In a project of this unprecedented scale, involving worldwide cooperation and billions of euros of expenditure, it would be naïve to believe that there could be unanimity in the scientific community on the aims and the scientific and technical basis of the project. A scientific consensus may be possible while discussions remain at the abstract level, but in a world of intense competition for research funding it is inevitable that scientists from various fields will criticize the decision to spend money on a large project, arguing that they would prefer to spend the money elsewhere.

What can be said about ITER is that for the scientific community working in the energy field, this project is considered by a strong majority as a major step that may provide a future energy alternative for all humankind. The present political and scientific approach to this project has not suddenly appeared out of lobbying by a few influential individuals. It is the result of decades of painstaking, step-by-step research by fusion scientists all over the world as well as intense discussions in the scientific administrations of involved governments who have debated the options, the costs and the risks and decided that the ITER project is a worthwhile investment in our common energy future. The proportion of papers directly concerned with ITER presented at leading international scientific conferences on fusion as well as in fusion journals has been steadily increasing for a number of years. The fact that research aimed at ITER is now such a dominant topic in these papers demonstrates how essential the project is to the advancement of fusion towards energy production.

Fusion research, and the role of ITER, has been subject to serious scrutiny by panels of independent experts established by funding agencies in Europe and most of the other ITER partners. The results of these investigations provide the most reliable measure of consensus in the scientific community. A few examples:

• In 2004 during the early stages of ITER negotiations, a high-level panel chaired by Sir David King (Chief Scientific Advisor to the UK government) concluded that the time was right to press ahead with ITER and recommended funding a "fast track" approach to fusion energy.

• The French Academy of Sciences organized a detailed review of the state-of-the-art and the remaining challenges of fusion both by magnetic confinement (including ITER) and using laser-driven systems. The review was published in a book in 2007 which emphasised the arguments supporting the construction of ITER.

• The United States went through a long process to decide to re-enter the ITER collaboration, after leaving it in the late 1990s. The US National Academy of Sciences convened a panel which included both fusion scientists and senior scientists from related fields such as nuclear fission power, high-energy physics and astrophysics. The non-fusion scientists were empowered to make the key recommendations. The panel strongly endorsed the renewed membership of the US in the ITER project as the best path forward to fusion energy.

The main answer to this question comes from the nature of these two sciences and their technological applications. In terms of complexity (in both science and technology), there is more than one order of magnitude of difference between fusion and fission.

On the physics side, the core science of fusion is plasma physics, which is highly complex due to its non-linear and stochastic processes. The mastery of the physics is not yet sufficient to enable the construction of a fusion power plant, which requires cutting-edge technologies like superconductivity, high vacuum, and cryogenics. An important mission of ITER is to prove once and for all that it is possible to integrate all these technologies into a single device. The technologies for fission, on the other hand, have evolved over generations of fission machines.

The next decades are crucially important to putting the world on a path towards much reduced greenhouse gas emissions. Current and near-term technologies should be deployed as soon as possible for this purpose. However world population will continue to grow and the proportion of populations living in cities is expected to continue to increase. Together with the need for a more equitable distribution of energy among the world's inhabitants, this means that even more large-scale, low-CO₂ sustainable energy will be needed later in the century. Fusion is a strong candidate.

Fusion is one of the few alternatives available for large-scale energy production and ITER is a major step, necessary to the demonstration of the physics and technology on the way to fusion power plants. Achieving success in ITER will not lead immediately to the building of fusion power plants; another step, usually called DEMO (DEMOnstration fusion power plant) will be necessary. Building on the knowledge and know-how acquired within ITER and parallel research, DEMO will mark the transition to the deployment of fusion energy systems.

The timescale to commercial fusion therefore extends until at least the middle of this century, depending strongly on the political will to invest in this area of research. Lev Artsimovitch, the famous Russian academician and one of the major figures in fusion history, used to say: "Fusion will be ready when society needs it."

