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ITER (originally the International Thermonuclear Experimental Reactor) is an international tokamak (magnetic confinement fusion) research/engineering project that could help to make the transition from today's studies of plasma physics to future electricity-producing fusion power plants. It builds on research done with devices such as DIII-D

, EAST, ADITYA, KSTAR, TFTR, ASDEX Upgrade, Joint European Torus

, JT-60, Tore Supra and T-15.

Background

On November 21, 2006, the seven participants formally agreed to fund the creation of a nuclear fusion reactor. The program is anticipated to last for 30 years – 10 for construction, and 20 of operation. ITER was originally expected to cost approximately €5bn, but the rising price of raw materials and changes to the initial design may see that amount double. The reactor is expected to take nearly 10 years to build and is scheduled to be switched on in 2018. If completed, ITER would be one of the most expensive modern technoscientific megaprojects. Site preparation has begun in Cadarache

, France

and procurement of large components has started.

ITER is designed to produce approximately 500 MW of fusion power sustained for up to 1,000 seconds (compared to JET

's peak of 16 MW for less than a second) by the fusion of about 0.5 g of deuterium/tritium mixture in its approximately 840 m³ reactor chamber. Although ITER is expected to produce (in the form of heat) 5-10 times more energy than the amount consumed to heat up the plasma to fusion temperatures, the generated heat will not be used to generate any electricity.

In assessing the potential for global and sustainable energy production in the long term it is clear that the diminishing availability and rising cost of energy based on carbon combined with the increased emphasis on low environmental impact energy sources generally, emphasizes the notion that nuclear fusion is one of very few candidates for the large-scale carbon-free production of base-load power.

Fusion has many potential attractions:

abundant fuel
intrinsically safe
no production of CO₂ or atmospheric pollutants
"clean nuclear stove" producing relatively short-lived waste.

ITER was originally an acronym for International Thermonuclear Experimental Reactor, but that title was dropped due to the negative popular connotation of "thermonuclear," especially when in conjunction with "experimental". "Iter" also means "journey", "direction" or "way" in Latin, reflecting ITER's potential role in harnessing nuclear fusion as a peaceful power source.

Objectives

ITER's mission is to demonstrate feasibility of fusion power, and prove that it can work without negative impact. Specifically, this includes:

To momentarily produce ten times more thermal energy from fusion heating than is supplied by auxiliary heating (a Q value of 10).
To produce a steady-state plasma with a Q value greater than 5.
To maintain a fusion pulse for up to eight minutes.
To ignite a 'burning' (self-sustaining) plasma.
To develop technologies and processes needed for a fusion power plant — including superconducting magnets and remote handling (maintenance by robot).
To verify tritium breeding concepts.
To refine neutron shield/heat conversion technology (most of energy in the D+T fusion reaction is released in the form of fast neutrons).

Reactor overview

See also: Nuclear fusion

When deuterium and tritium fuse, two nuclei come together to form a helium nucleus (an alpha particle), and a high-energy neutron.

+ → + +

While in fact nearly all stable isotopes lighter on the periodic table than iron will fuse with some other isotope and release energy, deuterium and tritium are by far the most attractive for energy generation as they require the lowest activation energy (thus lowest temperature) to do so.

All proto- and mid-life stars radiate enormous amounts of energy generated by fusion processes. Mass for mass, the deuterium-tritium fusion process releases roughly three times as much energy as uranium 235 fission, and millions of times more energy than a chemical reaction such as the burning of coal. It is the goal of a fusion power plant to harness this energy to produce electricity.

The activation energy for fusion is so high because the protons in each nucleus will tend to strongly repel one another, as they each have the same positive charge. A heuristic for estimating reaction rates is that nuclei must be able to get within 100 femtometer (1 × 10⁻¹³ meter) of each other, where the nuclei are increasingly likely to undergo quantum tunnelling past the electrostatic barrier and the turning point where the strong nuclear force and the electrostatic force are equally balanced, allowing them to fuse. In ITER, this distance of approach is made possible by high temperatures and magnetic confinement.High temperatures give the nuclei enough energy to overcome their electrostatic repulsion (see Maxwell-Boltzmann distribution). For deuterium and tritium, the optimal reaction rates occur at temperatures on the order of 100,000,000 K. The plasma is heated to a high temperature by ohmic heating (running a current through the plasma). Additional heating is applied using neutral beam injection (which cross magnetic field lines without a net deflection and will not cause a large electromagnetic disruption) and radio frequency (RF) or microwave heating.

