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

The structures and components of fusion power systems will also experience cyclic (fatigue) loading.
The interaction of fatigue and creep deformation is poorly understood. existing creep-fatigue
design rules are not based on the principles of materials science, but rather on experimental measurements
for specific materials and conditions. The traditional approach to establish acceptable
creep-fatigue operating limits relies on extensive testing, and large variations in these limits are
found for various materials. current asme [american society of mechanical engineers] creep-fatigue
design rules are based entirely on empirical fits to experimental data. hence, there is a compelling
need to apply advanced experimental techniques and sophisticated computational methods
for a better physical description of high-temperature deformation processes.
gap: The mechanisms controlling chemical compatibility of materials exposed to coolants and erosion
of materials due to interaction with the plasma are poorly understood.
For efficient power conversion, a high coolant exit temperature is desirable, which requires hightemperature
structural materials. a potential limit on the upper use temperature is dictated by
interaction of the structural material with the coolant. if the coolant/breeder material is not
compatible with the structural material, its high temperature capability cannot be fully exploited.
many variables affect the corrosion rate of a structural material in a particular coolant, including
temperature, chemical composition of the structural material and the coolant, coolant flow
velocity and velocity profile, coolant impurity concentration, and radiation. most of the corrosion
studies performed to date involve exposing a structural material in static coolant at a particular
temperature, or a flowing coolant in a temperature gradient. corrosion rate measurements are
empirically correlated to coolant temperature and flow velocity. These correlations do not capture
the fundamental physical mechanisms involved in the corrosion process and, therefore, are not
useful for predicting material performance outside the range of the experimental measurements.
a significant opportunity exists to improve the scientific understanding of corrosion processes
through applying advanced analytical techniques and modeling methods such as in situ electrochemistry
and computational thermodynamics codes.
gap: An integrated materials-structure development, design and testing approach to fusion systems,
including facilities to determine the fundamental performance limits of materials and components in a
fusion-relevant environment, is lacking.
materials and components for use in fusion power systems must ultimately be qualified to validate
the design and demonstrate adequate safety margins. Fusion power systems must cope with
time-dependent material properties in components with complex stress states, and long intended
service lives. existing thermo-mechanical property data and high-temperature design methodologies
are not adequate to permit the design of a robust fusion power system. development of fusion
relevant design rules will require close integration between materials development activities
and system design processes. Thus, fusion materials development necessitates the design of material
systems and development of multifunctional structures concurrently. The traditional “function-oriented”
material design approach will not be sufficient. instead, a concurrent “materialscomponent-structure
design” process must be implemented.
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