Of the "magnetic confinement concepts" for fusion (mainly tokamaks and stellarators) the main advantage of ITER and its tokamak technology is that for the time being, the tokamak concept is by far the most advanced toward producing fusion energy. It is consequently pragmatism that dictated the choice of the tokamak concept for ITER. Stellarators are inherently more complex than tokamaks (for example, optimized designs were not possible before the advent of supercomputers) but they may have advantages in reliability of operation. The W7-X Stellarator, presently under construction in Greifswald, Germany, will allow good benchmarking against the performance of comparable tokamaks. These results will be incorporated in decisions about how DEMO, the next-generation fusion device after ITER, will look.

The "inertial fusion concepts" are something quite different. These technologies have mainly been developed to simulate nuclear explosions and were not originally planned to produce fusion energy. The inertial fusion concept has not demonstrated so far that it offers a better or shorter path than magnetic confinement to energy production. In Europe, the Euratom Framework Programs do not fund research on inertial fusion, but the program maintains a "watching brief" on developments.

The first small-size tokamaks (1950s-1970s) were basic devices without sophisticated control systems and technology, but they demonstrated that high temperature plasmas could be generated and that energy could be confined. New plasma phenomena, such as anomalous transport, instabilities, and disruptions, were uncovered during these first experiments. Scaling laws indicated that energy confinement could be increased in larger devices with higher magnetic fields.

The second-generation, medium-sized devices in the 1980s introduced the extensive use of auxiliary heating techniques. The addition of the divertor demonstrated improved confinement; wall conditioning techniques were also introduced. The ASDEX Tokamak achieved high confinement mode for the first time in 1982.

A new generation of larger tokamaks—JET (Europe), JT-60 (Japan), TFTR (US) and T-15 (Soviet Union)—were built to study plasmas in conditions as close as possible to those of a fusion reactor, and regularly upgraded based on advances in fusion science. New features such as superconducting coils, deuterium-tritium operation, and remote handling were introduced. The experience accumulated on these machines contributed to the design of ITER.

Today, fusion research is at the threshold of exploration of a "burning plasma" in which sufficient heat from the fusion reaction is retained within the plasma and sustains the reaction for a long duration. Such exploration is a necessary step toward the realization of a fusion energy source; it must be done to establish the confidence in proceeding with demonstrations of practical fusion energy. Construction of ITER and implementation of the ITER research program would provide for such exploration.

The earthquake and tsunami in Japan on 11 March 2011 affected some of the installations producing components for ITER. In particular, the buildings for superconducting magnet test equipment and neutral beam test equipment were seriously damaged. In its intial assessment, the Japanese government estimated at one year the delay in its contribution of key components.

The ITER Organization did everything possible within the scope of its mandate to minimize the impact of the Japanese disaster on the ITER project schedule. With effort and ingenuity, and strong support from the ITER Domestic Agencies, the delay in First Plasma was contained to one year. The revised date for First Plasma—November 2020—remains within the boundaries of the ITER Baseline approved in July 2010 by the ITER Council.

The date for First Plasma is November 2020. Full deuterium-tritium operation is scheduled for March 2027. ITER Organization and Domestic Agency schedule milestones leading up to these dates are reviewed on a monthly basis and strategies developed to catch up lost time where necessary.

It took three years to adapt the roads, bridges and roundabouts of the 104 kilometre ITER Itinerary to the needs of the exceptional convoys that will transport ITER components arriving by sea. Two test convoys will be organized in 2013 on the French heavy haul Itinerary from Berre to Cadarache before the arrival of the first loads in 2014. 

Between 2014 and 2017, exceptional convoys will travel by night at reduced speeds along the ITER Itinerary with their extra-large cargo. The heaviest? 900 tons. The tallest? 10 metres. The widest? 9 metres. The longest? 61 metres. We're expecting each one of these exceptional convoys to be quite a local event.

ITER will be built collaboratively by the seven ITER Members.

During the Construction Phase of the project, Europe has responsibility for approximately 45.5 percent of construction costs, whereas China, India, Japan, Korea, the Russian Federation and the United States will contribute approximately 9.1 percent each. The lion's share (90 percent) of contributions will be delivered "in-kind." That means that in the place of cash, the Members will deliver components and buildings directly to the ITER Organization.

