The Need For Fusion

Fusion Engineering and Design 74 (2005) 3–8

The need for fusion Chris Llewellyn Smith Euratom/UKAEA Fusion Association, Culham Science Centre, Abingdon OX14 3DB, UK Available online 3 October 2005

Abstract World energy use is predicted to double in the next 40 years. Currently 80% is provided by burning fossil fuels, but this is not sustainable indefinitely because (i) it is driving climate change, and (ii) fossil fuels will eventually be exhausted (starting with oil). The resulting potential energy crisis requires increased investment in energy research and development (which is currently very small on the scale of the $3 trillion p.a. energy market, and falling). The wide portfolio of energy work that should be supported must include fusion, which is one of the very few options that are capable in principle of supplying a large fraction of need. The case for fusion has been strengthened by recent advances in plasma physics and fusion technology that are reflected in the forthcoming European Fusion Power Plant Conceptual Study, which addresses safety and cost issues. The big questions are – How can we deliver fusion power as fast as possible? How long is it likely to take? I argue for a fast track programme, and describe a fast-track model developed at Culham, which is intended to stimulate debate on the way ahead and the resources that are needed. © 2005 Chris Llewellyn Smith. Published by Elsevier B.V. All rights reserved. Keywords: Energy; Fusion

1. Introduction In this talk I shall 1. Describe the looming energy crisis. 2. Discuss what should be done, including recognising that only fossil fuels, solar power (in principle, although it is currently far too expensive in practice), nuclear fission and fusion can meet a large fraction of need. 3. Describe the prospects for fusion, as revealed by the recent European Power Plant Conceptual Study, which shows that (barring surprises) power stations E-mail address: [email protected].

with acceptable performance are accessible without major advances. 4. Describe a model of the fast-track development of fusion that has been developed at the Euratom/UKAEA Fusion Association, which shows that with a properly funded project-orientated approach, a prototype fusion power station could be putting power into the grid within 30 years.

2. The looming energy crisis The International Energy Agency predicts that energy use will increase 60% by 2030 and double by 2045. Currently, 80% is derived from burning fossil

0920-3796/$ – see front matter © 2005 Chris Llewellyn Smith. Published by Elsevier B.V. All rights reserved. doi:10.1016/j.fusengdes.2005.08.015

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Fig. 3. Annual number of closures of the Thames Barrier, 1983–2002.

Fig. 1. Atmospheric concentration of CO2 (in parts per million by volume) over the last 60,000 years.

fuels. This is driving potentially catastrophic climate change and generating debilitating pollution. There is therefore an urgent need to find alternatives, which is increased by the fact that fossil fuels will eventually run out, starting with oil. The atmosphere is a delicate system and it is being dangerously provoked by the increase in atmospheric CO2 that has occurred since the industrial revolution (Fig. 1). The result appears to be an increase in the average global temperature (Fig. 2). The temperature rise is already producing observable effects. Fig. 3, for example, shows the observed frequency of closure of the Thames barrier that protects London against tidal surges: it is increasing and much greater than the original expectation, based on the historical record, of once every 2 or 3 years. Major

Fig. 2. Observed average global temperature over the last 150 years compared to model simulations.

future effects could include rises in sea level that could put areas currently occupied by hundreds of millions of people under water by the end of the century, and major perturbations of the monsoon that could be catastrophic. The ambitious goal of limiting atmospheric CO2 to 500 ppm by 2050 is often quoted, which would ameliorate but not remove all problems. The US Department of Energy estimates that in order meet this goal, 20 TW – of the predicted total world power consumption of 30 TW – would have to be produced without CO2 . This 20 TW is almost 50% more than today’s total power market (of 14 TW). To quote the US Department of Energy ‘the technology to generate this amount of emissionfree power does not exist’. In any case, fossil fuels will not last forever. At current rates of consumption, there is enough coal for several hundred years (but consumption is currently growing 1.4% pa) and enough gas for about 150 years (but consumption is currently growing at 2.35% pa). There are also huge amounts of ‘unconventional’ oil (shale and tar sands), which however will mostly be very expensive to convert to usable forms, both in terms of the cost and in terms of CO2 production and energy. What about conventional oil? There is a Saudi saying ‘My father rode a camel. I drive a car. My son flies a plane. His son will ride a camel’. This may be true. It is generally believed, on the basis of past experience in particular regions (the USA, the North Sea, . . .), that when half the world’s original endowment of accessible conventional oil has been used, production will decline by perhaps 3% pa as pressure drops in the older (generally larger and more easily found) oil wells and new wells become harder to find. Estimates

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of the world’s original oil endowment (known and yet to be discovered) have been stable and consistent for around 50 years, with one exception. The exception is the estimate of the US Geological Survey, which was increased by 40% in 2000 on the basis of assumed future improvements in extraction. The mean USGS prediction implies that the peak of oil production will occur in about 25 years, which is not long to introduce alternative energy sources for transport, or develop and deploy the means for large scale conversion of coal and/or unconventional oil to usable oil. Many analysts believe that the peak will occur sooner, perhaps even in 5–10 years, following which we might anticipate ‘price increases, inflation, recession and international tension’. Better understanding is urgently needed of whether the peak really is imminent.

