The Charter of the ITER Council to this Special Working Group (SWG) read as follows:

"Preamble

- In accordance with Article 10 of the ITER EDA Agreement,

- with reference to the SWG Charter decided by the ITER Council at its thirteenth meeting, Attachment 1, taking account, in particular, of the ITER Council charges regarding its two tasks, i.e.,

1) the SWG would propose technical guidelines for possible changes to the current detailed technical objectives and overall technical margins, with a view to establishing option(s) of minimum cost still satisfying the overall programmatic objective of the ITER EDA Agreement,

2) pursuant to Art. 2(e), the SWG would also provide information on broader concepts as basis for its rationale for proposed guidelines, and articulate likely impacts on the development path towards fusion energy,

- recognizing that it is of crucial importance to the Parties' fusion programmes to pursue the joint activities during an expected three-year extension of the EDA with a general intent to enable an efficient start of possible, future ITER construction at the end of this period, and in this regard recognizing the importance of pursuing joint preparatory efforts in all relevant domains,

- recognizing that in case the Parties would eventually be unable, for financial reasons to proceed to the construction of the presently foreseen device, it is prudent to plan now to have available, at the time of decisions on construction, option(s) of ITER whose cost for the partners would be reduced. This should be accomplished by reducing the detailed technical objectives and possibly decreasing physics margins while insuring that the engineering margins remain such that safety and performance of the device are not impaired and retaining the overall programmatic objective of ITER."

Within Task #1, the SWG provided its answer on 19 May 1998.

The Special Working Group has agreed to the following as its answer to Task #2.

I. RATIONALE FOR FUSION POWER DEVELOPMENT

Energy availability has always played an essential role in socio-economic development. The stability of each country, and of all countries together, is dependent on the continued availability of sufficient, reasonably priced energy. Per capita energy consumption in the various regions of the world is correlated with the level of wealth, general health and education in each region. World energy consumption has increased over time and is projected to continue increasing, in particular to meet the need for a greater per capita energy consumption in the developing world. The growth in energy demand will be exacerbated by the almost doubling of the world's population expected to occur, mainly in the developing countries, within the next fifty years.

While, globally, there are significant resources of fossil and fission fuels, and substantial opportunities for exploiting renewable energies, numerous countries and some of the developing areas experiencing major population growth are not well endowed with the required resources. Further, utilization of some resources may be limited because of environmental impact. A sustainable development path requires that the industrialized countries develop a range of safe and environmentally-benign approaches applicable in the near-, medium-, and long-term. Continuing to meet the world's long-term energy requirements raises challenges well beyond the time horizon of market investment, and hence calls for public action.

It is becoming increasingly apparent that by continuing to burn fossil fuels even at the present rate, without substantial mitigation of the carbon dioxide emissions, mankind is conducting a major experiment with the atmosphere, the outcome of which is uncertain but fraught with severe climatological risks. Prudence requires having in place an energy research and development (R&D) effort designed to expand the array of technological options available for constraining carbon dioxide emissions without severe economic and social cost.

Fusion offers a safe, long-term source of energy with abundant resources and major environmental advantages. The basic fuels for fusion - deuterium, and the lithium which is used to generate tritium - are plentifully available. Even the most unlikely accident would not require public evacuation. During operation, there would be virtually no contributions to greenhouse gases or acidic emissions. With the successful development of appropriate materials, tailored to minimize induced radioactivity, the wastes from fusion power would not require isolation from the environment beyond one hundred years.

With successful demonstration of key fusion technologies and further optimization of the fusion power-plant concept, fusion is expected to have costs in the same range as other long-term energy sources. Thus, fusion power plants could eventually be deployed to provide a substantial fraction of world electricity needs.

If fusion R&D can be maintained as discussed in this report, with feasibility demonstrated by 2020, a power plant could be producing electricity by about 2050. Thus fusion can provide an attractive energy option to society in the middle of the next century. An important conclusion of a comparison with other energy sources is that fusion could begin to be deployed at a time when the utilization of other sources of energy is uncertain, and when the climate issue is likely to have become more critical than today. Accordingly, fusion R&D should proceed at least on the presently foreseen time-table to assure the availability of this energy option when and where needed.