The in-kind contributions of the ITER Members have been divided into approximately 140 Procurement Arrangements. These documents detail the technical specifications and management requirements for the procurement of plant systems, components or site construction. The value of each Procurement Arrangement is expressed in ITER Units of Account (IUAs), a currency devised to measure the value of in-kind contributions to ITER consistently over time.

Procurement allocations were assigned among the Members on the basis of valuations of components. Upon successful completion of a component, the corresponding credit value is credited to the Members' account. Contributing 9.1 percent of the project, therefore, becomes a matter of adding up the IUA value of the different contributions.

For the Operation Phase (roughly 2019-2037), the sharing of cost amongst the Members will be as follows: Europe 34 percent, Japan and the United States 13 percent, and China, India, Korea, and Russia 10 percent.

ITER Construction will be managed within an agreed capped ceiling of 4,700 kIUA (ITER Unit of Account in thousands). This construction cap is based on the ITER Baseline adopted in July 2010 by the ITER Council and cannot be exceeded.

Because multiple Members are collaborating to build ITER, each with responsibility for the procurement of in-kind hardware in its own territory with its own currency, a direct conversion of the value estimate for ITER construction into a single currency is not particularly relevant. The ITER Unit of Account was created as part of the ITER Agreement to equitably allocate the value of in-kind hardware procurement to each Member.  

For reference, the European Union has estimated its global contribution to the costs of ITER construction at EUR 6 billion. Other Domestic Agencies' contributions depend on the cost of industrial fabrication in those Member states, which can be higher or lower, and their percentage contribution to construction of ITER.

Based on the European evaluation, we can estimate the cost of ITER construction for the seven Members at approximately EUR 13 billion, if all the manufacturing was done in Europe. As production costs vary from Member to Member, it is impossible to furnish a more precise estimation.

ITER is financed by seven Members: China, the European Union (plus Switzerland, as a member of EURATOM), India, Japan, Korea, Russia and the United States. In all, 34 countries are sharing the cost of the ITER project.

For the other phases of the ITER project the cost estimates have not changed. Operation of the ITER installation during its experimental lifetime (2019—approximately 2037) is estimated at 188 kIUA per year. For the Deactivation (2037—2042) and Decommissioning phases, the costs have been established in euros at EUR 281 million and EUR 530 million respectively (EUR in 2001 values).

France contributes to the ITER project as a member of the European Union. This contribution, representing approximately 20 percent of the European budget, was estimated at EUR 1.1 billion for the ten-year Construction Phase. In addition, as Host to the ITER project, France has undertaken a number of specific commitments: providing a site for the project and carrying out all preparatory works including clearing and levelling, fencing, and networks for water and electricity; creating an international school for the families of ITER employees; and adapting the roads along the ITER Itinerary for the transport of ITER components.

Currently, France is building the ITER Headquarters in conjunction with Europe. At the end of the ITER experimental phase, France will also have the responsibility for the dismantling and decommissioning of the site.

Local government has been strongly implicated in the ITER project from the start on the basis of voluntary contributions. The General Councils from the six départements closest to ITER (Hautes Alpes, Alpes de Haute Provence, Alpes Maritimes, Vaucluse, Var and Bouches du Rhône)—together with the Provence-Alpes-Cote d'Azur (PACA) Regional Council and the Communauté du Pays d'Aix—have accepted to contribute a total of EUR 467 million over the ten-year Construction Phase of the ITER project.

This contribution is on par with the contracts and employment that have already been generated in the area by the ITER project. Contracts totalling EUR 1,420 million have been attributed to French companies; 65 percent of these (worth EUR 927 million) were attributed to companies based in the PACA region (statistics dated 31 December 2012).

Since 2007, 1,200 people have worked on the preparation of the ITER site, the construction of the Provence-Alpes-Côte d'Azur International School, and the ITER Itinerary. Today, approximately 1,000 people work for the ITER Organization in Cadarache (ITER staff, contractors, temporary agents, European Domestic Agency staff and subcontractors); these employees contribute, with their families, to the economic life of the region.

