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FAQs

Find answers to the most frequently asked questions about the ITER Project.

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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. One of the fusion fuels, tritium, 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, over time, 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! What happened in the fission reactors in northeastern Japan following the severe earthquake and subsequent tsunami in 2011 could not 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.

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, 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 beds. Their confinement performance will follow a very strict qualification program; losses from the 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 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.

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

At ITER, an integrated safety management system will be put into place to address all potential hazards in compliance with industrial safety regulations. Potential hazards will be addressed specifically by department, and appropriate safety measures put into place. Non-radiological hazards taken into consideration at ITER include fire, exposure to magnetic and electromagnetic fields, exposure to chemicals or cryogenic fluids, and high voltages. To protect workers, access to the Tokamak Building will be strictly forbidden during operation.

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 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.

First, let's take a foray into the world of neutrons. Lone—or "free"—neutrons are created naturally by cosmic rays interacting with the upper layers of the atmosphere. At their initial speed, it's only a short trip to the Earth's surface. But on the way they have every chance of encountering the nitrogen, oxygen or carbon particles present in the air, getting absorbed and forming an isotope ... or bouncing off the surface of the particle nucleus and losing energy in the process.

As a result, only a few of these "space" neutrons ever reach the Earth's surface—approximately 100-300 neutrons per second per square metre. If they have retained enough energy, they may be absorbed by elements present in the soil such as iron, silicon, potassium, etc. Or they'll die a quick death, decaying into a proton, an electron and a neutrino.

Neutrons will also be generated by the fusion reaction inside of ITER. At full power, the ITER machine will generate some one hundred billion billions of highly energetic neutrons per second. Instead of the thin air of outer space, however, fusion neutrons will face a succession of daunting physical obstacles, some exceptionally dense.

Thick shielding blankets; high-strength copper and stainless steel in the first wall of the vacuum vessel; ultra-dense neutron-hungry borated concrete in the bioshield—these materials will contribute to absorbing the neutron flux from the fusion reaction and keep radiation from escaping to the environment.

But given the proportion of void in even the densest materials, won't some neutrons pass all the obstacles unscathed? Yes, but not enough to worry about however—the survivors will be so few that they will be indistinguishable from the natural background "noise" of neutrons.