Materials Challenges in the U. S. Fusion Program
Fusion reactor materials will be required to function in an extraordinarily demanding environment that includes various combinations of high temperatures, chemical interactions, time-dependent thermal and mechanical loads, and intense neutron fluxes. This environment produces atomic displacement damage ultimately equivalent to displacing every atom in the material up to about 150 times during its expected service life, as well as changes in chemical composition by transmutation reactions, including the introduction of damaging concentrations of reactive and insoluble gases. Radiation damage degrades materials properties through processes that include hardening, embrittlement, phase instabilities, segregation, precipitation, irradiation creep, volumetric swelling, He embrittlement, and radiation-induced conductivity. A long-standing feasibility issue is the development of structural materials that can tolerate the intense fusion neutron environment. The U. S. Fusion Materials Program is engaged in a science-based effort to develop the scientific understanding of the damage mechanisms controlling performance-limiting phenomena of materials for fusion power systems. The program employs the full suite of experimental and computational tools to explore life limiting materials degradation phenomena in the fusion neutron environment. Our overarching goal is to develop experimentally validated, physics-based, predictive models of complex material behavior that can be used to improve existing materials or to design better ones. To a large extent, structural materials in the fusion blanket region most strongly impact the technical feasibility, economic attractiveness and environmental acceptability of fusion power systems. Therefore research on structural materials is the main focus of the program. To produce an economically attractive fusion reactor, while simultaneously achieving safety and environmental acceptability goals, the program is developing low or reduced activation materials so that when they are removed from service they will not require long-term deep geological disposal and may be recyclable. Only a limited number of materials possess the physical, mechanical and low-activation characteristics required: reduced activation steels, vanadium alloys, and SiC/SiC composites. In the recent past the fusion materials research emphasis was on defect production and migration mechanisms, low-to-intermediate temperature deformation and fracture behavior of these materials, as well as the fundamental effects of irradiation on the electrical and thermal properties of SiC. In the future the program focus will be on investigating the synergistic effects of He, tritium and neutron irradiation on the properties of bonded materials, as well as developing a mechanistic understanding of damage evolution at high-temperatures due to creep, fatigue and creep-fatigue interaction. In this article we choose to highlight recent and ongoing experimental and computational efforts to characterize and understand the effects of He on microstructural evolution in ferritic/martensitic steels, and an important revolutionary class of materials – nanostructured ferritic alloys (NFA).
- Research Organization:
- Pacific Northwest National Lab. (PNNL), Richland, WA (United States)
- Sponsoring Organization:
- USDOE
- DOE Contract Number:
- AC05-76RL01830
- OSTI ID:
- 993369
- Report Number(s):
- PNNL-SA-60516; AT6020100; TRN: US1008008
- Journal Information:
- American Nuclear Society Fusion Energy Division Newsletter, June 2008:9-12, Journal Name: American Nuclear Society Fusion Energy Division Newsletter, June 2008:9-12
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
36 MATERIALS SCIENCE
70 PLASMA PHYSICS AND FUSION TECHNOLOGY
ALLOYS
ATOMIC DISPLACEMENTS
BUILDING MATERIALS
CHEMICAL COMPOSITION
CREEP
EMBRITTLEMENT
FRACTURES
IRRADIATION
NEUTRONS
POWER SYSTEMS
SERVICE LIFE
STEELS
THERMODYNAMIC PROPERTIES
THERMONUCLEAR REACTOR MATERIALS
THERMONUCLEAR REACTORS
VANADIUM ALLOYS