It may indeed be the best way to get there.

The reason for the large size is that the amount of power generated is propor­tional to the volume of the plasma, which increases with the cube of its radius, while the losses are proportional to the surface area of the plasma, which increases only as the square of its radius. To take the next step beyond the four machines shown above, therefore, requires a much larger machine, one so large that its cost has to be shared among many countries. The idea of an international project to achieve fusion energy was born in the 1985 Geneva Superpower Summit, where President Mikhail Gorbachev of the USSR and President Ronald Reagan of the USA, with advice from President Frangois Mitterand of France, agreed to initiate a project involving the USSR, the USA, the European Union, and Japan. (It probably helped that Gorbachev’s advisers were Evgeniy Velikov and Roald Sagdeev, both plasma physicists.) More on what ensued afterwards will come later, but first let’s see what kind of machine ITER is.

Figure 8.23 is the diagram of the machine being built. Its size is indicated by the small figure at the bottom, representing a standard 2-meter person. The plasma chamber has the standard D-shape, 1.7 times as high as it is wide. The width is 4 m at its widest part, and the major radius (the distance between the center of the chamber and the axis of the whole machine) is 6.2 m. The D-shaped coils that produce the main magnetic field can be seen, but all the other equipment is shown simplified; otherwise, the vacuum chamber would not be visible at all!

Fig. 8.23 Diagram of ITER (http://www. iter. org)

That includes all the other coils for shaping the plasma, the neutral-beam injectors for heating, the neutron-absorbing blanket, the divertors for catching the plasma, pellet injectors for fueling, and a host of measurement devices. How much bigger ITER is compared with the current champion, JET, is shown in Fig. 8.24. The clutter surrounding a real machine can be seen in the pictures of existing large tokamaks in Figs. 8.3—8.6.

What is ITER designed to do? The primary goal is to produce, for the first time, a “burning” plasma. That is, a plasma that will keep itself hot once it has been heated to several hundred million degrees. Remember that 80% of the fusion energy from DT fuel is in the form of neutrons, and only 20% is in alpha particles (helium ions) which can give energy to the plasma because they are magnetically confined. Therefore, a Q value of at least 5 is needed for burning or ignition. To get a safety margin, ITER is designed to produce a Q of 10, where Q is the ratio of energy out of the plasma to the energy put into the plasma from external sources. Q = 1 is scientific breakeven (energy in equals total energy out), but most of that energy is in the form of neutrons, which produce the power plant energy but cannot heat the plasma. The best that JET could do was Q=0.65, below scientific breakeven. The large step from Q = 0.65 to Q = 10 is the reason that ITER has to be so big. The step is not trivial also from a physics point of view. The 3.5-MeV alphas may cause an instability that drives them out of the plasma. Although the stability conditions have been calculated, they have never been tested. The experiment will be consid­ered a success if enough self-heating occurs for these conditions to be established, even if Q = 10 is not achieved. The self-heating mechanism which powers the sun has never been seen on earth outside of a bomb, and plasma experts are eagerly

Fig. 8.24 Comparison of ITER with JET (http://www. iter. org)

anticipating this critical test. The term “ignition” may invoke fear that the reaction will run away and cause an explosion. This cannot happen in a fusion reactor because if the density or temperature gets too high, the plasma will disrupt and fizzle out. This may cause melting of parts of the tokamak, but it would be no worse than leaving a pot on a stove after the water has boiled out. The “pot” here would be an expensive one, though!

There are other objectives for ITER besides achieving Q = 10. It will produce 500 MW of power, about one-sixth that of a full-size reactor. Many large key compo­nents of a fusion reactor have to be designed, manufactured, and tested in operation. This includes superconducting magnet coils, wall materials and divertors that can withstand the heat and neutron bombardment, tritium handling, and remote control and maintenance after the walls become radioactive and cannot be approached by personnel. Instability control has to keep the plasma confined steadily for as long as 8 min, using a large amount of bootstrap current and generating 500 MW of power. There will be a first test of a neutron-absorbing “blanket” that can breed tritium. Tritium does not occur naturally. Most of the time, ITER will use tritium coming from fission reactors, of which it is a byproduct; but in a fusion power plant the tritium has to be made internally. This is done in a blanket that captures the 14-MeV neutrons from the reaction, slows them down, and generates heat to run a steam plant. A part of this blanket can be used to breed tritium from lithium, which is an abundant element on earth.