3. What needs to be done? First, wider recognition of the scale of the problem is needed, and that it can only be solved by new and/or improved technologies (although fiscal measures designed to change the behaviour of consumers, and stimulate R&D by industry, will also be essential). Second, increased investment in R&D on energy is crucial. In fact, despite growing concerns about pollution, climate change and security of energy supply, publicly funded energy R&D has gone down 50% globally since 1980 in real terms, while private funding has also decreased world-wide, e.g. by 67% in the USA in the period 1985–1998. The size of the world’s total energy market, which is US$ 3 trillion pa, provides a reference scale. A 10% increase in average energy prices would cost US$ 300B pa, while the market for a technology that captures just 1% of the market is US$ 30B pa. The solution will be a cocktail, and we must explore all sensible avenues. What should we seek? Increased energy efficiency—yes (much can be done and it should have high priority, although it will ameliorate rather than solve the problem). CO2 capture and sequestration—yes (although there are big challenges and uncertainties, and – if it is possible – it will add to costs). Development and deployment of renewables—yes (although, with the exception of solar power – which is currently very expensive, and not well matched to demand geographically or temporally – renewables do

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not have the potential to meet a large fraction of global demand). Energy storage—yes (new storage methods will be essential if intermittent energy sources are to become more than marginal players, but note that energy storage/retrieval inevitably produces significant losses). Alternative power sources for (or systems of) transport—yes (including the development of hydrogen as a carrier [NB not a source] of energy, although there are huge challenges to be met, and of bioethanols). Nuclear—yes (at least until fusion is available, although nuclear power faces political hurdles in many countries, despite remarkable improvements in its reliability, safety and cost, and breeder reactors will be needed sooner or later if there is a large expansion). Fusion—yes. Apart from burning fossil fuels (as long as they last), solar power (which is currently not viable or economical except for niche uses) and nuclear fission, fusion is the only known technology capable in principle of producing a large fraction of the world’s electricity. With so few options, I believe that we must develop fusion (as well as the other options) as fast as possible, even if the timetable for success is uncertain. JET has produced 16 MW of fusion power and, with results from other tokamaks, shown that controlled fusion can be achieved. The big question is: how long will it take to develop and test the materials and technology needed to make robust, reliable, economical fusion power stations?

4. The European fusion power plant conceptual study This study, which will be described in more detail by David Maisonnier and David Ward in later sessions, looked at four models (A–D) as examples of a spectrum of possibilities. Systems codes were used to vary the designs, subject to assigned plasma physics and technology rules and limitations, in order to produce an economic optimum. The resulting parameterisation of the cost of fusion-generated electricity as a function of the design parameters should be used in future to prioritise research and development objectives. The near-term models (A and B) are based on relatively modest extrapolations of the relatively conservative plasma performance assumed at ITER. Models

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C and D assume progressive improvements in performance, especially in plasma shaping, stability and divertor protection. Model A is based on a conservative choice of materials (blanket structure made of Eurofer—a ferritic/martensitic steel; tritium generation/neutron enhancement from lithium-lead in a water cooled blanket; a tungsten and copper water cooled divertor) and would have a coolant temperature of 300 ◦ C. Models B–D would use increasingly advanced materials and operate at increasingly higher temperatures (the most speculative model D would use silicon carbide as a structural material for the blanket; liquid lithium-lead as a tritium generator/neutron enhancer and coolant in the blanket; and have a lithium-lead cooled tungsten/silicon carbide divertor: the coolant temperature would be 700–1100 ◦ C). It was found (semi-empirically) that the cost of fusion-generated electricity decreases with the electrical power output (Pe ) approximately as Pe −0.4 . In the power plant study, it was assumed, conservatively, that the maximum output acceptable to the grid would be 1.5 GW. Given the increase of temperature and hence thermodynamic efficiency, the size and gross fusion power needed to produce Pe = 1.5 GW decreases from model A (with fusion power 5.0 GW) to D (fusion power 2.5 GW). The cost of electricity, which is dominated by the capital cost, also decreases with size from 9 Eurocents/kWh for an early model A to 5 Eurocents/kWh for an early model D (these costs would decrease as the technology matures). Even the first cost would be competitive with other generating costs if there was a significant carbon tax. The power plant study shows that economically acceptable fusion power stations, with major safety and environmental advantages, seem to be accessible through ITER with material testing, in parallel if possible, at IFMIF (but without major material advances).

