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.

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.

ITER (the Latin word for "the way") is a large-scale scientific experiment intended to prove the viability of fusion as an energy source. ITER is currently under construction in the south of France.  In an unprecedented international effort, seven partners—China, the European Union, India, Japan, Korea, Russia and the United States—have pooled their financial and scientific resources to build the biggest fusion reactor in history. ITER will not produce electricity, but it will resolve critical scientific and technical issues in order to take fusion to the point where industrial applications can be designed. By producing 500 MW of power from an input of 50 MW—a "gain factor" of 10—ITER will open the way to the next step: a demonstration fusion power plant.

On-site construction of the scientific facility began in 2010. In addition to the start of building construction, the project has made the transition from design to the fabrication of large-scale mock-ups and components. Beginning in mid-2014, the shipment of large components will begin from manufacturing sites throughout the world to the construction site in France where they will be assembled into the ITER device.

ITER is one of the most complex scientific and engineering projects in the world today. The complexity of the ITER design has already pushed a whole range of leading-edge technologies to new levels of performance. However, further science and technology are needed to bridge the gap to commercialization of fusion energy.

The choice was made from the beginning to share the manufacturing of the most strategically important components among the seven ITER Members. This has considerably added to the complexity of the Project, but the reasons for this decision were clear—by participating in ITER, each Member is preparing its industrial infrastructure, its scientific base, and its physicists and engineers for the next step on the road to fusion power, the construction of a demonstration fusion power plant.

It seems clear that no one Member has the financial and technical resources to build ITER alone. In this sense, by contributing only a portion of the Project's costs, each Member benefits from the totality of the development program (where, already, there have been discoveries in technology, materials, science and even the first applications for patents) and later the totality of the 20-year experimental program. 

Collaboration and coordination between the different entities of the Project are improving all of the time. What is remarkable about fusion research is that, for a very long time, it has been an international, collaborative venture where discoveries in one area of the world immediately benefit other research programs. This is true every day at ITER, where the Project benefits from the diverse experiences of its Members, including research underway on operational tokamaks in different parts of the world.

If ITER were only a construction project, its model would certainly have been organized differently. But as the world's largest and most challenging energy research project, the collaboration between seven ITER Members—all with decades of experience in fusion—has been most profitable in terms of pooling resources to solve the difficult challenges that remain on the road to fusion.

Recently, the ITER management implemented more efficient cooperation among the ITER Organization and the seven Domestic Agencies—the so-called Unique ITER team—in order to achieve faster decision making and improved work performance.

ITER is the experimental step between today's fusion machines, focused on plasma physics studies, and tomorrow's fusion power plants.

The plasma physics community will have access, in ITER, to a one-of-a-kind device capable of plasma pulses of a much longer duration than those achieved in other fusion devices. ITER will be twice as large as the largest fusion experiment currently operating, JET (UK), with ten-times the plasma volume. This unique experimental machine has been designed to:

• produce 500MW of fusion power (Q=10)
• confine a deuterium-tritium plasma in which alpha-particle heating dominates
• demonstrate the integrated operation of technologies for a fusion power plant
• test components required for a fusion power plant
• test concepts for a tritium breeding module

Today, fusion research is at the threshold of exploring 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. Scientists are confident that the larger, hotter plasmas of ITER will not only produce much more fusion power, but will remain stable for long periods of time. The scale of ITER is necessary to break new ground in fusion science.

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 target 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.

Soon!

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? 33 metres. We're expecting each one of these exceptional convoys to be quite a local event.

A test convoy will be organized from 16-20 September 2013. For four consecutive nights, a dummy load made of 360 concrete blocks (800 tons) will travel the full length of the 104-kilometre ITER Itinerary.

The roads, bridges and roundabouts of the Itinerary were modified by France to meet the needs of the exceptional convoys that will transport ITER components arriving by sea. A second test convoy will be organized to test transport logistics, before the arrival of the first loads in 2014. 

