Chamber Science & Technology Key Question #4:

1. For the development of fusion energy, what are the primary materials and materials-interaction feasibility issues for structural, insulator, liquid breeder, ceramic breeder, coolant, neutron multiplier, plasma-facing, optical, mirror and magnet materials?

3. What advances in materials development and modeling may be possible over the next 10 years that can contribute to improving the attractiveness and competitiveness of fusion energy systems, as well as lowering the cost and time for fusion R&D?

5. Are the key materials R&D issues being addressed in the current fusion technology programs? What is the proper balance between structural and non-structural materials R&D, irradiation vs. non-irradiation testing, and fundamental vs. applied studies?

Prospectus

The appropriate selection of materials is a key factor in realizing the full potential of fusion energy. The performance of first-wall and divertor structural materials has a significant impact on fusion economics, environmental issues and safety. In addition, numerous non-structural materials (e.g., plasma-facing, ceramic and liquid breeders, coolant, insulator, optical, etc.) are required to successfully design inertial- and/or magnetic-fusion energy power plants. Materials issues are specifically mentioned in the supporting objectives of four of the five elements of the OFES Technology Program: Enabling Technologies, Advanced Technologies, Advanced Materials, and IFE Chamber/Target Technologies (cf. C.C. Baker, The US Technology Program, Version 5, December 4, 1998, http://www.fusionscience.org/).

The emphasis on materials R&D is most clearly visible in the OFES Advanced Materials Program. The currently-defined goal of this program is “ to develop structural materials that will permit fusion to be developed as a safe, environmentally acceptable and economically competitive energy source ”. Materials R&D is also highlighted in the Enabling Technologies (develop high-performance low-cost superconducting magnets, understand plasma-materials interactions and develop reliable plasma-facing components, etc.), Advanced Technologies (perform R&D to establish knowledge base...), and IFE Chamber/Target Technologies Program (assess chamber and final optic materials development requirements, etc.).

There are a number of important questions with regard to the scope and direction of the current materials programs. Are the materials programs addressing the needs of the engineering design communities in their efforts to develop attractive and competitive fusion power systems? Is there adequate interfacing between the materials and plasma sciences communities to address issues such as the electromagnetic effects of ferritic steels in a magnetically-confined reactor? Within the materials programs, what is the proper balance and timing of activities in the areas of basic materials studies and modeling, development of engineering databases, and component testing?

Are there materials performance issues which would effectively elevate or eliminate certain blanket and divertor design concepts? Most blanket designs involve integrated structure/coolant/breeder systems. If a particular coolant, structural or breeder material is determined to be unfavorable, it can impact the entire blanket design. For example, if there are mechanistic reasons why SiC/SiC composites cannot maintain a high enough thermal conductivity in a radiation environment, then a number of designs may be rendered impractical. On the other hand, if high-performance SiC/SiC composites can be developed, the attractiveness of these high thermal-efficiency concepts increases significantly.

What are the state-of-the-art materials developments that may have a profound impact on fusion energy in the next decade? Examples of these are: stir-friction welding for field construction and in-situ repair of refractory materials; new non-structural materials such as KU-1 quartz, free-standing CVD diamond wafers and high T _C superconductors; creep-resistant oxide-dispersion-strengthened copper and ferritic-steel alloys which allow higher temperature operation; advances in rapid-prototyping fabrication methods and advances in computational materials sciences which allow “materials by design”.

What are the technical bases for the current materials R&D programs? Do the Advanced Materials and Technology Program road maps provide optimal interaction between these R&D efforts? What interaction checkpoints are needed? What resources and time scales are needed to develop particular structural and non-structural materials? Is there sufficient leveraging with international programs?

5. Prioritized list of recommended fusion technology R&D activities for the next ten years (irradiation and non-irradiation; include likely international collaborations): all