Between 2014 and 2017, the construction and assembly of the ITER site will require an additional 3,000-4,000 workers.

The original cost estimate of ITER was based on a 2001 design. In 2008, a detailed design review called for modifications to the machine based on advancements in fusion science; these modifications added to overall cost. Also, the number of ITER Members passed from four to seven, contributing to a larger number of interfaces within the design. Another important element of the cost increase: building construction costs have increased significantly since 2001. Raw material costs have doubled (steel) or tripled (concrete).

It is estimated that the costs of the ITER Organization in Cadarache have risen by 67 percent. This increase can be approximately attributed as follows: 29 percent due to finalization of the design; 24 percent due to extension of the schedule resulting from the increased design effort; 8.5 percent due to increased costs associated with machine assembly; and 5.5 percent due to hardware changes related to scientific developments.

The interinstitutional agreement between the European Union (EU) Council and the European Parliament that is presently in force defines the multiannual financial framework until 2013 and caps the amounts devoted to major categories of spending. Unfortunately, this agreement on ITER financing was based on the initial estimates of EUR 2.7 billion for the EU contribution during the construction period, and therefore did not include funding for the additional ITER needs identified during 2010. This multiannual agreement had to be modified by the Council and the European Parliament in 2011.

The European Union (EU) budget for 2011 was adopted by the European budgetary authority and included the required funding of the EU contribution to ITER in 2011. In December 2011, the EU agreed to allocate to ITER the additional funding of EUR 1.3 billion required for 2012-2013.

For the long-term financing beyond 2013, the EU Council has so far acknowledged the overall cost of the EU contribution to ITER construction and has capped the EU contribution at EUR 6.6 billion for the period 2007-2020, including all the F4E costs (running costs and other activities) and the contribution of the Host state. On 21 December 2011, the European Commission proposed to fund the EU contribution to ITER outside the Multiannual Financial Framework (i.e., the EU budget) after 2013. However, on 8 February 2013 the European Council reached an agreement to reintegrate ITER into the Multiannual Financial Framework.

It took several years to achieve the licensing of ITER as an "Installation Nucléaire de Base" under French law.

• The ITER Organization submitted the Preliminary Safety Report in March 2010 to the French Nuclear Safety Authority, which allowed the technical examination of the ITER safety files to begin;

• The French Environmental Authority, whose opinion on ITER's nuclear licensing files is required in accordance with the EEC Directive 97/11/EC of 3 March 1997 on Environmental Assessments, delivered its opinion on 23 March 2011. The opinion was favourable and included several recommendations to be taken into account by the ITER Organization;

• The Public Enquiry was held locally in the communes surrounding Cadarache from 15 June-4 August 2011. On 9 September 2011 the Public Enquiry Commission issued a favourable Advisory Opinion;

• The technical examination of the files by the Institute of Radioprotection and Nuclear Safety (IRSN), acting as the ASN's technical expert, began during the summer of 2010. In September 2011 the IRSN submitted a 300-page report—including 800 questions to the ITER Organization—to a group of 30 experts appointed by ASN, the Groupe Permanent. The Groupe Permanent issued a favourable report at the end of 2011.

• The ITER Organization was informed in writing by the French safety authorities (ASN) on 20 June 2012 that, following an in-depth technical inspection, the operational conditions and the design of ITER as described in the ITER safety files fulfilled expected safety requirements at this stage in the licensing process. Following this, the draft decree was communicated by the ASN to the French government for signature.

• On 10 November 2012, the French Prime Minister Jean-Marc Ayrault signed the official decree that authorizes the ITER Organization as an "Installation Nucléaire de Base."

ITER is the first nuclear installation in France to observe the stringent requirements of the 2006 French law on Nuclear Transparency and Security. It is also the first time in worldwide history that the safety characteristics of a fusion device have undergone the rigorous scrutiny of a Nuclear Regulator to obtain nuclear licensing. ITER has achieved an important landmark in fusion history.