For a project of such unprecedented nature and scale, involving worldwide cooperation and billions of euros of expenditure, challenges to the schedule along the way can be expected. It certainly took longer to build up the ITER Organization—and establish world-class systems for managing the project—than was originally foreseen.

Because the ITER Organization and the Domestic Agencies all have equal stakes in completing the ITER Project on time and within budget, strong measures have been set into place to track schedule performance. For critical areas, specific recovery actions are formulated and adopted.

The ITER Organization identified the following impediments to optimal schedule performance: delays in the signature of agreements and contracts, lengthy design review and design change processes, and complex approval procedures for nuclear components. Corrective actions are possible to improve performance in all of these areas.

First experiments are still seven years away. By working together, the ITER Organization and the Domestic Agencies have pledged to remain within the "schedule envelop" approved as part of the ITER Baseline in 2010 (the bottom-line document that details ITER's scope, schedule and cost). This envelop foresees to start the first experiments between November 2019 and July 2021, and Deuterium-Tritium operations in 2027.

First of all, we are working to improve the cooperation among the Members and between the Members and the ITER Organization in order to sort out the problems and accelerate the decision process. The establishment in the summer of 2012 of an integrated body (the Unique ITER Team) that associates the management of the ITER Organization and that of the Domestic Agencies was a decisive step in this direction. Through close collaboration and close tracking of the schedule, solutions are being sought to improve manufacturing performance for the systems and components required for the first experiments. Close collaboration with industry, for example, has already resulted in the recovery of some delay.

Quality control is also essential—we have to make sure all the components will fit and work together. Within the ITER Organization, there is a team dedicated to quality assurance (QA) and quality control (QC). Its members help oversee and ensure that the proper QA/QC practices are implemented at companies manufacturing the reactor's components.

Having the best talent on board is also crucial; the ITER Organization has set up a very efficient international recruitment process.

As in every large project, delays may cause cost increases. Because the budget for ITER Construction has been capped, management is seeking cost savings to offset potential increases—whether these increases are due to delay in the schedule or other unforeseen costs on the road to ITER Operation.

The ITER schedule is tracked very closely. Milestones for every aspect of ITER Construction—whether the signature of a contract, the construction of a building, or the fabrication of a component—are tracked against predicted delivery dates. Detecting delay is the first step towards recovering it; where delay is observed, mitigation measures are put into place to try and recuperate the lost time. ITER Construction ends with the first experiments: for the moment, the predicted date for the first experiments is still within the ITER Baseline "early" (November 2019) and "late" (July 2021) finish dates.

The governance of the project is managed collaboratively by the seven ITER Members. The top-level ITER Council and its advisory bodies, the Management Advisory Committee and the Science and Technology Advisory Committee, meet regularly to oversee the project and discuss all issues related to schedule and cost. A Financial Audit Board convenes regularly to ensure proper execution in the financial management aspects of the Project and a Management Assessor is appointed every two years to review and report on the overall management of the ITER Organization.

Once integrated and assembled, the ITER machine will go through a period of testing and commissioning. This is the equivalent of making sure that "all systems are go" before attempting the first experiment. Next, a several-year "shakedown" period of operation in pure non-nuclear fuels such as hydrogen, helium and deuterium is planned during which the machine will remain accessible for repairs and the most promising physics regimes will be tested. This phase will be followed by operation in deuterium with a small amount of tritium to test wall-shielding provisions. Only then, scientists will launch a third phase with increasingly frequent operation with an equal mixture of deuterium and tritium, at full fusion power.

The ITER superconductors have been the object of a particularly stringent development and qualification program. Conductor samples from every supplier undergo testing at the SULTAN installation, located at the Paul Scherrer Institute (PSI) in Villigen (Switzerland), before acceptance by the ITER Organization. At SULTAN, the samples are exposed to magnetic fields, current intensity and temperature conditions that are equivalent to those of the ITER operational environment.