At such high temperatures, particles have a vast kinetic energy, and hence velocity. If unconfined, the particles will rapidly escape, taking the energy with them, cooling the plasma to the point where net energy is no longer produced. A successful reactor would need to contain the particles in a small enough volume for a long enough time for much of the plasma to fuse.In ITER and many other magnetic confinement reactors, the plasma, a gas of charged particles, is confined using magnetic fields. A charged particle moving through a magnetic field experiences a force perpendicular to the direction of travel, resulting in centripetal acceleration, thereby confining it to move in a circle.

A solid confinement vessel is also needed, both to shield the magnets and other equipment from high temperatures and energetic photons and particles, and to maintain a near-vacuum for the plasma to populate.The containment vessel is subjected to a barrage of very energetic particles, where electrons, ions, photons, alpha particles, and neutrons constantly bombard it and degrade the structure. The material must be designed to endure this environment so that a powerplant would be economical. Tests of such materials will be carried out both at ITER and at IFMIF (International Fusion Materials Irradiation Facility).

Once fusion has begun, high energy neutrons will radiate from the reactive regions of the plasma, crossing magnetic field lines easily due to charge neutrality (see neutron flux). Since it is the neutrons that receive the majority of the energy, they will be ITER's primary source of energy output. Ideally, alpha particles will expend their energy in the plasma, further heating it.

Beyond the inner wall of the containment vessel one of several test blanket modules will be placed. These are designed to slow and absorb neutrons in a reliable and efficient manner, limiting damage to the rest of the structure, and breeding tritium from lithium and the incoming neutrons for fuel.Energy absorbed from the fast neutrons is extracted and passed into the primary coolant. This heat energy would then be used to power an electricity-generating turbine in a real power plant; however, in ITER this generating system is not of scientific interest, so instead the heat will be extracted and disposed of.

History

ITER began in 1985 as a collaboration between the European Union (through EURATOM), the USA

, the then Soviet Union

, and Japan

. Conceptual and engineering design phases led to an acceptable, detailed design in 2001, underpinned by US$650 million worth of research and development by the "ITER Parties" to establish its practical feasibility. These parties (with the Russian Federation

replacing the Soviet Union and with the USA opting out of the project in 1999 and returning in 2003) were joined in negotiations on the future construction, operation and decommissioning of ITER by Canada

(who then terminated their participation at the end of 2003), the People's Republic of China

, and the Republic of Korea

. India

officially became part of ITER on 6 December 2005.

On 28 June 2005, it was officially announced that ITER will be built in the European Union in Southern France

. The negotiations that led to the decision ended in a compromise between the EU and Japan, in that Japan was promised 20% of the research staff on the French location of ITER, as well as the head of the administrative body of ITER. In addition, another research facility for the project will be built in Japan, and the European Union has agreed to contribute about 50% of the costs of this institution.

On 21 November 2006, an international consortium signed a formal agreement to build the reactor.

On 24 September 2007, the People's Republic of China

became the seventh party who had deposited the ITER Agreement to the IAEA

.

On 24 October 2007, the ITER Agreement entered into force and the ITER Organization legally came into existence.

ITER will run in parallel with a materials test facility, the International Fusion Materials Irradiation Facility (IFMIF), which will develop materials suitable for use in the extreme conditions that will be found in future fusion power plants. Both of these will be followed by a demonstration power plant, DEMO, which would generate electricity. DEMO would be the first to produce electric energy for commercial use.

A "fast track" plan to a commercial fusion power plant has been sketched out. This scenario, which assumes that ITER continues to demonstrate that the tokamak line of magnetic confinement is the most promising for power generation, anticipates a full-scale power plant coming on-line in 2050, potentially leading to a large-scale adoption of fusion power over the following thirty years.

Technical design

Selected facts: The central solenoid coil will use superconducting niobium-tin, to carry 46 kA and produce a field of 13.5 teslas.The 18 toroidal field coils will also use niobium-tin. At maximum field of 11.8 T they will store 41 GJ. They have been tested at a record 80 kA. Other lower field ITER magnets (PF and CC) will use niobium-titanium.

Location

The process of selecting a location for ITER was long and drawn out. The most likely sites were Cadarache

in Provence-Alpes-Côte-d'Azur

, France

and Rokkasho

, Aomori

, Japan

. Additionally, Canada

announced a bid for the site in Clarington

in May 2001, but withdrew from the race in 2003. Spain

also offered a site at Vandellòs

on 17 April 2002, but the EU decided to concentrate its support solely behind the French site in late November 2003. From this point on, the choice was between France and Japan.

On 3 May 2005, the EU and Japan agreed to a process which would settle their dispute by July.

At the final meeting in Moscow

on 28 June 2005, the participating parties agreed on the site in Cadarache

in Provence-Alpes-Côte-d'Azur

, France

.

Construction of the ITER complex began in 2008, while assembly of the tokamak itself is scheduled to begin in the year 2011.