II. OVERVIEW: MAGNETIC FUSION DEVELOPMENT

Achievement of safe, environmentally attractive and economically competitive fusion energy systems depends on an integrated approach to development of materials and technology and optimization of the plasma configuration .

The development of a commercial fusion power plant based on the principles of magnetic confinement must address four main challenges:
- demonstration of scientific feasibility by developing a stationary burning core having high fusion power gain,
- demonstration of technological feasibility by developing required components and integrating them with the core,
- demonstration of the safety and environmental attractiveness of fusion, and,
- demonstration of the economical viability of fusion.

II.1. Development Path

The national and multinational programs are addressing these challenges by progressing along several paths. In the early days of fusion research, scientific feasibility was pursued by exploring a wide range of concepts independently. After a decade or so, based on its performance, the tokamak emerged as the main-line concept with other concepts investigated in parallel as alternatives which might, in the longer term, prove more attractive for power generation. Progress in the tokamak program has been significant, with fusion power (16 MW) now comparable with the input heating power and significant energy production (22 MJ). At the time of the start of the International Thermonuclear Experimental Reactor (ITER) partnership in the late 1980's, and after the joint experience gained from the earlier International Tokamak Reactor (INTOR) activity, each of the four ITER Parties had recognized that an integrated major step in fusion R&D was required, which would build upon the results from the then-current generation of large tokamaks, such as JET, JT-60 T-15 and TFTR, and would precede the construction of a demonstration power plant (DEMO). Conceptual design studies for such a step were well advanced. It was, therefore, both natural and desirable that all Parties joined together in the ITER partnership, to share cost and to accomplish more than could one Party alone.

II.2. ITER

Following an initial Conceptual Design Activity, the four Parties conducted the ITER Engineering Design Activities (EDA) from 1992-98, which succeeded in designing a tokamak-based integrated step towards a DEMO. The DEMO would demonstrate quasi-stationary generation of a significant amount of net electrical power. The overall programmatic objective of ITER, which has guided the EDA, is "to demonstrate the scientific and technological feasibility of fusion energy for peaceful purposes." ITER, as described in the Final Design Report, would accomplish this objective by demonstrating controlled ignition and extended burn of deuterium-tritium plasmas, with steady-state as an ultimate goal, by demonstrating technologies essential to a power plant in an integrated system, and by performing integrated testing of the high-heat-flux and nuclear components required to utilize fusion energy for practical purposes. Further development of the ITER design is described in Sec. III.

II.3. Concept Development

The common challenge for all the magnetic fusion concepts is the simultaneous optimization of stability, confinement and power and particle exhaust, in order to increase the attractiveness of the power-plant concept (for example, reducing the magnetic field, plasma current, and peak exhaust heat flux densities, providing easier maintenance, reducing demands on auxiliaries, achieving steady-state operation and mitigating or eliminating disruptions). These efforts include continued optimization of the tokamak performance, as well as the development of other lines such as the helical systems (stellarators, heliotrons, etc.), the reverse-field pinch, compact toroids (spheromak and field-reversed configurations), and the spherical torus/tokamak.

Not only is there promise, at varying degrees, in these different conceptual approaches, but, in addition, they contribute to the improvement and understanding of magnetic fusion systems in general. Furthermore the requisite technologies are largely common to the different approaches. Such studies are an important part of fusion research and are being developed in parallel with the ITER program and the long-term technology programs of the Parties.

II.4. Technology

Technology and materials R&D play an essential and multi-faceted role in the accomplishment of the challenges described in Sec. II. Progress in fusion science has depended on the development of the enabling hardware and methods to create, sustain and control high-temperature plasmas (e.g., magnets, heating and fueling systems, vacuum technology, etc.). A particular challenge continues to be the development of plasma-facing components to withstand high heat- and particle-fluxes, as well as off-normal events such as disruptions. In the longer term, technology R&D aims to develop materials and components that will achieve the desired levels of performance (e.g., high temperatures and wall loadings), lifetimes, availability (sufficient component reliability and acceptable change-out times), and safety and environmental attractiveness, with emphasis on in-vessel systems. Such technology R&D, as well as physics R&D, often has important near-term industrial spin-off applications to fields outside of fusion.

