Interview with Dr. Stephen O. Dean

In Japan, major research activities are for magnetic fusion whereas in the US, laser fusion research activities are also very strong. The president of the Fusion Power Associates Dr. Steve Dean has played a role to bridge the government and research institutes in the US. The journal heard from him about the future prospects of fusion research and the research strategies in the US, with focus on laser fusion research that has been led by the US.

Newton: Fifty years have passed since fusion research started in the US. How do you see the present status?

Dean: I think "fusion has a tail wind now". It is highly probable that soon or later fusion may become the most favored energy source. The reason is the fuel supply problem for energy production, in addition to global warming. Fossil fuels will become more and more expensive and eventually will be nearly exhausted.

Newton: what are the advantages of fusion?

Dean: One advantage of fusion is that the fuel can be extracted from water and and is thus available to everyone. Not every area of the world has access to frequent sun, wind, geothermal or coal but every country has water.

Newton: When will fusion electricity generation be achieved?

Dean: It depends upon the government policy. In my prediction, the first fusion power plant will be in operation by 2040, at a probability of 50 %, and by 2060 at 90 %.

Newton: Can fusion power compete, in its generation cost, with other energy sources?

Dean: If one builds a fusion power plant with the present knowledge, its generation cost might be about twice that of a conventional power plant. However, the cost of fusion power will be reduced in the coming few tens of years due to development, whereas generation cost of the fossil fuel plants will increase, due to fuel scarcity and/or environmental regulations.

Newton: What are the reasons for expecting a reduction in fusion electricity cost in the future?

Dean: As research advances, technology is improved and cost is reduced. Also, if many power plants are built, the cost is reduced further. On the other hand, if such things do not take place, fusion will not become practical.

Newton: In 1999, the US withdrew from ITER, but she announced to rejoin it in 2003. What are the reasons behind this?

Dean: In 1999, US fusion funding was cut by about 40 % so that there was a possibility to damage other fusion activities if the US joined the ITER construction. After that, ITER cost was reduced down to about a half, i.e. to 5 B$, compared with 10 B$ then estimated in 1999. The success of the cost reduction is one of the reasons of the US rejoining.

Newton: We understand that in the US, an important issue is electricity generation cost in the future.

Dean: In fusion, there are various approaches and among them are candidates that may produce far cheaper electricity. However, our knowledge on those candidates is limited so that we can not be so optimistic. Nonetheless, as our knowledge advances, a winner may appear and cost may be further lowered.

Newton: We understand fusion can be used for other than electricity generation. What are the other possibilities?

Dean: It is possible to think about generation of hydrogen from water, which can be used for fuel cells. It may be also possible to diminish radioactivities of radwastes from fission power plants, by irradiating the radwastes by neutrons generated in a fusion plant.

Newton: Comparing magnetic fusion with laser fusion, which is more close to practical use, in your view?

Dean: According to our present knowledge, it is not possible to answer clearly that question. However, at present it seems that inertial confinement fusion has a possibility to achieve electricity generation sooner, at less generating cost, with less R&D cost.

Newton: What are the advantages of laser fusion?

Dean: A laser fusion device has a simpler core structure and a device to generate a certain power is smaller. The reason for this is that all the fusion reactions in laser fusion take place in a tiny fuel pellet. Of course, we may encounter problems in the future. When we upgrade our present devices, we may encounter difficulties. Therefore, it is too early to make a definite comment.

Newton: In Japan, fusion research activities are more for magnetic fusion. How about in the US?

Dean: For magnetic fusion, 9.8 B$ was spent since it started in 1951, and for laser fusion 6.5 B$ since it started in 1963. Since US laser fusion research is supported as a part of the nuclear weapons (hydrogen bombs) program, at present the funding is about twice of that for magnetic fusion. Equations to predict the physics of laser fusion can be used also for designing hydrogen bombs, but one can not design a bomb only with the physics of laser fusion.

Newton: I now understand that laser fusion research does not connect directly to military. We know that in the US a large project of laser fusion called NIF is underway. What is this project?

Dean: Using 192 laser beams, NIF aims at, within 10 years, ignition of a small pellet of fusion fuel (energy generated by fusion exceeds that of the injected energy so that the fuel burns naturally). NIF is to generate about 10 to 20 times more energy from fusion than the injected energy. However, repeated irradiation by the NIF laser is not possible -- only one injection at a time.

Newton: In order to achieve laser fusion, a high repetitive irradiation laser is necessary. How do you think about the prospect to develop such a laser?