Participants

Currently there are seven national and supranational parties participating in the ITER program: the European Union (EU; see Fusion for Energy), India

, Japan

, People's Republic of China

, Russia

, South Korea

, and the USA

..

Canada

was previously a full member, but has since pulled out due to a lack of funding from the Federal government. The lack of funding also resulted in Canada withdrawing from its bid for the ITER site in 2003.

It was announced that participants in the ITER will consider Kazakhstan

's offer to join the program.

Funding

As of June 17, 2009, the total price of constructing the experiment is expected to be in excess of € 10 billion. Prior to that, the proposed costs for ITER were € 5 billion for the construction and € 5 billion for maintenance and the research connected with it during its 35 year lifetime. At the June 2005 conference in Moscow

the participating members of the ITER cooperation agreed on the following division of funding contributions: 50% by the hosting member, the European Union and 10% by each non-hosting member. According to sources at the ITER meeting at Jeju, Korea, the six non-host partners will now contribute 6/11th of the total cost — a little over half — while EU will put in the rest. As for the industrial contribution, China, India, Korea, Russia, and the U.S. will contribute 1/11th each, Japan 2/11th, and EU 4/11th.

Although Japan

's financial contribution as a non-hosting member is 1/11th of the total, the EU agreed to grant it a special status so that Japan will provide for 2/11th of the research staff at Cadarache and be awarded 2/11th of the construction contracts, while the European Union's staff and construction components contributions will be cut from 5/11th to 4/11th.

Criticism

Jan Vande Putte of Greenpeace International said that "Governments should not waste our money on a dangerous toy which will never deliver any useful energy". "Instead, they should invest in renewable energy which is abundantly available, not in 2080 but today."

A French association including about 700 anti-nuclear groups, Sortir du nucléaire (Get Out of Nuclear Energy), claimed that ITER was a hazard because scientists did not yet know how to manipulate the high-energy deuterium and tritium hydrogen isotopes used in the fusion process.

The ITER project confronts numerous technically challenging issues.French physicist Sébastien Balibar, director of research at the CNRS said "We say that we will put the sun into a box. The idea is pretty. The problem is, we don't know how to make the box".

A technical concern is that the 14 MeV neutrons produced by the fusion reactions will damage the materials from which the reactor is built. Research is in progress to determine how and/or if reactor walls can be designed to last long enough to make a commercial power plant economically viable in the presence of the intense neutron bombardment. The damage is primarily caused by high energy neutrons knocking atoms out of their normal position in the crystal lattice. A related problem for a future commercial fusion power plant is that the neutron bombardment will induce radioactivity in the reactor itself. Maintaining and decommissioning a commercial reactor may thus be difficult and expensive. Another problem is that superconducting magnets are damaged by neutron fluxes. A new special research facility is planned for this activity, IFMIF.

Rebecca Harms, Green/EFA member of the European Parliament

's Committee on Industry, Research and Energy, said: "In the next 50 years nuclear fusion will neither tackle climate change nor guarantee the security of our energy supply." Arguing that the EU's energy research should be focused elsewhere, she said: "The Green/EFA group demands that these funds be spent instead on energy research that is relevant to the future. A major focus should now be put on renewable sources of energy." French Green party lawmaker Noël Mamère claims that more concrete efforts to fight present-day global warming will be neglected as a result of ITER: "This is not good news for the fight against the greenhouse effect because we're going to put ten billion euros towards a project that has a term of 30-50 years when we're not even sure it will be effective."

A number of fusion researchers working on non-tokamak systems, such as Robert Bussard and Eric Lerner, have been critical of ITER for diverting funding that they believe could be used for their potentially more reasonable and/or cost effective fusion power plant designs.Criticisms levied often revolve around claims of the unwillingness by ITER researchers to face up to potential problems (both technical and economic) due to the dependence of their jobs on the continuation of tokamak research. An informal overview of the last decade of work was presented at the 57th International Astronautical Congress in October 2006.

Response to criticism

Proponents believe that much of the ITER criticism is misleading and inaccurate, in particular the allegations of the experiment's "inherent danger." The stated goals for a commercial fusion power station design are that the amount of radioactive waste produced be hundreds of times less than that of a fission reactor, that it produce no long-lived radioactive waste, and that it is impossible for any fusion reactor to undergo a large-scale runaway chain reaction. This is because direct contact with the walls of the reactor would contaminate the plasma, cooling it down immediately and stopping the fusion process. Besides which, the amount of fuel planned to be contained in a fusion reactor chamber (one half gram of deuterium/tritium fuel) is only enough to sustain the reaction for an hour at maximum, whereas a fission reactor usually contains several years' worth of fuel.In case of accident (or intentional act of terrorism) a fusion reactor releases far less radioactive pollution than an ordinary fission nuclear plant. Besides, tritium, being lighter than air, would rise up into the stratosphere and dilute to concentrations whereby the radiation released would be far below the natural background radioactivity of air. Proponents note that large-scale fusion power — if it works — will be able to produce reliable electricity on demand and with virtually zero pollution (no gaseous CO₂ / SO₂ / NO_x by-products are produced).