Particularly important is the development of radiation-resistant and low-activation materials, a key part of which is producing data on neutron irradiation effects. In the near-term, the program depends primarily on fission reactor irradiations. Reduced-activation advanced materials could be incorporated into the ITER blanket/shield components in later phases. In the longer term, there is the potential for recycling a significant fraction of power-plant materials. Facilities for testing materials subjected to 14 MeV neutrons will be required.

Until a tritium-generating blanket is developed, burning plasma experiments and all D-T fusion facilities will depend on external sources of tritium; the availability of such tritium must be taken into account in planning the size and timing of facilities.

II.5. International Collaboration

International collaboration has played a significant role in fusion R&D since its inception. As an international collaboration, the ITER framework, under the International Atomic Energy Agency (IAEA) auspices, is unique because of the sharing of the decision-making process and the sharing of costs and benefits. In addition, a number of multilateral international agreements under the International Energy Agency auspices, as well as a number of bilateral framework agreements have been implemented. All these arrangements have been adequate to make accessible to others devices hosted by one Party. However, large-scale projects, which fulfill world-wide needs recognized by all partners and which involve large investments by multiple parties, require different arrangements.

The ITER program was initiated in 1986 by summit level agreement of Heads of Government to emphasize the importance of the world-wide aim at developing fusion for peaceful purposes, and for the benefit of all human kind. The framework of ITER was established among the world's four major fusion programs at the governmental level. As such, the ITER collaboration represents a qualitative and quantitative advance beyond earlier international collaborative agreements through focusing on the science and technology, sharing the benefits of the investment and learning how to handle the complexities of relationships among the partners. The results from the ITER-EDA work have reaffirmed the benefits arising from the cooperation.

III. ITER APPROACH

In line with the detailed technical objectives set for the EDA, under the overall programmatic objectives, a fully-documented detailed design of ITER was produced on schedule, with its associated safety analyses and description of manufacturing processes and their associated costs. The Final Design Report (FDR) of the EDA, "ITER Final Design Report, Cost Review and Safety Analyses" was reviewed by the Technical Advisory Committee and by Parties individually, with a strong input from industry, and approved by the ITER Council. The FDR capital cost estimate was within the range foreseen at the beginning of the EDA by the ITER Council. It was concluded that the ITER machine would fulfill the overall programmatic objectives and the detailed technical objectives and is supported by the results of the technology R&D activities conducted during the EDA. Most of the R&D has been completed, with some validation tests still to be carried out. Furthermore, the physics program in experiments, theory, and modeling has increased the understanding of the constraints set by plasma physics -- confinement, pressure and density limits, helium removal, disruption effects, and divertor operation.

ITER represents a demonstration of fusion technologies under power-plant-relevant conditions: superconducting magnets, additional heating, fuel handling and vacuum pumping systems, plasma-facing components (divertor and first-wall) designed to be capable of handling heat and particle fluxes in the power-plant range with steady-state heat removal.

There is an important physics dimension to the integrated capability of an ITER, namely the opportunity to optimize, simultaneously, plasma-core and edge conditions sufficient to achieve good energy confinement, which are compatible with divertor conditions to accommodate the particle and heat fluxes. ITER also provides the opportunity to explore the compatibility of improved tokamak modes and profile control in regimes of strong self-heating and steady-state operation -- a test for tokamak power plants.

A major issue for fusion power plants will be achieving high availability. ITER operation would represent the first real test of achieving high reliability and practicality of maintenance in a fusion facility.

ITER would require radiation protection, remote handling, tritium handling, etc. The ITER-FDR design and safety analyses show the capability of fusion in regard to safety and environmental issues. The operation and maintenance of an ITER should demonstrate the capability to optimize the safety design of DEMO.

ITER would provide for tests of power plant-relevant, tritium-regeneration, blanket-test modules, with the option of a demonstration of electricity-generation.

