An alpha particle is produced by the alpha decay of a radioactive nucleus. Because the nucleus is unstable a piece of it is ejected, allowing the nucleus to reach a more stable state. The piece that is ejected is the alpha particle, which is made up of a two protons [...]
Of course the details would depend on the properties of the superconductor. If it had just the same properties as Niobium Tin, then you might save around 100 million dollars in plant costs (this is just a round number of course) and about 10 million a year on running costs, which [...]
Firstly we do use full power, in terms of input power. We have recently upgraded our beam power, and injected a record 26 MW late last 2012. This should be pushed at least another 4 MW during 2013 after maintenance shutdown. What we do not do often is to use [...]
198.8 M European Units of Account (EUA – predecessor to the Euro). JET was completed on time and on budget in 1983.
Most of the time we do not use the full-power fuel, deuterium/tritium mixture, however in our high power experiments in 1997 with this mixture the maximum output was 16.1 MW, from about 24 MW input power, giving a Q value of about 0.65.
The Li-7 transmutation reaction does have a threshold energy, that the neutron needs to have for the reaction to occur, but the Li-6 reaction can occur at any neutron energy. However in both reactions energy is released, the exact amount depending on the nature (energy, velocity, etc) of the incident [...]
There are transmutation reactions from both Li-6 and Li-7 to tritium however the Li-6 reaction is the dominant pathway.
The colour comes from the fuel, which is basically hydrogen. Hydrogen gives out two different colours, a strong red and aqua-blue, which combine to give the pink colour that shows up in most pictures. The two colours come from specific transitions of the hydrogen atom’s electron between different energy levels [...]
As fusion power generation is still in the research phase it is hard to say whether it will ever be feasible for ships. At this stage plans to achieve significant output power from fusion hinge on making the vessel larger, to overcome the energy losses from plasma: we expect that [...]
The first thing to note is that fusion reactors – producing commercial electricity – are not ready yet. We are still researching how to make this technology work in an economically and efficient way. The first true fusion power stations are probably 30 years away. All our work is focussed [...]
There was not one general contractor for the construction of JET in the early 1980s. As a European project, the project team placed orders with many contractors all over Europe to build parts of the device (vacuum vessel, magnetic coils etc).
At present, the current in the plasma, which is essential for plasma heating and providing poloidal field for confinement, is provided by the discharge of a transformer. The pulsed nature of the discharge is due to the fact that the transformer can only operate in one polarity. If it operated [...]
The Lawson criteria deal with the temperature, density and confinement time required to achieve energy gain from fusion. There is no limit to the volume; for example, the sun is a fusion reactor with a very large volume! In fact a larger volume is an advantage as it means a [...]
We run a series of open evenings through the year, approximately monthly, which enable the public (individuals or groups) to come and visit the JET and MAST fusion experiments. They are very popular, so book early!
In JET, the vessel walls are maintained at a high temperature of 325 degrees Celsius all the time. The main increase in temperature during plasma operations is noted in the lower (divertor) region where the wall tiles are in contact with the plasma. Typically, temperatures here would rise to 1000 [...]
JET does not have a lithium blanket. It is an experimental facility, and not a power reactor, so it is focussed on exploring the behaviour of plasma, rather than producing a long stable output. Most of the time it does not even run with tritium, as deuterium only plasma is [...]
The plasma chamber in a tokamak like JET has to be pumped down to a very good vacuum before decent plasma can be created. Any impurities, for example, atmospheric gases such as oxygen or nitrogen, need to be removed to keep the plasma stable. A typical base pressure inside JET [...]
Fusion processes do involve radioactive materials. A device like ITER, or the fusion powerplants that will follow, will become radioactive through two mechanisms. One of the fuels – tritium – which is a heavy isotope of hydrogen, is radioactive. Inevitably, some tritium gets stored in the infrastructure of the tokamak, [...]
There are reasons we do not let anyone near a device like JET or ITER when it is operating. The plasma ejects significant amounts of X-rays that would be harmful to anyone standing close to it. Also, very high voltage (10,000s of volts) circuits are used to feed the powerful [...]
We have just finished a major refurbishment of the JET machine, where all the old carbon tiles have been removed and replaced with new beryllium and tungsten tiles, of the type planned for use in ITER. This was mostly done by our advanced handling robotic system, and took around 18 [...]
Fusion has many advantages over existing power generation methods. Firstly it has widely abundant and cheap fuels, which could supply us for millions of years. Secondly it has the ability to operate in a base load capacity, which is not easy for generation methods based on unreliable sources, such as [...]
