Research Needs for Magnetic Fusion Energy Sciences - US Burning ...

emphasis on modeling and expertise in high-performance computing must also be a key element
of addressing power extraction gaps. incorporating the knowledge base into models and simulation
tools gives researchers the capability to predict component behavior beyond parameters
of the experimental database. development of integrated simulation of the multi-physical phenomena
unique to fusion systems is an important requirement. This capability is critical in fusion
where true demo reactor conditions will likely not be fully reached prior to demo itself. as
is clear from iteR experience, a fusion demo will be a nuclear device that must be designed and
fabricated using vigorously validated codes acceptable to nuclear standards and regulatory agencies.
MatERialS SciENcE iN thE FuSioN ENviRoNMENt
overcoming the challenges confronting first-wall, blanket, plasma facing and functional materials
systems is as difficult and important for fusion energy generation as achieving a burning
plasma. Fusion materials and structures must function in a uniquely hostile environment that
includes a combination of high temperatures, reactive chemicals, time-dependent thermal and
mechanical stresses, and intense neutron fluxes. atomic displacement damage alone in a demo-
type reactor will be equivalent to ejecting every atom from its lattice site up to 200 times. displacement
damage undergoes complex interactions with high concentrations of reactive and insoluble
gases that lead to the degradation of a host of performance sustaining material properties;
these include hardening, low-temperature embrittlement, phase instabilities, segregation, precipitation,
irradiation creep, volumetric swelling, and high-temperature helium embrittlement.
Plasma facing components must also withstand heat fluxes comparable to those experienced by
rocket nozzles. While key fusion structures are subject to a wide variety of poorly understood failure
paths, they must clearly demonstrate high safety margins over long lifetimes. indeed, the unprecedented
demands placed on materials from thermo-mechanical loading alone are a feasibility
issue, even without the severe effects of radiation damage.
Research gaps
The materials panel considered the research gaps presented in the ReneW resource document titled
“Priorities, Gaps and opportunities: towards a long-Range strategic Plan For magnetic Fusion
energy” that was published in october 2007. after careful consideration the panel decided
to reformulate the gap statements to provide a more comprehensive assessment of the numerous
challenges facing the many materials needed to construct a prototypical fusion power system.
The following seven gaps capture the essential elements of what is missing from the current fusion
materials research portfolio.
gap: The overarching scientific challenge facing successful development of a viable fusion power system
is acquiring a firm scientific understanding and devising mitigation strategies for the deleterious
microstructural evolution and property changes that occur to materials in the fusion environment.
although considerable progress has been made exploring the resistance of structural materials
to neutron irradiation in fission reactors (to damage levels on the order of ~30 dpa), the current
knowledge base for reduced-activation structural materials exposed to fusion-relevant irradiation
conditions is almost nonexistent. in a fusion reactor structural (and other) materials will
152