In addition, for the 18 D-shaped toroidal field coils, the ITER Council has requested that a common set of specifications be developed for the cold testing at 77 K (minus 196°C) of the first three coils in each series of toroidal field winding packs as a risk mitigation measure.

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 4700 kIUA (ITER Units of Account in thousands), in accordance with the Baseline adopted in July 2010 by the ITER Council. 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. 

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 relevant. The European Union has estimated its global contribution to the costs of ITER construction at EUR 6.6 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 the 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, 35 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. The country's commitment to ITER "at the level of EUR 1.2 billion through to 2017" was confirmed by French Minister of Research and Higher Education Geneviève Fioraso on the occasion of the ITER Headquarters inauguration (17 January 2013). Furthermore, France has contributed a number of in-kind contributions for a total of approximately EUR 260 M€ (ITER site preparation, the International School in Manosque and the realization of the heavy haul Itinerary). The French financial and in-kind contributions originate from the French government as well as from the local governments of the Provence-Alpes-Côte d'Azur region where ITER is located, who have pledged a total of EUR 467 million to the ITER Project over a period of 10 years.

This contribution is on par with the contracts and employment that have already been generated in the area by the ITER Project. (See next question on economic advantages.)

For all Members, the potential benefits of participation are significant: by contributing a portion of the Project's costs, Members benefit from 100 percent of the scientific results.

Based on the 2001 design, the original cost estimate of ITER was EUR 5 billion for construction costs. This estimate, based on the best available information at the time, did not include some labour costs, escalation and contingency.

In 2008, a detailed design review called for modifications to the ITER machine based on advancements in fusion science; these modifications, such as the addition of vertical stability and Edge Localization Mode (ELM) coils, were incorporated into the 2010 Baseline and added to overall cost. The fact that the number of ITER Members passed from four to seven also contributed to cost increases by creating a much larger number of interfaces (and hence, complexity) within the design. The third important element of the cost increase is that building construction costs have increased significantly since the 2001 estimate. 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 over the original 2001 estimate. 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.

In a global context of rising oil and gas prices, decreased accessibility to low-cost fossil fuel sources, and an estimated three-fold increase in world energy demand by the end of this century, the energy question finds itself propelled to centre stage. How will it be possible to supply this new energy without adding to greenhouse gases?

Investing in renewables such as solar, wind and geothermal is important. Just like in fusion R&D ... with significant investment comes advancements in technology, and with advancements in technology comes a decrease in price. All calculations point to an increase in the importance of renewables in the decades to come.

The ideal future energy mix would hold a mixture of generation methods instead of a large reliance on one source. Fusion offers advantages that make it worth pursuing: widely abundant, inexpensive and virtually unlimited fuels, and the ability to operate in a base load capacity, which is not easy for generation methods based on intermittent sources, such as wind or sun.

The fusion community doesn't see itself in competition with renewable forms of energy. Rather, in a world ever more dependent on energy, it is important to follow all of the promising options for our common future.

The ITER Organization manages its cost estimate and associated risk in the same way as any large project, using industry-standard software and risk analysis. There is always a risk for a construction project managed over several years that certain "external" factors (labour, building materials) or "internal" factors (the complexity of increased interfaces in the design, design changes, nuclear safety authority requirements or inspections, etc.) have an impact on the budget.

To track the risk of cost increase, each activity in the ITER Organization cost estimate is assigned a level of uncertainty in accordance with a risk classification system. The values of the activities and their uncertainty classifications are then analyzed to predict confidence levels. These important tools allow management to identify and react to possible cost increases.

To compensate for the risk associated with the uncertainty in the cost estimate, the ITER Organization is actively looking for cost savings to be able to offset potential cost increases. 

ITER is creating jobs, and not only locally.