According to researchers at a demonstration reactor in Japan, a fusion generator should be feasible in the 2030s and no later than the 2050s. Japan is pursuing its own research program with several operational facilities exploring different aspects of practicability.

In the United States alone, electricity accounts for US$210 billion in annual sales. Asia's electricity sector attracted US$93 billion in private investment between 1990 and 1999. These figures take into account only current prices. With petroleum prices widely expected to rise, political pressure on carbon production, and steadily increasing demand, these figures will undoubtedly also rise as known oil reserves are depleted. Proponents contend that an investment in research now should be viewed as an attempt to earn a far greater future return for the economy. Also, worldwide investment of less than US$1 billion per year into ITER is not incompatible with concurrent research into other methods of power generation.

Contrary to criticism, proponents of ITER assert that there are significant employment benefits associated with the project. ITER will provide employment for hundreds of physicists, engineers, material scientists, construction workers and technicians in the short term, and if successful, will lead to a global industry of fusion-based power generation .

Supporters of ITER emphasize that the only way to convincingly prove ideas for withstanding the intense neutron flux is to experimentally subject materials to that flux — one of the primary missions of ITER and the IFMIF, and both facilities will be of vital importance to the effort due to the differences in neutron power spectra between a real D-T burning plasma and the spectrum to be produced by IFMIF. The purpose of ITER is to explore the scientific and engineering questions surrounding fusion power plants, such that it may be possible to build one intelligently in the future. It is nearly impossible to get satisfactory theoretical results regarding the properties of materials under an intense energetic neutron flux, and burning plasmas are expected to have quite different properties from externally heated plasmas. The point has been reached, according to supporters, where answering these questions about fusion reactors by experiment (via ITER) is an economical research investment, given the monumental potential benefit.

Furthermore the main line of research—the tokamak—has been developed to the point that it is now possible to undertake the penultimate step in magnetic confinement plasma physics research—the investigation of ‘burning’ plasmas in which the vast majority of the heating is provided by the fusion event itself. A detailed engineering design has been developed for a tokamak experiment which would explore burning plasma physics and integrate reactor relevant technology. In the tokamak research program, recent advances in controlling the internal configuration of the plasma have led to the achievement of substantially improved energy and pressure confinement in tokamaks—the so-called ‘advanced tokamak’ modes—which reduces the projected cost of electricity from tokamak reactors by a factor of two to a value only about 50% more than the projected cost of electricity from advanced light-water reactors. In parallel, progress in the development of advanced, low activation structural materials supports the promise of environmentally benign fusion reactors, and research into alternate confinement concepts is yielding promise of future improvements in confinement.

Finally, supporters point out that other potential replacements to the current use of fossil fuel sources have environmental issues of their own. Solar, wind, and hydroelectric power all have a relatively low power output per square kilometer compared to ITER's successor DEMO which, at 2000 MW, should have an energy density that exceeds even large fission power plants.

Assessment of the vacuum vessel

ITER has decided to ask AIB-Vinçotte International (an inspection organisation located in Belgium and accredited by the French Nuclear Authorities ASN) to assess the confinement (vacuum) vessel, heart of the project, following the French Nuclear Regulatory requirements.

The Vacuum Vessel is the central part of the ITER machine: a double walled steel container in which the plasma is contained by means of magnetic fields.

The ITER Vacuum Vessel will be the biggest fusion furnace ever built. It will be twice as large and 16 times as heavy as any previously manufactured fusion vessel: each of the nine torus shaped sectors will weigh between 390 and 430 tonnes. When all the shielding and port structures are included, this adds up to a total of 5,116 tonnes. Its external diameter will measure 19.4 m, the internal 6.5 m. Once assembled, the whole structure will be 11.3 m high.

The primary function of the Vacuum Vessel is to provide a hermetically sealed plasma container. Its main components are the main vessel, the port structures and the supporting system. The main vessel is a double walled structure with poloidal and toroidal stiffening ribs between 60 mm thick shells to reinforce the vessel structure. These ribs also form the flow passages for the cooling water. The space between the double walls will be filled with shield structures made of austenitic stainless steel which is corrosion resistant and does not conduct heat well.The inner surfaces of the vessel will be covered with blanket modules. These modules will provide shielding from the high-energy neutrons produced by the fusion reactions and some will also be used for tritium breeding concepts.

The Vacuum Vessel has 18 upper, 17 equatorial and 9 lower ports that will be used for remote handling operations, diagnostic systems, neutral beam injections and vacuum pumping.