Nuclear fusion, where are we in Europe

Nuclear fusion, where are we in Europe

Nuclear fusion

In Cadarache, in the research center of the Iter project on nuclear fusion, Europe's largest, technicians and engineers are starting to assemble the energy generators that will power a component comparable to the probably largest microwave oven in the world. With a small difference. Instead of heating a plate of pasta at 700-800 watts, the Electron Cyclotron Resonance Heating system will deliver 20 million watts of energy to the plasma in the toroidal chamber, located more than 100 meters away from the system that will generate the waves.

Electron resonance is one of three external heating systems that will be used to heat fusion gas to 150 million degrees in the tokamak, where nuclear fusion will take place. Just to activate these electromagnetic waves requires 24 gyrotron devices whose development began twenty years ago, and are now arriving from Japan, Russia, Europe and India. They will be positioned in the Radio Frequency Building, an imposing structure on three levels measuring 50 meters by 43 and 25 high.

These are some of the works in progress for the Iter, an hour's drive from Marseilles, while from the Lawrence Livermore National Laboratory in California came the announcement that fusion ignition had been achieved for the first time in history. Researchers at the National Ignition Facility (NIF) said they produced more energy than was input to trigger nuclear fusion itself.

The announcement on nuclear fusion: for the first time the energy produced is greater than that used The scientists of the National Ignition Facility in the Lawrence Livermore National Laboratory explained it: they managed to produce about 3 megajoules of energy using laser beams for about 2 megajoules, a gain of about 1.5

Divergent paths

Iter is a scientific "journey" intertwined with an international geopolitical adventure that began with an agreement between Ronald Reagan and Mikhail Gorbachev in 1985. The first magnetic fusion technologies were designed in the United States and the Soviet Union: Lyman Spitze conceived the stellarator at Princeton University in 1951, while Natan Yavlinsky of the Kurchatov Institute of Atomic Energy built the first tokamak in 1958.

After that summit in Geneva almost 40 years ago, the European Union, Japan, India, China and South Korea joined the project, bringing together 3,500 researchers from 140 i research institutes from 35 countries. Nuclear fusion to obtain a self-sustaining energy source soon became the holy grail of energy physics research, pursued primarily by two methods: magnetic confinement (at the European ITER) and inertial confinement (at the US NIF). Using the latter method, against 2 megajoules of energy input, the Nif obtained about 3 megajoules of energy on 5 December, with an energy gain of 1.5. An important result, but in Europe work is done on a different scale.

"Livermore has already achieved a positive balance of fusion energy that has yet to be achieved at Iter, but Iter has an even more ambitious goal because instead of 150% he wants to do 1000%, i.e. achieve a power gain factor of 10, obtaining 500 mW of fusion power for several tens of seconds", explains Paola Batistoni, head of the development section of Enea, the National Agency for new technologies, energy and sustainable economic development.

Enea coordinates the 21 Italian scientific partners present in the Eurofusion research group, which includes 26 European Union states plus Switzerland, the United Kingdom and Ukraine. The consortium, also financed by the European Commission with a grant, conducted the experiments of the Joint European Torus in Oxford with record results. In February, the tokamak had managed to maintain the fusion conditions at conf magnetic induction for five seconds, producing 11 mW of power and 59 mJ, an amount of energy already much higher than that generated by the Livermore.

There is still a long way to go for nuclear fusion Despite the recent breakthrough in the sector , it will take a long time before obtaining sufficient quantities of clean energy

Research and more

"In California, attention has been paid to obtaining a scientific result , while Iter will already be an experimental reactor which, in addition to obtaining a scientific test it will also serve to define the technological feasibility, going beyond the size of the laboratory - explains Batistoni -. Iter will not only be a tokamak, a donut-shaped toroidal chamber with magnetic coils like the experimental machines used up to now, but it will already be equipped with all the necessary systems, for example it will already have superconducting magnets, a divertor and components for self-sufficiency of the tritium that one day we will be able to use in the Demo reactor for the production of energy for civilian use to be fed into the grid. The technologies to create some of these components are still lacking, but we are working on them in parallel".

Jet is an experimental machine equipped with copper magnets for plasma confinement which constitutively limit the possibility of the tokamak to work for no more than five seconds, but it still achieved fusion and confirmed the performance predictions of Iter, a project to which it is connected. obtained only a third of the power compared to that entered, but we went close to breaking even – explains Batistoni -. In Iter we will be able to work for longer durations thanks to superconducting magnets, this gives us the confidence to be able to achieve the goal. Around the plasma we will have to build a reactor with all the technologies to operate in safe and economic conditions, although essentially two are missing: the development of materials to be used inside the reactor and a closed cycle for tritium self-sufficiency".

Italy plays an important role in this challenge: "To build Iter it has already been necessary to develop technologies that did not exist at the beginning and since 1985 Enea has focused on those that could offer a strategic growth line to the system Italian production - recalls Batistoni -. To date, Italian industry has had contracts for the construction of Iter for a total of over 1.8 billion euros, becoming a case of good collaboration between laboratories and the entrepreneurial system".

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Italian technological research

For example, no country wanted to do without the order for superconducting magnets One of these left the port of St. Petersburg on 1 November for Cadarache, demonstrating how scientific research has been able to overcome the crisis between Russia and Europe. But Italy also has a part in the chapter.The Divertor test tokamak (Dtt) is the research infrastructure of Enea in Frascati where, among other things, over 40 kilometers of cables are tested on for conductors. Arranged in coils, they will operate at a temperature of 269 °C below zero, generating a magnetic field of up to 13T on the magnet (niobium-3 tin) and 6T (niobium-titanium), to allow the magnetic confinement of the plasma, heated to the temperature of 100 million °C, just a few centimeters away.

