Kinetics and transport of hydrogen in graphite at high temperature and the effects of oxidation, irradiation and isotopics

Lorenzo Vergari, Raluca O. Scarlat

Research output: Contribution to journalReview articlepeer-review

Abstract

The kinetics of uptake and desorption impact the performance of graphite as a vector for tritium in high-temperature fission reactors and in the blanket of fusion reactors. Graphite components in these reactors are exposed to temperatures > 500 °C and H2 partial pressures of few Pa and desorption temperatures are limited to < 1600 °C; limited data is available at these conditions. We review the mechanisms for uptake in, transport and desorption of hydrogen from graphite at high temperature, compiling data on uptake rates, diffusion coefficients and activation energies and providing a discussion of the impact of irradiation, pre-oxidation and isotope. At FHR conditions, trapping impacts uptake rates, leading to a reduction in apparent diffusivity by 35 to 80% compared to higher partial-pressure uptake. Timelines for desorption are not clearly defined; extrapolating from available data, at 1150 °C desorbing 80% of tritium uptaken at FHR conditions may take from 100 to 10,000 h.

Original languageEnglish (US)
Article number153142
JournalJournal of Nuclear Materials
Volume558
DOIs
StatePublished - Jan 2022
Externally publishedYes

Keywords

  • Graphite matrix and nuclear graphite
  • Hydrogen absorption kinetics
  • Hydrogen thermal desorption
  • Molten salt
  • MSR and FHR
  • Tritium management

ASJC Scopus subject areas

  • Nuclear and High Energy Physics
  • General Materials Science
  • Nuclear Energy and Engineering

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