Following the nuclear accident at the Fukushima Daiichi Power Plant, the European Union declared "that the safety of all 143 nuclear power plants [in Europe] should be reviewed on the basis of a comprehensive and transparent risk assessment." These assessments are known as stress tests.
 
As the first fusion reactor to undergo full nuclear licensing, the French safety authorities have requested that ITER also pass this complementary safety assessment.
 
As a first step, the ITER Organization drafted a report on the methodology of the stress tests, which was approved. The ITER Safety, Quality & Security Department then carried out the stress test evaluation and provided a nuclear safety stress report to the French safety authorities on 15 September 2012.

Taking into account the current content of the request from the regulator and the robustness of the ITER safety design, this stress test report should not lead to additional cost.

Although 100 million degrees Celsius is an extremely high temperature, the density of the plasma (atoms per cubic metre) is very low—about one million times less than air—and the total energy in the plasma is not very great. The very rapid release of the energy could cause superficial damage to some plasma-facing components (i.e., surface melting) but would not be sufficient to produce structural damage.

Cadarache is classified as an area of moderate seismic activity: in application of the French regulation and based on the geological analysis of the area, the ITER project and the French authorities have decided to ensure that the ITER facility is designed to resist an earthquake of amplitude 40 times higher and energy 250 times higher than any earthquake for which we have historical references in the area.

The ITER Tokamak Building will be made of specially reinforced concrete, and will rest upon bearing pads, or pillars, that are designed to withstand earthquakes. This technology has been used to protect other civil engineering structures such as electrical power plants from the risk of earthquake, and to ensure that their behaviour in the case of earthquake satisfies safety requirements. The ITER facility will be equipped with seismic sensors around the site to record all seismic activity, however minor.

The ITER design takes into account external hazards in accordance with French regulation and practices. The Preliminary Safety Report submitted by the ITER Organization to the French licensing authorities includes an in-depth analysis of external hazards. Extreme weather conditions such as hot, cold, wind, snow, rain and flooding are taken into account as well as lightning and forest fire. The analyses of man-made hazards include the consequences of events such as aircraft crashes, and part of the Preliminary Safety Report is dedicated to providing evidence of ITER safety even against malevolent acts.

To define the safety requirements of the buildings, the maximum height of water due to dam failures as a result of extreme rainfall was taken into account. In this hypothetical situation, more than 30 m remains between the maximum height of the water and the first basemat of the nuclear buildings.

Only a small fraction of the tritium in the tokamak is actually consumed during a plasma burn. Tritium will be separated from the exhaust gases pumped from the tokamak vessel, purified, and stored for reuse. The effectiveness of tritium removal from the room atmosphere and from the liquid effluents and recovery during tritium plasma operation is independent of the fusion performance of the tokamak. The design is based on a scenario in which no tritium is burned but it is all returned from the tokamak vessel to the recovery system.

Many provisions are implemented into the design to avoid losses of tritium. An efficient static confinement barrier will be installed in the areas where tritium is handled and air pressure cascading in the buildings will inhibit the outward diffusion of tritium. The static and dynamic confinement systems as well as radiological and environmental monitoring will be available for several years before tritium is put in the machine (i.e., from the beginning of the deuterium-deuterium phase of operation). Even the small amounts of tritium generated during deuterium-deuterium operation will be removed and eventually recovered through fuel cycle processing systems.

Tritium will be stored as metal hydride (i.e., chemically bound to a metal) in dedicated vessels, so-called metal hydride beds. Metal hydride beds are very efficient for tritium collection and provide a safe way of storing tritium. Only the amounts necessary for operation of the fuel cycle will be liberated from the metal hydride beds. The confinement performance of these beds will follow a very strict qualification program. Losses in these storage beds will only be due to the natural radioactive decay of tritium (half the tritium decays into inert helium every 12.3 years).

ITER has implemented not only state-of-the-art confinement methodologies but also above-and-beyond technologies to provide removal and recovery of tritium for the very unlikely event of tritium spilled into rooms. Control of stock is maintained is through a tritium tracking procedure and regular inventory measurements. Security measures will be in place to protect the tritium in stock.