ITER is the logical next step toward fusion power, but it is still primarily a physics experiment. It will lead to DEMO, a demonstration power plant that will run without breakdown and produce a usable amount of power. However, many believe that an

intermediate step between ITER and DEMO is necessary to develop engineering concepts that will work in a real reactor. Some of the difficult problems are, for instance, (1) the material to be used in the plasma-facing components (the “first wall”), (2) the handing and breeding of tritium, (3) continuous operation for long periods, (4) maintenance procedures, and (5) plasma exhaust and waste treatment. ITER can provide only a first try on such topics. Engineering will be the topic of the next chapter; this is only an introduction. As an example, the first-wall material has to take the heat of facing a 100,000,000-degree plasma, and it has to allow a large flux of neutrons to pass through without causing such damage that it has to be replaced often. It also cannot contaminate the plasma with impurities of high atomic number, which would cool the plasma. Tests of suitable materials can be done without a tokamak; a fission source of neutrons would do. In fact, most of these engineering tests can be done on a much smaller, cheaper machine than ITER, and such a machine can be built and operated simultaneously with ITER to save time. Most large laboratories have proposed such a machine. For instance, the Fusion Development Facility proposed by General Atomics is a tokamak using normal-conducting coils and producing only 100-250 MW of power at Q less than 5. But it is designed to run continuously for weeks at a time over 30% of a year and breed up to 1.3 kg of tritium per year. Such machines and DEMO are still in the talking stage, but the ITER project is up and running.

As can be imagined, a cooperative project among seven nations is an administra­tive nightmare. It took over 20 years to get to the present stage. After the initial Gorbachev-Reagan agreement, the four partner nations managed to agree to start Conceptual Design Activities in 1988, and the design was finished in 1990. The resulting tokamak was much larger than the present design. In 1992, an agreement was made to start more serious Engineering Design Activities. Each country had its own home team, and a Joint Central Team was stationed in La Jolla, California. The directors of ITER for this study was at first Paul-Henri Rebut and later Robert Aymar, both of France. After six years of work, it was decided that the tokamak was too large and too expensive, and the activity was extended to 2001. The final design, finished in 2001, is half the price but achieves almost the same objectives. The physics basis for ITER, which we discussed in Chap. 7, was worked out in this period and contrib­uted to the efficiency of the new design. Some $650M was expended to design ITER, with the original agreement that the European Union and Japan would each bear one — third of the cost, while the USSR and the USA shared the other third. To everyone’s chagrin, the USA withdrew from the project in 1999, not to return until 2003. The project continued without funding from the US Congress.

Meanwhile, in 1991, the USSR collapsed and was replaced by the Russian Federation. In 2003, the Peoples’ Republic of China and South Korea joined ITER. India joined in 2005, raising the number of partners to seven. Canada was temporarily involved but dropped out when its proposed site was turned down. With an area larger than that of Western Europe, Kazakhstan has been considering joining in spite of the fact that it has large fossil reserves. The seven current nations supporting ITER are shown in Fig. 8.25. These countries represent more than half the world’s population. Without public support, the USA has been a

Fig. 8.25 The seven nations in the ITER organization

lukewarm partner in this path-breaking enterprise, and again failed to contribute its financial share in 2008.

By 2003, ITER’s design had been agreed upon, and the project was ready to move ahead. The estimated cost was calculated to be five billion euros (about $7B) for ten years of construction, and another 5B euros for 20 years of operation.13 Then came a totally unexpected delay. There was a deadlock on the site for ITER. The site had to have sufficient power and accessibility for such a large machine. The final­ists were a site in Japan and a site in Europe, at first in Spain, but finally in France. The EU, China, and Russia voted for France; and Japan, Korea, and the USA voted for Japan. India had not yet joined. The impasse lasted for two years. Finally, in 2005, the deadlock was broken, and France was chosen. As compensation, Japan was to supply 20% of the staff and had the right to choose the Director. Furthermore, the EU was required to purchase 20% of its ITER material from Japan. As host, the EU has to bear 5/11ths of the cost of ITER, and the other six countries 1/11th each. Kaname Ikeda was chosen to be Director. The 45% contribution by the EU will stimulate its economy.