5. The Culham fast-track study This recent study (I. Cook et al., UKAEA FUS 521) produced a critical path analysis and plan for fusion development, designed to be used to (i) prioritise future research and development, (ii) drive forward the rapid development of fusion power, and (iii) provoke discus-

sion. Using technical targets derived from the power plant conceptual study, it began by identifying issues that still need to be resolved, and which will be resolved by existing devices, ITER, IFMIF or the first prototype power station, which has become known as DEMO (for Demonstrator), respectively—see Fig. 4. The next step was to identify information that will be needed to finalise the design of DEMO. Assuming just in time provision of the necessary information, this leads to the construction timetable for DEMO shown in Fig. 5, which also shows feed-through of information from ITER, IFMIF and DEMO to the first generation of commercial fusion power stations (although this is obviously much more speculative). Several comments on Figs. 4 and 5: 1. Although IFMIF does not produce many ‘hits’ in Fig. 4, they are unique and it is absolutely essential. 2. The first phase of operation of DEMO is not expected to display high availability, and will be used to test concepts, e.g. for blanket and divertor design. There will then be a change of blankets and divertors (similar to that which will occur at intervals in the life of a commercial power plant), and DEMO will move on to a phase 2 of higher availability that should demonstrate the commercial viability of fusion power. 3. Testing of blanket designs, etc. does not need a device anything like as large as DEMO. It could be done with a smaller Component Test Facility (CTF) that would not be required to produce a net power gain or to generate its own tritium. The Culham study shows that if a CTF could be built and brought into operation with tritium in the year 21, which would seem reasonable assuming the necessary will and funding, the first phase of DEMO could be skipped and phase 2 operation advanced from year 33 to year 29 (the advent of commercial fusion power would correspondingly be advanced to year 39). 4. The Culham fast-track timetable reflects an orderly, relatively low risk, approach. It could be speeded up if greater risks were taken, e.g. starting DEMO construction before in situ tritium generation and recovery have been demonstrated. Risks could be reduced by constructing several DEMOs, and several ITERs and IFMIFs, without compromising – indeed possibly speeding up – the timetable.

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Fig. 4. How issues to be resolved before construction of a fusion power plant will be addressed by different devices.

Fig. 5. Results of the Culham fast-track study.

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5. The fast track assumes that ITER and IFMIF come in to operation in parallel, which is highly desirable but may not be realistic (some delay in IFMIF construction might however be tolerable without comprising the end date, especially if a CTF is built). It should be stressed generally that the fast-track model is a technically feasible plan, not a prediction. Meeting the timetable will require a change of focus in the fusion community to a more projectorientated ‘industrial’, approach, accompanied of course by the necessary political funding and backing.

6. Concluding remarks The world needs major sources of environmentally responsible energy. Fusion is one of very few options. The results of the Power Plant Conceptual Study imply that the time has come to move to a project-orientated fast-track approach designed to lead to the construction of DEMO as soon as possible. In parallel there should be a ‘Concept Development’ line in the programme, focussed on stellarators and spherical tokamaks (which could be the basis for later DEMOs and power plants), with the possibility of some ‘blue skies’ work on both materials and plasma physics. These activities are pro-

ducing additional physics, that feeds into the fast-track line, and provide an insurance policy should there be major surprises. Delivering fusion on the timescale suggested by the Culham fast-track study will require a change of culture in the fusion community to a project oriented, ‘industrial’, approach, accompanied by the necessary political backing and funding. The first step is, I believe, for the fusion community to agree an aspirational/guiding fast-track model. I hope that the Culham study will stimulate the adoption of such a model. We then need to persuade governments of the importance of turning our aspirations into reality. I would like to end with Lev Artsimovitch’s celebrated reply to the question: ‘When will fusion be ready?’ which, roughly translated, was: ‘Fusion will be ready when society needs it’. I believe that the need is already very clear. We must aspire and work to deliver fusion as fast as we can. Let us hope that we are not too late.

Acknowledgements This work was funded by the UK Engineering and Physical Sciences Research Council and Euratom.