Last month marked the official launch of the High Power laser Energy Research or HiPER project. HiPER is a proposed international laser facility that aims to demonstrate the feasibility of laser fusion as a future source of clean power. PEi talks to Professor Mike Dunne, director of the Central Laser Facility at the Rutherford Appleton Laboratory, UK, and the HiPER project leader.

PEi: Can you describe what HiPER is and how it is being funded?

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Mike Dunne (MD): HiPER is a very large-scale laser facility that is aimed at demonstrating the feasibility of laser fusion as a future energy source. The project is a collaboration between scientists from 26 institutions from ten countries, with six of those countries participating at a national level.

The project itself is a very long-term undertaking, with the aim of the HiPER facility becoming a reality towards the end of the next decade.

The project is divided into four phases. We have just completed phase one, which was a two-year feasibility study and we are now entering the second phase, which is a three-year development phase. The funding for this phase comes in two parts.

There is around €13 million ($16.6 million) of hard cash from three sources – the European Commission, the UK government and the government of the Czech Republic.

There is also a large amount of what is called ‘work in kind’, whereby countries will let us use their staff, equipment, facilities, and so forth. France, for example, is putting in a lot of ‘work in kind’. It is difficult to quantify exactly what ‘work in kind’ contributions amount to, but is probably in the region of €50 million for this phase of the project.

The next phase is a prototyping and detailed development phase, and we believe the scale of that will be in the order of €100 million. The final phase of the project is of course the construction of the HiPER facility itself.

At the moment, however, we simply don’t know with any accuracy what the construction costs will be – it is one of the objectives of the current phase to determine that. Without doubt, however, it will be in the billion euro class, which means it could be €0.5 billion or €2 billion.

PEi: Scientists has been studying laser fusion for close to 50 years. What developments have taken place in recent years to enable the establishment of a project such as HiPER?

MD: There have been two major developments that have lead to the launch of the HiPER project at this time.

The first one is the Americans, and subsequently the French, have heavily invested in building large-scale laser facilities, which are anticipated by the end of this decade to be able to provide the ‘proof of principle’ of laser fusion. So after 50 years of trying we are just a couple of years away from the demonstration that you can get more energy out from laser fusion than you put in by as much as a factor of 30 or so.

The second major development is that scientists have been working on the way in which this ‘proof of principle’ can be taken forward in a far more efficient manner in terms of energy output than the initial ‘proof of principle’. This innovation in efficiency is known as ‘fast ignition’

Thus, the design of the HiPER facility will not directly follow what the USA is doing, with their National Ignition Facility, but will take laser fusion down a more efficient route and move it into detailed development, and as such lay the scientific and technological foundations for a demonstrator reactor.

PEi: Let’s go back to fundamentals, how does fusion work and how can it be used to produce electricity?

MD: It goes back to Einstein. When you force together two small atoms to form a slightly larger one lots of energy is released – typically millions of times more energy than is produced when you burn coal, gas or oil. Fusion, therefore, is essentially mass converting into energy, but in the opposite way to fission. In fission, you break apart large atoms like uranium to create smaller atoms.

In our case with laser fusion, we use isotopes of hydrogen to create helium. At the same time a lot of energy is released in the form of a particle called a neutron. The neutron is absorbed in a blanket that surrounds the reaction chamber, which then heats up. The blanket heats up to around 1000 ºC to super-heat water, which gives off steam that is then used to drive a steam turbine and generate electricity.

In addition to fusion being a source of large-scale energy, it achieves this in a way that is fundamentally clean. That is, there are no carbon-based emissions and no long-lived radioactivity. Furthermore, the hydrogen based fuel required for fusion is plentiful because it is present in ordinary seawater.

We know fusion works because that is the way the Sun works, so the challenge we face is getting it to work here on Earth.

PEi: Currently, there are two methods to drive fusion – magnetically confined fusion, known as magnetic fusion, and inertially confined fusion, known as laser fusion. How do they differ?

MD: Think of magnetic fusion as a furnace where you are holding a large amount of fuel, but in magnetic fusion’s case the fuel is being held together within a magnetic field. You heat it up and it continuously burns and continuously produces energy.

Laser fusion, in contrast, is a repetitive process so think of it more as a car engine, but on a much bigger scale.