Dean: Prospect is high. For example, a method using a gas laser (one using gas discharge for laser source) can irradiate repetitively. Or, instead of using a laser, there is a technique to use ion beams from an accelerator. It can generate repetitive pulses. There are other options.

Newton: In laser fusion, Osaka University achieved a success in fast ignition process that attracted attentions of people. How do you think about it?

Dean: The success on fast ignition by Osaka University is praised very much among the experts in the US fusion community. In the US also, this method is pursued as one of the methods to reduce the cost of fusion power plant. Newton: Thank you very much.

Interview with Dr. Robert J. Goldston

The Princeton Plasma Physics Laboratory has led world fusion research since its dawn time. The Mecca of magnetic fusion research PPPL conducts research aiming at development of a low cost fusion reactor in the era after the next step experimental machine of ITER. The director of PPPL Dr. Goldston told Newton of the possibility of realization of a magnetic fusion reactor as well as others.

Newton: Are you sure about the realization of a fusion reactor?

Goldston: We have a great confidence to generate fusion energy at an industrial level. In experiment with ITER, it will definitely be able to generate fusion energy at an industrial level. The most difficult issue is to make it competitive, i.e. to the one usable at a commercial base. I think it is possible. If one can not make it sufficiently cheap, it will not be usable as an energy source and valuable as we expect.

Newton: There may be many issues to be resolved for a commercial reactor. Will it be possible to develop a reactor wall material that can withstand high heat as well as neutrons generated by fusion reactions?

Goldston: Yes, I think it will be possible. A recently achieved dramatic advancement is with so-called ferritic steel. It has a high resistance to neutrons. Another hopeful material is a composite material, a silicon carbide sandwiched by silicon carbide fibers. It is a very advanced material which remains at a very low radioactivity with neutron bombardment.

Newton: Would you please tell us the achievements made with the large Tokamak at PPPL (TFTR) that completed the experiments in 1997?

Goldston: In TFTR, we discovered that plasma current could be maintained by the plasma itself. It is called bootstrap current. With the results, people came to consider plasma completely differently.

Newton: We now understand that with the results of TFTR, a large Tokamak at JAERI JT-60 could operate continuously by this bootstrap current. At present, Tokamak is main line in magnetic fusion research. Will the Tokamak line be also the most attractive for commercial reactor in the future?

Goldston: A simple Tokamak system which will not have a large bootstrap current will be very expensive, so that it will not be able to make a success as a commercial fusion power plant. In order to make Tokamak system successful, I think we need to improve it to a so-called "advanced Tokamak". The advance Tokamak will have a possibility to become a commercial reactor.

Newton: We understand that a spherical Tokamak experiment studied at PPPL, NSTX, is an advanced Tokamak.

Goldston: In a spherical Tokamak, we need a simple and cheap magnet to hold a big plasma. Therefore, it has a possibility to become a less expensive machine. We consider that some of the problems of Tokamak may be resolved by the spherical Tokamak.

Newton: The US announced to rejoin ITER project in 2003. How will the US participate in the ITER project?

Goldston: It may not participate suddenly at the same magnitude as those of EU and Japan, but will enhance gradually the degree of its participation.

Newton: Considering both magnetic fusion and laser fusion, which will realize first a commercial fusion power plant?

Goldston: I believe that both be pursued. If ITER is built, it becomes a powerful machine of magnetic fusion path. In view of demonstrating technology, not only science, it will become a far larger one than NIF. If ITER achieves a big success, probably people will say "Great! Probably OK! Let us go with magnetic fusion!". If ITER can not generate good results, in due course advantage may be given to laser fusion. At present, both lines are competing closely. I myself have been studying magnetic fusion so that I have a strong confidence, but it is undoubtedly that both lines are competing closely. This competing race may be finished at about 5 years after initiation of ITER operation, i.e. 2019.

Newton: When will fusion reactor be realized?

Goldston: If everything goes well after ITER, perhaps a decision will be made by 2030 as to whether to build a demonstration power plant. The demo will start operation 5 to 6 years after the decision, so that electricity will be supplied to the grid.

Newton: Since global environmental problems are increasing, hopes are given also to the natural energies, such as solar power and wind power.

Goldston: Because of fluctuation in the natural energies, many people believe that in practice the natural energies can not become the major electric power source. In the past 100 years, among the people hunting for the concessions for energy resources such as oil, many wars were fought. If fusion power plant is realized, troubles for seeking for energy resources can be avoided, so that such wars can be avoided.

Newton: We sincerely wish it be realized. Thank you very much.