First, consider the R&D and fabrication activities that are going on for ITER around the world. In 2012, the ITER Domestic Agencies estimated the number of contracts awarded related to the development and procurement of ITER systems, components and infrastructure at over 800—the direct beneficiaries of these contracts are in laboratories, universities and industry in ITER Member countries. (Contracts are also awarded directly by the ITER Organization.) These contracts—many of which demand skilled contributions in engineering—are significantly more labour-intensive than conventional industrial manufacturing.

It is estimated that over three-fourths of the total European construction contribution to ITER will be directed to industry, a proportion that is similar in other Members.

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.

During the peak of construction works (2014-2017), 3,000-4,000 workers will be employed on the ITER site.

Contracts totalling EUR 1,473 million have been attributed to French companies since 2007 by the ITER Organization, the European Domestic Agency for ITER (responsible for the in-kind contribution of Europe to ITER, including all buildings), and Agence Iter France. Sixty-four percent of these (worth EUR 938 million) were attributed to companies based in the PACA region (statistics for the period ending 30 June 2013).

No, it's not. The workers on the ITER construction site will be protected by French law, which stipulates that all companies operating on the ITER site, whatever their "nationality", are subjected to French labour regulations and more specifically to the collective agreements (called conventions collectives) that govern particular branches. This is already the case on the ITER site.

The ITER Organization benefits from a particular legal status in France—like UNESCO or the United Nations, the ITER Organization is an international organization created by international treaty; as such it benefits from a specific legal status recognized by international law (for example, the inviolability of its territory).

In accordance with Article 14 of the ITER Agreement, the ITER Organization shall observe applicable laws and regulations in France in the fields of public and occupational health and safety, nuclear safety, radiation protection, licensing, nuclear substances, environmental protection and protection from acts of malevolence. On-site inspections by the competent authorities will be a regular part of ITER Construction, just like they are for any large construction project in France. 

Of the 3,000 workers expected, the majority will be recruited in France. Ten to twenty percent only will originate from the rest of Europe. For those who do not live locally housing and transportation will be organized by the companies operating on the ITER site, who have a contractual obligation to provide it.

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 natural disaster in Japan in March 2011, and the resulting tsunami and nuclear accident at Fukushima Daiichi, the French government requested the French Nuclear Safety Authority ASN to carry out complementary safety assessments. The decision was made to assess not just nuclear power plants, as requested at the European level, but also research infrastructures in order to examine the resistance of a facility in the face of a set of extreme situations leading to the sequential loss of lines of defence, such as very severe flooding, a severe earthquake beyond that postulated in the ITER safety case, or a combination of both.

The ITER Organization provided a nuclear safety stress report to the French safety authorities on 15 September 2012. The technical examination of the report was concluded in July 2013 by a standing session of the Groupe Permanent in France. This group of experts appointed by ASN communicated only one recommendation to the ITER Organization: to study extreme climatic conditions such as tornado, hailstorms, etc.

Taking into account the robustness of the ITER safety design, this stress test report should not lead to additional cost.

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.

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.

The ITER facility is designed to resist an earthquake of amplitude x40 and energy x250 higher than any earthquake for which we have historical or geological references in the area of Saint Paul-lez-Durance, France. 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 is used to protect other civil engineering structures such as electrical power plants from the risk of earthquake). The risk of flooding, too, has been taken into account in ITER's design and Preliminary Safety Report. In the most extreme hypothetical situation—that of a cascade of dam failures north of the ITER site—more than 30 metres remains between the maximum height of the water and the first basemat of the nuclear buildings.

Following the natural disaster in Japan in March 2011, and the resulting tsunami and nuclear accident at Fukushima Daiichi, the French government requested that the French Nuclear Safety Authority (ASN) carry out complementary safety assessments. The decision was made to assess not only nuclear power plants, as requested at the European level, but also research infrastructures in order to examine the resistance of a facility in the face of a set of extreme situations leading to the sequential loss of lines of defence, such as very severe flooding, a severe earthquake beyond that postulated in the ITER safety case, or a combination of both.