First of all you inject your fuel, which in our case is a small pellet (about 1 mm in size) of the hydrogen isotope fuel. You then use a piston to compress the fuel. In our case, the piston is not mechanical, but a laser. A car would then use a spark plug to light the fuel. In laser fusion, we also use a spark plug to light the fuel, but it is ‘spark plug’ laser. Finally, as in a car engine you exhaust the spent fuel and repeat the cycle.

Thus, the way a car engine and laser fusion works is conceptually the same – you have injection, compression, spark plug and exhaust, and then repeat, repeat. In the case of a car engine you do this tens of times a second, but with laser fusion it is five times a second, and produces a gigawatt-scale power output – millions of time more energy than in a car.

PEi: With the International Thermonuclear Experimental Reactor Organization (ITER), which will be sited in Cadarache, France, magnetic fusion is seen as being relatively well advanced, so why is there a need to develop the HiPER facility?

MD: There is no doubt that ITER is well on the way to demonstrating large-scale fusion power output – anticipation is the early 2020s. However, the scale and the importance of the energy problem facing the world makes it inconceivable to me that we should only adopt a single solution.

Laser and magnetic fusion have received similar levels of investment and are predicted to mature within a similar time-scale – somewhere around the middle of this century. Our contention, therefore, is that both technologies should be taken forward to offer a balanced and risk-mitigated strategy for long-term, abundant, clean energy.

If you look at how we tackle current energy production we have a whole range of different carbon-based products – coal, oil and gas, and within renewables, we are exploring multiple options, including wind, wave, solar, etc

Thus over the longer term it does not make sense to narrow it down to one solution, so we should take forward all of them.

One point to make is that neither laser nor magnetic fusion is an immediate solution to our current problem of climate change and energy production. I am not saying that we should pull back from what we are currently doing. We need to push strongly forward with options such as energy efficiency, renewable energy and nuclear fission. However, I believe that fusion offers the best way to tackle the long-term problem, and that both these viable options should be pursued.

PEi: Does laser fusion have any advantages over magnetic fusion?

MD: Both types of fusion have pros and cons. However, from a laser fusion perspective we know absolutely that inertial fusion works as the physics are proven that you can get substantially more energy out than you put in. What remains of course is how to harness that in a way that is amendable to a power plant.

Laser fusion offers another significant advantage, which is that in the longer term it offers the potential for greatly reduced residual radioactivity. It has modes of operation, which uses much less tritium, which is one of the hydrogen isotopes, input, so there is far less neutron output, and therefore less radioactivity induced in the infrastructure.

Deuterium and tritium are bonded to create a neutron, which can be captured to heat water to drive a steam turbine
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One of the big problems in fusion is that you have to contain the fusion reaction itself, so you have some extremely difficult material science problems to solve. The first wall, which is the wall that faces the plasma, has to withstand extremely harsh conditions. At the moment we simply don’t know what material will be able to withstand these conditions, and although we have ideas it has yet to be solved.

One risk is that this first wall could melt, which you do not want to happen. Laser fusion, unlike magnetic fusion, can offer the ability to pre-melt this wall, i.e. have a flowing liquid wall, thereby overcoming the material science problem. Having said that, this obviously introduces its own issues such as how you manage the flowing liquid wall, but people have ideas as to how this can be achieved.

PEi: You mentioned that the HiPER facility would take advantage of ‘fast ignition’. What does that mean, and how does it differ from what I will refer to as ‘conventional ignition’?

MD:Conventional ignition is what the Americans are adopting at the National Ignition Facility, and as I mentioned above, is due to demonstrate laser fusion’s ‘proof of principle’ by the end of this decade.

It is probably helpful to think of conventional ignition as a diesel engine, where you compress the fuel until it ignites, i.e. there are no spark plugs. What this means in terms of laser fusion is that you require a very large laser and incredibly tight controls in terms of the manufacture of the fuel pellet and of the operation of the laser itself.

How the proposed HiPER research facility may look. Construction of the HiPER facility is envisaged to start in the middle of the next decade, with operation set to commence in the early 2020s.
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Although we know the physics works, this adds lots of costs, complexities and inefficiencies to the solution.

Fast ignition innovation is not to adopt a diesel engine-like approach, but to adopt a petrol engine-like approach – you don’t just compress the fuel you use a spark plug to light it. So by decoupling the fuel compression from the heating the process becomes much more efficient. You do not have to compress the fuel as much so your laser can be smaller by say a factor of five, and because you use a spark plug laser to light the fuel you can burn a lot more, so your energy efficiency can be higher by up to a factor of ten. Thus fast ignition creates the opportunity to develop laser fusion into a system that is more compatible with a power plant.