Despite the general achievements presented in the FDR, it appears prudent in the present socio-economic situation to be in a position to offer lower-cost options to enable an effective start of possible future ITER construction. Recognizing this situation, the ITER Council assigned to this Special Working Group the task to "propose technical guidelines for possible changes to the current detailed technical objectives and overall technical margins, with a view to establishing option(s) of minimum cost while still satisfying the overall programmatic objective of the ITER EDA Agreement." Guidelines for a modified-objectives (reduced-cost) ITER were given in the SWG report on Task #1 of 19 May, 1998.

These guidelines would shift the focus of detailed technical objectives from achieving ignition to achieving high fusion-energy gain, without precluding the possibility of achieving ignition. Because progress has been made during the EDA in design, technology development and physics, it appears possible to design a reduced-cost option with attractive performance characteristics. From the preliminary results of the analysis made by the JCT and the Parties, it appears that a machine at approximately half of the direct capital cost of the ITER-FDR machine could satisfy ITER's overall programmatic objective, although with modified fusion objectives, while ensuring that the engineering margins remain such that safety and performance of the device are not impaired.

In the discussion below, the ITER-FDR design is referred to as ITER-I and the reduced-cost options as ITER-II.

The table below shows a comparison of some ITER-I reference parameters with corresponding ranges of representative parameters of ITER-II options, which have been developed by the ITER team taking advantage of the engineering and technology developed during the EDA.

Note that the range of extrapolation to ITER is approximately the same, in physical size, as the Parties had to make when commencing the design of the present generation of devices.

While additional theoretical and experimental work is required in some areas, projections of ITER's plasma performance show that sustained burn (Q = 10 -> [infinity]), and adequate plasma power and helium exhaust can be obtained with operation in a plasma subject to edge-localized modes (ELM's) and internal sawtooth activity. Experimental results from tokamaks and modeling codes confirm the ITER divertor concept of detached or partially-detached operation with controlled additions of recycled impurities. Furthermore, due to its better plasma-shaping capabilities compared to ITER-I, ITER-II still does not preclude the possibility of reaching ignition. For a power plant, Q >= 20 is sufficient.

All ITER designs have sufficient flexibility provided by the poloidal field coils and heating and current drive systems to exploit plasma operational scenarios necessary to obtain steady-state operation at Q = 5.

Advanced materials (e.g., low activation ferritic steels, etc.) would be incorporated into blanket/shield test modules, and would be considered for replacement of in-vessel components in the later phases of both ITERs. These activities will allow further demonstration of the potential of the safety and environmental aspects of fusion.

IV. BROADER CONSIDERATIONS WITHIN THE
MAINLINE TOKAMAK PROGRAM

In Task 2 of its charge from the ITER Council, the SWG was asked to, ". . . also provide information on broader concepts as basis for its rationale for proposed guidelines, and articulate likely impacts on the development path towards fusion energy." Keeping in mind the fusion development path described in Sec. II., the SWG has restricted its attention to the next major steps in the mainline tokamak program.

The overall programmatic objective of ITER is "to demonstrate the scientific and technological feasibility of fusion energy for peaceful purposes," in order to proceed to a subsequent demonstration power plant, DEMO. As discussed earlier, such an accomplishment requires the integration of many scientific and technological features under power-plant-like conditions, and an integration step such as ITER would inevitably be required prior to DEMO.

There are many physics and physics-technology issues to be addressed in advance of DEMO. Examples of such issues include:
- steady-state burning plasma with current-driven profile control and a high bootstrap current fraction,
- a high-performance core with an effective divertor, including high heat-flux steady-state components,
- superconducting magnets with a high power DT burning plasma,
- remote maintenance in a full-scale fusion power system,
- testing of tritium-producing blankets and of structural materials, and
- tritium processing.

Two strategies may be considered to accomplish these objectives. One is the ITER strategy as discussed in Sec. III. The second strategy is to delay the integration step and embark in the near term on separate specialized facilities addressing selected critical issues. These facilities would be of the same range of size and cost as the present largest experimental devices ($1B to $2B). Within this latter strategy, two classes of such facilities have been considered:
- short-pulse, copper magnet, DT-burning plasma experiments, and
- long-pulse, superconducting magnet, DD steady-state experiments.