Once a Joint Implementation Agreement was signed in November 2006 by the seven parties, the ITER Organization sprang into action. Hundreds of scientists, engineers, and administrators began to migrate to Cadarache, settling into tempo­rary offices. Bulldozers began to move two million cubic meters of soil to prepare the flat site for ITER, shown in Fig. 8.26. This amount of dirt would fill the Cheops pyramid, and the area is that of 57 soccer fields. The roads had to be widened to accommodate nine-meter wide truck convoys which will carry the major compo­nents of the tokamak. Even traffic circles (roundabouts) like the one at the upper left of Fig. 8.26 had to be enlarged. Those parts manufactured outside Europe would be shipped to the Mediterranean port of Fos-sur-Mer and then barged and trucked to Cadarache. A three-story office building was built in 2008 to house 300

Fig. 8.26 Preparation of the ITER site in 2008

employees, but this was still temporary and off-site. To accommodate their families, a multilingual school was established in Manosque; by 2009 it had 212 students from 21 nations and 80 teachers. In 2010, the school will have its own building and include a nursery school and a junior high. The first ITER baby was delivered in 2008. A weekly bulletin14 covers not only technical and personnel news but also includes cultural events and introduces the entire international community to the his­tory and traditions of this region in southern France.

ITER is truly an international project. For instance, the vacuum vessel will be made by Europe and Korea, with other parts from Russia and India. The largest components, the magnet coils, will weigh 8,700 tons and will be made of Nb3Sn and NbTi superconductors. Many different types of magnet coils and their feed-ins are required, and the manufacture of the superconductor material and their forma­tion into coils are shared among most of the ITER partners. The USA will supply 40 tons of expensive Nb3Sn conductors for the toroidal field, and those for the poloidal field will be shared among China, Russia, and Europe. Superconductor wire is very complicated, wound in many strands and cooled with liquid helium. That these actually work in large coils has been tested in the LHD stellarator in Japan and will be further tested in the new superconducting tokamaks in China, Korea, and Japan.

Domestic Agencies have been established in each country to organize the manu­facture of its in-kind contributions to ITER by local industries. Through these agencies, Procurement Agreements have to be drawn up and signed by each member country. As of 2010, 28 PAs have been signed. The site in Fig. 8.25 has been completely leveled, and the construction of 38 buildings on it has begun. The first of these is a six-story 253-m long building for winding the poloidal field coils, which are too large to be shipped, and the superconductor cable is all in one piece.

Fig. 8.27 The original ITER timeline

New office buildings will replace the temporary ones. Off-site in Manosque, a new school, will be built for the community.

It is clear that the ITER project is in for the long pull. Figure 8.27 shows the originally agreed schedule for the construction and operation of ITER. The site preparation will not be finished until 2012, but meanwhile the components are being designed, fabricated, and tested in various countries. It will take four years to get all the parts delivered and the tokamak assembled. The first plasma is scheduled to be made near the end of 2016. At first, experiments will be done with hydrogen, which is not radioactive. Remote handling will then be implemented so that deuterium can be used; the D-D reaction creates some neutrons, but not as many as does DT. In 2020, operation with DT will start, first in pulsed (low-duty) operation, to achieve the designed Q value. In the later stages, emphasis will be on quasi-steady state operation (high-duty) to test whether bootstrap current and non­inductive (no transformer) drive can sustain the plasma. At the end of 2026, a decision will be made whether to decommission the machine or to continue it with modifications. De-activating, decommissioning, and disposing of the machine is expected to take another 11 years. The ITER machine will have 30,000 components in ten million pieces. To get these to be delivered on time and fit together requires numerous groups and oversight committees. Their acronyms are overwhelming, but that’s the price you pay for organizational efficiency.