If you went with conventional ignition you would have to invest a huge sum of money in your plant, not least in the laser, which is unlikely make it commercially viable. Whereas if you adopt the fast ignition approach it offers a much smaller capital investment in your plant and offers a more efficient process at the end of the day.

The only downside is it introduces a bit of physics that we haven’t yet proven, and that is one of the reasons to build the HiPER facility, and for doing research at other facilities.

PEi:The HiPER is a European, if not an international, project, so do you have an idea of where the facility is most likely to be based?

MD: There are indications, but no decisions yet. That decision will be taken over the course of the next few years. However, the UK is leading the HiPER project and my organization the Science and Technology Facilities Council is the host institution. We have sites in Oxfordshire (the Rutherford Appleton Laboratory) and Cheshire (the Daresbury Laboratory), and also a good working relationship with the Cullen Laboratory, also in Oxfordshire, which runs the magnetic fusion programme. All three of those sites are credible candidates for the HiPER facility.

Although other nations also may wish to host the HiPER facility, I would say that the UK is definitely one of the frontrunners.

PEi:What do you foresee as the global power industry’s role in the HiPER project?

MD:So over the next few years we would be seeking contact the power industry to help establish and define the objectives and goals we should be aiming at, and to keep our feet firmly on the ground when it comes to what we want to achieve in the longer term.

We will need some guidance from the power community to tell us that if you are going to be credible and anything like a commercial engineering reality you need to live within these constraints and parameters.

As the HiPER facility matures and develops, and demonstrates that this can be made into a reality we would hope to be working ‘hand in glove’ with the power industry to help make the demonstrator reactor a reality.

In terms of technologies and how you couple the fusion process to a power plant, there is a strong overlap between laser fusion and magnetic fusion. Thus, whichever approach you take there are common technology solutions and power plant solutions. So we would looking for guidance and input from the power industry to take us through the technology development phase and commercial engineering development phase. However, we are still ten or so years away from having that substantive discussion.

PEi: Looking to the future, when would you anticipate the first fusion power plant being ready for commercial operation, and what output capacity would you anticipate it to have?

MD: The answer is broadly the same for both laser and magnetic fusion, which means we are talking about a demonstrator reactor being available in this half of this century, so it is really the middle part of this century before you could conceive of anything approaching a commercial power station coming online.

Then over the latter half of this century, with everything progressing as it should, you would then see a rapid escalation of that commercial product.

With regard to an output capacity of a commercial fusion power plant, the majority of the conceptual designs of the power plants are in the range of 2-3 GW of electricity per power plant. There are also designs for smaller plants, as well as conceptual designs for larger plants.

This is one of the areas that the power industry’s input could help by letting us know what it wants and what it needs. When does it become commercially viable to build a few hundred MW power station or a few GW power station? And is it ever commercially viable to build a 10 GW power station?

PEi:Do you have an idea of how much it would cost to build and operate a fusion power plant?

MD: People have done some economic models on what the cost of electricity might be, albeit the ones I’ve seen are probably more than ten years old, and they predict in the region of $0.05-0.08/kWh. The figures are broadly the same for both laser and magnetic fusion. However, you must keep in mind that these models are based on a range of assumptions that may not have held out.

Therefore, the honest answer to your question is that at the moment we don’t know with any certainty. This is the kind of work that needs to be done in the current phase of the HiPER project, so that we can determine whether it is worthwhile progressing to the next phase.

We believe we have a scientific reason for doing it that is very compelling, and we believe we can offer a long-term power production opportunity. What we now need to do is incorporate some harsh commercial and engineering reality to make sure we are pitching ourselves in the right direction.

PEi: If all goes well with the HiPER project, how much do you foresee laser fusion contributing to the world’s total power generation mix?

MD: I have seen studies not so much on the laser fusion, but on magnetic fusion, which predict towards the end of this century 50+ per cent if not the majority of energy supply could feasibility come from fusion production. These studies are of course based on the assumptions that fusion works and is commercially viable.

In contrast to fossil-based fuels, fusion is not limited by fuel or the supply of that fuel. Instead its degree of impact on the market will be dictated by the commercial success or otherwise of it, and at the moment that error bar is huge.

As mentioned above, with current predictions, the cost of electricity fusion should be competitive if the assumptions have held out. This is where I believe common working between the power industry and the scientific community would pay real dividends over the next ten years.