We are entirely focussed here at JET on developing fusion as a source of electricity here on earth – and that is certainly challenging in its own right! As for the potential of using fusion power in spaceflight, it is certainly envisaged in many science fiction books, films etc. In [...]
One of the hot topics in plasma physics is how increased turbulent flows can improve plasma stability. Indeed on the MAST experiment here at Culham, we have an active series of experiments studying how increased plasma flow (up to supersonic speeds) in toroidal and poloidal directions affects plasma stability and [...]
The time between pulses is normally more than 20 minutes and is usually determined by data collection and analysis and preparation for the next pulse. The main reason that JET has to operate in pulsed mode is because of the operation of the electromagnets that provide the magnetic field. To [...]
The operation of a tokamak relies on the hot plasma being confined within a magnetic bottle, created by large electromagnets. At JET, the electromagnets are made of copper, and carry currents of many thousands of amperes, which generate large amounts of heat because of their resistive losses – this heat [...]
All of the resistive loss is removed by the cooling system, which runs continuously. The pulse lasts about 30 seconds and the cooling time is about 20 minutes so about 2% of the loss is removed during the pulse.
The total power required to run the coils at JET is about 700 MW, of which 400 MW is consumed by the toroidal magnets. The losses in these coils are about 280 MW, which totals to energy losses of 5.5 GJ per pulse. Future fusion facilities such as ITER will [...]
The toroidal coils weigh about 380 tonnes, about the weight of a Jumbo Jet
The gaseous fuel – either deuterium or a deuterium/tritium mix – are released into the JET vessel at room temperature. A very large voltage is applied by the toroidal coil, which causes the atoms to break down, as happens in lightning: the energy strips the electrons from the nuclei , [...]
Fusion research is a long term project, with a target of working fusion reactors putting electricity on the grid in about 30 years. JET is not a power station, it is an experimental device which is playing a key role in answering technical and engineering questions, such as how best [...]
There are several ways that we use to heat the plasma – first passing a large current through it (ohmic heating) and then microwave and neutral beam heating methods. Ohmic heating schemes typically get the plasma to 40-50 million degrees Celsius. However they cannot go much further as the effectiveness [...]
The graphite components you worked on would almost certainly have been used to line the inner walls of the JET vessel. These walls are the first contact point with the very hot fusion plasma in JET, and need to be made from tough heat-resistant materials. Hence graphite and CFC tiles [...]
You are correct that fusion takes place at high pressure in the core of the Sun, and not actually in the surrounding vacuum; gravity is what holds the plasma together. Strangely enough, the sun is a very inefficient fusion reactor, producing only 1 watt per cubic metre – luckily it [...]
The next step for fusion research is the construction of the ITER, a large international fusion experiment in the south of France, ITER will test the materials, engineering and science which will enable the first commercial fusion plants to be built. The first of these is expected to cost in [...]
We have taken enormous strides in the last 30 years, but on the way discovered fresh challenges; for example, we have made incredibly hot plasma – over 100 million degrees, ten times hotter than the sun – only to discover it’s incredibly difficult to confine it! We now have created [...]
In order for fusion to occur in the very hot gas – or plasma – we create inside JET, the plasma must be heated to temperatures in excess of 150 million degrees Celsius. In order to achieve this, the plasma is actively held away from the walls of the tokamak [...]
The next step fusion device, ITER, which is being constructed in France, will test blanket modules . As well as absorbing the heat from the reaction, the idea is to also wqithin the blanket breed tritium, which is rare and expensive, but is formed when neutrons bombard lithium. The design [...]
You are correct that the very hot (150 million degrees Celsius) plasma in JET is held away from the walls of the container using very powerful magnetic fields. However, if the plasma becomes unstable it can break free from this confinement and hit the walls of the container, in the [...]
Annual consumption is very dependent on whether JET is operational or in shutdown. The peak of consumption here is during a 300s JET pulse – where over 300 megawatts of electrical power is pulled from the grid, and up to 400 megawatts is supplied from two large flywheels located here [...]
There are a number of ways that we heat the plasma. One of the main ways is using a transformer to induce a large current in the plasma (termed Ohmic heating). We also use powerful microwave systems (using the same principles as a microwave oven) and intense beams of fast [...]
Yes. In tokamak devices such as JET, we do use magnetic fields to confine and contain the plasma away for the walls of the vessel. These are a combination of fields that the plasma creates itself and external ones we apply. We have 32 D-shaped copper coils around the vessel, [...]
