Frequently asked questions

	Will Fusion Power Plants be able to contribute to energy supply by 2040? The next step after ITER will be a demonstration power plant, which will be self-sufficient in its fuel cycle and deliver electrical power to the grid. It will differ only slightly from the first generation of commercial power plants, the construction of which could be started within the first half of this century. According to studies carried out to assess the feasible impact of fusion on the future energy market, fusion can win considerable market shares by the year 2100 and provide a significant fraction of energy.
	Will Fusion Power Plants reduce global warming, acid rain and air pollution? Fusion energy is generated through nuclear reactions, which do not involve any kind of combustion. Therefore no greenhouse gases are generated as a result of these reactions. The fact that no such gas is emitted into the atmosphere means that fusion doesn’t contribute to any of the current environmental plagues, such as acid rain, global warming and air pollution.
	Can fusion power plants keep us independent of international energy imports? The fusion reaction between deuterium and tritium is the easiest to achieve. The two hydrogen isotopes are largely available on earth. There are about 35 grams of deuterium in every cubic metre of water. Tritium can be produced artificially from lithium, which is one of the most abundant light metals in the earth’s crust. Therefore deuterium and lithium reserves are evenly distributed on earth and are not property of a limited number of countries as it is the case for fossil fuels. Fusion would therefore give to any country the possibility of having an independent energy supply. This is a very important issue for areas such as Europe, which, according to the published sources, has currently a 50% dependence on external energy imports and is going to increase it to 70% until 2020 if no countermeasures are adopted. These values explain why two of the largest world economies such as the European Union and Japan, which largely depend on external energy supplies, are carrying out the largest effort in fusion research.
	What is the difference between a machine like JET and ITER? The JET tokamak, in operation since 1983, has provided important results which give a high degree of confidence in the feasibility of magnetic fusion reactor physics. JET, for instance, has proven the principle of plasma self-heating by fusion reactions. However, only about 15% of the total power needed to maintain the plasma at the required temperatures was provided by these reactions, the rest was supplied externally. In ITER, as in future fusion power plants, self-heating of the plasma will be the dominating effect. ITER’s aim is to confirm and optimise the physics of the future reactor and to demonstrate the techno-logical feasibility of magnetic fusion power. Key technologies, such as the tritium fuel cycle and re-mote handling, will be extensively used in ITER, and it will be of paramount importance to demon-strate the viability of such techniques with an adequate degree of reliability.
	Will all ITER parties have the same rights to use the machine for their research purposes? Negotiations among the current participants (i.e. Canada, the EU, Japan and the Russian Federation) started in 2001 towards an agreement on the construction of ITER. Other countries are known to be considering joining them during the next 2-3 years. All the countries, which will provide the financial support for the construction and operation of the machine, will most likely have the same rights in the use of ITER. All the knowledge derived by the exploitation of the experiments will be shared among them. Bilateral agreements will most probably be stipulated with other countries for participating in ITER experiments.
	Industry has helped the laboratories to build the current fusion devices and to develop the technology for fusion research. Did industry itself benefit from this relationship? The benefit achieved by industry in its co-operation with the fusion laboratories is twofold. The direct advantage is due to the know-how accumulated on the topic while working together with fusion experts, both physicists and engineers. This has allowed industry to increase its knowledge in all critical aspects linked to the design of fusion device components. The second, indirect, benefit originates from the spin-offs, which inevitably derive from working in a high-technology environment. New materials, techniques and procedures, developed while working on fusion, have been used also for solving problems in other areas and have had a positive influence in the development of other kinds of components and products. Examples include advances in superconducting technology, fabri-cation processes, and measurement techniques.