Another Italian research area for a new technology concerns the Neutral beam test facility project conducted in Padua by the Rfx consortium (National Research Council, Enea, National of nuclear physics, University of Padua, Acciaierie Veneto). The objective is to develop one of the three external heating systems of the plasma, i.e. a beam of high-energy and powerful negative ions (16.5 megawatts), with an almost continuous operation of the system.

The Italia will also play a leading role in the development of an alternative solution for the Iter divertor, a key component of the reactor which gives its name to Enea's Dtt and which will also have to be suitable for Demo, the demonstration energy plant planned as a successor of Iter. Since the magnetic confinement of the plasma is not perfect, a system has been devised to convey the particles (helium nuclei, positively charged) that escape with an outgoing power load into a region dedicated to receiving this flow, a place somewhat ' separated from the heart of the machine and placed at the bottom, the divertor.

The expected heat on the divertor Dtt and in perspective of Demo, is greater than 10 million watts per square meter, comparable with that of the surface of the Sun The solutions offered by current technology are not able to achieve these specific power levels. "While for Iter we have found a solution, made up of tungsten tiles and copper alloy pipes, for Demo we expect higher flows and for longer periods that require new answers - explains Batistoni -. Italy has applied to lead the experiment, we will evaluate the possibility of reducing the fluxes by changing the magnetic configuration, installing the flux on larger surfaces or using different materials, as one of the problems is the damage of the divertor surface.The use of liquid metals could be for example a solution". Dtt will thus be the main European tokamak and the most complete and flexible experiment in the world for tackling and solving the problem of waste heat disposal.

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Governing the neutrons

The still open challenges concern the materials to be used inside the reactor and the closed cycle for the self-sufficiency of tritium. Neutrons are involved in both cases. "The products of nuclear fusion are not radioactive, i.e. the reaction does not produce waste, however the reactor structures become radioactive due to the neutron bombardment", explains Batistoni.

Escaping from the magnetic field and therefore from the plasma, the neutrons impact at very high energy on the mantle, the internal component of the reactor which heats up and allows the water to be vaporised, starting the traditional electricity generation processes. “For Demo we are developing steels which, in addition to resisting from the point of view of thermomechanical properties, are advanced in two senses: resistant to neutron bombardment and low induced radioactivity, i.e. they must have non-long-term radioactivity and decay within a couple of of centuries. These steels will not need a permanent geological deposit and will be able to be managed with simpler systems than the materials resulting from fission”, says the expert.

Another technology to be developed concerns the closed cycle of tritium, used as fuel together with deuterium (both are isotopes of hydrogen), but which unlike this is not found in nature, comes from nuclear fission power plants and is very scarce worldwide. "Iter is already a reactor, but it won't yet have the self-sufficiency of tritium and we won't be able to buy it on the market, because it won't exist - explains Batistoni -. We will have to produce it and for this reason all the technological tests that demonstrate its feasibility still need to be done. The The idea is to develop components in lithium, a metal abundant in nature, to be placed inside the reactor itself so that, by reacting with the neutrons released from the plasma, it produces tritium which we can thus recover to support the fusion with deuterium".

New materials, divertor and closed tritium cycle are challenges that will have to converge in Demo but will also concern private initiatives, which are multiplying around the world, for a total of about 4.8 billion dollars raised. Someone has already announced that they can quickly feed energy into the grid. "It is one thing to declare that you have achieved fusion, another to obtain energy gains (which in Iter will be possible in the 1930s), yet another to be able to put energy into the grid, do it with new materials capable of lasting decades and with a tritium self-sufficiency cycle: I don't see all of this possible within the next ten years.For our part, in Iter, also thanks to the progress made with Jet, we have a roadmap: compared to 40 years ago, today we know the road that will take us will lead to demonstrating the feasibility of fusion for a reactor that feeds energy into the grid. And it will have to do so in safety and economy. For us, the horizon remains 2050".

There is still a long way to go for nuclear fusion Despite the recent breakthrough in the sector, it will take a long time before obtaining sufficient quantities of clean energy

Nuclear fusion and climate

Nuclear fusion therefore risks not yet be usable to pave the way for a zero emissions scenario (NZe) envisaged for that date by the International Energy Agency (IEA). The IEA estimates that in thirty years global energy production will be 90% from renewables and 8% from nuclear power, which should rely on the extension of the life cycle of power plants in advanced countries and the development of new ones in emerging ones (over 90% of global growth). Nuclear's share of the total will be decreasing, but in reality it will have to double its power in absolute terms, from 413 gW in early 2022 to 812 gW in 2050, to support the Net zero emissions scenario still with fission power plants .

“ The vast majority of energy in 2050 will come from renewable sources, but 10-20% of the continuous and programmable base power that nuclear power can supply will still be needed - Batistoni states -. Fission will still dominate in 2050 , but fusion may replace it in the long term . Of course, a new industrial chain will have to be created, but the expected benefits are so many that many countries have wanted to participate in the research. Magnetic confinement nuclear fusion poses no risk of nuclear proliferation, the fuel is practically inexhaustible and is distributed homogeneously on the Earth, it leaves no waste, it does not cause accidents with major impacts in the long term, it is possible to stop the process at any time and of course it does not emit greenhouse gases. Nuclear fusion therefore represents a desirable solution in supporting an effective energy transition, in a context of climate crisis, the worst problem of our time”.

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