The maximum amount of tritium in the facility will be set by the French safety authorities, and will not exceed 4 kg. The actual amount in ITER at any time will be determined by operational needs based on the ITER Research Plan.

The ITER design is such that, even if the containment were accidentally to be breached in the tokamak, the levels of radioactivity outside the ITER enclosure would still be very low. The ITER Preliminary Safety Report presents an analysis of risks and events that may cause accidents in the facility.  During normal operation, ITER's radiological impact on the most exposed populations will be one thousand times less than natural background radiation and in "worst-case scenarios" such as fire in the tritium plant, evacuations or other countermeasures for the neighbouring populations would not be required.

The safety analyses presented in the Preliminary Safety Report of ITER take the complete surroundings into account, including all installations, either nuclear or conventional, that could have an influence on ITER. These studies show that ITER safety will not be impacted by accidents occurring in surrounding installations.

In a tokamak fusion device, the quantity of fuel present in the vessel at any one time is sufficient for a few-seconds burn only. It is difficult to reach and maintain the precise conditions necessary for fusion; any disruption in these conditions and the plasma cools within seconds and the reaction stops, much in the same way that a gas burner is extinguished when the fuel tap is turned off. The fusion process is inherently safe; there is no danger of run-away reaction or explosion.

No! What happened in the fission reactors on the northeast coasts of Japan following the severe earthquake and subsequent tsunami cannot happen at ITER. This is due to the fundamentally different physics and technologies used in fission and fusion reactors.

In a fusion reactor, there will only be a very limited amount of fuel inside the reactor at any time. The ITER fuel is a gaseous mixture, a plasma of deuterium and tritium. In order to maintain the fusion reaction we rely on the continuous supply of fuel. If the fuel supply is interrupted for any reason, the fusion process stops immediately. There is absolutely no danger of a nuclear meltdown or a runaway reaction.

Moreover, loss of the cooling function due to an earthquake would not affect the confinement barrier at all. Even in the case of the total failure of the water cooling system, ITER's confinement barriers will remain intact. The temperatures of the vacuum vessel that provides the confinement barrier would under no circumstances reach the melting temperatures of the materials.

It's true that continued cooling is required in a fission reactor because even after shutdown there is a substantial decay heat to be eliminated that is produced by the fission decay of the tons of nuclear fuel in the vessel.

In ITER or in future fusion power plants, this kind of scenario is impossible. The thermal power induced in the ITER vacuum vessel will be low. Even if no active cooling of the vacuum vessel is provided, as in the case of total failure of the cooling system, the resulting temperature would not threaten the integrity of the vacuum vessel.

Physicists have been exploring the properties of plasmas within tokamak devices since the 1960s. It is well known that beyond certain operational boundary conditions—for example, when plasma current or pressure or density is raised too high for a given magnetic field—the plasma can become unstable.

A disruption is an instability that may develop within the tokamak plasma. Disruptions lead to the degradation or loss of the magnetic confinement of the plasma; because of the high amount of energy contained within the plasma, the loss of confinement during a disruption can cause a significant thermal loading of in-vessel components together with high mechanical strains on the in-vessel components, the vacuum vessel and the coils in the tokamak.

In some cases, because of the large electric fields created during the disruptions, a relativistic electron beam (containing 'runaway electrons') forms that can penetrate several millimetres into the in-vessel components when it is eventually lost from the plasma.

Unless mitigating action is taken, plasma-facing components can suffer local damage due to the thermal loads and to the deposition of runaway electrons during disruptions. In addition, in extreme cases, the mechanical strains on the components during disruptions may cause some deformation.

Disruptions are not triggered randomly; they only occur when well-defined limits are exceeded. Disruptions have been observed, avoided and mitigated in most operating tokamaks. One of ITER's objectives is to perfect a stable operating scenario through experimentation so that disruptions become a relatively rare event. During the first years of operation, ITER operators will most likely deliberately provoke disruptive events. Their aim will be to analyze, and to learn to control, these events at reduced plasma parameters and low plasma energy so that disruptions cannot cause damage to the ITER components in experiments at the highest plasma current and energy. 