	Potentially how much electricity could be made by one Tokamak power station? Fusion power stations producing 1-2 GW should be feasible - much the same size as standard fossil fuel power stations.   Source: EFDA-JET
	How long is the longest sustained fusion reaction achieved by JET and elsewhere? JET is the only operational machine to observe fusion from D-T (Deuterium-Tritium) reactions. Such fusion reactions have been maintained on JET for around five seconds. Experiments in a device called TFTR in Princeton, USA also observed fusion neutrons from their plasma but TFTR is no longer operational. The next step tokamak (ITER), which has been designed and should be built in the next ten years or so, will demonstrate much more powerful fusion reactions for 5-10 minutes and will, hopefully, provide the stepping stone to commercial fusion powerplants.   Source: EFDA-JET
	Could you tell me how the magnetic fields contain the plasma and how these fields are set up and powered? As the ions in the plasma are charged (the plasma is so hot all the electrons are stripped off the atoms, leaving them with a positive charge) they respond to magnetic fields. By setting up magnetic field lines toroidally around the interior of the tokamak, the ions and electrons in the plasma are forced to travel tightly around these field lines, preventing them from escaping the vessel. Extra fields help shape the plasma and hold it stable within the tokamak interior.   Source:EFDA-JET
	When using neutral beams to heat up the plasma do they not pollute the plasma and cause it to disrupt and how do you accelerate these neutral atoms? Neutral beams atoms do not pollute the plasma - they will be Deuterium atoms that will actually fuel the fusion reaction and increase it by making the background fusion ions hotter and increase their density (via collisions and ionisation).   Source:EFDA-JET
	How does fusion work? Fusion releases energy when the nuclei of two forms of Hydrogen (in our case, called Deuterium and Tritium) are collided together at such high velocities that they stick together or fuse. Shortly after this, they break apart, forming a neutron and a Helium nuclei and some net energy (mostly contained in the neutron). In a fusion powerplant, the neutrons will be used to heat water and drive a steam turbine. The fusion reaction is maintained as the Helium nuclei will help keep the remaining Deuterium and Tritium nuclei hot enough to keep fusing together.   Source:EFDA-JET
	Tell me about the ways to heat plasmas In magnetically confined plasmas that we study at Culham, there are three main ways of heating the plasma. The first is to use the strong electric current that is generated in the plasma (to help its stability and control) - this heats the plasma just like the current in a wire heats the wire. This current is very large (3-4MA on JET) and can heat the plasma to very high temperatures. However, to access the temperatures required for fusion to occur (which has been observed on JET) other methods are required. Powerful microwaves, injected in different frequency ranges (MHZ to GHz) can (under the right plasma conditions) give up their energy to the electrons or ions in the plasma and heat it up. Another method is to use very powerful neutral beams - these are beams of highly accelerated neutral atoms which are injected into the plasma and give up their energy as they undergo collisions with the background plasma ions.   Source:EFDA-JET
	What is plasma current and what is a pulse? A large currrent is generated in the plasma for two reasons. The current produces a powerful magnetic field which, in addition to externally generated fields, confines the plasma within the tokamak vessel. It also heats the plasma up to high temperatures (just like a current in a wire heats the wire up). The pulse is the short plasma that we generate in any of the tokamak experiments we run (e.g. JET) - it only last a few seconds due to the large amounts of energy required to maintain it. We then study it and conduct experiments to try and improve its performance etc.   Source:EFDA-JET
	What are the minor and major radii of the plasma? The major radius of a tokamak plasma is the radius of the tokamak as a whole (from the centre of the hole down the centre of the device to the the centre of the plasma) and the minor radius is the radius of the plasma itself.   Source:EFDA-JET
	I read somewhere that the energy released by the tritium-deuterium fusion reaction is given by the strong force. Could you explain this more clearly? The forces at work in the fusion process include two main important ones. The powerful Coulomb electrostatic force acts over long distances (compared to the size of the nuclei) and prevents the nuclei coming close enough to fuse (as they are both positively charged), unless their energy (temperature) is high enough to overcome this. This why the plasma temperature needs to be high (in a tokamak) for fusion to occur. However, the STRONG force is the very short range force that holds the protons and neutrons together in the nuclei. When fusion occurs these forces rearranged (in going from a Deuterium and Tritium nuclei to He and a neutron) - ending up with a lower potential energy (or mass) and a release of energy. To summarise, the Culomb force is a long distance, inter-nuclei force and the strong force is a short distance force acting only within the nuclei.   Source:EFDA-JET
	At what point, during the fusion process, do the helium nuclei stop adding to plasma heating and become an impurity to be removed? About 20% of the net energy gained from the fusion reaction is carried by the Helium ion - the remaining 80% is carried by the neutron which, in a powerplant, will leave the confining magnetic field, penetrate and heat a surrounding blanket, heating water to make steam and drive a turbine. The net energy gained by the Helium ions will remain within the plasma and, through collisions with the Deuterium and Tritium fuel ions, will be transferred to these fuel ions, maintaining the high temperature required for the reaction to occur. This effect has been observed and verified on JET (the only existing device to observe fusion power being produced from a magnetically confined plasma). When the Helium ions have slowed down (through these collisions) and no longer can heat the plasma, they essentially become an impurity to be removed - in fusion research this Helium is known as Helium ash. The removal of this Helium has been one of the major challenges facing the realisation of fusion energy from devices like JET. The basic approach is to form a D shaped plasma which touches the bottom of the vessel in a so-called divertor structure. The helium ions will naturally (like all ions) move to the edge of the plasma, where a powerful flow will transport them to the divertor - where they will be pumped away.   Source:EFDA-JET
