Nuclear fusion: the road from dream to reality is long, very long!

Jérôme Paméla / Director of ITER-France / 2015-03-16

Rising energy consumption round the world, rarefaction of fossil energy sources, climate change, the necessary reduction of greenhouse gas (GHG) emissions… The development of new and renewable energy sectors, emitting few or zero GHGs has become primordial. Faced with this inevitable energy transition phase, nuclear fusion could be justified, provided we can prove its feasibility, thereby enabling a move to industrial fusion power production. This is the challenge assigned to the ITER international research facility.

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ParisTech Review – What idea prompted the birth of the ITER project?

Jérôme Paméla – The underlying idea was that, in a not too distant future, nuclear fusion could become a new, abundant, carbon-free source of energy, with controlled wastes which, moreover, would be largely recycled. Consequently, fusion technologies could be included in the energy mix, alongside renewable energy sources. Its characteristics offer uncontested trump cards in today’s energy sector context.

The world’s energy consumption, estimated today to be 12 billion tons oil equivalent (TOE) is on the increase and this trend will continue. Some experts think consumption could increase twofold or threefold by the start of the 22^nd century. In parallel, the fossil reserves (oil, coal and natural gas) are being depleted, while the cost to extract and exploit them is increasing. Lastly, climate change forces us to seek energy sources that emit less GHGs. These are some of the reasons that motivate research into (and development of) any new energy source. The question is not to oppose different energy sources but to provide the policy decision makers, when it becomes opportune, with all the solutions possible.

What exactly is nuclear fusion?

Instead of bombarding heavy atomic nuclei such as those of uranium or plutonium, to the point that they disintegrate, viz., undergo fission, nuclear fusion consists of creating collisions among the lightest nuclei to the point that they fuse together and transmute into heavier elements. In doing so, the collisions set free nuclear energy. This kind of nuclear reaction, that takes place in the Sun and other stars, is the source of all their energy. Nuclear fusion, in this respect, is the primordial “mother of energies” inasmuch as all our sources of energy have their origins in the Sun, whether they are fossil energies (from photosynthesis) or, more obviously, solar energy and also wind turbine energy.

Decades of research and development has demonstrated that the nuclei of deuterium (one proton, one neutron) and tritium (one proton, two neutrons) – both of which are hydrogen isotopes – produce the most “efficient” reactions. There are large quantities of deuterium on Earth and tritium can be produced from lithium.

Fusion of either deuterium or tritium creates a helium nucleus with its two protons and two neutrons, plus one free neutron. The process frees an enormous amount of energy. To give you an idea of the scale, the quantity of lithium and deuterium contained in a laptop battery and forty liters of water would satisfy the energy requirements of an average European for thirty years. Obtaining the equivalent electric energy from coal would require burning forty metric tons at the power station!

In order for the fusion reaction to take place, the nuclei must be sufficiently close to each other. To achieve this, their temperature is raised to (and maintained at) approximately 150 million degrees Celsius. This places the atoms in the fourth state,viz., a plasma which essentially is a gas with a temperature so high that the gaseous matter is totally ionized, i.e., the electrons are no longer held in orbit round their atomic nuclei. To trigger a fusion reaction, we use a tokamak, i.e., a machine that confines the plasma using magnetic fields. The magnetic fields trap the electrically charged particles of the plasma. In this way, the deuterium and tritium nuclei, the “fuel” for the fusion reaction, as well as the helium nuclei created in the process, remain confined in the plasma. Neutrons are not electrically charged and are therefore are insensitive to the surrounding magnetic fields. The neutrons transport about 80% of the energy produced in the fusion process outside the plasma, transferring it in the form of heat to the walls of the tokamak, where it can be recovered.

Europe has the largest tokamak in the world, called the JET (Joint European Torus) installed near Oxford in England. It was my privilege to direct the JET for seven years. This research establishment currently holds the world record for fusion energy output: 16 MW.

Can you present ITER?

The objective is to prove the scientific and technological feasibility of magnetic confinement fusion in a tokamak. Compared with the JET, which consumes more energy than it can produce, ITER should be able to prove it can generate ten times more power than is injected into the system. In other words, the output should reach 500 MW for an input of 50 MW, used mainly to heat the plasma. ITER is the biggest tokamak ever. The volume of the plasma will be 840 m³, compared with 100 m³ for the two other largest tokamaks, in Europe and Japan.

By 2030, we hope to be in a position at ITER to demonstrate that fusion energy production is ‘sustainable.’ Following this, a first prototype will allow us to certify this process for no-break electricity production, as well as the production of tritium from lithium inside the reactor vessel. By 2050, we should have a working pre-industrial nuclear fusion reactor.

It is an extremely complex project, both scientifically and technologically. Only a large-scale international collaboration can successful conduct, implement and finance such a programme. In the long term, ITER will represent approximately a thousand research, engineering or technician positions, all of which are specialized in fusion physics, in plasmas or in cryogenics (the science of cold) and other specialists, employed in computer sciences, project management, electronics…

To give you an idea of the cost levels involved – on the basis of an assessment made by the European Union – for the construction phase for ITER, the estimate is 13 billion euros over 10 years, for all the Members party to the project – this is only an extrapolation. To the extent that the real cost borne by each Member is different, it is impossible to give a detailed evaluation. For the operational phase, which should last 20 years, the initial estimate – 15 years ago – was a little less than 5 billion euros, a sum that will also need to be revalued upwards. The sums involved are quite considerable, but costs in research into new energy sources should be compared with costs for energy procurement: the world’s energy market today represents an annual volume of approximately 3,500 billion euros.