By "pushing" the machine toward disruptions at modest plasma parameters, ITER operators will find its stability boundaries. Once these stability limits have been identified, there is no reason for plasmas in the ITER Tokamak to become disruptive spontaneously as the plasma current and plasma energy is increased, provided that this is done within the stability region identified.

There is abundant literature on the subject of disruptions (see, in particular, Nuclear Fusion) and on the operational strategies to avoid disruptions and to mitigate their effects when they cannot be avoided.

Disruptions are an integral part of the official (and public) physics basis for ITER, which has been extensively refereed by the scientific community ("ITER Physics Basis," Nuclear Fusion, 47; 2007 complemented the initial 1999 report). Disruptions represent an active field of research in the fusion community in order to perfect the avoidance and mitigation schemes being developed for ITER.

The European tokamak JET and the French tokamak Tore Supra, as well as many others in the world, have been operated in a completely safe and satisfactory manner since 1983 and 1988 respectively. When exploring new plasma regimes, or during dedicated experiments to study disruptions and their mitigation, disruptions can occur several times a day in these two machines and others, but they have never led to the destruction or rupture of their vacuum vessels.

Because disruptions are expected in ITER, they have been planned for. The ITER vacuum vessel and in-vessel components have been designed to withstand the forces produced by about 3,000 disruptions at full plasma performance over the course of their lifetime. ITER's resistance to disruptions is based on scaling laws ("engineering laws") that have determined the values chosen for ITER; these values have been validated by experiments on other tokamaks.

It is important to understand that disruptions are not a safety-class issue for ITER: there is absolutely no risk for the integrity of the vacuum vessel. But as the high energy loads during disruptions can, over time, damage the surface of plasma-facing components such as divertor targets and first wall panels, these components may need—and have been designed—to be replaced. This takes time and reduces the availability of ITER for experiments. It is, therefore, important to develop disruption mitigation techniques that reduce the forces and the energy loads on ITER's components so that the time between interventions to replace these components is as long as possible, thereby optimizing the scientific exploitation of ITER.  

During the progressive commissioning of ITER, the machine will be tested with plasma currents and plasma energies lower than the nominal values required for fusion energy production. In this way, the potential degradation of ITER's components by disruptions during this initial learning phase will be minimized. We will begin with low current and low-energy plasmas to learn how to avoid and mitigate the effects of disruptions on ITER before moving on to more advanced operational scenarios with higher currents and higher energies (thus larger forces and energy loads on components).

This ITER strategy is not radically different from that already followed in the operation of the largest existing tokamak JET, which achieved plasma currents of 6-7 MA, as compared to the 15 MA nominal plasma current planned in ITER.

In summary, the ITER engineering design allows for disruptions to occur in approximately 10 percent of plasma pulses. The early, low-energy/low-plasma-current phase of ITER will permit physicists to characterize disruptions on ITER without risks to the machine. Disruption mitigation is one of the specific scientific missions of ITER, with direct relevance to the future development of fusion power plants based on the tokamak concept.

ITER's Disruption Mitigation System (DMS) is currently in its design phase. In determining the best method, or combination of methods, for disruption mitigation, the ITER Organization is taking into account performance, reliability, flexibility, and cost.

Two promising methods are on the table that will be further refined in the coming months and years for ITER scenarios. Massive gas or pellet injection—in which massive amounts (up to 500 g) of particles or gas are introduced into the plasma within 10 milliseconds—has been demonstrated to disperse the energy of a disruption before it can concentrate its load on the wall of the containment vessel. These are well-known techniques, but none of them has yet been demonstrated on the ITER scale and environment.

An R&D program in disruption mitigation for ITER is currently underway. Experiments run on the ASDEX Upgrade (Germany), Tore Supra (France), DIII-D (US), and JET (EU), to cite a few of the tokamaks involved in this research, are contributing to the refinement of predictions for disruption mitigation in ITER. The ever-increasing capability for numerical simulation of disruptions is also being applied in the elaboration of the ITER disruption mitigation strategy.