At this time, the goal of achieving first plasma in 2016 seems a long way off, but the worldwide economic downturn in 2008-2009 has made it even worse. Both the budget and the schedule had to be revised in 2010. The project will be delayed two years or more by economic constraints. The new construction schedule will look something like Fig. 8.28. DT plasmas will not be attempted before 2027.

These estimates notwithstanding, the project is proceeding nicely under new Director Osamu Motojima. The digging and flattening of the ITER site has been finished and is shown in Fig. 8.29. Parts of the machine are coming in from different countries. Figure 8.30 shows the buildings planned for the site. These will be earth­quake-proof, and some will have containment for radioactivity. The long coil-winding

ITER CONSTRUCTION 2008 2009 2010 2011 2012 2013 2014 2015 2016 2017 2018 2019 DIG I BUILD TOKAMAK SITE___________ |________________ BUILD TOKAMAK FIRST PLASMA

Fig. 8.28 The revised ITER timeline [32]

Fig. 8.29 The ITER site in June, 201014

Fig. 8.30 Planned buildings for the ITER site [32]

building mentioned above can be seen at the top for scale. It is exciting to see international teamwork functioning so well.

Contrary to popular perception, fusion is no longer in a guessing stage. The timeline for its development has been set. Each country has its own ITER organiza­tion and its own specialized manufacturing capabilities to contribute to the project.

At the current level of funding, it will take until 2026 to get the information from this experiment. Concurrently, materials testing facilities can be built and run to support DEMO. Design, construction, and operation of DEMO will take until 2050; and, if it is successful, commercial reactors can follow soon thereafter. The present plan is to achieve fusion power by 2050, in time for the present generation of children to enjoy. However, with increased international ambition, the time can be shortened.

There may be some confusion in the public’s mind between ITER and another large experiment, the Large Hadron Collider, or LHC, at CERN near Geneva. Geneva can be seen in Fig. 8.21 north of Cadarache. It is quite a coincidence that the two largest physics experiments in the world should be located only a few hundred kilometers from each other. The LHC is a particle accelerator 27 km (17 miles) in circumference, buried in a circular tunnel under France and Switzerland. It is similar to ITER in internationality, cost (6.3B euros), and the extensive use of superconductors; but it is entirely different in technology and purpose. The LHC is a basic physics experiment to explore the subatomic structure of matter and energy: quarks, Higgs bosons, dark matter, and so forth. Protons and antiprotons are accelerated to multi-TeV (trillions of eV) energies and hurled against one another to break them up, one particle at a time. ITER, on the other hand, deals with a gas of multi-billions of particles at KeV (thousands of eV) energies. In the LHC, large magnetic fields are used to bend the protons into circular orbits, their Larmor radius being measured in kilometers. In ITER, large magnetic fields are used to hold a plasma, which exerts a large pressure not because the particles are so energetic but because there are so many of them.

The LHC and its predecessors were inspired by man’s urge to understand his place in the universe, not by any practical need. ITER, on the other hand, is being built to develop an energy source that will save mankind, and, if done soon enough may also solve current problems in climate change and fossil fuel depletion. We are living in a golden age in which civilization has advanced to such a point that we can afford to reach for lofty goals. Let us hope that our reach does not exceed our grasp.

http://www. toodlepip. com/tokamak/gallery-ext. htm. Alternate concepts have been described by Bishop [1] and Chen [11, 12]. Dale Meade, Astronomy 225 seminar notes, Princeton University, 2005. http://www. pppl. gov/projects/pages/tftr. html. http://www. jet. efda. org/pages/multimedia/brochures. html. PCAST report, 1995: http://www. ostp. gov/pdf/fusion1995.pdf. Massachusetts Institute of Technology. nG (1020 m-3) = IJpa2 (MA/m2), where Ip is the toroidal current and a is the minor radius. There are recent attempts to explain the limit theoretically [29]. This original reference does not give the formula that is now used.