For either strategy, a 14 MeV neutron source for materials development is likely needed in parallel.

A burning plasma experiment would provide information on confinement and stability of high-performance DT plasmas. A superconducting DD experiment would provide information on steady-state operation of a diverted tokamak plasma. All three facilities, including the 14 MeV neutron source, would provide valuable experience with fusion materials and technologies.

However, while the first two of these facilities would be designed to address some of the same important plasma science issues as are to be addressed in ITER and could make important contributions, they would do so in conditions falling far short of those in ITER in several important respects:
- they operate at either much reduced fusion-power conditions or much reduced pulse length,
- by addressing issues in separate facilities, they fail to address key issues of physics-physics and of physics-technology integration,
- by focusing on plasma science objectives, they do not address the full range of fusion technology objectives of ITER, a prime example being ITER's capability of testing operational blanket modules.

Clearly, the important class of physics performance issues associated with burning plasmas in full non-inductive steady-state operation could not be addressed. The full non-linear interplay between alpha-particle heating, confinement barriers and pressure and current profile control, and their compatibility with a divertor, can only be addressed in an integrated step.

A key question effectively asked of the SWG is whether the combination of specialized facilities under consideration could replace ITER. Given the arguments presented above, the answer is that they could not.

Furthermore, if such facilities were constructed in the place of ITER, and the construction of the integration step were to await results from these facilities, the integration step would presumably be improved, but would be delayed very substantially, perhaps ten years or more, and the total cost of the program would be much increased. The impact in cost and schedule of unnecessarily delaying this integrated demonstration could be devastating to the international effort to develop fusion power, and to the ability of fusion to contribute to the world energy economy in a timely fashion.

It is an important conclusion that fusion development is now scientifically and technically ready to take a step such as ITER, i.e., to enter the regime of fusion energy demonstration.

V. CONCLUSIONS

The successful development of fusion energy requires meeting the basic challenges of scientific and technological feasibility as well as environmental attractiveness and economic viability. The long-term goal is a convincing demonstration of the resolution of these issues in a demonstration power plant (DEMO). A critical prior step is to integrate high energy gain plasmas at or near steady-state conditions with power-plant-prototypical technologies, and demonstrate safe operation of a fusion power system.

The international program is technically ready to proceed with the construction of an experimental facility which in an integrated manner addresses scientific and technological issues before DEMO. Many of these issues can be addressed only in near-power-plant conditions. ITER will provide the conditions required for these critical tests, and it has focused the attention of the world fusion community on key scientific and technical issues. Through this collaboration, the cost and benefits of this important step can be shared by the ITER Parties.

Because of concerns of cost, but coupled with advances in physics and technology made during the ITER EDA, there is now both increased incentive and opportunity to seek an attractive lower-cost design by modifying the detailed technical objectives. A device, in which it is expected to achieve energy gain of at least 10 and explore steady-state operation, at a direct capital cost of approximately 50% of ITER as described in the Final Design Report, would still satisfy the ITER overall programmatic objective, which is "to demonstrate the scientific and technological feasibility of fusion energy for peaceful purposes."

Successful operation of ITER would provide experience of broad, generic value to fusion energy development:
- the study and control of burning, steady-state plasmas;
- the study of the interaction of such plasmas with material walls, together with the removal of thermal energy and helium ash;
- the development and performance testing of blankets capable of generating tritium and high-grade heat compatible with efficient electricity generation;
- the demonstration of required supporting technologies, and,
- the demonstration of the safety potential of fusion.

The SWG has examined a strategy in which the integration of ITER's long-pulse/burning-plasma scientific and technological objectives, which are essential before moving to DEMO, would be deferred until after experimentation has been completed on a new generation of separate specialized facilities addressing selected critical issues. The SWG concludes that this would delay by 10 years or more the key fusion demonstration and integration step, and would increase the total cost of fusion development substantially. It is the unanimous opinion of the SWG that the world program is scientifically and technically ready to take the important ITER step.