By Ron Stambaugh, Vincent Chan, and Clement Wong
General Atomics
May 25, 2007

1.0 Mission Scope Summary

A Fusion Development Facility(FDF) is proposed to make possible a
fusion demonstration power plant (DEMO) as the next step after
ITER. To make possible an advanced DEMO of the ARIES-AT type the
mission of the FDF should be:

To carry forward Advanced Tokamak physics and enable development of
fusion's energy applications.

This two part mission may be further elaborated. For AT physics, FDF
should: Demonstrate advanced physics operation of a tokamak in
steady-state with burn.  FDF must be the first tokamak designed using
already proven and conservative implementations of all elements of
Advanced Tokamak physics to produce 100-250 MW fusion power with
modest energy gain (Q<5) in a modest sized device. The many advances
made in the last decade must be captured in a next step device in
order to make progress toward the even more advanced physics called
for by ARIES-AT. Modest size (we envision a device between DIII-D and
JET in size) is needed to minimize the cost consistent with the
mission. Even so, the cost will be substantial and the ambition of the
mission must match the cost. Modest size means modest Q; in tokamaks
size and Q are strongly coupled. FDF with Q<5 does not compete with
ITER for the high energy gain burning plasma mission.

A conservative expression of AT physics means ?N = 4 at the DIII-D
aspect ratio. Such high ?N is essential to utilize full non-inductive,
high bootstrap operation to demonstrate continuous operation of a
tokamak for periods up to two weeks, a necessary step before DEMO and
essential to a blanket development mission. Besides using AT-physics
for its baseline operating modes, FDF must be capable of further
developing all elements of AT physics, qualifying them for an advanced
performance DEMO. In practical terms this means striving for operating
modes with ?N up to 5.

By realizing the volume neutron source described above, FDF will be
able to develop fusion's energy applications. With neutron fluence at
the outer midplane of 1-2 MW/m2 and a goal of a duty factor on a year
of 0.3, FDF can produce fluences of 3-6 MW-yr/m2 in ten years of
operation onto complete blanket structures and/or material sample
volumes of about one m3. This level of fluence should enable
qualification of at least the first few years of DEMO operation. This
fluence is less than the 15 MW-yr/m2 to show lifetime irradiation of
materials in IFMIF, but IFMIF will only irradiate a 0.5 liter volume
of samples and not with realistic heat and neutron dpa gradients
possible in FDF.

Before a DEMO project can be committed, net tritium production must be
demonstrated and assured. We do not believe it is practical to first
make this demonstration in the first phase of DEMO operation, owing to
the high tritium consumption rates. This assurance of tritium supply
must be made first in a more modest device. FDF will have a goal of
producing its own tritium and building a supply to start up DEMO. The
approach taken will be to engineer a first full blanket with the
simplest technology that just produces net tritium. All other design
requirements are secondary. Then in parallel, more advanced blankets
will be tested in port blanket modules and successful ones will then
be engineered into second generation full blankets. FDF will be
designed to facilitate change-out of the full first wall/blanket
structures and will do so 2-3 times in the life of the project.

In the port blanket modules, the development of blankets suitable for
both tritium production and electricity production will be made. FDF
will provide the necessary facility to test perhaps ten different
blanket concepts or variants in 2-3 ports over a ten year time
period. FDF will be the necessary facility to learn how to make
blankets that support high temperature, high thermodynamic efficiency
for power conversion for electric power production. Another port site
should be devoted to the development of blankets that can support
hydrogen production, which can require even more demanding
temperatures of extracted coolant, over 900 0C. Although FDF will not
attempt electric power production from its full blankets, actual
demonstrations of both electricity production (300 kW) and of hydrogen
production (one metric ton per week) should be made on port blankets
that are sufficiently successful to warrant that effort.

The above mission elements for FDF, with ITER and IFMIF, and other AT
devices, will provide the basis for a fusion DEMO power plant of the
ARIES-AT type (figure 1).  (