The CCFE Graduate Scheme concentrates on recruitment of engineers at present – as that is where our most acute staff shortages are at present. Of course, most of the scientists here are physicists – with physics degrees, MScs and PhDs – so your thoughts are along the right lines. It [...]
You are correct that most careers here require a physics background – or some kind of engineering. It is also worth pointing out that vacancies are few and far between at present – as we go through a bit of a financial squeeze. However, there are in principle areas of [...]
We definitely achieve fusion reactions here at JET, it’s just that so far we have needed more power to get it going than we have created. The power generated in JET (best so far = 16 megawatts) is limited to a level much lower than it could be by the [...]
The plasma is certainly magnetically squeezed somewhat inside JET. However the magnetic field, and therefore the plasma, is more or less symmetric around the torus, there are no pinch points. If the flow of nuclei becomes really constricted, the plasma stability can start to become adversely affected.
The most obvious thing is that it is the biggest fusion tokamak in the world that is currently operational. It is also the only one which can actually observe thermal fusion reactions, as it is the only existing device able to run with tritium – all others are deuterium only. [...]
It is of the order £50 million per year. This is contributed in various amounts by the European Commission, through Euratom; the UK fusion budget, from UK government, and each of the fusion programmes in EU member countries.
There is a lot of information on our websites : EFDA and JET (http://www.efda.org/, in particular the Focus On section) and Culham (http://www.ccfe.ac.uk/). Also ITER (http://www.iter.org/) has an extensive website. In terms of more detailed books, there is a book all about tokamaks – Tokamaks by John Wesson. This goes [...]
JET consumes large amounts of power – for fusion to occur we need to create and maintain plasma at extremely high temperatures. Additionally we need to contain the plasma by energising large magnetic coils. In total, when JET runs, it consumes 700 – 800 MW of electrical power (the equivalent [...]
A fusion powerplant will indeed produce about 1500 megawatts 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 per second – in other words, this powerplant will produce 1500 [...]
We have scientists and engineers here working on possible future fusion reactor designs and the largest capacity considered so far is about 3 gigawatts (this compares to typical current coal-fired stations at 1 – 2 gigawatts). In theory, the larger the reactor, the more efficiently it would operate, and the [...]
A nuclear fusion power plant would be no different from a conventional power plant in the sense that there would be a heat exchanger connected 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 [...]
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 powerplants would occupy buildings no bigger than presently house [...]
There would be enough lithium in a typical blanket to last the lifetime of a powerplant (the blanket is large, completely surrounding the plasma). However, a blanket would have to be replaced in a powerplant about every 5-10 years as they will be gradually damaged from the intense neutron bombardment [...]
The blanket is a layer surrounding the vessel in a 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 proposal is to embed lithium in [...]
The next step from JET (and the other tokamak research being undertaken around the world) is a device called ITER, an international tokamak project, 2-3 times bigger than JET, costing several billion pounds and capable of producing significantly more fusion power for longer periods. This will demonstrate the feasibility of [...]
The problem was the unrealistic expectations regarding our abilities to control the extreme temperatures in which fusion can burn (hundreds of millions of degrees Celsius). As it turns out it was easier to create the high temperatures than it was to control the plasma we had created. However we have [...]
The magnetic field coils planned for use on ITER and potential fusion powerplants will use superconducting materials, such as alloys of niobium and tin, or niobium and titanium, which become superconductors below -264 degrees Celsius. The idea is that the ITER vessel and its coils will be surrounded (in fact [...]
ITER will generate fusion power that is ten times more than the power used to directly heat the plasma. Additional power is required for the magnetic field coils, although this will be much reduced at ITER as they will be superconducting. Nonetheless, as you suggest, in the fusion process there [...]
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 difficult to say, however, whether they will be providing the majority of the electrical power in most countries. [...]
The feasibility, in terms of the way the plasma behaves, is pretty well understood (from experiments on JET and other tokamaks) and scientists are confident that larger, hotter plasmas (such as ITER) will not only produce much more fusion power, but will remain stable for long periods of time. There [...]
ITER is being built in Cadarache in southern France. Cadarache is one of the major sites of the France’s Commissariat a l’Energie Atomique, and includes the French tokamak, Tore Supra.
ITER is a fusion experiment like JET – a tokamak – being built in the south of France. It will be 2 – 3 times larger than JET, and is planned to commence operation in 2019. The research in tokamaks, and JET especially, has given us confidence that fusion power [...]
Firstly, we do not endorse the research, development or production of nuclear weapons in any form. The reaction that we seek to make use of for fusion is between the nuclei of atoms, and its large energy release can be used for weapons, however, that is where the connection ends, [...]