How does the organization work?

In fact, this is the first time that an international scientific organization has been created on such a scale. Its gestational period was long, given that it was the first evocation of an international programme to develop nuclear fusion technologies as “an inexhaustible source of energy serving mankind” going back to 1985. We recall that this research field was declassified in 1958, during the tense moments of the Cold War. Russians and Americans had agreed to publication of the results …

After several summit meetings, the signing of international agreements, a decade or more of increasingly detailed design work and a final three year period of negotiations, Cadarache was selected to be the construction site and the ITER organization expanded rapidly. Today, ITER is a group of 7 partners: China, South Korea, the United States, Europe, India, Japan and Russia, representing a total of 35 countries with more than a half of the world’s population. Each country contributes in kind, i.e., finances and assembles designated components needed for the final installation.

How is the construction of ITER progressing?

It is progressing well. Several buildings have already been erected or are under construction. The buildings housing the office premises and the organization home office are operational. The nuclear building – which will house the tokamak – needed sizeable foundations, notably to comply with paraseismic constraints. Some 20 meters below ground level, 493 paraseismic columns, each 2m high, were installed.

The tokamak alone weighs 23,000 tons. If we add the paraseismic devices, the ancillary equipment and the building proper, the total weight is 360,000 tons.

Two other buildings are also terminated. The first of these, 250m long, will be used to assemble the huge superconducting coils that constitute the tokamak magnets. The largest coils measure up to 24 m diameter and are assembled in several stages (to undergo various in situ treatments).

The second building will be used to assemble the cryostat, the responsibility for which lies with India. The cryostat is a sort of large box used to insulate the superconductor magnets designed to operate at an extremely low temperature: – 269° Celsius, i.e., just 4° above the absolute zero! The construction will consist of two walls separated by a vacuum – it works exactly like a Thermos® flask. The cryostat is one of the largest component parts of the tokamak, measuring 44 m in diameter and 27 m high. The various parts of the cryostat, in stainless steel, are made in India, brought by boat to a French port, then by road to Cadarache where they are assembled and welded together.

What reception arrangements have been implemented for a site on such a scale?

A work site of this size attracts numerous companies and their personnel and they must be suitably accommodated. In close connection with the authorities of the nearby towns and the State authorities, we are working on a comprehensive ‘welcome’ package including housing, transport, training and jobs. In economic terms, the past experience of major international research organizations tends to demonstrate that creating one job within the organization leads to the creation of a second, spin-off job. Already over 500 local company personnel have been sub-contracted by the ITER organization. Another interesting feature is that the PACA (Provence-Alpes Côte d’Azur) Region has established an international highschool teaching some 500 pupils, with 27 different nationalities, from kindergarten up to and including the baccalaureate.

The road infrastructures have been upgraded between Berre, the port where certain parts arrive by ship and Cadarache to allow passageway for outsized truck loads (up to 800 tonnes). The road works have made the local populations in the Region aware of the sheer scale of the ITER programme.

What are the main challenges?

The challenges, in the main, are technological. Confining the plasma, for example, is no small task. If we intend to move on to industrial energy production, i.e., continuous electric supply, then we must also develop materials that can withstand neutron bombardment the energy of which is transferred to the reactor vessel walls over long periods of time. Production of the fuel needed, viz., tritium inside the reactor to trigger the fusion process is under careful investigation. The fuel production function will be assigned – among others – to the inside wall of the reactor chamber cover. In the case of ITER, experimental so-called ‘tritigenic’ covers must prove that they have the capacity to generate tritium from the neutron-lithium collisions. The process will enable one of the two fuel components, viz., the tritium, to be produced within the reactor vessel. Consequently, the only elements that need to be delivered from outside the reactor are deuterium and lithium.

Fusion produces waste matter. How will this be handled?

The fusion process does not, in fact, produce any radioactive wastes directly. It is our responsibility to treat the wall coatings of the tokamak in such a way that nuclear wall activation by neutron bombardment is minimized. This is the aim of an important materials development programme, on “reduced activation” materials. Our objective is to ensure that the activated elements have a very short operational life expectancy – what we scientifically call the “radioactive period”, this enabling a recycling of most of the materials used in the reactor after approximately a century in operation. Studies are being conducted in a European research framework, in a partnership with various teams round the world. We have already identified several proposing options, notably using certain ferritic stainless steels.

Have you also envisaged maintenance and dismantling of the site facilities?

Of course! Dismantling is an important aspect when you are seeking to develop a new sector. The technical responsibility for dismantling this site will lie with France, as the host country. We are therefore already involved and it is our firm commitment to include all the key-aspects of dismantling even as we proceed with the design and assembly phases of the tokamak.

In terms of maintenance of ITER, the procedures will be largely remotely conducted,i.e., conducted by robots capable of both intervening and operating in a nuclear radiation environment and moving parts that can weigh several tons each.

When do you think fusion will produce continuous energy production?

A priori, by 2030, we shall have demonstrated the scientific and technological feasibility of fusion and our capacity to amplify a power input tenfold or more. But the initial continuous production of electricity is something we envisage more for a date beyond 2050! It is an extremely ambitious project with numerous scientific and technological hurdles to cross. As I see it, our project is every bit as ambitious as sending Men to Mars and bringing them back safely! But the challenge for Mankind is such that we simply cannot lower our guard. There have been difficulties in the past and more assuredly lie ahead. But we shall overcome them.