Modeling Helium Segregation to the Surfaces of Plasma-Exposed Tungsten as a Function of Temperature and Surface Orientation

Journal Article · Mon Jan 02 00:00:00 EST 2017 · Fusion Science and Technology

DOI:https://doi.org/10.13182/FST16-112· OSTI ID:1524075

Blondel, Sophie ^[1]; Hammond, Karl D. ^[2]; Hu, Lin ^[3]; Maroudas, Dimitrios ^[3]; Wirth, Brian D. ^[4]

---

1. University of Tennessee, Department of Nuclear Engineering, Knoxville, Tennessee 37996; Oak Ridge National Laboratory, Computer Sciences and Mathematics Division, Oak Ridge, Tennessee 37831
2. University of Missouri, Department of Chemical Engineering, Columbia, Missouri 65211; University of Missouri, Nuclear Engineering Program, Columbia, Missouri 65211
3. University of Massachusetts, Department of Chemical Engineering, Amherst, Massachusetts 01003-9303
4. University of Tennessee, Department of Nuclear Engineering, Knoxville, Tennessee 37996; Oak Ridge National Laboratory, Fusion and Materials for Nuclear Systems Division, Oak Ridge, Tennessee 37831

We provide a description of the dependence on surface crystallographic orientation and temperature of the segregation of helium implanted with energies consistent with low-energy plasma exposure to tungsten surfaces. Here, we describe multiscale modeling results based on a hierarchical approach to scale bridging that incorporates atomistic studies based on a reliable interatomic potential to parameterize a spatially dependent drift-diffusion-reaction cluster-dynamics code. An extensive set of molecular dynamics (MD) simulations has been performed at 933 K and/or 1200 K to determine the probabilities of desorption and modified trap mutation that occurs as small, mobile Hen (1 ≤ n ≤ 7) clusters diffuse from the near-surface region toward surfaces of varying crystallographic orientation due to an elastic interaction force that provides the thermodynamic driving force for surface segregation. These near-surface cluster dynamics have significant effects on the surface morphology, the near-surface defect structures, and the amount of helium retained in the material upon plasma exposure, for which we have developed an extensive MD database of cumulative evolution during high-flux helium implantation at 933 K, which we compare to our properly parameterized cluster-dynamics model. This validated model is then used to evaluate the effects of temperature on helium retention and subsurface helium clustering.

• Research Organization: Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States). National Energy Research Scientific Computing Center (NERSC)
• Sponsoring Organization: USDOE Office of Science (SC)
• DOE Contract Number: SC0008875; AC02-06CH11231; AC02-06CH11357
• OSTI ID: 1524075
• Journal Information: Fusion Science and Technology, Vol. 71, Issue 1; ISSN 1536-1055
• Publisher: American Nuclear Society
• Country of Publication: United States
• Language: English