Studies have concluded that the cost of producing fusion power will be roughly the same as clean coal or fission, as the overall process is similar – a reaction heats water which turns a turbine to generate electricity. Fusion does differ slightly from fission in that the reaction requires more [...]
The fusion reaction releases neutrons, the energy of which will be used in future power stations to heat water to heat drive the power plant. The neutrons would be quite dangerous to humans, but when the plant is turned off the production of neutrons ceases within milliseconds. The neutron bombardment [...]
Fusion is in the research stage, with the first power plant demonstration planned for construction around 2030. The current and immediate future fusion facilities, such as JET and ITER, are experiments, and do not have the infrastructure for generating power. Design and planning indicates that fusion power plants will be [...]
Unlike nuclear fission, the nuclear fusion reaction in a tokamak is an inherently safe reaction. The reasons that have made fusion so difficult to achieve to date are the same ones that make it safe: it is a finely balanced reaction which is very sensitive to the conditions – the [...]
The answer is one of the key advantages of fusion as a potential energy source over nuclear fission power stations – its inherent safety. Although the plasma in a tokamak is extremely hot, it is at low pressure, and so its total heat energy is not large – there is [...]
Europe has for a long time been the leader in fusion research. EFDA laboratories all across Europe are very active in magnetic confinement fusion research both in their domestic programmes and via the EFDA-JET collaboration. The EU has been investing almost twice as much into fusion research as Japan or [...]
This is difficult to answer. The conversion to a power generation infrastructure based on fusion would require a large investment, which is perhaps why governments are waiting for more solid proof that fusion will work. We believe this will come from ITER (the successor to JET, currently built in Cadarache [...]
Energy demands will increase even more dramatically over the next fifty years as the developing world comes to expect the same standard of living as the industrialised countries. Nuclear fission is a possible energy source, which has the advantage of having a negligible carbon footprint. However nuclear fusion, is even [...]
All developments in fusion technology are published in scientific journals, and therefore are in the public domain. Thus it should be commercially available to any country as an alternative to conventional forms of energy production. Indeed ITER, the next generation of fusion experiment is funded by seven countries (EU, USA, [...]
There are downsides to fusion power but we believe the potential advantages (almost limitless fuel supply, no greenhouse gas emission, no dangerous waste products or possibility of explosion) heavily outweigh them. The main downside is that it is difficult to achieve – hence we are still researching the concept rather [...]
The tokamak is probably the most advanced fusion technology at the moment, however it has also probably had the most investment in it. All fusion approaches have their advantages and drawbacks, so it would be unwise to put all our eggs in one basket. Other possible fusion methods, inertial confinement, [...]
It is true that ITER will require more power to heat the plasma than JET as the plasma is bigger and will need to be hotter. However, the confinement is key: ITER, as it is hotter and bigger, will lose proportionately less energy than JET and so will produce a [...]
The basic heating system in a fusion reactor is electromagnetic: Huge coils are electrified, which create a magnetic field that drives the plasma around the donut-shaped tokamak, known as the plasma current. However this plasma current is not every charged particle marching in step. The plasma is at an extremely [...]
Gravity has very little effect on the dynamics and/or stability of the plasma so operation of a tokamak in zero gravity would make little difference. The particles are moving at such high speeds, because of their heat, that they experience much stronger magnetic forces than gravitational.
Breakeven is achieved when the energy from fusion reactions is larger than the energy required to sustain the plasma. So far JET has reached about 60 percent of this level, but in ITER we expect to exceed breakeven by a factor of ten. In the process of converting the energy [...]
The major radius of a tokamak plasma is the radius of the ring of the tokamak, measured from the centre of the “donut hole” down the centre of the device to the centre of the plasma. The minor radius is the radius of the cross section of the chamber – [...]
There are many tokamaks in operation around the world, all contributing to international efforts to realise commercial fusion power. As well as JET, there are many other tokamaks in Europe, which are part of the EFDA agreement. There are also tokamaks operating in the USA and Japan, and smaller tokamak [...]
Yes, at first sight it doesn’t make much sense. The key is in how tightly the protons and neutrons are held together. If a nuclear reaction produces nuclei that are more tightly bound than the originals then energy will be produced, if not you will need to put energy in [...]
In fission, energy is gained by splitting apart heavy atoms (uranium), into smaller atoms (such as iodine, caesium, strontium, xenon and barium, to name just a few) whereas fusion is combining light atoms, (in current experiments two isotopes of hydrogen, deuterium and tritium), which forms a heavier one (helium). Both [...]
