Effects of Helium on Radiation Damage Processes in Iron
Conference
·
OSTI ID:15005493
Molecular dynamics calculations were performed to evaluate the energies of helium-related defects in ?-iron for investigation of helium behavior during irradiation. The interatomic potentials employed here were the Ackland Finnis-Sinclair N-body potential, the Wilson-Johnson potential and the ZBLBeck potential for describing interactions of Fe-Fe, Fe-He and He-He, respectively. The migration energy of interstitial helium is extremely low, indicating that an interstitial helium atom can migrate rapidly in the metal even at extremely low temperature, until the helium atom is trapped or escapes outside. One of the most efficient trapping sites for helium is a vacancy or small vacancy clusters (nanovoid). The formation energy of helium-vacancy clusters in iron was calculated as a function of the number of helium atoms and vacancies. The binding energy of an interstitial helium atom, a substitutional helium atom and a vacancy to the cluster was also determined as a function of the helium-to-vacancy ratio of the cluster. Helium is strongly bound to the helium-vacancy cluster, and it can stabilize the cluster, thereby increasing cluster lifetime by dramatically reducing thermal vacancy emission. The binding of helium and vacancies to a helium-vacancy cluster greatly depends on the helium-to-vacancy ratio of the cluster. For clusters with extremely high helium-to-vacancy ratios, it was observed that the collective motion of helium atoms produces bubble pressures large enough to spontaneously create additional vacancies and associated self-interstitial atoms at the periphery of the cluster. Finally, the possibility of athermal production of self-interstitial atom (SIA) loops (i.e., dislocation loop punching) from the cluster is discussed.
- Research Organization:
- Lawrence Livermore National Lab., CA (US)
- Sponsoring Organization:
- US Department of Energy (US)
- DOE Contract Number:
- W-7405-ENG-48
- OSTI ID:
- 15005493
- Report Number(s):
- UCRL-JC-144458
- Country of Publication:
- United States
- Language:
- English
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