	What is a "lithium blanket" and how does it work?What happens to the neutrons after they're "absorbed" by the lithium blanket? The Lithium blanket is a layer of Lithium that will surround the burning plasma in a potential fusion powerplant. It will absorb the energy from the fusion neutrons produced in the plasma, boiling water via a heat exchanger, which will be used to drive a steam turbine and produce electricity. The Lithium will also react with the neutron to produce Tritium (a heavy form of Hydrogen) which will be used as a fuel for the plasma, along with Deuterium (another heavy form of Hydrogen).   Source:EFDA-JET
	And if the bigger the plasma the bigger the energy gain factor, so how large might fusion reactors become once the technology has been proven? It is true to say that the bigger the plasma, the better the confinement and the bigger the fusion gain factor. However, increasing the plasma temperature and density also achieve an increase in gain factor. It is envisaged that future fusion power plants would occupy buildings no bigger than presently house fission or coal fired power stations.   Source:EFDA-JET
	Even if you could sustain fusion for prolonged periods, how do you extract power from the reactor? A nuclear fusion power plant would be no different from a "conventional" power plant in the sense that the path of energy to the grid would be via a heat exchanger to a steam generator to turbines. The heat would be extracted from the lithium "blanket" inside the reactor wall which would absorb the neutrons created by the deuterium/tritium fuel.   Source:EFDA-JET
	How do fission and fusion reactions compare? In fission, energy is gained energy by splitting apart heavy atoms (Uranium) and use this excess energy to boil water to drive a steam generator, thus producing electricity. Experiments such as JET are still researching how to use the energy gained from nuclear fusion reactions - where light Hydrogen-like nuclei are fused together, producing an excess of energy. This is reproducing what is happening in the Sun. Here, a hot gas (or plasma) of Hydrogen-like nuclei is formed, held in place using powerful magnetic fields, and heated until fusion starts to occur - indeed, JET, a European experiment based here at Culham, has achieved temperatures where fusion products have been observed. It is hoped that fusion powerplants (similar but larger than JET) will be producing electricity in 40 years or so.   Source:EFDA-JET
	You state that a fusion reactor would generate ~1500 Megawatts but what is the time span in which that amount is produced? A fusion powerplant will indeed produce ~1500 MW of power (similar to an average conventional fossil fuel power station) and will produce this amount of power all the time it is operational. Watts are a measure of energy usage per second - in other words, this powerplant will produce 1500 Million Joules of energy each second it is operational.   Source:EFDA-JET
	The projected time for a fully operational reactor is 30-50 years; by this point renewables (solar PV, wind etc) and hydrogen fuel (with its use in fuel cells) are predicted to be completely commercially viable and have large market shares. How do you see fusion's ability to compete with these inherently 'clean' technologies when at that point in time they will be cost-effective and a large part of the power infrastructure? Whilst being a revolutionary technology, will fusion be too late and too expensive when more 'environmentally friendly' solutions are already in place? It is true that fusion power plants are 30-40 years in the future and, by that time, renewable energy sources will probably have a greater share of the energy market. It is arguable, however, whether they will be providing the majority of the electrical power in most countries. We, in fusion research, would hope to see fusion power contributing to the energy needs of the world as part of a well balanced strategy - where there is not the reliance (largely, as at present, with fossil fuels) on one source. We certainly never see ourselves in competition with renewable forms of energy - on the contrary, fusion power, with its key environmental advantages (no greenhouse gas emissions and short lived (50-100 year) radioactive waste burden with the activated powerplant structure) could be seen as closer to renewables than other forms of energy. Obviously we cannot see into the future, but I do believe a balanced and varied approach to energy in the future using environmentally acceptable and efficient schemes will be to everyone's benefit. It is also worth pointing out that the fusion community is more confident than ever before (after recent results from JET and other devices) that 30-40 years to commercial fusion power is now realistic.   Source:EFDA-JET
	How do you plan on making ITER's coils superconducting? The superconducting magnetic field coils planned for use on ITER (a tokamak 2-3 times larger than JET and planned for construction in the next ten years or so) and potential powerplants will use conventional superconducting materials that require cooling to very cold temperatures. The idea is that the ITER vessel and coils will be surrounded (in fact immersed) in a suitable coolant to maintain the coils at low enough temperatures. Although the plasma is hot, remember it is being confined inside the vessel, well away from the walls and the coils are outside the vessel. The technology does exist for these types of coils - indeed a prototype ITER coil has been built and tested successfully.   Source:EFDA-JET
	Is research at JET still aimed at the ultimate goal of commercial energy production? Yes. Results from JET and other tokamaks around the world have given scientists tremendous confidence that they can control and confine the plasma sufficiently that ITER will deliver sustainable fusion power production. However, work continues on JET and other machines to optimise the plasma confinement etc. - work in the areas of how to exhaust plasma impurities in the divertor of the tokamak and how to reliably induce so-called "transport barriers" in the plasma (and thus improve the insulation of the burning plasma core) are particularly important at the moment.   Source:EFDA-JET