What is ITER and how is it supposed to work?
A: The research in tokamaks to date has given us confidence that fusion power can be obtained from future tokamak devices - probably within 30-40 years' time. ITER has been designed as a stepping stone to fusion power plants. It is a tokamak 2-3 times larger than JET and will demonstrate the scientific and technical feasibility of fusion power.

Q: Where will ITER be built?
A: ITER will be built in Cadarache in southern France.

Q: Is there any possible way that we can prove the feasibility of fusion by not building this large ITER reactor?
A: 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. However, ITER is required to also test the materials and technologies required in a powerplant. This step to a powerplant is definitely required to answer the remaining questions and prove to the world that magnetically confined fusion plasmas will work.

Q: 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?
A: 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 large reliance on only one source of fuel as there is at present with fossil fuels. 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 from the activated powerplant structure) could be seen as closer to renewables than other forms of energy.

Obviously we cannot see into the future but we believe a balanced and varied approach to energy in the future using environmentally acceptable and efficient schemes will be to everyone's benefit.

Q: If it takes massive amounts of power/energy to produce fusion, and the power output of it is generally only 20% of the power taken to produce it, what is the point of continuing? If it is viable, and all the safety aspects etc are better than anything we've got at the moment, then this is certainly a very exciting and welcome development.
A: JET is the largest tokamak experiment in the world at the moment and (as you have read on the web site) has observed fusion power (although not produced any electricity). However, as you rightly point out, the maximum fusion power observed in JET amounts to only 60% or so of the power required to heat the plasma to fusion temperatures. Indeed, in most experiments in JET, no fusion power is observed at all, as we operate with Deuterium only (both Deuterium and Tritium fuels are required for a fusion powerplant) to investigate how the plasma behaves and to optimise its stability, confinement and overall performance. However, larger tokamaks will attain higher temperatures, densities and confinement in the plasma, thus enabling much higher fusion gains to be observed. The next step tokamak, ITER, is 2-3 times larger than JET and will operate with fusion gain factors, Q (the ratio of fusion power out to plasma heating power) approaching 10, and is specifically designed to investigate the physics of hot, burning plasmas. Eventual fusion power plants (30-40 years away) will have even higher Q's, thus producing far more electricity than power required to maintain the plasma. Given the operational experience of JET and other tokamaks around the world, confidence is high that ITER will perform really well and will pave the way for future commercial fusion powerplants.

Q: Since ITER is expected to produce 10 times the power consumed, does this not mean that the substance produced and reused will by further extrapolation reduce the power needed by a reduction of 10? And this reduction lead to a further reduction of 10 and so on until almost no power is used?
A: ITER will generate fusion power that is ten times more than the power used to directly heat the plasma and the power requirements for the magnetic field coils will be much reduced as they will be superconducting (i.e. as long as they are maintained at very cold temperatures, the coils will essentially require no voltage to maintain the current in them for generation of these fields). The plasma is not really reused as you suggest - it is constantly refuelled with Deuterium and Tritium (to replace that fuel which is used up in the fusion reaction), but this fuel is cold and needs to be reheated and ionised when it enters the plasma. However, designs of potential fusion powerplants have indicated that significant net gains in energy (similar to conventional power stations, 1-3GW) are feasible.

Q: How do you plan on making ITER's coils superconducting?
A: The magnetic field coils planned for use on ITER and potential fusion powerplants will use materials which become superconducting at very cold temperatures. The idea is that the ITER vessel and its coils will be surrounded (in fact immersed) in a suitable coolant to maintain the coils at low enough temperatures. Although the plasma is extremely 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 already been built and tested successfully.

Q: When are we going to use fusion as a source of energy? I remember 50 years ago they were talking about it, and so far I have not seen any of the present nuclear reactors replaced by fusion reactors. What is the problem??
A: The problem was the unrealistic expectations regarding our abilities to produce and control the extreme conditions in which fusion can burn, namely the extreme temperatures (hundreds of millions deg C). Scientists - sometimes encouraged by fund raising issues - often believed that one technical concept or another would produce a breakthrough, even occasionally announcing breakthroughs but in fact they were premature. Instead, up to now there has been a steady progress towards the target parameters, see the figure. In 1997 JET demonstrated a significant release of fusion power - 16MW, which is about 65% of what the plasma consumes from external heating sources.

Today, by extrapolating the "evolution not revolution" fusion experience, we are confident that the next step device, ITER, will actually produce controlled releases of fusion energy. As a consequence, a lot of consideration is now devoted to the technological challenges of fusion, such as the selection of materials that will face the heat of burning plasmas. These details have been hardly ever considered before.

ITER has finally received large political support on a global scale, and will be built within ten years. After a few years of tuning experiments, we expect to see first burning plasmas before 2020. It is expected that at least 20 more years will be needed to transfer the technology from research to industry.

Q:What would be the soonest fusion power could be operable in Europe if funding were increased, and energy funding diverted from fossil fuel energy research, and finally, if the fusion research projects of the USA, EU, and Japan were combined, what is the soonest fusion power could be efficiently operated?
A: 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 plasma physics and fusion engineering of a potential power plant and, given the present funding, is planned to be built in the next 10-15 years - an eventual commercial power plant probably being 30-40 years away. However, if the present international funding for fusion were increased, ITER could definitely be built more quickly and fusion power could be a reality much more quickly - in possibly half the time if the present funding levels were increased significantly.

Q: What is a "lithium blanket" and how does it work? What happens to the neutrons after they're "absorbed" by the lithium blanket?
A: 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). The breeding of Tritium occurs through the reaction Li⁶ + neutron becomes He⁴ + Tritium.

Q: If the lithium blanket reacts to form deuterium and tritium will it eventually get used up and need replacement and might the lithium melt?
A: There would be enough Lithium in a typical blanket design to last the lifetime of a powerplant (the blanket is large, completely surrounding the plasma) - however, blankets will have to be replaced in a powerplant (about every 5-10 years) as they will be gradually damaged from the intense neutron activation they will undergo.

Many different blanket designs have been modelled - but have not been physically tested yet. They vary in composition - some have pebbles of Lithium alloys, others have a Lithium (alloy) liquid flowing through them. Many things need to be considered in the blanket design - robustness, how radioactive it will become from constant neutron bombardment (this depends on the exact materials used), how easily the heat can be extracted via a suitable transfer fluid and heat exchanger, and once the Tritium has been formed, how we extract it etc. The blanket designs need to consider all these issues and more - and will be tested for real with a blanket module on ITER.

Q: 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?
A: 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.

Q: Even if you could sustain fusion for prolonged periods, how do you extract power from the reactor?
A: 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.

Q: How much electricity could be produced in the best scenario?
A: I have consulted with one of my colleagues here at Culham who studies possible fusion reactor designs and the largest considered so far is about 3GW (this compares to present typical coal fired stations at 1-2GW). In theory, the larger the reactor, the more electricity it would produce, so this is not an upper limit.

Q: You state that a fusion reactor would generate ~1500 Megawatts but what is the time span in which that amount is produced?
A: 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 its 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.