APEX Primary Objectives

The purpose of the APEX study is to identify and explore novel, possibly revolutionary, concepts for Chamber Technology that might in the near-term enable plasma experiments to more fully achieve their scientific research potential and in the long-term substantially improve the attractiveness of fusion as an energy source. The vision for the APEX study is to contribute toward achieving a more affordable and cost-effective fusion energy sciences research program, as well as toward a safer, more economical, and more environmentally friendly fusion energy product.

A key feature of the study is providing a research environment conducive to innovation with emphasis on understanding and advancing the underlying engineering and physics sciences as a prerequisite for innovation. The study covers conceptual design, modeling, and experiments for new and evolutionary ideas for the Chamber Technology.

The APEX study is being carried out by a multi-disciplinary, multi-institution integrated team. The team members are drawn from twelve US institutions that include universities, national laboratories, and industry. In addition, there is significant international participation by scientists from Germany, Japan, and Russia.

The composition of the APEX team and the study approach emphasize partnership between plasma physics and technology and strong interactions among the key technical areas and functional disciplines such as thermofluids, thermomechanics, magnetohydrodynamics, materials, plasma-material interactions, system studies, nuclear, and safety.

OFES Letter of Charge

Download a copy of the letter in pdf format

July 16, 1997

Professor Mohamed Abdou
School of Engineering and Applied Science
43-133 Engineering IV
Box 951597
University of California, Los Angeles
Los Angeles, CA 90095-1597

Dear Mohamed:

As you know, the ALPS effort is being organized to plan activities aimed at evaluating high heat flux removal concepts that use liquids for plasma-facing surface applications in divertors.

A more general issue for long-term attractiveness of fusion energy is advanced concepts for extracting both high bulk heat flux and high surface heat flux, which is necessary for power handling in fusion devices that operate at high neutron wall loads.

Now is the time to undertake bold initiatives that might revolutionize the way that we think about fusion power extraction and create a broad design envelope for exploiting future gains in plasma performance.

Toward this end, I request that you organize and lead a group effort to plan activities aimed at identifying and evaluating the feasibility of advanced concepts capable of safe and efficient extraction of high bulk and surface heat flux in fusion power cores operating at high neutron wall loads.


In the “Strategic Plan for the Restructured U.S. Fusion Energy Sciences Program”, issued by OFES in August 1996, one of the three policy goals supporting the program mission is to:

“Develop fusion science, technology, and plasma confinement innovations as the central theme of the domestic program”

In October 1996, sixty members of the U.S. fusion community and OFES met at a planning workshop to chart the future of the program. The report from this workshop emphasized the need to “explore the scientific basis for innovative technologies and materials options capable of achieving the full potential of fusion energy” and recommended the following as a five-year goal:

“Marked progress in the scientific understanding of technologies and materials required to withstand high plasma heat flux and neutron wall load”

Relative to this goal, the following specific deliverable was recommended:

“Identify and evaluate new high performance concepts for advanced technology with high neutron wall load capability and attractive safety and environmental features”

This deliverable recognizes that technologies for surface and bulk heat flux extraction must advance considerably beyond near-term capabilities in order to handle the high neutron wall loads expected for economically competitive fusion energy systems.

Next-step concepts, such as ITER, have an average fusion core power density that is over two orders-of-magnitude less than in present-day water cooled fission reactors and a peak-to-average heat flux in the coolant that is over an order-of-magnitude greater than in present-day water cooled fission reactors. Longer-term concepts of an EVOLUTIONARY nature (i.e., based on ferritic steel, vanadium alloy, or silicon carbide composite structural materials) may not be able to achieve the average fusion core power densities and peak-to-average heat fluxes needed for competitive economics.

Along these lines, there should be an element of fusion research that nurtures creativity and innovation toward exploring REVOLUTIONARY power extraction concepts that may be of high technical risk, but have high payoff performance characteristics, such as:

  • high bulk and surface heat flux handling capability
  • large design margins
  • assured fuel self-sufficiency
  • low failure rates
  • high thermal efficiency

Of course, research on evolutionary concepts must continue toward proof-of-principle experimentation and determination of performance limits. The proposed research on revolutionary concepts, which will be of more fundamental nature moving toward feasibility assessment, will stimulate the conception of new ideas that utilize fundamentally different approaches and offer order-of-magnitude higher payoffs, even if the development risks appear high.


The APEX (Advanced Power EXtraction) planning group is requested to prepare a draft plan for activities aimed at identifying and evaluating the feasibility of advanced concepts capable of safe and efficient extraction of high bulk and surface heat flux in fusion power cores operating at high neutron wall loads.

Emphasis should be given to advanced concepts that have applicability to a broad spectrum of magnetic confinement approaches.

These activities should systematically consider all fusion core components associated with power handling and extraction and should devise innovative concepts that integrate these components into self-consistent design approaches that consider particle exhaust, safety, and environmental issues.

Consideration should be given to plasma performance issues due to their influence on surface heat flux distribution. In particular, means to reduce peak-to-average surface heat flux on plasma-facing components should be considered.

One of the goals of APEX research should be to determine the upper limits of fusion power core operation through a combination of plasma physics approaches that reduce peaking factors and innovative in-vessel component designs that can handle high peak heat loads. This will require cooperation between physicists and engineers and a bridging of the interface issues between plasma performance and plasma energy extraction.

The following guidelines should be followed by the APEX planning group:

  • The APEX program will be carried out in 3 sequential phases: a planning phase, beginning as soon as possible and lasting for no more than 4 months an evaluation phase, beginning in FY 1998 and lasting for no more than 3 years an R&D phase, beginning after the evaluation phase.
  • The group should have representation from U.S. fusion community institutions with capabilities and interests toward addressing feasibility issues of advanced power extraction concepts. Membership should provide for adequate involvement by and interactions between physicists, designers, and both analytical and experimental technologists. In most cases, one group member per institution would be appropriate. In those cases where more than one member per institution is deemed necessary, please limit the number of members from any one institution to no more than 2.
  • The APEX planning group will carry out the planning phase effort by preparing a plan for the evaluation phase effort, which should begin by the end of 1997 and provide the technical basis for initiation of a significant R&D effort beginning in FY 2001. The activities in the evaluation phase effort are suggested to include the following:
    • Specification of requirements and evaluation criteria for advanced power extraction concepts
    • Conceptual design and analysis of candidate concepts selection of most promising concepts
    • Identification of generic experimental research that could be conducted in parallel with design and analysis activities
    • Detailed design and evaluation of the most promising concepts identification of feasibility issues and assessment of overall attractiveness
    • Description of R&D required to resolve feasibility issues of the most promising concepts prioritization and planning of R&D programs

To the extent possible, the group should estimate the costs required to perform a complete and thorough set of activities in the evaluation phase effort, as well as the costs associated with performing a reduced scope set of activities that involves minimum levels of design and analysis and addresses only key feasibility issues.

The group should consider opportunities for international collaborations and make recommendations accordingly.

The group should establish appropriate interfaces with the ALPS effort and the Advanced Design community.

A draft plan for the evaluation phase effort should be available for OFES review by the end of October 1997. When finalized, the plan will guide the implementation of APEX evaluation studies in FY 1998, subject to the availability of OFES funds for such a purpose.

I appreciate your willingness to lead the APEX planning group in this exciting endeavor.

Sam Berk
Team Leader for Technology Programs
Office of Fusion Energy Sciences
Office of Energy Research
U.S. Department of Energy