The ITER Organization provided a nuclear safety stress report to the French safety authorities on 15 September 2012. The technical examination of the report was concluded in July 2013 by a standing session of the Groupe Permanent in France. This group of experts appointed by ASN communicated only one recommendation to the ITER Organization: to study extreme climatic conditions such as tornado, hailstorms, etc.

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, including man-made hazards. This includes 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.

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.

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.

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 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.

It's true that the nuclear fusion reaction in a tokamak is inherently safe. Achieving fusion requires very precise conditions; if a plasma is too cold or too hot, if there is too much fuel or not enough, if there are contaminants in the plasma, or if the magnetic fields are not optimal ... the reaction dies out.

However fusion processes do involve radioactive materials. ITER, or the fusion power plants to follow, will have to manage the radiation produced through two mechanisms. Tritium, one of the fusion fuels, is a radioactive form of hydrogen with a half-life of 12.3 years; the tritium absorbed by the infrastructure of the tokamak will give rise to some radioactivity. In addition, very fast neutrons produced by the fusion reaction will activate the material structures of the vessel.

The amount of tritium used during plasma pulses is very small—only a few grams at any one time. Careful procedures have been established for the handling and containment of tritium that have been well tried in other fusion facilities and through tritium applications in medicine and technology. 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. 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 that demonstrates that during normal operation, ITER's radiological impact on the most exposed populations will be one thousand times less than natural background radiation. Even in "worst-case scenarios," such as fire in the Tritium Plant, evacuations or other countermeasures for the neighbouring populations would not be required.

Fusion reactors, unlike fission reactors, would produce no high activity/long life radioactive waste. The "burnt" fuel in a fusion reactor is helium, an inert gas. Activation produced in the material surfaces by the fast neutrons will produce waste that is classified as very low, low, or medium activity waste. All waste materials will be treated, packaged, and stored on site. Because the half-life of most radioisotopes contained in this waste is lower than ten years, within 100 years the radioactivity of the materials will have diminished in such a significant way that the materials can be recycled for use in other fusion plants, for example. This timetable 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.

The activation or contamination of in-vessel components, the vacuum vessel, the fuel circuit, the cooling system, the maintenance equipment, or buildings will produce an estimated 30,000 tons of decommissioning waste that will be removed from the ITER facility and processed.

The ITER Organization was licensed as a nuclear operator in France in November 2012, following the in-depth technical inspection of its safety files. Because it is the first nuclear installation to be licensed in France since 2006, ITER is the first one to observe the 2006 French law on Nuclear Transparency and Security and the first fusion device in history to have its safety characteristics undergo the rigorous scrutiny of a Nuclear Regulator to obtain nuclear licensing.

No. There are no enriched materials like plutonium or highly enriched uranium in a fusion reactor like ITER that could be exploited to make nuclear weapons. Tritium is used commercially, in small quantities, for medical diagnostics and sign illumination. The use of tritium in ITER will not open a new way for the production of mass destruction weapons.

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.

Fusion reactors, unlike fission reactors, produce no high activity/long life radioactive waste. The "burnt" fuel in a fusion reactor is helium, an inert gas. Activation produced in the material surfaces by the fast neutrons will produce waste that is classified as very low, low, or medium activity waste. All waste materials will be treated, packaged, and stored on site. Because the half-life of most radioisotopes contained in this waste is lower than ten years, within 100 years the radioactivity of the materials will have diminished in such a significant way that the materials can be recycled for use in other fusion plants, for example. This timetable 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.

The activation or contamination of in-vessel components, the vacuum vessel, the fuel circuit, the cooling system, the maintenance equipment, or buildings will produce an estimated 30,000 tons of decommissioning waste that will be removed from the ITER facility and processed.

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.

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-CO₂sustainable 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."

ITER is the essential bridge between today's smaller-scale experimental fusion devices and the demonstration fusion power plants of the future. ITER is a scientific experiment that will open the way to industrial and commercial production of fusion energy.

