The evolution of He+ irradiation-induced point defects and helium retention in nuclear graphite

Mingyang Li, Chuanqing Shi, Henk Schut, Zhengjun Zhang, Zhengcao Li

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1 Citation (Scopus)

Abstract

The atomic-level study of point defect evolution in nuclear graphite is essential for a deep understanding of irradiation-induced property changes. The evolution of helium ion irradiation-induced point defects and helium retention in nuclear graphite ETU-10 and ETU-15 were studied by positron annihilation Doppler broadening (PADB) experiments and thermal desorption spectroscopy (TDS) measurements. The graphite samples were implanted with 1015, 1016, and 1017 cm−2 of 200 keV He+ at operation temperatures below 373 K. Frenkel pairs were created during ion irradiation and they annihilated during annealing. Three stages of interstitial-monovacancy annihilation are suggested. At low temperatures, the initial annihilation would be refined only to the recombination of intimate metastable Frenkel pairs. When temperature increases, the annihilation would expand to a larger extent that isolate interstitials and vacancies annihilate with each other. In the case of high doses irradiation, vacancy clusters form at elevated temperatures. The retention and release of helium is tightly related to the evolution of the defects, especially the vacancies. The small over-pressured He-V clusters (HenV) are thought to be the most possible form of helium retention under irradiation.

Original languageEnglish
Pages (from-to)744-751
JournalJournal of Nuclear Science and Technology
Volume56
Issue number8
DOIs
Publication statusPublished - 2019

Keywords

  • helium
  • irradiation
  • Nuclear graphite
  • point defect
  • positron annihilation

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