The Disruption Mitigation System in ITER will function automatically, triggered as disruptions occur during plasma pulses by dedicated sensors and algorithms that can evaluate the likelihood of an impending disruption. With at least 10 pulses planned per day during operational phases, and disruptions expected in approximately 10 percent of these, it is accurate to say that the Disruption Mitigation System will operate routinely—probably daily—during operation, at least during the initial phases as the ITER operational scenarios are being developed.

ITER, as operator, will bear the financial responsibility for the temporary and final storage of operational radioactive waste. The host state France will be in charge of the dismantling phase and the management of the waste resulting from this dismantling; the cost for these activities will be provisioned by ITER during the operation phase. France will also be responsible for providing temporary storage for part of the operational waste, pending its final disposal; this will be financed through ITER operation cost.

Electrical supply to the ITER site will be assured by an existing network that feeds the Tore Supra Tokamak—part of the adjacent CEA Cadarache research facility. The French electricity provider RTE completed a 4-hectare switchyard on the ITER platform and the connection to the main network in June 2012. Operating the ITER Tokamak will require from 120 MW to up to 620 MW of electricity for peak periods of 30 seconds. No disruption to local users is expected.

Concerning water supply, approximately 3 million cubic metres of water will be necessary per year during the operational phase of ITER. This water will be supplied by the nearby Canal de Provence, and transported by gravity through underground tunnels to the fusion installation. The volume of water needed for ITER represents only 1 percent of the total water transported by the Canal de Provence. The combined effect of the ITER installation and the adjacent CEA facilities remains below 5 percent of the total volume of water transported by the Canal de Provence.

Nuclear fusion reactors produce no high activity/long life radioactive waste. The "burnt" fuel is helium, a non-radioactive gas. Radioactive substances in the system are the fuel (tritium) and materials activated while the machine is running. During the operational lifetime of ITER, remote handling will be used to refurbish parts of the vacuum vessel.  All waste materials will be treated, packaged, and stored on site. The half-life of most radioisotopes contained in this waste is lower than ten years, which means that within 100 years, the radioactivity of the materials will have diminished in a significant way.  This time span of 100 years could possibly be reduced for future devices through the continued development of 'low activation' materials, which is an important part of fusion research and development today.

Maintenance waste during ITER operation will amount to about 1,200 tons over 20 years. Upon the dismantling of the ITER installation, the waste that will be removed and processed will be composed 90 percent of very low level or low and intermediate level short-lived waste. After 100 years of natural decay, ITER will be left with about 6,000 tons of waste (packaged, that is equivalent to a cube with edges measuring 10 m). 

The irradiated material will be transferred within a confinement cask to enclosed, shielded compartments ("hot cells"). Inside the hot cells several operations will be performed, such as cleaning and dust collection, detritiation, refurbishment, and disposal. The waste, which is classified as medium level, will be stored in the ITER hot cells. All of these procedures are a part of the ITER operation as presented in the Preliminary Safety Report, and consequently are also submitted to examination of the French Nuclear Safety Authority as part of the licensing process.

The fusion scientific community has an experience of more than twenty years operating large superconducting magnets, i.e., Large Helical Device (Japan), Tore-Supra (France).

Any loss of superconductivity is easily detected, and safety circuits place external resistors in series with the coils to absorb the stored energy. If the safety system and its backups were to fail the coils might suffer damage, but there is no possibility of threat to the integrity of the first confinement barrier.

All the conceptual power plant studies performed in the European fusion program have shown that the commercial deployment of fusion would not be limited by the availability of fuels and raw materials. Deuterium fuel and lithium (the raw material for tritium fuel, which is produced by fusion neutrons interacting with lithium), are both widely distributed on Earth:

deuterium is a naturally occurring isotope of hydrogen, available in water and easily extracted from it;

lithium from proven, easily extractable resources would provide a stock sufficient to operate fusion power plants for more than 1,000 years (each fusion plant would need only about 3 tons of lithium per year). Worldwide resources of lithium are presently estimated at 25 million tons and studies have shown that competition with other uses, such as batteries, will not be an issue.