Building on the knowledge and know-how acquired within ITER, as well as research carried out in parallel on other fusion devices, the next-step machine—an industrial demonstrator (DEMO)—would demonstrate the large-scale production of electrical power and tritium fuel self-sufficiency. Several conceptual designs for such a machine are already on the table in the ITER Members; these designs will be refined as ITER enters operations.

In 2012 the European Fusion Development Agreement EFDA, which reunites European fusion R&D laboratories, published "A Roadmap to the Realisation of Fusion Energy" that outlines its plan for bringing fusion electricity to the grid by 2050—a goal that it considers ambitious, yet realistic. It foresees a DEMO that will produce net electricity at the level of a few hundred Megawatts in the early 2040s. The EFDA Roadmap takes into account R&D currently undertaken by Europe and Japan within the framework of the Broader Approach activities.

Of course there are likely to be political and economic constraints that we cannot foresee—the final timescale to commercial fusion depends strongly on political and private sector will to invest in this area of research. DEMO conceptual design programs are underway in other ITER Members. China, for instance, has launched an aggressive program aimed at fusion energy well before 2050.

The power output of the kind of fusion power reactor that is envisaged for the second half of this century will be similar to that of a fission reactor, i.e., between 1 and 3 gigawatts (or two-to-six times the power output of ITER). In theory, the larger the reactor, the more efficiently it would be to operate and the more power it would produce, so it may be advantageous to go larger in the future. For the moment, it is envisaged that future fusion power plants would occupy buildings no bigger than those that presently house fission or coal-fired power stations.

The main goal of ITER and future fusion reactor-based power plants is to develop a new, sustainable and virtually unlimited energy source. The average cost per kilowatt of electricity is expected to be similar to that of current fission reactors ... slightly more expensive at the beginning, when the technology is new, and less expensive as economies of scale bring the costs down.

In order to have a rapid market penetration, fusion will have to demonstrate the potential for competitive cost of electricity. Although this is not a primary goal for DEMO, the perspective of competitively priced electricity production from fusion has to be set as a target. One way to do this is to minimize DEMO capital costs (and that of fusion power plants). The ITER Tokamak is a first-of-a-kind experimental machine, built with a vast array of diagnostic systems (over 40!) to learn as much as possible about what is happening in the plasma. A fusion power plant on the other hand would be conceived in quite a different way.

Fusion and fission are totally different scientific and technological concepts, although both involve nuclear reactions. The fuel assemblies in the core of a fission reactor contain several tons of radioactive fuel which generates energy by the splitting ("fissioning") of atomic nuclei in a chain reaction. Fusion is not a chain reaction. The entire system contains a few kilograms of the radioactive fuel component (tritium) with only a few grams reacting at any given time in the reaction chamber.

Three very unique safety features make fusion technology an attractive option to pursue for future large-scale electricity production.

First, fusion presents no risk of nuclear proliferation. Unlike fissile materials such as uranium and plutonium used in fission reactors, tritium is neither a fissile nor a fissionable material. There are no enriched materials in a fusion reactor like ITER that could be exploited to make nuclear weapons.

Second, nuclear fusion reactors would produce no high activity/long-life nuclear 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. The goal of the ongoing R&D program is for fusion reactor material to be recyclable in less than 100 years.

Third, fusion reactions are intrinsically safe. A "runaway" reaction and the resulting uncontrolled production of energy is impossible with fusion. Fusion reactions cannot be maintained spontaneously: any disturbance or failure stops the reaction. This is why it is said that fusion has inherent safety aspects. Moreover, the loss of the cooling function due to an earthquake or flood 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.

Nuclear risks associated with fusion relate to the use of tritium, which is a radioactive form (isotope) of hydrogen. However, the amount used is limited to a few grams of tritium for the reaction and a few kilograms on site. During operation, the radiological impact of the use of tritium on the most exposed population is much smaller than that due to natural background radiation. For ITER, no accident scenario has been identified that would imply the need to take countermeasures to protect the surrounding population.