There is not a perfect confinement of the plasma; all plasma components (including the fuel – deuterium and tritium) diffuse across the magnetic field. This means that the divertor actually is receiving flow of all plasma components, ie fuel, helium ash, and impurities. Also, only a very tiny percentage of [...]
About 20% of the net energy gained from the fusion reaction is carried by the newly-created helium nucleus – the remaining 80% is carried by the neutron which, because it is not charged can escape the confining magnetic field. The net energy gained by the helium ions will remain within [...]
Physicists have worked out that all the interactions in the universe are governed by only four different forces, only two of which we see in every day life: gravity and electromagnetism (sometimes called the coulomb force). The other two, imaginatively named the “strong” force and the “weak” force come into [...]
It is true that the fusion collisions in the plasma in a tokamak are essentially random, although due to the high plasma ion temperatures, these collision are quite frequent. The big challenge is to maintain the high temperature in these plasmas for a long enough confinement time (i.e. the time [...]
FIssion is splitting the nucleus – an effective energy source for very large elements, such as uranium, especially if they have unstable nuclei. Deuterium and tritium (which are very light nuclei) would be almost impossible to split. No energy would be released, instead you would have to inject energy. This [...]
In magnetically confined plasmas that we study in JET, 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 is known as Ohmic heating and heats the plasma [...]
Fusion releases energy when the nuclei of two forms of hydrogen (in our case, we use 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 nucleus. In this conversion a small [...]
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 significant fusion power output. ITER will nonetheless still be an experimental facility. Plans are already afoot to begin work on the first [...]
The funding for EFDA-JET is spread across the whole of Europe. This supports the operation and maintenance of the tokamak (undertaken by CCFE on behalf of Europe) and the undertaking of experiments by groups of scientists from EFDA laboratories all over Europe.
There are many ports into the vessel that allow heating, cooling, fuel, vacuum or diagnostic systems access to the chamber. The pictures of the plasma are taken through ports with transparent glass, by fast framing CCD cameras (the latest ones digitally) positioned outside the vessel. It is worth noting that [...]
In the JET tokamak plasma is contained in a doughnut shaped vessel and is heated up by (amongst other methods) passing a current through it. Temperatures around 100 million degrees C have been achieved and fusion (albeit at a relatively low level) has been observed. An eventual fusion power plant [...]
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). The energetic neutral atoms are created by first accelerating a beam [...]
Normally in JET, the plasma is controlled (by powerful magnetic fields) so that it stays away from the walls of the vessel. In this way the plasma can be sustained and heated to fusion temperatures. However,if the magnetic field system is unable to control the movement of the plasma for [...]
The hot plasma created in the tokamak (such as JET) needs to be confined and controlled in order for sustained fusion to occur. The solenoid, which is positioned around the plasma, induces a powerful electric current in the plasma, thus heating the plasma up (much as a wire is heated [...]
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 [...]
I cannot put a number on the amount of electricity consumed by JET I am afraid, although, suffice to say it is a lot!! Each JET pulse uses ~700MW of electricity (used to directly heat the plasma and also to provide the magnetic fields required to keep the plasma confined).
In fusion power demonstrations there are usually two different goals. One is to produce a steady, sustainable level of power, the other is to reach as high a power as possible, even if this is only possible for a short time. In the 1997 JET experiments, for instance, a steady [...]
Most of the experiments that are carried out in fusion research use only deuterium, rather than a combination of deuterium and tritium (D-T). This is because tritium, as a radioactive gas, is more expensive and has significantly more complicated handling requirements than deuterium. Deuterium-only plasma is sufficient for most of [...]
Plasma current is the flow of charged particles around the tokamak’s donut-shaped vessel (as opposed to the random movement of the hot plasma particles). It is induced in the same way that a transformer works. The primary coil is a large electromagnetic coil in the centre of the donut (its [...]
The JET machine is at the Culham Science Centre near Abingdon, about 9 miles south from Oxford in the UK.
Most of JET’s experimental campaigns use deuterium only plasma; deuterium is almost identical to tritium and so the plasma is very similar and is perfect for researching the behaviour and stability of fusion experiments, without the expense and complications of handling tritium, which is radioactive. We have however run three [...]
In fusion, energy is released when deuterium and tritium nuclei fuse together to make a helium nucleus and a neutron. This energy release is all to do with something called binding energy – the fundamental energy which binds any nucleus together. Essentially the deuterium and tritium nuclei require more binding [...]